We are heading out this weekend. I just noticed I have two different tires on my pop up. One says 60 max psi the other is 90 psi. They are the same size tires just different brands. Should I go with 60 in both. It is a 97 Palamino pulled by a Ford Ranger. Pulling about 55 miles. Any help appreciated. Thanks MB
Quote from: M BaxterWe are heading out this weekend. I just noticed I have two different tires on my pop up. One says 60 max psi the other is 90 psi. They are the same size tires just different brands. Should I go with 60 in both. It is a 97 Palamino pulled by a Ford Ranger. Pulling about 55 miles. Any help appreciated. Thanks MB
It would be best to correct the problem by having 2 tires that require the same pressure.
That being said, if I were faced with the same problem and timing, I would put the correct pressure in each tire then keep the speed down.
The tire pressure in trailer tires is designed to hold the side walls off of the pavement. By under-inflating the one tire, you are risking a blow-out IMHO.
I was worried it would pull funny with 90 in one and 60 in the other. The road Im going on is 55 MPH so hopefully it will be ok. Has any one else faced this problem? Waverly thanks for the info. MB
Quote from: M BaxterI was worried it would pull funny with 90 in one and 60 in the other. The road Im going on is 55 MPH so hopefully it will be ok. Has any one else faced this problem? Waverly thanks for the info. MB
I doubt that you will notice a difference in towing at 55-60. If you notice any swaying (which I doubt), slow down :D .
If you ran that 90# tire at 60# you probably would notice a difference while towing. Basically, those tires are as hard as a rock when fully inflated.
Quote from: M BaxterI was worried it would pull funny with 90 in one and 60 in the other. The road Im going on is 55 MPH so hopefully it will be ok. Has any one else faced this problem? Waverly thanks for the info. MB
You are a lot more likely to notice a difference with one tire at full pressure and the other underinflated. If at first you you don't, you will soon enough, and you won't be happy.
IMNSHO, the best way to fix this is to change one (or both) of the tires so they are the same. Using whatever random tire you can scrounge up may be acceptable for an around-town utility trailer, but for a trailer on the highway, you want the right tires for the job.
Austin
Quote from: M BaxterWe are heading out this weekend. I just noticed I have two different tires on my pop up. One says 60 max psi the other is 90 psi. They are the same size tires just different brands. Should I go with 60 in both. It is a 97 Palamino pulled by a Ford Ranger. Pulling about 55 miles. Any help appreciated. Thanks MB
Tire brands should not make a difference, what makes a whole BIG difference is the LOAD RANGE rating of the tires. You did'nt list the size of the tire so I'm going to make a wild guess ... is the tire size 4.80 X 12"? In the particular case of this size trailer tire the 4.80 X 12" (Load Range "B") tire requires 60 psi and at that pressure is rated to carry 780 lbs. ~ the 4.80 X 12" (Load Range "C") tire requires 90 psi to carry a load of 990 lbs.
What you need is two tires the same size AND the same load range carrying capacity. Different manufactures are not as important. I personally like having the same manufacture tires, however, there have been times when I did not but all went well anyway.
The top reason for trailer tire failure is under inflation. Second on the list is tire overloading. Having a tire not up to load capacity, i.e., using a load range "B" where it calls for a load range "C", is asking for trouble.
The load range ratings are on the tire sidewall.
Fly
Fly you are correct. One is a B the other is a C. The tire size is 4.80X12. Man I am statring to get worried now. I took the spare off and it is brand new and callsfor 90 PSI. The only problem is the wheel is bigger than the two on the camper. Ive never had it off until today. I guess Ill have to call in sick tommorow and figure it out. Thanks so far. MB
Quote from: M BaxterFly you are correct. One is a B the other is a C. The tire size is 4.80X12. Man I am statring to get worried now. I took the spare off and it is brand new and callsfor 90 PSI. The only problem is the wheel is bigger than the two on the camper. Ive never had it off until today. I guess Ill have to call in sick tommorow and figure it out. Thanks so far. MB
This has been a not all that uncommon of an error when someone goes to replace a tire. Even tire shops get it buggered up ... a load range "B" will be sold and mounted where a load Range "C" is called for.
Is your camper per chance a Viking or Coachman? Do you know it's base weight? And it's total weight carrying capacity (called GVWR ... "gross vehicle weight rating")?
Finding a trailer tire that size ought not be that difficult ... just be sure it's a load range "C".
Fly
I just had a brilliant idea. Im going to take the spare and have it mounted on the wheel that has the 60 psi tire. The brands will still be different but they are both Cs and call for 90 PSI. Thanks again I can sleep better tonight. MB
Quote from: M BaxterI just had a brilliant idea. Im going to take the spare and have it mounted on the wheel that has the 60 psi tire. The brands will still be different but they are both Cs and call for 90 PSI. Thanks again I can sleep better tonight. MB
Be sure to check the "Max PSI" on the wheels too :eyecrazy: . I didn't even think about that :morning: . I know that my (13") wheels have "Max pressure 60#" stamped right on them. :yikes:
I know you're only going 55mi one way, but you might consider the value of having 2 new tires and the peace of mind and safety for your family that comes with that value and compare that to the money you'll save potentially blowing a tire, possibly damaging or losing the camper or it's axle assembly.....and depending on how big of a tow rig you have, damaging or wrecking your rig.
