Tire Selection limited by size?

Here is a link to someone that has done that.

Bigger tires

Are you sure that is the original tire size? You can check the placard on the door jam to verify that it's the original size.

Check again. I think your profile will be 2-twenty-5/75R16, and they are very common on Class C chassis. You'll probably end up with Load Range "E" tires even if your chassis first came with "D"", nothing wrong with that.

Some of us have gone from 225/75 to 215/85. The 215 has the same weight ratings as the 225 but it's slightly taller and slightly narrower. If you want to increase tire size, have a qualified tire shop look into 235/85. The 235 would be taller still, so clearance could be an issue. But if it's wider in 85 series than the 225/75 is, then you need to verify that the "Dual Spacing" is adequate, and that's determined by your wheels. IN NO CASE can you have less than minimum required spacing. If the dual sidewalls don't have room to flex without chafinc (kissing each other) you'll have tire failure in VERY short order.

I double checked, 255 is correct, here's a photo of the sticker.

It's on a 05 Chevy Workhorse chassis.


Photo of sticker

Interesting,My 2006 Chevy RV on a 2005 Chassis is spec for 225/75/R16 your Tires are 10 inches wide to my 8.9 inches and taller.

The tall part I would not worry about but the width,like jd has said would worry me.

I would not want them below the minimum required spacing.

My suggestion would be to go with the 225/75/R16

I really like my Michelin LTX M/S 2 they ride nice are quiet.

How do your GAWR's compare to mine? Mine is a 32' model, I'm wondering if it's a higher gross weight than yours.
Front GAWR is 4600 lb,
Rear GAWR is 9450.

Initially, My concern with going with a narrower tire is a reduced load rating. The more I think about it though, I think I've got the wrong idea. A narrower tire would just mean a higher PSF to the road surface.

I suppose if the tire rating X number of tires per axle is more than the GAWR, I should be ok?

rdhetrick wrote:

Front GAWR is 4600 lb,
Rear GAWR is 9450.

EDIT: These add up to 14050. Probably makes it a "Workhorse" chassis, where WH upped the rating of a 3500 to compete with Ford E450

See above... What the Workhorse licensed people did was up-rate the 3500 and the tires seem to be one of the things they did. You don't need any more capacity than the 225/75 or 215/85 offers. Both will get you to your rear axle rating. I like what WH did with tires that multiply to above that capacity. Ford should have.

With Ford, we can't go way crazy oversize on dual tires because of the rim offset dimension. It looks like you might have wheels with more offset, meaning you could go with 235, 245, both of which I've seen.

The challenge will be the offset. It's NOT the spacing you can see between sidewalls. It's two wheels, as mounted. Picture bolted together at their faces. Offset is center to center of the two rims' beads. Say a wheel has its bead surfaces 8" apart. Center is 4" so measuring between the two 4" centers might give you 10", but could be more or less. Take that dimension (10" in this example) to a tire chart and see which sizes require an offset of 10" or less, and still meet your load. That'd be 9450/4, and be sure to use the "Dual" column of the rating chart.

rdhetrick wrote:
The more I think about it though, I think I've got the wrong idea. A narrower tire would just mean a higher PSF to the road surface.

Also .... a narrower tread width (in the front steering tires) helps a bit in reducing "steering wander". The vehicle seems to track straighter with less constant correction effort by the driver.

I've learned the above over the years .... starting with my first new car (a Mustang fastback). Big fat tires sure "looked good" on it ... but it tracked and drove a lot better with stock tread width tires on it! My personal opinion is that narrower tires - on hard surface roads but with a couple of inches of slush or snow in their surface in the winter - "push through" this top slippery layer better so as to be down onto the hard surface underneath. This would be due to the increased pounds per square inch of pressure for each square inch of tread contact surface.

Our Class C is now on it's 2nd set of 215/85R16E tires after changing from the stock 225/75R 16E tires that came on it new. Both sizes have the same load rating, but the 215's have a Green X rating (less rolling friction), and are a bit taller for a higher overall gearing - thus providing slightly improved fuel mileage along with about 0.6 inches of higher ground clearance everywhere (unlike lifted vehicles - which only have higher body ground clearance but not always more running gear ground clearance).

Since the 215's also provide more clearance between the rear duals, better air ventilation between them is probably going on - resulting in longer hot weather life.

All of the above are very subtle advantages, but since their load rating is the same ... I figure why not use them instead.

rdhetrick wrote:
How do your GAWR's compare to mine? Mine is a 32' model, I'm wondering if it's a higher gross weight than yours.
Front GAWR is 4600 lb,
Rear GAWR is 9450.

Initially, My concern with going with a narrower tire is a reduced load rating. The more I think about it though, I think I've got the wrong idea. A narrower tire would just mean a higher PSF to the road surface.

I suppose if the tire rating X number of tires per axle is more than the GAWR, I should be ok?

My Gawr is the same as yours, it is on the Workhorse Chassis.Yes you will be OK with the 225/75/R16.

The offset on the Chevy wheels is a bit larger giving a wider stance and better handling than the Fords so you can run a wider tire with no problems.

Have you weighed your rig? It is important to have these axle weights to get the right air pressure for the load on the tires.

You can use This Table for that.

Finally got a chance to get out and see what tires are actually on the motorhome. To my surprise, they are 225/75R16.

Actual weights on a scale from the last trip fully loaded and a full tank of fresh water with the toad hooked up:
Front axle: 4460
Rear axle: 9100
Toad: 3120 (2014 Ford Focus with full gas tank)

I'm close, but under the axle limits.

Now I'm wondering if the tire size on the door sticker was a typo from Fleetwood. Next time out I'll check the speedometer vs. the GPS and see if they agree.