The right tire pressure - WOW!

[PushedAround]

I finally got around to weighing my coach last weekend and set my tires to the proper pressure. Previous to that, I set them at 105 psi, knowing that based on GVW plus a little more, I would not be under-inflated. Well I looked at the Michelin chart and was able to drop my pressures down to 95 lbs.

It doesn't sound like much but the difference was remarkable. My coach tracks straighter and most of the harshness over expansion joints has gone away. I am amazed at how much difference that 10 lbs made. If I had known, I would have made it a top priority. If you haven't done it yet, I highly recommend it.

[CLIFFTALL]

It's a top priority for sure. Thanks for reminding those that didn't know.

[Dr4Film]

It should be Top Priority with everyone!

Running tires over-inflated has it drawbacks, maybe not as severe as running tires under-inflated but the best and most economical method is to corner weigh if possible and set your tire pressures accordingly. I always add 5 lb's for just for kicks.

Dr4Film ----- Richard

[vsheetz]

[Tony Lee]

Another convert to doing things the right way.

[jadatis]

Did you weigh per axle or per wheel(pair).
And can you give the values and the specifications of tires here.
Then I can put them in my made motorhome tire pressure calculator to see what the outcome would be then.

I need those weights ( wheel or axle) and configuration of the vehicle like number of axles and tires per axle.

From tires maximum load and pressure needed for that ( maximum load xxxx lbs AT yyy psi( cold)) at minimum , but rather also sises and speedcode or maximum speed of tire ( probably N= up to 140 km/87m/h).

Yust so that I can get a better picture of my determined bumping border.
ofcource I will make a picture of the filled in spreadsheet to share here.

[PushedAround]

I weighed it twice, once properly on the scales and again with the right side tires off the pad. One thing that I do need to take care if is that the cross weights are off by a good margin, even though the side to side is with-in 300 lbs. Have to figure out how to do a ride height adjustment on the left front (or right rear).

[Dr4Film]

Larry,

What are you referring to when you say the cross weights are off?

Also, ride height is a standard value for each coach model. I don't think it has anything to do with weight but has everything to do with height.

Dr4Film ----- Richard

[TLGPE]

I'll weigh in on proper corner weights. We were at the escapees park in Bushnell, FL, and got the four-corner deed done (early April). I was pleased to note that we were well within out rated weights, and the tires were not overloaded. I did not change anything, because it was all safe on weights and pressures.

Later this spring, I got tired of feeling the expansions joints banging us around and got out the weight/pressure charts. My fronts were good, but the rear tires were about ten psi high. I dropped them to 85 psi, per the charts, and as Larry experienced, the ride is inordinately better. I will echo that: WOW!

I'm too lazy to start an original thread, but I'll respond to this one. Thanks, Larry.

Tom

[PushedAround]

Originally Posted by Dr4Film

Larry,



What are you referring to when you say the cross weights are off?



Also, ride height is a standard value for each coach model. I don't think it has anything to do with weight but has everything to do with height.



Dr4Film ----- Richard

Richard, what I mean by cross weights is the difference between the left front plus the right rear vs the right front plus the left rear. Cross weights are more important than having specific ride heights. If you have a diagonal imbalance , it is just like having a chair with one short leg, and like the chair, your coach will teter-toter.

I have 40 years of race car suspension "engineering" and modification experience and from what I am seeing, these beasts are no different, just heavier. The side to side imbalance may be less noticeable on a big old truck chassis than in a stiffly sprung Porsche, but the effects are still the same. In my experience, you should get a median ride height for the front and back, and then adjust a specific corner up or down to get the cross weights right and the ride height close.

[deandec]

I understand that on a DP, the drive shaft is affected by incorrect ride height. Just something else to consider when adjusting away from the manufacturer settings.

[Hugmongous]

So about 4 days ago, I had new Michelins installed .. $'s.., yes I used the FMCA discount! total cost for 6 x 275/70/22.5 was $3648.. all charges including taxes, balance, installs, etc.. So, really not so bad. I filled up with fuel and water before the install and had the coach weighed. Not individual wheels, but each axle. When I showed the Michelin pressure recommendation to the tire guys they kinda were like.. well we inflate them to app. 10 psi below max and allow for temp/pressure expansion... yada, yada. They would have done as I asked, but ... so, they inflated to 120 psi (tires called for max of 130psi). I assumed I can always lower the pressure easier than increasing it! Michelin calls for 90 psi on the fronts and 85 on the duals. I drove it home about 30 miles .. plan to lower it as per Michelin recommendation before taking it on any trip.

[Musikboy]

Two Newbie Questions:

- How does someone get their coach weighed?
- Once I get the coach axles and individual wheels weighed, how do I know exactly what tire pressure to use for each wheel?

[Francesca]

For those using Michelin's inflation chart, the following instructions seem especially important, emphasizing as they do the importance of knowing the weight of each axle end before determining air setting for the tires on that axle.

Here quoting from this Michelin load/inflation page

-The loads indicated represent the total weight of an axle end in an RV application.

-When one axle end weighs more than the other, use the heaviest of the two end weights to determine the unique tire pressure for all tires on the axle.