Lower tire pressure for smoother ride??

dougb · 01-10-2021, 06:42 PM

Has anyone lowered the tire pressure on your Class A, especially in front, to get a smoother ride. I lowered mine from the manufacturer's recommendation of 82psi to 75psi on both front tires. Is this a bad idea? This is a 2019 Winnebago Adventurer 27N. Thanks.

powercat_ras · 01-10-2021, 07:54 PM

Yes, it is a bad idea. Tires below recommended minimum cold tire pressure overheat and fail. They will also have un-even tread wear on the outside edges of the tires.

At worst, I'd never go more than 5% below the recommendation, that would be 78 PSI.

I'd be shocked if you can actually tell any difference in ride with the lower pressure.

**macnut** · 01-10-2021, 07:58 PM

I can actually tell a great difference by lowering the tire pressure from that recommended on Winnebago’s sticker. I use 85 instead of 100, BUT that was after weighing all for corners and going with the tire manufacturer’s recommendations. The weighing and recommended tire pressure was done my Henderson’s Lineup in Grants Pass, OR. I agree that it would be risky business to just lower the pressure without this vital information.

dougb · 01-10-2021, 09:04 PM

I did check with Henderson's for the tire pressure but they were reluctant to give me the green light on 75psi though they said it could be fine. I guess I will go back up to 80 to be safe and sure. Definitely don't want any tire issues. Been there, done that.

Reniram · 01-11-2021, 06:23 AM

The whole problem remains with travelling in the heat of summer temps or winter...my tires are set at 82 psi but on our annual winter trip to Florida from Iowa the pressure increases with a 10 - 15* fluctuation at times! so now I am running in the 95 psi average range...I dont think its rocket science but drastic underinflation will ruin a tire in short order...

**creativepart** · 01-11-2021, 07:42 AM

The problem with your approach isn’t that you lowered your tire pressures, it’s that you did so without first weighing your coach and consulting your tire manufacturer’s tire pressure charts for PSI for the actual weight of your motorhome.

All of this is well documented on the internet and the process is fairly simple and is safe.

All you need do is to load your RV for a trip and weigh it at a truck scale. The hardest part is you need to approximate the heaviest weight your RV will be: Fully loaded, all passengers, full of fuel and fresh water.

Once you’ve documented the weight on each axle (each wheel is better, but axel will work) you consult the Recommended PSI charts for your exact tire brand, model and size. These charts tell you the proper PSI for the actual weight that your tires are carrying.

With that information then you can safely set your tire’s PSI and it may be even less than your arbitrary settings you made without weighing your loaded coach.

Lowering your tire pressures is not a problem. Doing it without the above steps is the problem.

**creativepart** · 01-11-2021, 08:00 AM

And, tire pressures are always set cold. Cold is when you have not driven your RV at all that day or past few hours.

The pressures will go up with driving, sure, but the only pressure setting that counts is the cold setting.

The Ford F53 chassis your RV rides on is a heavy-duty truck chassis. It’s built to work hard and carry a lot of weight. It’s used on dump trucks, tow trucks, ambulances, delivery trucks and yes... RVs. So, yes it rides like a dump truck loaded with gravel. There is only so much you can do about that.

BobC · 01-11-2021, 08:08 AM

As others have mentioned, this all depends on your actual MH weights (per axle or four corner weights, fully loaded for travel) and your tires' weight tables. This can seem complicated at first but really is fairly simple.

Tireman9 (Roger Marble) is a Winnieowner and retired tire engineer who has a blog that covers these issues:

https://www.rvtiresafety.net/2011/03...and-roger.html

There's also a pretty good overview of the issues here:

https://www.goodyearrvtires.com/pdfs...care-guide.pdf

powercat_ras · 01-11-2021, 08:34 AM

POST EDITED TO REMOVE REFERENCE TO GOODYEAR TIRES AS IT APPEARS THAT FORD NO LONGER USES GOODYEAR G670 TIRES ON F53 CHASSIS SOLD TO WINNEBAGO.

