New tire psi question...

goufgators wrote:

FormerBoater wrote:
How do you know 85 PSI is the correct cold inflation pressure for your load?

Based upon your post, it sounds like it may not be.

Very rare for the same tire pressure to be correct for all six or eight tires on a Class A.

FormerBoater: Thanks for your reply. And, yes, I do not know that 85 is correct and yes I do know that having each corner weighed and then inflated according the manufacturer's chart is necessary (I did that on my previous MH). I haven't done so yet with this MH but have only made a couple of fairly short trips. I do, however, intend to have it weighed before my next trip. After having it weighed, let's assume that weight on one of the wheels requires that tire to be inflated to...say 90 psi. I inflate to that pressure and then when I start driving on these hot Florida roads won't the pressure still increase 10 to 15 pounds over the required pressure as is occuring now and again resulting in harsh ride and steering difficulties? I believe I know the answer to that question and that it is that there is likely no preventing pressure increase due to road heat. Am I correct? Again, thanks for your reply. / Larry

You are correct Larry. That is why the charts are all based upon Cold PSI....the pressure and temperature will increase as you roll down the road, but the tire manufacturer's engineers factor that in for their Cold PSI recommendations.

BTW, tire temperatures once a tire has been in service for a few hours will rise to as much as 60 degree F above ambient and that is also considered normal.

I use an IR gun and shoot the tires at each stop. My new Hankook's run quite a bit cooler than 60 degrees above ambient so far. Last week all six were within 1-2 degrees of each other on a 400 mile trip up to and back from a music festival.

I own Michelin tires and my recommended PSI to weight on my coach is 100 lbs. according to the chart on Michelins website. The recommended tire pressure without all the weight I carry is 85 lbs. rear and 90lbs. front. Keep in mind the less air you have in a tire, the more tire you have touching the road surface so therefore the tire is creating more heat. It says that on Michelins website. I like you am not happy about the harsher ride at 100 PSI, but I enjoyed running my tires for 10 years do to proper air pressure, quality tire, quality maintenance.

FormerBoater wrote:
How do you know 85 PSI is the correct cold inflation pressure for your load?

Based upon your post, it sounds like it may not be.

Very rare for the same tire pressure to be correct for all six or eight tires on a Class A.

FormerBoater: Thanks for your reply. And, yes, I do not know that 85 is correct and yes I do know that having each corner weighed and then inflated according the manufacturer's chart is necessary (I did that on my previous MH). I haven't done so yet with this MH but have only made a couple of fairly short trips. I do, however, intend to have it weighed before my next trip. After having it weighed, let's assume that weight on one of the wheels requires that tire to be inflated to...say 90 psi. I inflate to that pressure and then when I start driving on these hot Florida roads won't the pressure still increase 10 to 15 pounds over the required pressure as is occuring now and again resulting in harsh ride and steering difficulties? I believe I know the answer to that question and that it is that there is likely no preventing pressure increase due to road heat. Am I correct? Again, thanks for your reply. / Larry

Recommended tire pressures are tire pressurse at cold and can go up a lot when driving on warm pavement.

To get the proper pressure, you really need to weigh your coach and use a pressure chart for your tire. I believe the posted tire pressure is for the coach at GVWR so if you aren't running fully loaded, you might very well be overinflated for your weight.

All that being said, running at a lower tire pressure often does give a softer, nicer ride but that doesn't mean it's better (or safe). Your rims / tires migh have a minimum pressure level that you have to keep even if it makes them feel overly hard.

How do you know 85 PSI is the correct cold inflation pressure for your load?

Based upon your post, it sounds like it may not be.

Very rare for the same tire pressure to be correct for all six or eight tires on a Class A.