Tires look low at 100psi need help

[bearscat]

I recently got new tires installed and the tire shop set them at 120psi. I took it on a few trips and it seemed to ride a little rough, so i thought I should lower the pressure. I lowered all 6 to 100psi and now they appear to be low.

I have had it weighed and front is 9200lb while rear 18500lb according to the tire charts I should only need 90psi?

Tires are 275/70/22.5

[LaurenceStarr]

If looks were correct, no one would own a tire gauge. The tire manufacture spent a lot of money and time to determine load Vs pressure ratings. If your weight and tire chart says 90, that is all you need. I've bumped mine up to 100 psi (ten psi over char), and my tires "look" low. I know they are good to go by the charts.

[windsorbill]

Originally Posted by bearscat

I recently got new tires installed and the tire shop set them at 120psi. I took it on a few trips and it seemed to ride a little rough, so i thought I should lower the pressure. I lowered all 6 to 100psi and now they appear to be low.

I have had it weighed and front is 9200lb while rear 18500lb according to the tire charts I should only need 90psi?

Tires are 275/70/22.5

Be sure your gauge is accurate and go with the pressures published in your tire manufactures tire chart based on axle weight. I add 5% more as a cushion.

Note, it's best to get 4 corners weight and then take the heaviest tire and use that number for all tires on that axle. I know I'm 1100 pounds heavier on the right than the left.

[luvlabs]

Go to the tire charts for the brand and size tires you bought and look up the inflation pressures for the tires you purchased. Divide the front axle weight by 2 and then multiply the wheel weight by 1.05 to compensate for side to side differences. Look this new weight up in the front axle charts. Inflate your tires to that amount and add 5 psi for a "fudge" factor. Do the same calculation for the rear (note, use the tire charts are for dually tires). Now you have the proper air pressures for the weight you are carrying.

[Ron_H]

Simply having a total front axle and rear axle weight is insufficient. You need the weight of each of the 4 corners. As an example, if your front axle has a total weight of 9200 lbs, you cannot assume the weight is equally distributed on both sides - it typically is not. If one side is 4200 lb and the other is 5400 lb then you should set both front tires for a load of 5400 lb. Your tire pressure must be equal on both sides and set for the weight of the heaviest tire on that axle.

When you have your coach weighed, it must be done with a full fuel tank, full weight holding tanks (ie: full fresh and empty blank & grey) andand all the people and cargo you would normally be carrying. Also, when you lookup the correct tire pressures on the tire chart, it is good to add an additional 5 psi to help compensate for weight fluctuations.

Without the correct 4-corner weights any tire pressure setting you come up with is strictly a guess and likely inaccurate. We weight our coach yearly at an Escapees park that offers the SmartWeigh program. It's $45 that is well worth the piece of mind. Our weight does change from year to year, but fortunately it is going down.

[MSHappyCampers]

If you got accurate weights, then I would trust the tire manufacturer's charts. Just be sure the chart you are looking at is for that specific tire!!! Yes, they are going to look low at 100 PSI.

I always add 5 PSI to the chart recommendation.