Foretravel Owners' Forum

Before leaving FOT I checked tire pressure and they recommend 85 in the steer, 90 drive and 70 tag cold.  Reading previous posts around 105/110 seems to be preferred pressure at cold for both axles.  Not sure about the tag.

I have driven about 900 miles on rough, smooth and wet highways and the coach has handled great.  My concern is at these pressures I could be putting stress on side walls.

Tires are 295/80R22.5 LRH

Weight is 11,440 steer/24,620 drive.....gross 36,060

Each brand of tire maker has tables to use for the air pressures based on your measured weight.  I printed the Michelin page for my coach, and highlighted the pressures for my tire model and load range.  Mine happen to be different load ranges front and rear.

GFM,

You will find almost as many views on tire pressure here on the forum as religions in the world. While RV owners may have opinions, it wouldn't hurt to talk to mega mile commercial trucking companies and municipal operators where safety and economy are two of the most important factors.

Pierce

Each coach is unique.  As a starting point, use the numbers on the placard to the left of the driver's seat.  These are based on you loading it up to the maximum.  At least you won't be running under inflated.

If you have actual measured weights for each of the six wheel positions, then you can use the Michelin charts to determine the optimum pressure, then add a bit for insurance.  The RV weighing services give accurate recommendations for the coach at the time it was weighed.

The Escapees Club offers individual wheel weighing at their rallies, and all the time at their parks in Livingston, TX, Congress, AZ and Bushnell, FL.

What others have said regarding individual weights.  And you need the coach loaded for typical travel, including driver, passengers, and tank levels.

Coach individual wheel weight experience (http://www.foreforums.com/index.php?topic=15182.0)

Assuming the tires are 275/80R22.5 LRH Michelins XZA3's and loads are equal at both ends of the axle,

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

You want at least 95 psi in the steers (11440/2= 5720 lbs per end), 100 would be much better so you have margin.  You're definitely underinflated there.

The weight you list for drive axle is EXCEEDINGLY high for the drive axle.  In fact, it's higher than the Gross Axle Weight Rating for the drive axle.  I'm guessing that's the single combined weight of the rear given that you have a tag axle coach.  You definitely need separate drive and tag weights to know how to inflate the rear.  If it truly is just the drive axle, you need to unload some weight or figure out what's going on with the tag.

We run 105/85/75 minimum for 6200 lbs max per end front, 8300 lbs max per drive end, 3700 lbs max per tag end.

ETA at least one of our members found the PO's overinflating of the tag tires (to the same pressure as the drive axle) caused excessive center wear on the tag tires.

110 psi cold all the way around 295/75. Works well for us.

Pierce

GFM:  I was told the same nrs at the factory but since have  talked with Powers Tire there in Nacogdoches and they recommended 100 front and 90 rear no tag.  I try to keep cold 103 and 93 to 95 in rear  and this seems to work just fine.

We have measured coach at 9 points and have determined for our lifestyle and coach that 100 psi at each tire position is best for us. On cold mornings or high altitudes we see pressures all over the place depending where the sun is shining. We don't try to even them out very often, and in fact with Pressure Pro sensors on each tire, we don't go outside to check pressures, and because our Pressure Pro is powered 24/7 on our coach dash, we can check as many times a day or night as we want. And if a tire goes low while parked we know it right away, or if someone attempts to steal a sensor it causes an immediate alarm.

Optimal tire pressures need to take in maximal loads from turns, road crowns, side winds, altitude changes, ambient air temps and coach side to side imbalances. So going by the book and scale may leave some underinflated sometimes. Too high PSI harder ride, but usually difficult to feel in our big motorhomes, too low PSI may cause overheating and dangerous situations. The 'right' pressure is probably more of a coach owners preference.

Does anyone know if the wheel weighers will be at the Grandvention?
 
Trent

Great debate on this forum - Michelin suggests calculating correct TP per weight and add 5 lbs. Â (THis was at last years Granvention) Â Here are charts for various tread patterns in your size from Michelin web site -

The tire pressure is a direct ratio of the load.

Says so right on the tire.  110/6,700?  Single.

As I said in another post we are close to the max on gvw and so the pressures.

Countless conversations as a Foretravel sales manager about this issue.

As carol said escapees weigh the axles as was also available at FMCA rallies since the 80's.

Every single owner noticed the more precise steering with less wander from under or over inflation.

Too much air at 110 means the coach is riding on a narrow center rib.

Used to drive customers through a water puddle.  Then onto white concrete. As the tire dried out you could see the lighter contact at the edge that was from over inflation.

Everyone was a skeptic. Plus or minus 2 pounds was noticeable.

I prefer a coach that drives straight as an arrow and that can be steered from the bottom of the wheel.

Light pressure on the wheel is all mine takes to stay straight.

Have not checked the air for a while but I feel a small variation to the right.  Bet one tire is 1-2 pounds low.

Tested this countless times.

Nice service from the escapees as I bet they found it much safer to have the exact correct pressure in the tires.

Off my soapbox.

Cost myself quite a few sales long ago in fixing the tire pressures.  "We do not need a new coach, bob.  This one rides perfect now that you fixed it".

email Beverly at FT for the definitive answer - Â RVSEF is who did it at last years - here is the weighing schedule from their web site - it does not list the GranVention

Weighing Schedule | RVSEF (http://rvsafety.com/weighing-schedule/)

Get the Michelin RV Tire Guide (available online). Weigh the coach when it's loaded as you normally use it. Set the tire pressures according to the Michelin RV Tire Guide. Simple!

Per Michelle's comment about the tag axle pressure being the same as the drive axle.  If you inflate to the same as the drive axle, you will be buying new tag tires within the year.  Been there , done that.  Our coach when we took delivery, had a horrible thump thump thump coming from the rear.  FOT and Howard Tire in NAC determined the cause was over inflated tag tires.  Bought new steer tires, transferred steer to tag, lowered inflation and everything has been fine since.  We owned that coach for 10 plus years and changed all tires at least twice without any more "Thump thump thump"... 

Very much appreciate all the input.  At the fuel stop this morning I purchased a tire gauge, never had the need for a gauge that goes to 140 psi.  I went ahead and used the placard pressures until I can have the coach properly weighed.  Still have imprint from the asphalt on my knee caps.

Looked at the Cat Scale and from what I could tell you are only able to get a steer and drive axle weight which would include the tag.  Attending an Escappees Club rally or heading up to Bushnell is in the very near future.

Know that I have the first trip (1,229 miles)in our FT under my belt I must a say it is better than I ever expected.

Gotta go, Jeannie baked me my favorite cake to welcome me home....yummmmm

We attended the fmca rally in Indio last January.  Although nothing was mentioned on the fface website or rally info,  there was in fact an RV weighing service there.  I was very happy to finally have my coach weighed,  and even more happy with the results.  It turns out the placard pressures are spot on,  and I
 Have lots of carrying capacity to spare.

We had our coach weighed at an Escapees Escapade in Stockton, CA in 2007 I think. Full fuel, fresh water tank, travel gear, and the extras we "have to take."  I use Toyo tires with which I am quite satisfied.  Following the Toyo chart and the recommendation from getting it weighed, I run 97psi on the steer axle, and 87psi in the drive tires.  I've 5lbs extra for good measure in each tire.  I check cold pressures before each trip, and frequently while traveling.  They rarely need adjusting. Peace of mind.