Foretravel Owners' Forum

Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: lavocat on May 17, 2013, 06:57:16 pm

Title: Individual tire weights
Post by: lavocat on May 17, 2013, 06:57:16 pm
I finally was able to get my coach weighed at each wheel location.  I have Michellin XZA2 295 80R22.5 tires.  My weights are as follows:
Left steer-6,600lbs Right steer-6,900lbs
Left dual-9,600lbs Right dual 10,100lbs
Left tag 4,400lbs Right tag 4,500lbs

I have misplaced the info from Michelin.  Can anyone recommend inflation
Title: Re: Individual tire weights
Post by: Michelle on May 17, 2013, 07:03:23 pm
What load range?

http://www.michelinrvtires.com/michelinrv/tires-retreads/load-inflation-tables.jsp (http://www.michelinrvtires.com/michelinrv/tires-retreads/load-inflation-tables.jsp)

Oops - looks like that size is only in LRH

I think the general recommendation is 5-10 psi above heaviest axle end

Steer 105-110

Dual 85-90

Tag 75 (overkill but the chart doesn't go lower)

-M
Title: Re: Individual tire weights
Post by: lavocat on May 17, 2013, 07:29:37 pm
Well even without the weights I have been running 110 steer 90 duals and 80 tag so I was really close.
Title: Re: Individual tire weights
Post by: lavocat on May 17, 2013, 07:37:21 pm
The guy who weighed the coach suggested having FOT adjust the air bags to move some weight from the duals to the tag. Anyone know if this can be done and how.
Title: Re: Individual tire weights
Post by: Michelle on May 17, 2013, 08:15:51 pm
The guy who weighed the coach suggested having FOT adjust the air bags to move some weight from the duals to the tag. Anyone know if this can be done and how.

What percentage of GAWR are the steer, drive, and tag axles?  The tag on our '03 is rated at 9000 lbs.  We're running 7300 on it so 81%.  Our drive is at 16.6K of 21K, 79% and our steer is 12175 of 13880, 87.8 %

I might guess the ride height valve settings would be involved in adjusting those percentages.
Title: Re: Individual tire weights
Post by: amos.harrison on May 18, 2013, 01:26:58 am
Don't mess with trying to shift tire loads except by shifting cargo locations.  My weights are tire pressures are the same as yours.  The duals have the most excess capacity.  I don't think your weigh guy knew what he was talking about.
Title: Re: Individual tire weights
Post by: lavocat on May 18, 2013, 09:53:40 am
Michelle my tag GAWR is 10,000 and I am running 8900 or 89% so I really dont think I need to add anything there.
Title: Re: Individual tire weights
Post by: Michelle on May 18, 2013, 10:25:28 am
Michelle my tag GAWR is 10,000 and I am running 8900 or 89% so I really dont think I need to add anything there.

There ya go! 

And a shout-out to Brett Wolfe as the one who clued me in to weight distribution/% GAWR back when we had our weights done.
Title: Re: Individual tire weights
Post by: 2Escapees on May 18, 2013, 11:51:10 am
Back when I had a SOB tag coach, the Freightliner factory service center in Gaffney told me adding weight to the tag also tended to shift weight to the front axle. So if anyone is running too close to front axle capacity they can decrease the tag weight which has the effect of transferring some weight off the front axle and increasing the load on the duals which usually have plenty of capacity.
Title: Re: Individual tire weights
Post by: Roland Begin on May 18, 2013, 02:01:40 pm
Back when I had a SOB tag coach, the Freightliner factory service center in Gaffney told me adding weight to the tag also tended to shift weight to the front axle. So if anyone is running too close to front axle capacity they can decrease the tag weight which has the effect of transferring some weight off the front axle and increasing the load on the duals which usually have plenty of capacity.
I must be missing something here. Moving weight further back decreases weight on the front axle. When I was hauling freight cross country living the trailer axles forward, essentially moving weight back, decreased tractor rear and front axle weight......or am I remembering incorrectly. ::)

