Front Tire Size

[Mike & Nancy]

Need info on reasons (or why) for installing larger front tires on MH. Present size on all rims 295 x 80 x 22.5........some higher end coaches have 315 x 80 x 22.5 on fronts only......with 295's on rear and tag.

[robbstein]

The only reason I can think of would be to increase the load carrying capability on the front. However, you are probably going to be heavier than the rating on the front axel if you do this, since the OEM tires are generally rated to handle the gross weight capability of the axel(s) involved.

[Diplomat Don]

Mike.....If you're right at your maximum load for your current tires, changing to something larger/more capacity might be a good idea. If you're okay, you could substantially stiffen/worsen your ride by adding a tire that is way over rated for your axle weights.

The ride height may be an issue too. The ride height settings are pretty critical on these coaches. If you lift the front end and inch or so, you could throw off the geometry.

[stuhly]

If you don't change to a 9 inch wheel the 315s will hump up in the center and wear the centers and cause the outer sides to cup very fast. I know this to be a fact because we put them on three Freightliner trucks and had this happen until we changed wheels from 8.25s to 9 in wheels. That ended the problem.

[islandtees]

I have a Dynasty and just put 2 new tires up front.Went with Mich XZA2 energy in the 295.I was thinking of going to the 315.First you can use the 8.25 rims with no problem.Mich says 8.25 or 9 is OK.I have friends with the 315 with 8.25 rims with many miles and no problems.You will have no lift problem in your ride height since the tire is only a little larger than the 295 in diameter.No adjustment to ride height is needed.Those who do it want to reduce the air pressure to carry the weight that is allowed on the axel.Some do it for a safety factor.I didnt feel I had to do it.When I weighed my coach I was not near the axel capacity.I just wanted to get rid of those junk Goodyear G670 tires.

[stuhly]

You can think what you want, but I went thru 3 sets of 315 -80-22.5 on three trucks before I changed to 9 in. wheels, and not all the same brands. The 8.25 wheel does not let the face of the tire set flat on the road.

[islandtees]

I dont think nothing.Im telling what people who own Monaco motorhomes(like the OP owns) that put them on,not trucks, without problems.They are wearing without problems!

[Norm4015]

According to Michelin the preferred wheel for 315 tires is 9.0" and Michelin says they will also fit 8.25" wheels, but they must be derated on the smaller wheels. For 315 tires on the steer axle, if mounted on 8.25" wheels the tires must be derated 820 pounds per tire.

[ShapeShifter]

Quote:

Originally Posted by Norm4015 For 315 tires on the steer axle, if mounted on 8.25" wheels the tires must be derated 820 pounds per tire.

Perhaps derating them is there way to say the maximum pressure needs to be reduced to allow the tread face to flatten out and help avoid center tread wear issues? Just a guess...

[walt2137]

Mike when you change to the 315/80 22.5 is made for a 9 inch rim when a 8 1/4 rim instead of airing up to the max of 125 with the 9 inch rim you will not be able to go to 125 with the 8 1/4 rim I am not sure whether the max is 115 or 120 psi but it will be less.

The ride height will not be changed by installing larger tires, think about it the tires have nothing to do with the height from the H frame to the coach frame.

[Mike & Nancy]

Walt and All.....Thanks for all the input. Reason for asking this is that I am going to replace the inside dual Steel Rims with Alum ..........did this on our 04 Alpine and it made a difference in temp readings .....about 15 to 20 degrees. Anyway I thought if there was an advantage to going larger on front (ride-handling-etc) like Monaco does with Signature Series. I would use present 8 1/4 alum rim on inside duals and purchase 9 in rims for front with 315's.....Make any sense.

[walt2137]

Mike if that is what you want that is what you should do, temp has never been a problem on our coaches inside dual, it does run a little hotter but not enough to hurt anything.
There are a lot of Monaco coaches that are running the 315's on the 8 1/4 rim and have not reported any problems.

[Mike Canter]

Just put two of the 315 Michelin XZA2 Energy on the front of my 2004 Signature. Love the tire. Got almost 4000 miles on them so far and no complaints. They are a 20 ply tire vice the 16 ply of a 295. I love that safety factor on the front. There is no measurable difference in ride height. The tire is only one inch greater in diameter which means a half an inch difference in radius and resultant ride height. I needed no balance weight on the left tire and only 6 oz on the other tire which is not much on a tire/wheel that size. They are smooth as glass.


Also let me add that the two tires cost me $1300 out the door with them buying back my Goodyear G670's at $100 each.