Not trying to put the fear in you, but sometimes you have to play the tape forward and think......When this stupid $120 pair of unknown tires fail out on the road, in traffic, miles from nowhere, in the middle of my vacation trip, with my family on board......how much money am I gonna save?
Quote from: M BaxterI took the spare off and it is brand new and callsfor 90 PSI. The only problem is the wheel is bigger than the two on the camper. Ive never had it off until today. MB
Not quite following you here ... I don't understand how one wheel (tire rim?) can be larger ... can you explain this a little for me?
Also, this site may be of some reference help for you in the future.
http://www.easternmarine.com/em_store/tech_info/trailertires_tech_info.htmlFly
When I stand them against each other one is taller. The tires are the same so Im assuming one wheel is bigger. This is my first time on this site and it is VERY HELPFULL. I called in sick today and am getting ready to go th the tire place. Ill give an update when I get back. Thanks again MB
Providing the rims are the same, i.e., all are 4-bolt hole rims, the difference in the height might be due to the spare tire being new plus maybe that tire manufacturer having a deeper tread design.
If that being the case, I would put the taller tire on the curb side of the camper in that most of the highways are crowned and the curb side of the road being lower.
Fly
I had the same problem. Somehow, I got two tires of different load ranges, and thus different cold tire pressures.
I knew I'd get mixed up at some point, so I went ahead and fixed the problem, like others have advised. I bought two tires (extra for a spare) to match the higher load range. Felt better that way.
Larry
I just came from the tire shop. A brand new tire was only 20 dollars. Now I have two exact towing tires and they are both brand new. Im getting the other C rated tire mounted as the spare. The 35 dollar total is very much worth the piece of mind. Thanks again. MB
Quote from: M BaxterI just came from the tire shop. A brand new tire was only 20 dollars. Now I have two exact towing tires and they are both brand new. Im getting the other C rated tire mounted as the spare. The 35 dollar total is very much worth the piece of mind. Thanks again. MB
Now you're talking! There's nothing like fresh rubber on the road and the peace of mind it promotes. Now run off and have a care free camping weekend tooling down the road with your family on board........amongst a hailstorm of intoxicated drivers!
Cheers!
Quote from: austinado16Now run off and have a care free camping weekend tooling down the road with your family on board........amongst a hailstorm of intoxicated drivers!
While I'm not interested in mixing it up with intoxicated drivers, encountering intoxicated campers is what I'd be more worried about. We seldom camp on holiday weekends any more.
Austin (camping NEXT weekend)
If the 60 & 90 PSI tires are the same physical size, then you're not as bad off as you think. At 60 PSI, both tires should be rated to carry close to the same amount with the same "softness".
The pressure you should use is NOT NOT NOT what is printed on the tire, but the pressure that is on your camper's vehicle rating tag - should be on the driver side near the front, that has the GVWR, axle, etc on it.
The "C" tire needs 90 PSI in order to support its max weight = 990
The "B" tire needs 60 PSI in order to support its max weight = 780
However, if you put less than 90 PSI in the C tire, it can still carry the correct weight for that PSI.
That is why all vehicles have a manufacturer's label with the PSI. What does your camper's label say is the recommended pressure?
For example, my Explorer has tires rated for 45 PSI on it. However, the label says 35 PSI is what the manufacturer requires, and what my warranty is rated for. Over-inflating a tire (ie, over the recommended amount, but under the max) will cause your tires to wear in the middle badly, because they are not being compressed enough to wear evenly. Over-inflating can also make them more susceptible to road-damage from potholes, etc.
National Highway Traffic Safety Administration says to inflate your tire to the manufacturer's recommendation.
http://www.usatoday.com/money/consumer/autos/mauto849.htm
I've always aired up according to the tire's ratings and never had a tire wear out in the middle first, or suffered from pot-hole damage. I find that the air pressure recommendations by the auto manufacturer generally leave the tire way too soft for either good performance, or good gas mileage.
I run the PUP tires at the tire's rating, 80psi. They survived 12hrs in 100+*F temps, 70mph and 135*F tread temps on our trip to the Grand Canyon.
That's just how I role....
Quote from: zamboniIf the 60 & 90 PSI tires are the same physical size, then you're not as bad off as you think. At 60 PSI, both tires should be rated to carry close to the same amount with the same "softness".
The pressure you should use is NOT NOT NOT what is printed on the tire, but the pressure that is on your camper's vehicle rating tag - should be on the driver side near the front, that has the GVWR, axle, etc on it.
The "C" tire needs 90 PSI in order to support its max weight = 990
The "B" tire needs 60 PSI in order to support its max weight = 780
However, if you put less than 90 PSI in the C tire, it can still carry the correct weight for that PSI.
That is why all vehicles have a manufacturer's label with the PSI. What does your camper's label say is the recommended pressure?
For example, my Explorer has tires rated for 45 PSI on it. However, the label says 35 PSI is what the manufacturer requires, and what my warranty is rated for. Over-inflating a tire (ie, over the recommended amount, but under the max) will cause your tires to wear in the middle badly, because they are not being compressed enough to wear evenly. Over-inflating can also make them more susceptible to road-damage from potholes, etc.
