Community Forums

NC2MT · 06-07-2021, 12:38 PM

21 foot class c. Use 6 225/75/16s. Replaced Firestone Transforce with Iron Man, both load range E, but the driving is soft by itself and if I try flat towing my car it swings side to side. Is it the tires?

wolfe10 · 06-07-2021, 12:39 PM

Are the new tires properly inflated?

What PSI?

Skip426 · 06-07-2021, 12:47 PM

Welcome to iRV2.

Sorry your first post is about problems .

Do you have any info on the age of the tires ?

I had a set of 3 week old Michelin tires installed on my truck , and it floated down the road for the first 6 weeks of use ; rubber wasn't fully cured was my best guess .

Also what are you towing ?
Some Jeep models/years will set up problems when towed.

NC2MT · 06-07-2021, 07:31 PM

Carefully checked all tires to max inflation of 80 psi listed on tires. Checked the car tires, too. Towing a 2004 Honda CRV. Don't know the age of the tires, but I'll check that out. Other tire guys have since told me that heavy truck drivers often complain about softness or waller on new tires for the first couple of thousand miles. I was also told the problem is likely softer sidewalls on a less expensive tire. These Ironmans are made in Vietnam.

Flyer15015 · 06-07-2021, 07:44 PM

Take them to you local tire shop to get them balanced, and WATCH them do it, so you can check for "hop and run out" yourself. Could be the tire or rim. Most likely tire.

Mike in Colorado

dons2346 · 06-07-2021, 09:24 PM

Ii would give it some time before blaming the tires. I put a new set on and had terrible rear end sway. Took a couple hundred miles before everything settled down

theroc · 06-07-2021, 11:30 PM

My guess is that your inflation may be too high. Why are you using the maximum psi? A 225/75R16 can be as low as 35 to 40 psi depending on the weight of the vehicle. I realize you will not want the pressure that low but I'm not sure you need it at the maximum that the manufacturer says it should not exceed ...and that is 80 psi, the maximum pressure for most 225/75R16.

But just a guess on my part. But also as others have said, it always takes some time for new tires to "settle down."

NC2MT · 06-08-2021, 05:12 AM

Many thanks to all. We need to head across the country asap and I can't wait in hopes it will improve. I think I'll get my tire guy to drive it and see what he thinks. He and I already talked about the problem. I understand new tires feeling softer when driving the rv, but I don't understand why that would make it swing and sway dramatically when flat towing a car we have pulled for thousands of miles without a problem. I'll post what I learn. Again, many thanks. This is the first time I've ever posted anything anywhere and it is encouraging to know people care enough to respond.

cwit · 06-08-2021, 12:56 PM

Somewhere on your rv there should be a chart with maximum inflated pressure for your rv. Find it and drop about 10 lbs. try and see if that helps,betting it will.

NC2MT · 06-09-2021, 05:11 AM

All the tire guys I talked to recommended the max pressure written on tire saying with less pressure there would be more sway. I have 80psi in all right now. The door says 65psi, so I will try that and see if it helps. Thanks.

LETMGROW · 06-09-2021, 05:47 AM

Quote:

Originally Posted by NC2MT

All the tire guys I talked to recommended the max pressure written on tire saying with less pressure there would be more sway. I have 80psi in all right now. The door says 65psi, so I will try that and see if it helps. Thanks.

I would disagree with all the "tire guys" you have talked to. The maximum pressure written on a tire is nothing more than a "Do not exceed" number. Too much pressure will put additional stress on a tire and eventually lead to a blowout.
Follow the recommended pressures on the door sticker and give it a try. With the excess pressure you are currently running you are pushing the center tread of the tire out so you are actually riding on just a small amount of the tire's available footprint.

SC182 · 06-09-2021, 10:40 AM

X2 - go with whats on the door. Or weigh the coach and cross reference the tire mfgr inflation chart if you can find one

tap4154 · 06-09-2021, 10:57 AM

Definitely go with what the door says. If you have them over inflated, they will tend to wander. My door says 75 front and 80 rear, but I actually run at 70 front and 75 rear. They handle great, and once they get up the temperature they increase anywhere to 8 to 10 psi. I also don't carry anywhere near my cargo capacity.

sandwip · 06-09-2021, 07:42 PM

Definitely weigh it and set pressure as indicated in a tire chart. If you can't find a chart for your manufacturer then one will do from Toyo etc for your size and range. I have a 30' class C and only run 70 psi. Any more and it will wander around, same for my last unit a Class A. Tires will take a few hundred miles to scuff in and wear off the coating from manufacture as well.