Calculating tongue weight using dual hitch

[tknick]

I have seen the dual hitches talked about in several posts.  Does anyone know how to accurately calculate the new tongue weight using one of those types of hitches?  HERE is a link to a commercially made model.  I have a 5000lb towing/500lb tongue rating on my frame hitch (and a 7000lb+ rating on the TV).  The Bayside is on the heavy side as PUs go, but well below the 500lb tongue rating.  I would like to use the dual hitch with a bike rack and 4 bikes.  If this question can't be resolved, I'll defer to the front mounted hitch.  Just exploring all the options!

thanks!

[mike4947]

Well they don't mention tongue weight in the ad, but normally the weight limit drop also applies to the tongue weight. So the 4000 pound limit on the dual extension also applies to the tongue weight as well which would mean a 400 pound tongue weight limit.

Calculating a "true" tongue weight involves having the original weight, length from the rear axle center to the old and new ball locations, type and figures for the rear suspension, etc. In other words a very complex calculation.
 
BUT, for your application you have to remember the bikes and racks are tongue weight as well as the trailer. So you only have the difference between the actual measured tongue weight of the Bayside and the 400 pound new limit with the dual extension.
If The Expidition has a step bumper with a place to mount a ball they make a bolt on 2" receiver opening that allows use of a bike rack.
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_43576_43576
 
You just mount it upside down on the step where the ball would go.

[tknick]

...BUT, for your application you have to remember the bikes and racks are tongue weight as well as the trailer. So you only have the difference between the actual measured tongue weight of the Bayside and the 400 pound new limit with the dual extension.

Am I understanding correctly that as long as I don't exceed the 400lbs with my actual tongue weight + the weight of the bikes and the rack, the added length of the dual hitch is NOT going to exceed the 500lb rating on my receiver?  BTW, I dont want to have to bolt on and unbolt the receiver plate like you suggested, but thanks for looking for other possible solutions

thanks

[AustinBoston]

Am I understanding correctly that as long as I don't exceed the 400lbs with my actual tongue weight + the weight of the bikes and the rack, the added length of the dual hitch is NOT going to exceed the 500lb rating on my receiver?

I'm not sure that is what he is saying.  I think what he is saying is that if the use of the device drops your tow rating from 5,000 lbs to 4,000 lbs, then your tongue weight rating drops by at least the same proportion (from 500 lbs. to 400 lbs.)  Then, at best, the most you can have is 400 lbs dead weigth on the tongue.  Your Bayside needs to have a tongue weight near 350 lbs to be stable to tow (we're talking actual weight here, not rating), so you get no more than 50 pounds for bikes and racks at the most.  How many bikes do you plan on carrying?

To get an estimate (this is only a rough estimate because it leaves a lot of things out), measure from the center of the rear axle to the center hitch ball without the adapter.  Multiply this by your tongue weight rating (we'll call this Y).  Then measure from the center of the rear axle to the center of the hitch ball with the adapter in place.  Divide the first result (Y) by the second measurement.  That would be a ballpark figure for the new tongue weight.

An example might help:
Distance from rear axle to tow ball (no adapter): 30 inches.
Tongue weight rating: 500 lbs.
30 X 500 = 15,000 (this is Y).
Distance from rear axle to tow ball (with adapter): 38 inches.
15,000 / 38 = 395 lbs. estimated new max tongue weight.

There are other factors that get involved, so your actual rating would probably be lower.  If you get a number higher than the 400 lbs we talked about before, you are still limited to the 400 lbs. - you have to use the smaller number.

Austin

[tknick]

I'm not sure that is what he is saying.  I think what he is saying is that if the use of the device drops your tow rating from 5,000 lbs to 4,000 lbs, then your tongue weight rating drops by at least the same proportion (from 500 lbs. to 400 lbs.)  Then, at best, the most you can have is 400 lbs dead weigth on the tongue.  Your Bayside needs to have a tongue weight near 350 lbs to be stable to tow (we're talking actual weight here, not rating), so you get no more than 50 pounds for bikes and racks at the most.  How many bikes do you plan on carrying?

To get an estimate (this is only a rough estimate because it leaves a lot of things out), measure from the center of the rear axle to the center hitch ball without the adapter.  Multiply this by your tongue weight rating (we'll call this Y).  Then measure from the center of the rear axle to the center of the hitch ball with the adapter in place.  Divide the first result (Y) by the second measurement.  That would be a ballpark figure for the new tongue weight.

An example might help:
Distance from rear axle to tow ball (no adapter): 30 inches.
Tongue weight rating: 500 lbs.
30 X 500 = 15,000 (this is Y).
Distance from rear axle to tow ball (with adapter): 38 inches.
15,000 / 38 = 395 lbs. estimated new max tongue weight.

There are other factors that get involved, so your actual rating would probably be lower.  If you get a number higher than the 400 lbs we talked about before, you are still limited to the 400 lbs. - you have to use the smaller number.

Austin

Thanks a million Austin.  Although it's not necessarily the answer I wanted to hear, it does explain the situation clearly and will allow me to figure out if the dual hitch will even work.

Just did the calculations and it aint gonna work  Oh well, back to the front mounted option.
travis