National Highway Traffic Safety Administration says to inflate your tire to the manufacturer's recommendation.
http://www.usatoday.com/money/consumer/autos/mauto849.htm
Sorry, you are mistaken on this one.
Trailer tires are different than car tires. They should be inflated to their max pressure.....cold.
When a trailer tire is not inflated to it's max pressure, it will ride on the side wall and quickly damage the tire. A tire that is rated at 90PSI could get away with slightly less but certainly not 60PSI as the tire may well blow out in a short period of time.
http://www.discounttire.com/dtcs/infoTrailerTireFacts.dos;jsessionid=FvxW3ZBHVFRY7BVpLC69PQNK7d52L91WWghQK30FM0Hj9ZzN
Quote from: waveryTrailer tires are different than car tires.
Boy, isn't that the truth. More than once, we've been hooked up to go, and I've noted that the van tires are
way bigger than the trailer tires in every dimension except pressure. Then I remember that the van runs around 1,000 lbs. per tire, while the trailer is over 1,600 lbs per tire. :yikes:
Not only are they different, but they are asked to do
a lot more.
Austin
Please do not confuse advise listed for P (passenger) grade tires and ST (special trailer) tires.
ST tires have a different construction than P grade tires and the same rules do not apply. ST tires are designed to only be run at the maximum inflation pressure listed on the sidewall. That's from at least 3 makers of ST tires.
From the Trailer Manufacturer's AssociationQuoteWheel and tire manufacturers recommend adjusting the air pressure to the trailer manufacturers recommended cold inflation pressure, in pounds per square inch (PSI) stated on the vehicles Federal Certification Label or Tire Placard when the trailer is loaded.
http://trailermanufacturersassociation.org/regulations/regulations4.html
Quote from: waveryTrailer tires are different than car tires.
They are? American Institute standards are just that - measurable, repeatable, calculated values. The same tests are used on all tires. Why would a trailer tire be different values from a vehicle in terms of calculations of weight ratings?
Quote from: waveryWhen a trailer tire is not inflated to it's max pressure, it will ride on the side wall and quickly damage the tire. A tire that is rated at 90PSI could get away with slightly less but certainly not 60PSI as the tire may well blow out in a short period of time.
Are you smarter than all manufacturers? Why on earth would they even bother putting values on the vehicle labels, then?
All tires, trailer or TV or big rig or car, should be inflated to the manufacturer's specs. PERIOD. Even the NHTSA says so. Sorry, but I believe them, and all auto manufacturers, over Discount Tire.
An over-inflated tire will NOT compress the necessary amount when under-loaded. Imagine a tire that could hold up to 2000 lbs, but you only have 1000 lbs (but still max pressure). That means when you hit a pothole, there is not enough weight pushing DOWN on the tire to compress the tire and make it absorb the shock. Instead, the strong, over-inflated tire says "neener-neener", and you bend a rim or break a spring instead.
A trailer tire will
only "ride on the side wall" if there were sufficient WEIGHT to compress it. If the tire could hold enough weight, then a lesser amount at a lesser pressure would ensure that the tire DID compress to the "ideal" amount.
We are talking a difference between 780 & 990 lbs per tire. Assuming you want the tire to compress say 8%, then if you put 90 PSI into a 990 lb tire, without sufficient load, then it might only compress 3% - making it WRONG.
Quote from: waveryhttp://www.discounttire.com/dtcs/infoTrailerTireFacts.dos;jsessionid=FvxW3ZBHVFRY7BVpLC69PQNK7d52L91WWghQK30FM0Hj9ZzN
Doesn't say anything about not following your manufacturer's standards (they sidestep it and say inflate to tire, but do not say "ignore manufacturer"). It does say something about different SIZED tires, but not different weight rating (but does say do not mount trailer tires on cars). It also says the combined carrying capacity should exceed the trailer by 20%. It doesn't say you can't use different rated tires, FYI.
My trailer's tires are rated for 1480 lbs each @ 50 PSI. There are 4 of them. That makes 5920 lbs. My manufacturer label also recommends 50 PSI, but the GVWR is 4947. However, the NHTSA says the pressure should be 20% over GVRW. Thus, 4947 * 120% == 5936. OK, so this is 16 lbs over the theoretical perfect tire rating.
It is highly likely that the manufacturer had 4933 (the perfect ratio to the tires) as the target weight, and tweaked their manufacturing to get as close as they could.
Quotes from Canadian gov't website:
"The pressure recommendations molded into the side of the tire are maximum pressures for maximum load.
Using these pressures at less than maximum load can adversely affect tire and tractor performance."
"Follow manufacturer's tire pressure recommendations when inflating tires"
The Auto Channel:
"When asked where a vehicle's proper tire-inflation pressure information is located, 67 percent of men and 45 percent of women said on the tires' sidewalls. In fact, that's wrong. "Proper tire pressure is vehicle-specific," Ferner said. "Tire sidewalls list the maximum pressure recommended by the tire manufacturer. Proper tire pressure information for a vehicle is found on a decal typically in the vehicle's door jamb or in the vehicle owner's manual.""
http://www.theautochannel.com/news/2006/05/10/006266.htmlAAA and Goodyear also agree:
http://www.theautochannel.com/news/2001/08/29/028414.htmlTowing World:
"Always follow the tire manufacturers recommendations on inflation, rotation and balancing"
http://www.towingworld.com/articles/steeringcontrols.htmWeb Bike World
"Make sure you follow the trailer manufacturer's recommendations for tire pressure"
http://www.webbikeworld.com/motorcycle-trailer/motorcycle-cargo-trailer/
Hey Glen,
That's some great research, but seriously......tires do just fine when inflated past what the sticker says in the door jamb or in the cabinet. And no, you're not going to dent a rim or destroy a tire by hitting a pot hole.
