Tire pressure

[vfauto]

OK I was at the Tampa RV show and talked to the Freightliner people. He made a big deal out of getting the coach Weighed at each corner so that I could use the Michelin chart and set tire pressures accordingly. Just looking for some quick answers on how many people have done this and has it really made a difference in the operation of the coach and tire life.

[Chuck Q]

I just monthly check pressure and set it at the MFG reccommendations. Tires last as long as the sidewalls let them. 11 years no tire problems.

[Steve Ownby]

Originally Posted by vfauto

OK I was at the Tampa RV show and talked to the Freightliner people. He made a big deal out of getting the coach Weighed at each corner so that I could use the Michelin chart and set tire pressures accordingly. Just looking for some quick answers on how many people have done this and has it really made a difference in the operation of the coach and tire life.

It's a "peace of mind" issue. Without the corner weights, the only safe inflation practice is to inflate to the GAWR for the tires on each axle. Even then, you have no idea if there is a significant weight imbalance than you should be aware of. You can be within your GAWR on an axle but due to side to side imbalance, you could be over the weight carrying capacity of the tire on that side.

[TonyDi]

[wildtoad]

The advice is true for both DP's and gasser's. However to answer your question No. I know the mh was in balance when delivered to me, and way under the GAWR on both axles. We don't carry a lot of water, we don't collect rocks, and I've set my pressures to the PSI as stated in the Goodyear chart based on the GAWR. I sleep well at night.

[Gary RVRoamer]

Steve is right on target.

I weighed mine a couple times so that I had a feel for the weight distribution by axle and axle-end and adjust the tire pressures accordingly. I don't really fine tune the psi, but don't want to be significantly over or under either. Under pressure is courting a blow-out as well as poor handling, while over is mostly just a ride comfort thing. However, extreme over-pressure can cause squirrelly steering.

In our usual traveling mode, my coach was near max on the rear axle but had 2000 lbs to spare up front. That means the tire pressures shown on the coach builders tire placard were fine for the rear axle but 15 psi high for the front axle. Reducing the front tire pressure gave a softer ride (especially on RR tracks and similar abrupt bumps).

As for tire life, if you run the tires at the pressures recommended on the coach builder tire placard (federal weight & tire sticker by the driver seat), your tires will wear fine. However, you should not run any less without at least an axle-by-axle scaled weight. If you have only axle weights rather than corner weights, you can estimate the individual tire load (divide by 2 or 4), but make sure you allow some extra for the likelihood that one end of the axle is heavier than the other. It is not unusual for one to be 300-800 lbs heavy and that's enough to require more psi on both ends.

[markbarendt]

It is definitely worth doing, once. Once you figure your numbers you are typically good to go for the life of the tires or you change something big.

Do it fully loaded, fuel, water, canned goods, fishing gear, trailer, people...

[Tireman9]

Originally Posted by markbarendt

It is definitely worth doing, once. Once you figure your numbers you are typically good to go for the life of the tires or you change something big.

Do it fully loaded, fuel, water, canned goods, fishing gear, trailer, people...

Absolutely correct. very few RVs have side to side loading at 50/50%. Some owners have discovered one end as much as 1,000# heavier than the other.

Once you know for a fact that you have at least a few hundred pounds "cushion" under GAWR and GVWR you don't need to do corner weight again unless you make a major change or re-model of the RV (Residential refrig or granite counter-top) have a reasonable balance.

I do suggest at least once a year a quick check of axle loading by going through a truck stop scale. You can compare the truck scale numbers with your corner weight totals to confirm your RV hasn't suffered from weight creep as some of the drivers may have noticed over the years.

[luvlabs]

Originally Posted by vfauto

OK I was at the Tampa RV show and talked to the Freightliner people. He made a big deal out of getting the coach Weighed at each corner so that I could use the Michelin chart and set tire pressures accordingly. Just looking for some quick answers on how many people have done this and has it really made a difference in the operation of the coach and tire life.

Tires are never inflated to the individual wheel weights - they are always inflated the same on an axle to the highest loaded tire on that axle. Handling problems await you if you inflate each tire individually.

