Do these tire pressures sound right?

[Sundog]

I just weighed my DSDP 40' and got 4 corner weights. I have been having what I felt was a front tire "hopping" and thought maybe I had a tire problem. Got the front tires looked at and they said the curbside was out of round. THey trued that tire and balanced both fronts. The ride is beter, but still not what I would expect. Not as smooth as my previous coach which was on a 25,000 lb freightliner chasis (38' Expedition without air suspension). My corner weights are: Front curb=5850, front road side=5400, rear curb=9200, and rear road side=8800. According to the Michlein chart I have (XZA1) the front should have 85 and 90 lbs and the rear should have 75 lbs. This seems real low to me. I have never had a coach with tire pressures that low. I have usually run them at 105 - 110 all the way around. Any comments? Are these tire pressures correct? Thanx for your input. We are getting ready for a big trip out west in a week or so. I would expect that the weights on each corner would increase by about 200 to 300 lbs when we get our clothes, food, and selves inside.

Chris and Sue
Gainesville, FL

[Sundog]

I just weighed my DSDP 40' and got 4 corner weights. I have been having what I felt was a front tire "hopping" and thought maybe I had a tire problem. Got the front tires looked at and they said the curbside was out of round. THey trued that tire and balanced both fronts. The ride is beter, but still not what I would expect. Not as smooth as my previous coach which was on a 25,000 lb freightliner chasis (38' Expedition without air suspension). My corner weights are: Front curb=5850, front road side=5400, rear curb=9200, and rear road side=8800. According to the Michlein chart I have (XZA1) the front should have 85 and 90 lbs and the rear should have 75 lbs. This seems real low to me. I have never had a coach with tire pressures that low. I have usually run them at 105 - 110 all the way around. Any comments? Are these tire pressures correct? Thanx for your input. We are getting ready for a big trip out west in a week or so. I would expect that the weights on each corner would increase by about 200 to 300 lbs when we get our clothes, food, and selves inside.

Chris and Sue
Gainesville, FL

["007"]

Chris, looking at the table and adding 500lb to the higher # front and back would have 100 psi front and still 75 psi for the back duels each.
The only trouble is you should have it weighed fully loaded full fuel, LP,food, cloths,what ever water level you want plus number of people traveling. Some people add the 500 each axel on a fully load coach.

[Lug_Nut]

You didn't indicate whether you have 70 or 80 series tires. I run 80 series ZXA-2's with 110 front and 100 rear. I calculate 100 front 90 rear and add 10 psi. Last time I check, and I just returned from doing 6,500 miles, front were 108 rear were 98. The coach rides great. I'm real happy with both ride and handling. Your pressures sound low to me.

[Sundog]

My tires are the 70 series. And I agree with 007, I should increase the weight at each corner by 500 lbs to allow for a loaded coach. But even with adding 500 lbs to each corner the tables still call for 75 lbs in the rear tires. That just sounds way too low to me. THe issue is compounded by this nagging "hop" or "jiggle" that I have when driving. IT doesn't feel like the front end is out of alignment as it doesn't pull and drives straight. But is does feel like "somethin' ain't right". I had the front tires balanced and trued and am having the rears done as we speak. I am leaning toward putting 100 psi in the front and 95 in the rear. If I can't get rid of this nagging "jiggle or wiggle or vibration" what do you think I can do to fix it? I have been to the Spartan Chassis people in this area and they checked and adjusted everything as it was way out of specs. It made it better, but not right.

[Lug_Nut]

Increase the pressure in your tires and give it a run. I prefer a good margin over the weight required pressures. While driving at a fair clip on most highways the dips and rolls put far more weight momentarily on each corner. The best thing I ever did on my rig was replacing the 275 70 22.5 ZXA-1 with 275 80 22.5 H ZXA-2 tires. The 70 series were not too bad riding but the 80 were noticably smoother.
Anyway, give it a try. Increase your pressures to 100/110 front and 90/100 rear and take it for a spin.

["007"]

Something you might do is give Spartan factory a call and explain what you coach tires are doing, have a friend AJBJ that took his coach to Spartan, because they do care, his had some suspension problems with the front end his coach was a 2002, yours is 2004 so may not be same thing but its worth a try. "007"

[tmitchell]

What year and model do you have?
I have a 2004 DSDP 3807. According to the Michelin tire chart dated 8/03, for my loaded weight:
5,400 driver front; 5,700 pass.front:
11,100 front axle: Calls for 105psi, I put in 110psi.
8660 driver rear; 8760 pass.rear:
17,420 rear axle: Calls for 75psi, I put in 90psi.

[Sundog]

Tom,

Ours is a 2004 4025. Sounds like you are reading the charts like I am. I will check with Michelin again and then with Spartan. THey have always been top notch and wonderful to deal with. THank you to each of you for contributing. You are why I enjoy this group so much.

[Digital Boy]

Sundog,

I think that the RV chart pressures are designed to provide a more comfortable ride.

I had my '98 3865 DSDP weighed at each wheel and the result was lower pressures than I expected. Even so, I run 105 psis on the front tires (rather than the recommended 100 psi) and 100 psi on the rears (rather than the recommended 85 psi). The ride is smooth and comfortable.

[ajbjrvers]

To, Sundog and others,

You might want to review my posting, 5 minutes ago above in MOHO's problems and solutions. It's on your subject of tire inflation and I know a lot of us are traveling, I used to, on improperly inflated tires, it all goes by weight.

Hope you look up.

Thanks== Aime== AJBJRVERS==

[mthom12]

Question,
If the tires, engin, trans, are the same on the w22 and w24 workhorse. What makes one able to carry 22,000# and the other 24,000#?

[Digital Boy]

That is probably exactly why one chassis is the W22 and the other W24. I suspect that the 24 is built to handle the additional pounds.

["007"]

mthom12 welcome to irv2
Axel loads will determind the load of your chassis. your MA must be on the 24000# chassis it didn't show up in your signature profile. Because you own a Newmar you are able to be a member of the Newmar Owners forum I can put it in for you, if you like. Enjoy the forums and post often. "007"