First, remember that when a car is built, there is quit a bit of thought that goes into the overall ride characteristic. Since automobiles have to be dumbed down to the lowest common denominator of the American buying public, they are built to ride a certain way. Tire brand choice and inflation has a big part in that.....and it's why a lot of people jump ship and install better tires, better wheels, better shocks/struts, springs, sway bars, etc.
Some interesting things about recommended psi on the manufacturer's decal.
1) That info is based on when the vehicle was built and could be very outdated comprared to current tire construction and other "things."
2) That info is to provide a certain ride quality.
3) That info doesn't tell you to increase the tire pressure in order to raise the hydroplaning speed of the vehicle.
4) That info doesn't tell you that an increase in tire pressure will improve gas mileage
5) That info doesn't tell you that an increase in tire pressure will stiffen the sidewalls and help the vehicle handle more crisply.
If I buy a Goodyear Assurance Triple Tread for my Audi Quattro and it's rated at 44psi, but my decal says 29psi, I'm gonna be rolling around on $400 worth of marshmallows. Not my cup of tea, and guess what? The car rides, drives and handles better with the pressure up at 42psi........18,000mi a year like that and we've still not hit a pot hole and dented a rim or destroyed a set of tires by prematurely wearing out the centers.
And speaking of this whole dent-a-rim theory. Remember that tires are rubber. When you hit a curb or pothole or rock in the road, the tires do not transfer that force as if they were solid material. It's dissapated all over the tire and a harder tire is going to withstand the impact much better, because it is firm enough to dissapate the energy. Drive around on a soft tire, and that is a tire that will smash out under an impact and have more potential for the actual tire beads to come into contact with the offending object.....and bend the rim.
Sometimes it's easy to get all wrapped around the axle of "This is what they tell me to do, so I better do it." May I suggest that you go out and try some real world testing of your own and then make an opinion based on that? But don't take the Explorer. That whole "roll if upset, land on the roof, cave in and kill the occupants" thing isn't worth the risk. We'd like to have you and your family around for more camping fun and discussions here!
Hey - one more thing to think about MB ---
How old is your spare tire? If it is original to your camper and is the ripe old age of 10, you probably don't want it on the road. While it might be in 'new' condition and look okay, it is likely to be dryrotted and prone to blowing under weight/speed/usage.
Sorry Dude - good luck,
Todd
Quote from: zamboniThey are? American Institute standards are just that - measurable, repeatable, calculated values. The same tests are used on all tires. Why would a trailer tire be different values from a vehicle in terms of calculations of weight ratings?
Because they don't do the same things. Does your trailer steer? Mine sure doesn't. Does your trailer have a drive axle? Mine doesn't. Does your trailer cary passengers? Mine doesn't.
QuoteAre you smarter than all manufacturers? Why on earth would they even bother putting values on the vehicle labels, then?
Because in the United States, they are required to do so. If you look carefully at the label, the pressure they give is for a
SPECIFIC TIRE. On every trailer I've seen, when you go to that specific tire, it is the maximum pressure for that tire.
QuoteAll tires, trailer or TV or big rig or car, should be inflated to the manufacturer's specs. PERIOD. Even the NHTSA says so. Sorry, but I believe them, and all auto manufacturers, over Discount Tire.
That's why you included this link:
QuoteTowing World:
"Always follow the tire manufacturers recommendations on inflation, rotation and balancing"
http://www.towingworld.com/articles/steeringcontrols.htm
The tire manufacturers say inflate trailer tires to the max pressure.
QuoteAn over-inflated tire will NOT compress the necessary amount when under-loaded. Imagine a tire that could hold up to 2000 lbs, but you only have 1000 lbs (but still max pressure). That means when you hit a pothole, there is not enough weight pushing DOWN on the tire to compress the tire and make it absorb the shock. Instead, the strong, over-inflated tire says "neener-neener", and you bend a rim or break a spring instead.
I'm at a loss for how to respond to this.
First, tires don't absorb shocks, they add a time delay to them.
Second, an over-inflated tire will only bend a rim if an under-inflated tire was going to totally smash the rim beyond all recognition. Under inflated tires bend rims, over-inflated tires reinforce them.
Third, with a lighter trailer, less absorbtion is necessary, so less compression is necessary.
QuoteA trailer tire will only "ride on the side wall" if there were sufficient WEIGHT to compress it. If the tire could hold enough weight, then a lesser amount at a lesser pressure would ensure that the tire DID compress to the "ideal" amount.
I'm glad you put "ideal" in quotes, because there really is no such thing.
QuoteWe are talking a difference between 780 & 990 lbs per tire. Assuming you want the tire to compress say 8%, then if you put 90 PSI into a 990 lb tire, without sufficient load, then it might only compress 3% - making it WRONG.
I can tell you're not a tire engineer. We're talking the difference between perhaps 8% and 7%.