Individual weights are not needed to set tire inflation pressures but axle weights are. Just about every truck stop has a CAT scale and you can easily get your axle weights in one pass and couple of minutes. Multiply the axle weight by 1.05 (5%) and use the resulting weight and tire load tables to determine your inflation pressure.

At some point, if you can get individual wheel weights, do so. Many coaches demonstrate some tire positions that are heavier than other end of the axle. While it is unlikely that you can correct this by shifting cargo, sometimes this can be relieved somewhat having the ride height adjusted (if you have air suspension) which can shift some weight fore and aft or left and right.

[Gary RVRoamer]

The reason for corner weights rather than axle weights to to identify situations where the axle load is not split 50/50, and that is a VERY common situation. Usually the balance isn't too far off, though, and estimating 300-500 extra lbs per axle-end is enough to cover it. But "usually" isn't "always", so corner weights are wise. At least once, anyway.

[JFXG]

Good advice already given. We got corner weights at an FMCA rally a few months after we started in 2012, and found we were right at max gross and surprisingly well balanced. But we knew we could soften the ride a bit.

We got corner weighed again about 2 years later at Escapees in Livingston. There we learned that we had gained a bit in the front, and about 400 Lbs at the right rear. WTH?? Too much accumulated stuff. Too many books in the bedroom, the new air compressor.... couldn't really see where it all came from, but we adjusted the pressure and commenced to culling stuff out.

About time to do it again, I'd say. My tires seem happy.


John & Diane, fulltiming since '12 02 DS40, FL, Cat, '04 Element NHSO RVM103

[Bill2]

Originally Posted by luvlabs

Tires are never inflated to the individual wheel weights - they are always inflated the same on an axle to the highest loaded tire on that axle. Handling problems await you if you inflate each tire individually.

Individual weights are not needed to set tire inflation pressures but axle weights are. Just about every truck stop has a CAT scale and you can easily get your axle weights in one pass and couple of minutes. Multiply the axle weight by 1.05 (5%) and use the resulting weight and tire load tables to determine your inflation pressure.

At some point, if you can get individual wheel weights, do so. Many coaches demonstrate some tire positions that are heavier than other end of the axle. While it is unlikely that you can correct this by shifting cargo, sometimes this can be relieved somewhat having the ride height adjusted (if you have air suspension) which can shift some weight fore and aft or left and right.

Hello can you tell me if these Cat scales cost something or what they cost ?

[4x4van]

Originally Posted by wildtoad

I know the mh was in balance when delivered to me, and way under the GAWR on both axles. We don't carry a lot of water, we don't collect rocks, and I've set my pressures to the PSI as stated in the Goodyear chart based on the GAWR. I sleep well at night.

How do you know your rig was "in balance" when delivered and "way under GAWR"? Did you weigh it yourself? The reason I ask is because we cannot assume anything.

I weighed my rig (4-corner) when I got it home, with full fuel, full LPG, full water, empty black/gray. Surprisingly, while well under on my GAWRs, I am 1300lbs heavier on driver side than passenger side. This is with very little "stuff" loaded yet. Of course, both slides are on the driver side, along with many of the appliances, so an imbalance is not surprising, but the amount of that imbalance definitely surprised me. My point is that if I simply assumed that an axle weight was near evenly split, I could easily be running insufficient air pressure.

Notably, when my rig was aired up to the pressures listed for GAWRs on the door tag, it handled terribly; adjusting the tire pressures down to match the actual weights (based on the heaviest side) resulted in vastly improved handling AND ride.

[LarryJB]

Originally Posted by Bill2

Hello can you tell me if these Cat scales cost something or what they cost ?

There is only one CAT scale within about a 100 mile radius of me and they charge $11 to weigh your vehicle. The also told me they charge $2 for each additional weighing.
Their scale actually has 3 segments labeled steer axle, drive axle and trailer. You position your rig on the scale where each axle is on a segment and they take a reading. ($11). You can then re-position your rig, or maybe hookup your toad and weigh again. ($2). The CAT scale I went to was setup to where it was pretty much impossible to do a 4 corner weight, due to railings along each side of the scale. I am not sure where I can go to get a 4 corner weight. It's like they go out of their way to prevent you from doing it.