Tire pressure

[Neal]

Mkern......My Kountry Star appears to be a lot heavier in the front (13600 on the Cat scale) and uses the same 275/70r22.5 size tires, I have to run them near max 130psi cold to cover that weight. I am concerned that is not the best idea to have engineered a design that relies on running a tire at the very top of its load range. Am looking at the possibility of fitting the 295/70r22.5 for the added margin, but no idea yet on clearance. Glad you got it sorted out!

What is the weight limit on the front axle per the tag just behind the driver's seat, left wall? Take a picture and post it if you want.

 

[Scotttkd2]

I had to dig, but found a pic on my phone, 13500 front, 24000 rear with 130 front and 120 psi rear recommended on both FL label and Newmar label. Actual cat scale said 13660 front and 21800 rear. I have since offloaded a lot of weight we found we didn't need but at that time we were just starting full time so didn't know what we were or were not going to miss. I need to get it back on a scale once it's on the road again and see what our current load out looks like. Still think Newmar should have spec'ed a heavier tire for the front based on the tire chart recommendations though, I have my fingers crossed I have the clearance for the additional 2 inches in diameter, I would feel a lot better being able to run the fronts at less than max PSI rating given what has happened recently.

 

[Neal]

I think being cognizant of axle limits and getting corner weights is critical. We should not need to be running at sidewall max pressures. I'm running well above my chart mins which I think are 90 front and 75 rears. I run 105 front and 90 rears.

 

[Rich W.]

I think being cognizant of axle limits and getting corner weights is critical. We should not need to be running at sidewall max pressures. I'm running well above my chart mins which I think are 90 front and 75 rears. I run 105 front and 90 rears.

having a tag helps….a lot!

 

[Rich W.]

I had to dig, but found a pic on my phone, 13500 front, 24000 rear with 130 front and 120 psi rear recommended on both FL label and Newmar label. Actual cat scale said 13660 front and 21800 rear. I have since offloaded a lot of weight we found we didn't need but at that time we were just starting full time so didn't know what we were or were not going to miss. I need to get it back on a scale once it's on the road again and see what our current load out looks like. Still think Newmar should have spec'ed a heavier tire for the front based on the tire chart recommendations though, I have my fingers crossed I have the clearance for the additional 2 inches in diameter, I would feel a lot better being able to run the fronts at less than max PSI rating given what has happened recently.

I’d also be concerned about an under rated front axle. Wouldn’t be the first time Newmar did that. Do you have the build sheet with factory four corner weights? That would be telling.

This is page 4 (of six) of my build sheet provided by Newmar after I bought the coach used. It shows 10,050lbs on a 12,000lb axle providing a margin and some forward CCC. I don’t see how you can shed much weight off the front unless you have some heavy cargo forward.

 

[Rustymayes]

What tire temps do you guys see at your pressures? I run 95 in the rear and 115 cold in the front and I occasionally see 130 + on the inside drive tires. Of course the TPMS is constantly warning of high temps and pressures. I have yet to do a four corner weigh but I know we are going to be light as we really only weekend it the coach and have very little gear on board. I bet if I weighed every thing but water and fuel I would be under 500lbs of personal gear. I need to see if I can find my build sheet and see where my start point was. I can WAG a figure to add for gear pretty easily.

 

[BGMAC]

I run at max psi. Several reasons.
1. Tires run cooler; less friction.
2. Tires last longer; less friction.
3. Less chance of hydroplaning; tread is open up more and less flatness of the tire.
4. Less stress on the side walls when weighted down.
5. Less chance of sidewall blowout if tire hits bad pothole or something.
6. Better fuel economy. Not much of a reason on an RV, but it helps

Yes it does ride a little harder, but I drive slower to compensate.