QuoteDoesn't say anything about not following your manufacturer's standards (they sidestep it and say inflate to tire, but do not say "ignore manufacturer"). It does say something about different SIZED tires, but not different weight rating (but does say do not mount trailer tires on cars).
I wonder why...perhaps because trailer tires are, um, different?
QuoteIt also says the combined carrying capacity should exceed the trailer by 20%. It doesn't say you can't use different rated tires, FYI.
My trailer's tires are rated for 1480 lbs each @ 50 PSI. There are 4 of them. That makes 5920 lbs. My manufacturer label also recommends 50 PSI, but the GVWR is 4947.
Big clue here, but you miss it.
QuoteHowever, the NHTSA says the pressure should be 20% over GVRW.
It says the tire's rating (meaning weight rating) should be 20% over GVWR. Keep in mind that that is not the axle weight, since another 10-15% is supposed to be on the tongue.
QuoteThus, 4947 * 120% == 5936. OK, so this is 16 lbs over the theoretical perfect tire rating.
It is highly likely that the manufacturer had 4933 (the perfect ratio to the tires) as the target weight, and tweaked their manufacturing to get as close as they could.
So these tires are still at maximum pressure by
everyone's recommendation, even though they are at 30-35% less than the rated load...the tires Wayne said to inflate to Max had a weight rating difference of 27%. (990-780)/780x100%=26.9.
Austin
Wow. Where to begin...
Quote from: AustinBostonBecause they don't do the same things. Does your trailer steer? Mine sure doesn't. Does your trailer have a drive axle? Mine doesn't. Does your trailer cary passengers? Mine doesn't.
No, but my trailer, just like my car, categorically:
a) Carries MASS, designed to do so at an optimum setting. PERIOD.
No, my trailer does not steer or drive, but nor do most cars' rear axle (all front-wheel-drive). Sorry, dumb argument.
Tires are designed to primarily do one thing: Suspend mass over a traveling distance at a pre-determined ratio of compression to rolling resistance, and primarily to smooth out shock.
Please look up the benefits of a pneumatic tire, and how they are superior to a solid tire (which is what an over-inflated tire approaches to acting like). Note, the critical importance of the cushion - if it is overinflated, the cushion properties diminish.
Quote from: AustinBostonBecause in the United States, they are required to do so. If you look carefully at the label, the pressure they give is for a SPECIFIC TIRE. On every trailer I've seen, when you go to that specific tire, it is the maximum pressure for that tire.
Not me. At rallies, I've carried my digital pressure gauge around and checked friends' tires to compare them to the labels (and found that about 80% have under-inflated tires). The labels on trailers,
just like cars are designed by the manufacturers to support a correct weight.
Quote from: AustinBostonThe tire manufacturers say inflate trailer tires to the max pressure.
True, what I left out was that the tire manufacturer has no idea of the trailer it is installed on. Given that, their only leeway is to use the tire label - because if the trailer says 80 PSI, but you put a 60 PSI tire on it, and inflate to 80, you may have a very bad situation. Thus, all tire manufacturers say to inflate to their tire labels, because that is the only way THEY can protect them self. I included that link in the wrong section (meant to bolster the argument where of course Discount Tire will say to use the tire labels).
Quote from: AustinBostonFirst, tires don't absorb shocks, they add a time delay to them.
Tires "absorb" shocks by instead of transferring all those pounds-of-force IMMEDIATELY to the vehicle's shock absorbers, they instead bounce the force around inside the wheel and this enables the force to be
spread out over time. Not a time delay - huge difference. (Illustrative example, not accurate--) Instead of 1000 instant pounds of force on the frame in 10 milliseconds, it does 100 pounds of force spread over 100 milliseconds. This means that a shock absorber that can withstand 300 lbs of force can easily withstand the shock
with a suitably "bouncy" tire. If you have a "solid" tire (one that is at max PSI without much load), in physics, it acts as a SOLID tire.
Quote from: AustinBostonSecond, an over-inflated tire will only bend a rim if an under-inflated tire was going to totally smash the rim beyond all recognition. Under inflated tires bend rims, over-inflated tires reinforce them.
True; the over-inflated tire destroys shocks & bends frames. They act as if you have a solid piece of cement you are "rolling" on. You left out quoting my "they break a spring".
Quote from: AustinBostonThird, with a lighter trailer, less absorbtion is necessary, so less compression is necessary.
Not true at all. The rating of the axle is designed such that the tire absorbs a specific amount of the jolt of the gross mass of the trailer and spreads it out over time such that the axle can handle it. If the tires were solid blocks, the first pothole would smash the axle or springs. This is high-school physics (force over time).
Quote from: AustinBostonI can tell you're not a tire engineer. We're talking the difference between perhaps 8% and 7%.
So? I used illustrative numbers (because I do not posses the specific compression ratio numbers for the unknown types of rubber in the tire). I am, however, a mechanical engineer. The physics of tires is based on one simple thing:
PHYSICS. I can tell that you are not.
Quote from: AustinBostonIt says the tire's rating (meaning weight rating) should be 20% over GVWR. Keep in mind that that is not the axle weight, since another 10-15% is supposed to be on the tongue.
