225/75 R16

[93minnieWinnie]

My camper sways all over the road when traveling in moderate wind. I had the front end inspected and the steering dampener replaced. The tires are only 2 years old, but I'm wondering if replacing them now will help.

I have a 1994 Winnebago Minnie Winnie on a 93 Ford E350. The sticker in the door calls for LT225/75 R16D with a max psi cold limit of 50 on the front and 55 on the back.

The tires that I have now are Laufenn LT225/75 R16 load range E. The front tires are inflated to 75 on the front, and 55 on the back. The back tires tend to bulge on the bottoms if I am not parked on completely level ground. The front tires never seem to buldge, but are inflated way above the original ratings.

The tire walls on these tires give them a weight limit of 2470 lbs at 80psi. The door sticker demands a front GAWR of 4600 lbs, and a rear GAWR of 7810 lbs (GVWR 12200)

I am most concerned about safety. I have no desire to leave solid pavement or drive in the snow. I just want the most reliable and recommended tires that make sense to put on this camper. While it looks like the tires I have meet the weight ratings, I'm wondering what might be a better option.

Thanks!

[DUNEBUGGYDOUG]

I had the same problem a couple years ago. J-D is the man to listen to. Taking his suggestions, I was able to help my problem,not cure it, by lowering tire pressures, front and rear. The main problem I have is light on the front end, with no really good way to transfer weight. The way my compartments are ,there is no way to get more weight up front. I put Hellwig sway bars and Bilstein shocks on it. It still wants to wander around sometimes, worse on some roads.I just finally learned to live with it.

[j-d]

Then there's FoMoCo, messing with inflation recommendations on Explorers a few years ago. Firestone disagreed with Ford's "soft" numbers. Ford stayed with it. Explorers rolled, people died, lawsuits flew, Explorer was redesigned, Ford and Firestone are no longer the steadies they'd been for decades.

For RV's, I think we can SAFELY go with accurate Scale Weights, and COLD Tire Pressures based on a Weight to Pressure Chart.

[CapriRacer]

jolooote wrote:
Placards are for the smoothest ride and if manufacturer can swing it...maybe a little safety also. Weigh it and go by the TIRE manufacturers tire chart!

This comment puzzles me.

We know that less pressure gives a better ride - and we know that the placard pressure is supposed to be at least equal to the GAWR - so the placard pressure has to be higher than what the vehicle actually weighs - and therefore using the load table to set the pressure would result in a softer ride.

So how can the placard pressure be for the smoothest ride? Wouldn't that mean that anyone who is concerned about failing tires ought to use a higher pressure? And if using the load tables to set the pressure results in a lower pressure, doesn't that make this recommendation *less safe*?

So I'm confused.

Oh, and BTW, the tire load tables are MINIMUMS, not recommendations.

[j-d]

Those who said "interesting" or "peculiar" are right. There is usually a Chassis builder (Ford in this case) label as well as the one from the Coach upfitter (Winne in this case). The one from Ford will show the pressures needed to carry Gross Axle Weight Rating Front (GAWR-F) and of course GAWR-Rear. If the Chassis is under a Box Truck and you want to carry the most watermelons the Chassis is rated for, then those are the Front and Rear pressures.

Usually, perhaps recently, the Coach upfitter label would show the same pressures (for MAX Load, remember) that Ford did. Liability stuff no doubt. But years back the Upfitter DID recommend their own set of pressures. I think that's what we're seeing here. Winne did not believe that its coach would reach full GAWR on front or rear, and specified pressure accordingly.

In other words Winne anticipated 7500 rear with that 55 PSI dual tire pressure number. Likewise the 50 PSI single tire pressure for the front anticipated about 3900 front. Again, I think they shy away from that now on liability reasons.

Also note that stated GVWR is less than the sum of the axle ratings, suggesting they allowed for a little weight imbalance within GVWR.

They don't do that anymore either. Front + Rear GAWR's = GVWR

1997-2007 E-SuperDuty/E-450 is 4600 front and 9450 rear 14050 GVWR
2008-2018 E-450 is 5000 front and 9500 rear 14500 GAWR.

