Tire pressure

[RonR2440]

I drive a 32' Itasca Cambria. I keep the tire pressure at 80 psi and the air bladder bags at 35 psi. When we are driving the RV seems to feel every asphalt repair, expansion joints, road damage, etc. Makes for a really rough ride. What do people typically keep their tire pressure at. I realize for the best results you can weigh the vehicle and look at tire charts. I am thinking of reducing tire pressure to 75 psi. I am concerned about tire overheating if I reduce the pressure too much. Thanks ahead of time.

[Harvey51]

Thanks for the review, Ron! Nice to have an unbiased review that I can fully trust.
I need one like the “expensive truck wheel” one you tossed in order to check the inner and outer duals without special valve stems. I have two $20 ones like that, which I checked with a mechanic friend’s really expensive one and a Slime Digital one. All agree within a psi. I had an old one of my dad’s that had to be thrown away when it got inaccurate.

[enblethen]

Some one was pulling somebodies leg!
Continental Tire inflation chart

[pnichols]

RonR2440 wrote:
When we are driving the RV seems to feel every asphalt repair, expansion joints, road damage, etc. Makes for a really rough ride.

You're having what we had with our Itasca - only we probably had it worse, as we have only a 24 foot Itasca but on the E450 chassis instead of the usual E350 chassis used for small motorhomes. I run tire pressures of about 80 lbs. in the rear and 65 lbs in the front even though I don't need pressures this high for our weight. I run these too-high pressures to keep tire heat at a minimum by keeping sidewall flexing to a minimum - which is one of the benefits of higher tire pressures because heat ages tires faster. I use Michelin LTX Load Range E Defender tires all around and the pressures I use have not resulted in any excessive tire wear in the center portions of the tire treads..

Several years ago we changed just the rear shocks of the E450 to Koni FSD (Frequency Selective Damping) shocks. We used to have a shower door latch (the shower is in a rear corner) that never stayed latched after traveling a few miles on today's rouch roads and highways. Since installing those shocks, the latch now NEVER comes unlatched. We've also recently installed a couple of fairly shallow shelves in the rear of the coach and nothing bounces out of them when underway. I'm really scratching my head over those shelves and that shower latch! Those shocks are amazing and have taken away, estimating, at least one-half of the pounding in the rear.

Koni does sell "regular" shocks however, in addition to their FSD line. If you look into Koni shocks for at least the rear of your Class C, make sure it's Koni's FSD shocks that you check into.

Here's a link that explains the FSD technology:
http://www.koni.com/en-US/Cars/Technology/ACTIVE_Technology/

[Dakzuki]

I contacted Continental (the manufacturer of my OE tires) and they said to inflate per the placard in the door jam. They do not publish an inflation chart.

[ron_dittmer]

Dakzuki wrote:

ron.dittmer wrote:
And don't assume your tire gauge is accurate. I had a quality tire gauge that read 9 psi too much, meaning I was putting in 9 psi too little. You can read about my tire gauge evaluation HERE.

Ron,

A note on gauges. Those stick type gauges were not allowed in the VW/Porche/Audi shop I worked in years ago. I guess you now know why.

My tire pressure confidence jumped way up since my evaluation. I have not used any stick gauges since. I do keep the ones that passed, just in case.

[maillemaker]

My 1990 Winnebago Warrior has rims that are clearly marked "65 PSI Max". My door sticker says 65 PSI rear, 58 PSI front. I use Load rated E tires but their loads are de-rated due to the PSI limitations of my rims.

Steve

[Dakzuki]

ron.dittmer wrote:
And don't assume your tire gauge is accurate. I had a quality tire gauge that read 9 psi too much, meaning I was putting in 9 psi too little. You can read about my tire gauge evaluation HERE.

Ron,

A note on gauges. Those stick type gauges were not allowed in the VW/Porche/Audi shop I worked in years ago. I guess you now know why.

[Hank85713]

I have a 12 aspect by winnebago (28ft). its approx 12700 lightly loaded. We dont carry much for weight less than 1/2 tank water, dump grey and black when they indicate more than 1/3 full. Pull a hyundai elantra. run 75psi in rears, 60-65 in air bags, 65-70 in front tires and the air in the bags makes a big difference imo. too little it will wallow in winds and when being pushed by bow wave on semis and busses. found the sweet spot about 60 in the bags. Just need to play with the settings and TPs remember that is for MAX weight at 80psi

[klutchdust]

I own a 09 Cambria and experienced the same thing. I changed my shocks to Koni's and eliminated the rattling and banging.

There is a thread on shock absorber upgrades debating between Bilstein's and Koni's. Stock shock absorbers are worthless. I chased the issue with air pressure changes etc. The difference in ride was remarkable.

[harley-dave]

RonR2440 wrote:
I drive a 32' Itasca Cambria. I keep the tire pressure at 80 psi and the air bladder bags at 35 psi. When we are driving the RV seems to feel every asphalt repair, expansion joints, road damage, etc. Makes for a really rough ride. What do people typically keep their tire pressure at. I realize for the best results you can weigh the vehicle and look at tire charts. I am thinking of reducing tire pressure to 75 psi. I am concerned about tire overheating if I reduce the pressure too much. Thanks ahead of time.

We have a 31' Itasca and it requires 80 lbs. in the rear tires but only 75 on the front axle. I keep the air bags at 60 and it doesn't seem to effect the ride much but helps the sway/lean a little. I replaced the front shocks with Bilstein's which also helped the ride and steering. We've run various tire brands over the years and that also effects the ride and noise level. Now we have a pair of Michelin XPS rib tires that ride smoother and quieter than the others. We use the Escapee's Smart Weigh program and get it the weighed each year before the season starts so we can adjust the load front to back, and left to right as needed. They will also test your pressure gauge for you.

Dave

[ron_dittmer]

And don't assume your tire gauge is accurate. I had a quality tire gauge that read 9 psi too much, meaning I was putting in 9 psi too little. You can read about my tire gauge evaluation HERE.

[ksg5000]

Tire pressure s/b based on weight of the rig not what's on the side wall. Have the rig weighed and then use one of the charts published by Tire Mfg to set the correct pressure - my Class C rear tires are set closer to 65 than 80 and that's based on the weight on my rig.

[DrewE]

What does the door sticker say? That's generally the pressure required for the maximum axle weights and a reasonable starting point, at least until you can get a chance to weigh your unit (packed for travel) for yourself and see what the actual axle weights are. The tire companies have charts of weight vs. pressure to follow once you know the weights. (These are standard for a given tire size and type, so it's not really essential to find the chart from the company that made your tires.)

For the typical Ford chassis class C, the rear tires usually end up needing 80 psi but the fronts are somewhat lower, 60 psi or 70 psi or so. Reducing the pressure in the fronts if excessive would help the ride some. Realistically you are not ever going to get a Cadillac ride out of a class C motorhome, though; it's basically a box truck that happens to have an efficiency apartment in the box.

[enblethen]

5 pounds will not make much of a difference.
You should get the vehicle weighed. What chassis? Are the air bags front or back?
Are they factory or after-market?