Sorry, but the manufacturer must create a vehicle that can support its entire weight. Period. If you are going uphill, and your TV hits a bump, the entire weight (and more, some of your TV, hence the 20% leeway) can,
and does get transferred to the trailer.
Additionally, just because you are
supposed to have 10-15% on the tongue, does not mean that everyone does. Thus, the manufacturer must factor in the chance that 100% of the trailer weight will be carried by the wheels. That is why the axle must also be rated to carry the GVWR. Again, see the issues surrounding Rockwood Roo campers from before about 2005-6 (where the tires, hitch, frame - everything BUT the axle could easily carry more than the GVWR).
It would be incredibly foolish and fatal not to assume that all the mass may be on the wheels/axles. How many trailers out there have under-recommended tongue-weights? I'm sure many do, since people may have a load of firewood in the back of the trailer, things on the back bumper, full black & grey tanks with empty fresh, etc (or vice-versa, whichever puts the most load on the back).
Last, simply one thing to consider about trailers... There are 3 weights for a trailer:
1) Trailer Mass (weight)
2) Axle weight
3) GROSS vehicle weight
Very coincidentally, the GVWR for most campers may well be the tire's max PSI, because that is the LEGAL MAXIMUM you can carry! If the tires are rated for 2880 lbs (2 tires at 1440), then the GVWR cannot exceed that, and the manufacturer puts that on the label. On most campers, the frame and axles can support more, but the tires are the limiting factor. Usually, however, the tires are closely matched to the axle, making BOTH the limiting factor. Replace both of those, and then you branch into how much can the frame support.
However, if the tires are beefier than other parts (
NOTE: SEE ROCKWOOD HYBRIDS FROM 2+ MORE YEARS AGO), then the limiting factor is not the tire, so is not labeled to be at the max PSI. No, in some cases, the max rating is the AXLE capacity.
If you put tires on your trailer that are different from the trailer manufacturer's rating, then simply contact the tire manufacturer and ask for the correct PSI to support the trailer's GVWR. Thus, you ensure you have the correct "bounce" (shock absorption) in the trailer tire for your camper.
Quote from: zamboniThey are? American Institute standards are just that - measurable, repeatable, calculated values. The same tests are used on all tires. Why would a trailer tire be different values from a vehicle in terms of calculations of weight ratings?
Weavery is quite correct when he posted that trailer tires are different than passenger car and light truck tires.
Of course, here's a trailer manufacturer and parts supplier that says trailer tires are different, but then, what do they know? You might try emailing them and seeing if you can straighten out their folly, too!
http://www.championtrailers.com/tire_art.htmlFly
Good grief! I've never seen a thread get so wound up.
"over inflated tires acting as solid objects......walking around checking the tire pressures in other peoples tires......delay in transmitting shock isn't really time delay"
Pass the popcorn. This is starting to get interesting.
Quote from: zamboniNo, but my trailer, just like my car, categorically:
a) Carries MASS, designed to do so at an optimum setting. PERIOD.
No, my trailer does not steer or drive, but nor do most cars' rear axle (all front-wheel-drive). Sorry, dumb argument.
Only a dumb argument if cars don't have front axles.
QuotePlease look up the benefits of a pneumatic tire, and how they are superior to a solid tire (which is what an over-inflated tire approaches to acting like).
Nobody is talking about over-inflated tires but you. A trailer tire at 100% of it's rated presure is not over-inflated.
QuoteNot me. At rallies, I've carried my digital pressure gauge around and checked friends' tires to compare them to the labels (and found that about 80% have under-inflated tires). The labels on trailers, just like cars are designed by the manufacturers to support a correct weight.
And have you compared the trailer label to the tire label? I think you'll find it's always, always, always at 100% of the max pressure, just like yours is, even though the tire rating is 30-35% more than the axle rating, a comment I noticed you snipped out of your reply.
QuoteTrue, what I left out was that the tire manufacturer has no idea of the trailer it is installed on. Given that, their only leeway is to use the tire label - because if the trailer says 80 PSI, but you put a 60 PSI tire on it, and inflate to 80, you may have a very bad situation. Thus, all tire manufacturers say to inflate to their tire labels, because that is the only way THEY can protect them self. I included that link in the wrong section (meant to bolster the argument where of course Discount Tire will say to use the tire labels).
No, that is not the only thing they can do. They can easily say "for X pounds, inflate to Y, for Z pounds, inflate to W." They can do this
very easily, but they
don't. Because the tire is designed to always be at max pressure. Always.
QuoteTires "absorb" shocks by instead of transferring all those pounds-of-force IMMEDIATELY to the vehicle's shock absorbers, they instead bounce the force around inside the wheel and this enables the force to be spread out over time. Not a time delay - huge difference. (Illustrative example, not accurate--) Instead of 1000 instant pounds of force on the frame in 10 milliseconds, it does 100 pounds of force spread over 100 milliseconds.
Sounds like a delay to me.
QuoteThis means that a shock absorber that can withstand 300 lbs of force can easily withstand the shock with a suitably "bouncy" tire.
Not many pop-ups with shock absorbers.
QuoteIf you have a "solid" tire (one that is at max PSI without much load), in physics, it acts as a SOLID tire.
Wrong. It acts like an over-inflated tire. It just bounces a more. A solid dire does not bounce at all. In order for a tire to bounce, it must compress.