The pressure on the Winnebago sticker for your 27N is based on Winnebago using the tire manufacturer's tire pressure table for the tires that the chassis is built with and the maximum loading for the front and rear axles.

You'll have to google search for the manufacturer's tire inflation table for the specific tires on your RV to see if you can use less pressure than what is on Winnebago's sticker if your loading is less than the maximum allowed for your chassis.

As has been said you can use Escapees SmartWeigh or other service to get your weight on all 4 corners of your RV and can set tire pressure to less than what is on the sticker based on your actual weight. You want to set pressure on each side of an axle to about the same, even if the weights on each side are different, so that you don't have one tire inflated to a larger diameter than the other and cause premature tire wear.

**creativepart** · 01-11-2021, 08:37 AM

Randy, do we have info that the OP’s RV has Goodyear tires? If we do, I haven’t caught that. My Adventurer has Michelin tires.

thunderjet · 01-17-2021, 05:52 PM

Creativepart is right on, I had a hard time keeping it between the lanes. Every rut it followed, every passing truck pushed me right and left. After weighting, dropped front just 7 psi and its a whole different ride. Chart said I could drop 15 psi I tried 5 first then 2 at a time 7 was my magic number more didn't change it hot tires didn't get weird after driving. I also added plastic pellets for balance. all good for me now.
TJ

bigb · 01-17-2021, 06:08 PM

I was planning to get 4 corner weights at the Cat scale, we have one that is accessible from the ends and from one side. My plan is to weigh the whole rig then pull around and pull back onto the scales with the left wheels only on the scales, then do the math. Anyone see why this wouldn't work?

jadatis · 01-18-2021, 02:23 AM

Yes, only dropp te pressure after weighing fully loaded, as you go on tripp. Best per axle-end, second best per axle.

Then for a motorhome in the European situation, the front often can be dropped to sometimes even 45 to 58 psi. In Europe often D-load tyres
BUT this is the American situation, where weights are higher and build of motorhomes is different, and often even G- or H-load tires.

For Dualload axle behind , it is often the other way around, front has to be on maximum, and rear lower.

But if you done that weighing, first add 10% to the loads, before you look back in a list, for reserve.
Even weighing is not 100% acurate, and the pressure- measurement certainly can be 5 to 10% off. So you determine for reserve, but can end up with yust enaugh to give no overheating of tires, where it is all done for.

And if with luck the data is acurate, still acceptable comfort and gripp.

jerichorick · 01-18-2021, 06:49 AM

Never drop tire cold PSI below manufactures weight chart. Soft tires heat more quickly. More than a 10% drop in cold PSI required for the load carry of the tire is considered FLAT. Internal damage may occur. There are many threads on tire care and problems. Tire pressure is often the central theme along with age.

LizandBruce · 01-19-2021, 03:29 PM

If you have not done so, then have 4 corners of your coach weighed professionally. Our coach is heaviest in the rear with engine and appliances. Weighing confirmed that our coach and tires should run 88 lbs in front and 110-115 lbs in rear. Much better ride and still safe.

Wyatt · 01-19-2021, 07:32 PM

Quote:

Originally Posted by bigb

I was planning to get 4 corner weights at the Cat scale, we have one that is accessible from the ends and from one side. My plan is to weigh the whole rig then pull around and pull back onto the scales with the left wheels only on the scales, then do the math. Anyone see why this wouldn't work?

Interesting idea, but I suppose it would depend on how level one side you’re weighing would be to the side not being weighed.

If there’s a big slant, then you may be redistributing weight to the other side, and getting a false (lower) reading on the scale...

Reniram · 01-20-2021, 05:29 AM

I still think that we are overthinking the process..How can you be happy if you leave the frozen North heading for Florida, knowing that during the 2 or 3 day trip your tire pressure will fluctuate between 10 or 20 psi...Would you take a guess at 80* say.. hoping that after a few hours they should be at the manufactures suggested pressure but then worried that they may be over inflated driving the interstate in the deep South when the ambient temp could be 80+ degrees hotter.. the tires would be operating over 100 psi so would you stop to let some air out....in my mind it remains a guessing game between safety - handling -and peace of mind to arrive at your destination..