Roland
Title: Re: Individual tire weights
Post by: Dave M (RIP) on May 18, 2013, 02:36:05 pm
Roland, Think your referring to the 5th wheel position, here I think they are referring to A coach with a tag ale.  It is true with a tag axle you can add or retract weight to the drive ale and also slightly affect the steering weight, but only slightly as I see it.
I like enough wight on the steering to keep wheels from skidding in a turn such as a wet or slick road, while not overloading it..  As I keep saying there are massive opinions here .
Some real good and some lesser, again we all have opinions, so beware !
Title: Re: Individual tire weights
Post by: Roland Begin on May 18, 2013, 03:10:25 pm
Roland, Think your referring to the 5th wheel position
Yes

Roland
Title: Re: Individual tire weights
Post by: wolfe10 on May 18, 2013, 03:16:14 pm
Yes, taking more weight on the tag axle REMOVES weight from the drive axle and ADDS weight to the front axle.  Think of the drive axle as the fulcrum.

And, best balanced weights are the same percent of GAWR on each axle.  BTW, this can significantly effect handling.  At one of the Diesel RV Club Rallies, the rally gift was all wheel position weighting of each coach.  Of 5 tag axle coaches weighed, only one had close to the correct weight distribution.  Dick Lorntson (Precision Frame and Alignment) did the weighing and on the 4 tag axle coaches that weren't close we had them stop and open the engine bay. We then adjusted tag air pressure (these happened to all be Monaco products of one variety or another, and adjustment is quite easy).  All but one "passed" next time around.  The last one took one more fine tuning to get the percents on each axle within 2%.
Title: Re: Individual tire weights
Post by: PatC on May 18, 2013, 03:42:06 pm
I must be missing something here. Moving weight further back decreases weight on the front axle. When I was hauling freight cross country living the trailer axles forward, essentially moving weight back, decreased tractor rear and front axle weight......or am I remembering incorrectly. ::)

Roland
Roland,
Think of a flat bed with a 9 foot  spread axle  with the lead axle being a air controled tag.  If you knew what you were doing, and could somehow cover the air exhaust sound, you could have all kinds of fun at the scales.
Title: Re: Individual tire weights
Post by: J. D. Stevens on May 18, 2013, 03:44:05 pm
I suggest that there may be a difference in how different people are interpreting "moving weight to the tag axle." Weight can be moved there by physically shifting the load in the coach. It could also be moved by adjusting pressure between the tag axle and the structure of the coach while not moving any cargo. The two methods of "moving weight" would have opposite effects with respect to load on the other axles of the coach.

Brett's description of the adjustment on the Monaco coaches demonstrates adjusting pressure between the coach structure and the tag axle. Increasing the pressure on the tag would unload the drive axle and load the front axle. An example of changing distribution by moving cargo would be to move all the heavy stuff from the front of the storage bays to the rear of the storage bays. The would unload the front axle, and load both the tag and drive axles.

Brett, did I comment correctly regarding the two ways to "adjust load on the tag axle?"
Title: Re: Individual tire weights
Post by: wolfe10 on May 18, 2013, 03:57:02 pm

Brett, did I comment correctly regarding the two ways to "adjust load on the tag axle?"

Absolutely correct.  While it would be great to physically move personal gear to the tag axle, the reality is there are VERY few coaches that have much storage that far aft.

Brett
Title: Re: Individual tire weights
Post by: Dave M (RIP) on May 18, 2013, 04:05:12 pm
Wondering what is the EXACT percentage of the total weight per axle ? 
Steer ?  Drive. ?  Tag. ?
There must be an exact number here  Or is it more opinion ??
This dummy is wondering.
Title: Re: Individual tire weights
Post by: wolfe10 on May 18, 2013, 06:47:40 pm
Dave,

That is a design question and varies by chassis.  Again, in an ideal world, each axle will carry the same PERCENT of its GAWR.

Different chassis have different GAWR axles, particularly in front and drive positions.  And, with the new rulings that allow more than 20,000 pounds on one axle for RV's, I suspect things will continue to evolve.