QuoteTrue; the over-inflated tire destroys shocks & bends frames. They act as if you have a solid piece of cement you are "rolling" on. You left out quoting my "they break a spring".
That "break a spring" part was wrong too. Now are you happy?
QuoteNot true at all. The rating of the axle is designed such that the tire absorbs a specific amount of the jolt of the gross mass of the trailer and spreads it out over time such that the axle can handle it.
This still happens with "over-inflated" tires. But of course we are talking properly inflated; only you are talking over-inflated.
QuoteIf the tires were solid blocks, the first pothole would smash the axle or springs. This is high-school physics (force over time).
Again, I would agree, if we were talking over-inflated. But a 90 PSI max tire with 90 psi in it is not over-inflated, and does not act like a solid tire
QuoteI am, however, a mechanical engineer.
...
Sorry, but the manufacturer must create a vehicle that can support its entire weight. Period. If you are going uphill, and your TV hits a bump, the entire weight (and more, some of your TV, hence the 20% leeway) can, and does get transferred to the trailer.
You know, every so often, I see things that just amaze me.
If you are a mechanical engineer, then it's time to change careers.
There is absolutely no way for even one ounce of the weight from my tow vehicle to end up on my trailer's axle. It can't even start to do so; before even one ounce could get on the trailer's axle, the tongue would be on the ground.
What does happen is that the dynamic load on the axle can be several times the actual weight of the trailer. There may be a negligible amount of tow vehicle weight involved where there is more than one axle on the trailer,
but it is negligible.
QuoteAdditionally, just because you are supposed to have 10-15% on the tongue, does not mean that everyone does. Thus, the manufacturer must factor in the chance that 100% of the trailer weight will be carried by the wheels.
If you really are a mechanical engineer, you'd have a better explanation than that.
QuoteThat is why the axle must also be rated to carry the GVWR.
This is rediculous. I can't believe I am reading this. Many pop-ups are at the rated weight for the axle,
after you subtract the tongue weight. They MUST be rated to hold the GVWR? Then why are so many pop-ups NOT rated to hold the GVWR?
QuoteIt would be incredibly foolish and fatal not to assume that all the mass may be on the wheels/axles.
How many trailers out there have under-recommended tongue-weights? I'm sure many do, since people may have a load of firewood in the back of the trailer, things on the back bumper, full black & grey tanks with empty fresh, etc (or vice-versa, whichever puts the most load on the back).
Ever had a trailer sway? If you don't have that 10%, you will sway. Manufacturers don't need to worry about this; the laws of physics correct the problem for them.
QuoteLast, simply one thing to consider about trailers... There are 3 weights for a trailer:
1) Trailer Mass (weight)
2) Axle weight
3) GROSS vehicle weight
Very coincidentally, the GVWR for most campers may well be the tire's max PSI, because that is the LEGAL MAXIMUM you can carry! If the tires are rated for 2880 lbs (2 tires at 1440), then the GVWR cannot exceed that, and the manufacturer puts that on the label. On most campers, the frame and axles can support more, but the tires are the limiting factor. Usually, however, the tires are closely matched to the axle, making BOTH the limiting factor. Replace both of those, and then you branch into how much can the frame support.
However, if the tires are beefier than other parts (NOTE: SEE ROCKWOOD HYBRIDS FROM 2+ MORE YEARS AGO), then the limiting factor is not the tire, so is not labeled to be at the max PSI. No, in some cases, the max rating is the AXLE capacity.
And the trailer manufacturer will still recommend max pressure.
QuoteIf you put tires on your trailer that are different from the trailer manufacturer's rating, then simply contact the tire manufacturer and ask for the correct PSI to support the trailer's GVWR. Thus, you ensure you have the correct "bounce" (shock absorption) in the trailer tire for your camper.
I'm going to try that. I bet I get max pressure every time.
Austin
Austin, I hate to say it but there are people who are instant experts and know more than the company engineers that have over 100 years of experience to rely on when giving recommendations for inflation and usage of the proper grade/type of tire.
You are argueing with one, and no amount of facts will convince them they are wrong and the rest of the world is right...LOL
It don't "fool" them that every tire company that manufactures ST ( special trailer) tires recommends that they only be used at maximum inflation pressure listed on the sidewalls. They know better.
They "know" that "tires are tires" and P, St, LT, commercial don't have a thing to do with anything and most likely also perpetuate myths such as:
you have to leave tires a few pounds low when inflating them because they build up pressure and don't care that tire engineers have realized that for at least the last 80-90 years and have set their maximum pressure ratings to account for the increase.
As for me I just keep an eye out for them along side of the road with the blown out tire (and maybe body damage) so I can honk and smile and be glad they "knew" what they were doing...LOL
[Moderator ON]
Let cooler heads prevail here, please. I'd hate to lock a thread about tires. Yes, it is animated, and there potentially is a safety issue here.
[Moderator OFF]
I pulled our PU on hot summer roads nearly 10000 miles over the past 5 years. Maxed out the pressure every time. No problems at all. And trailer was likely underloaded (below the tires max weight).
This thread has made me concerned that my ATV's tires are aired up too much....at 4 psi. They are supposed to be at 3 psi. That is a 33% increase!!! :yikes: :D
Larry
Quote from: mike4947Austin, I hate to say it but there are people who are instant experts and know more than the company engineers that have over 100 years of experience to rely on when giving recommendations for inflation and usage of the proper grade/type of tire.