[whizbang]

Basically, it's a wheel base/over all length problem.

We have the same tires on a 24-1/2 foot, 2002, E350 Minnie. Unfortunately, our E350 is a 157 inch wheel base. So, we have a long rear end beyond the rear axle. The rear end acts like a wind sail in cross winds. Not good. I think Minnie Winnies are longer than Minnies??? You may have even more wind sail effect.

So far, we have put on new tires and new Bilstein shocks on all four corners. Our Minnie has a little rear end sag. We are having the rear springs replaced next week. I hope that stiffer springs improve the ride in general, not just in cross winds.

I agree with the other posts that you don't want to over inflate your tires.

[jolooote]

Placards are for the smoothest ride and if manufacturer can swing it...maybe a little safety also. Weigh it and go by the TIRE manufacturers tire chart!

[j-d]

Welcome!

With your coach loaded (people, supplies, stuff, as for a trip) go weigh it at a truck stop CAT scale. Then adjust tire pressure to what a load/inflation chart tells you to. If your tires are hot when you get to the scale, go 5 PSI higher than chart and set it accurately when cold the next day.

I can promise you it's way overinflated on the front, and that will make handling very squirrely. 55 may be enough for the rears. This is an E350 that made GVWR with "D" tires. You can use the "E" chart for "D" but not above 65 PSI and the respective weight.

[CapriRacer]

93minnieWinnie wrote:
Got it, thanks for your replies!

Here is the door sticker:

https://goo.gl/45jwi3


Here is the inflation table on the sidewall of the current tires:

https://goo.gl/zLDD9E

And here is what the rear tires look like inflated to 55psi:

https://goo.gl/K7cfF9

My concern is the bulge that appears. Doesn't this increase heat and tire wear?
Would a load range D tire show less bulge when inflated to the recommended psi? After long drives I swear I can smell more "rubber off-ing" on the rear tires than on the front.

Thanks!
(Apparently I haven't learned the trick to posting pictures here yet. Those links are shortened url's to images in my google drive.)

That's really, really odd!

The placard calls for 50 psi in the front - which is 3,880# - BUT - the GAWR is 4,600# - which should be 65 psi.

The rears are 55 psi = 7,500# - BUT (again!) - the GAWR is 7810# = 59 psi.

Something is seriously amiss!

For right now, 65/60 seems to be the right answer - although this assumes the weight is perfectly centered (hardly ever!!) - and I think weighing the rig is in order - and since Winnebago screwed this up so badly, I wonder if they got the side to side variation correct. If possible, weigh each corner separately, (or figure out how to get that info.)

[Mich_F]

According to Michelin's website
http://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation...

65# in the front tires is enough pressure to support 4,670#, slightly above your GAWR, so at 75# you're over inflated.


55# in the rear is only adequate for 7,500#, so you're most likely under inflated.

You should have your MH weighed, all set for a trip and adjust your tire pressures accordingly.

Your MH cams with load range D tires, which was the norm back then. They now come with load range E tires.

[93minnieWinnie]

Got it, thanks for your replies!

Here is the door sticker:

https://goo.gl/45jwi3


Here is the inflation table on the sidewall of the current tires:

https://goo.gl/zLDD9E

And here is what the rear tires look like inflated to 55psi:

https://goo.gl/K7cfF9

My concern is the bulge that appears. Doesn't this increase heat and tire wear?
Would a load range D tire show less bulge when inflated to the recommended psi? After long drives I swear I can smell more "rubber off-ing" on the rear tires than on the front.

Thanks!
(Apparently I haven't learned the trick to posting pictures here yet. Those links are shortened url's to images in google drive.)

[tobydad]

The door sticker tells what the psi should be for a reason. Too mush air in the front tires causes wander and you are running 25 psi too much.

[CapriRacer]

OK, the placard calls for 50/55 psi and you are running 75/55 psi.

I would think that would cause the vehicle to be kind of sensitive to cross winds. Try lowering the front pressure in increments and see if that helps. I would start with 65/55.

You might even consider raising the rear pressures.