I know how that works, and it's one thing I will cut some slack on. The reason is I've been caught doing things like that myself. :yikes:
Austin
Quote from: brainpause...I pulled our PU on hot summer roads nearly 10000 miles over the past 5 years. Maxed out the pressure every time. No problems at all. And trailer was likely underloaded (below the tires max weight).Larry
This is exactly my point: You can armchair jockey this kind of stuff all day long and play engineer-of-the-day quoating theory/specs/websites/etc. Or you can get out there in real world conditions and experience real world results.
I've never owned or towed a PUP before so had no experience with the little 5.30x12's on my Starcraft Nova. On the day I picked it up, the tires looked like eggs and maybe had 20psi in them. I drove around the corner to an auto repair shop and put them at the 80psi it says they should be. Why? Because I had this sneaking suspicion that they needed to be super hard, not only to hold the weight, but to reduce rolling friction and thereby reduce the heat build up in the tire. I've been around cars and tires long enough to know lower air pressure creates a big contact patch on the road, forcing the tire to really flex alot as the tread strikes the road, and this creates friction and heat in the belts and causes tire failure big time.
When we headed to the Grand Canyon I kept them at 80psi cold and headed off. The only thing I monitored during the 5 day 1,200mi trip was tire tread tempurature, and I only checked that when we stopped for fuel or to use a restroom. As I mentioned, I wasn't towing easy,70mph, and it was hotter out in the Mojave, Barstow, Needles, etc. then I think I've ever personally experienced (which was 114 in Tuscon, AZ)
It ain't rocket science, and we're not flying them to the moon.
Quote from: austinado16I drove around the corner to an auto repair shop and put them at the 80psi it says they should be. Why? Because I had this sneaking suspicion that they needed to be super hard, not only to hold the weight, but to reduce rolling friction and thereby reduce the heat build up in the tire. I've been around cars and tires long enough to know lower air pressure creates a big contact patch on the road, forcing the tire to really flex alot as the tread strikes the road, and this creates friction and heat in the belts and causes tire failure big time.
This is why I keep them at their max pressure.
Larry
First of all...I would like to say Thanks to this thread and it's participants. As a trailer 'Beginner', I have learned a lot from both sides of the argument, if in no other regard than it makes me think.
As a totally objective observer (I know very little about the subject and I don't know the participants) I thoroughly enjoy the banter, the links to websites where facts or other information and opinions reside, and the detailed 'picking apart' of eachothers arguments. This is as good as a thread gets in my opinion.
However, the problem is that the participants have to ride a fine edge of continuing the argument without getting personal. We're on that edge now and it makes it all the more enjoyable. I for one hope AB and Zamboni can agree to disagree and keep the banter going. I see merit on both sides and would like to continue my education. I think that we can all agree that you can put a stack of facts in front of a group of people and come away with many interpretations.
Thanks again and when you hear the BELL, come on out for round 2...or 3...or whatever round we're at now.
'DING'
Quote from: waygard33First of all...I would like to say Thanks to this thread and it's participants. As a trailer 'Beginner', I have learned a lot from both sides of the argument, if in no other regard than it makes me think.
As a totally objective observer (I know very little about the subject and I don't know the participants) I thoroughly enjoy the banter, the links to websites where facts or other information and opinions reside, and the detailed 'picking apart' of eachothers arguments. This is as good as a thread gets in my opinion.
For sure, a lot of good and useful information has been posted on this board over the years. But as a relatively newcomer you need to know that all that is posted is not necessarily correct. Sometimes it can be just a matter of opinions. Indeed, sometimes there will be some real superfluous B.S. (and I don't mean Brown Sugar!), and that will be sorted out most directly.
Fly
:book: Darn :swear: .....I was gone for the Holiday and missed all the fun.
Zamboni.....calm down....it'll be OK ;)
I posted some stuff on here that was wrong when I first started out and got my butt kicked for it.........That's how we all learn.
However, I would just caution anyone about making definitive statements like, "The pressure you should use is NOT NOT NOT what is printed on the tire". It may be wiser to state, "In my opinion........." because that is exactly what it is, your opinion. Anyone can have respect for another person's opinion, even if it may be contrary to his own. However, when you make definitive statements like that, it suddenly puts people that really know the facts on the defensive and they feel like they need to correct that mis-information in a clear and meaningful manner to avoid any problems for the OP.
Had the original poster acted on your advise and that resulted in an accident and/or injury, I don't think you would feel very good about it. Even if you felt that your potentially flawed laws of physics were correct. :D
Well we made it!!!! The pop up pulled GREAT with the MAX pressure. Thanks to all involved I learned something and wont be afraid to ask if I run into somethin else. Any tips on getting the campfire smell out of the PU. Thanks again MB.
Glad you had a good pull home.
We pop ours open when we get home and leave it sit unzipped, door open for a day or so to air it out. That also gives us a chance to clean it out, clean it up, and have it ready for next time.
Thats what we usually do and did this time. The first night the smoke was going the other way. Second night it came right in. It usually isnt that strong of a smell. This time it was though. We sprayed her down with Fabreeze when we cleaned up tonight. It should be OK. MB