Been awhile since we had a debate about; if any issues with replacing stock 225/75/16 tires with much taller and a little wider 235/85/16 tires on a Ford E350/450 with Duallies???
Recently put 235/85/16 tires on our 2009 E350 and there are no dually kissing-spacing issues. Used aftermarket outer Rims but the offset 'looks' the same as Ford stock inner steel rims.
Anyone else running 235/85/16 tires on a E350/450?
Last summer when I replaced seven 225/75R16 stock Michelins (including the spare) on our E450 Class C I looked at 235/85R16 tires ... but noticed that they violated the rear dully rims' specified tire cross-sectional widths so as to control sidewall contact .. plus they were a bit too tall for the DW to climb up into the already tall-for-her cab passenger seat.
I bought seven 215/85R16 LTX MS2 Michelins instead. These are still taller than the stock Michelins and gave greater sidewall spacing for improved air flow between the sidewalls in hot summer travel.
The 235 mm wide tire is to wide for the stock rims, so you bought a wider offset rim, similar to what would be used on the F-53 chassis that has 235 mm wide tires with a higher offset than the E-350 rims.
So great, you have two special rims that have extra offset than the stock rim, so that works great until you have to mount the standard rim on the rear axle, and the tires will probably kiss each other.
And I guess that you already understand that a different width rim will make the overall outside diameter of the tires larger or smaller, and you can not run two different diameter tires on one side of the dually rear tire. So I sure hope the rim width is the same for both the stock and replacement rim.
So great, you have two special rims that have extra offset than the stock rim, so that works great until you have to mount the standard rim on the rear axle, and the tires will probably kiss each other.
Fred.
Since I purchased 6 new rims (4 alloy outers for front and back and two steel inners for back) and also have the 6 old rims with 225/75/16 tires, I can measure the kiss-spacing of old 225/75/16 and the new 235/85/16 combinations.
I'll do these measurements within a few days before I put the new wheels on.
1. two stock steel rims with 225/75/16 tires
2. two new steel rims with 235/85/16 tires.
My guess, the kiss-spacing will be no than a 1/4" difference for all of the above combinations, taking into account the less side-wall bulge of a 235/85/16 tire mounted on a narrow 6" rim.
If I'm wrong on the 1/4" kiss-spacing measurement between 225/75/16 and 235/85/16 tires, then I'll have to use longer lug nuts with spacers.
* This post was
edited 06/19/12 03:21pm by McZippie *
I'm not going to suggest that anybody here wants to run their rear axle in overload, but I can safely say that the dual tire sidewall ratings of the 225/75 and 215/85 that Phil has, multiplied by 4, come very close to Ford's rating of the E450 rear axle. Many don't want to run their tires so close to their max capability, logic being they're close to blowout and sepration failure.
The OEM size (215/75) and Phil's (215/85) have the same ratings and in Load Range E, work out to very little reserve capacity. Couple that with the unequal loading we see side-to-side in RVs, some folks want to hedge their bets with a higher rated tire, either Load Range G, or a different size. The 235's mentioned above would add a little capacity. I'll call it reserve tire capacity since changing tires doesn't help the axle, changing the axle doesnt' help the springs, changing the sprigs doesn't help the frame... Where to stop? For me, stopping point is Ford's specs.
God Bless, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100
Quote: The OEM size (215/75) and Phil's (215/85) have the same ratings and in Load Range E, work out to very little reserve capacity. Couple that with the unequal loading we see side-to-side in RVs, some folks want to hedge their bets with a higher rated tire, either Load Range G, or a different size. The 235's mentioned above would add a little capacity.
I agree 100%.
In my case, our Class C's total weight is about 11,800 lbs., which of course is well under the chassis max capability of 14,050 lbs. So Load Range E tires provide all the margin I need with respect to raw weight carrying capacity versus tire reliability.
I couldn't take the vehicle height increase of the 235's and didn't trust the reduction in rear dual sidewall spacing to be a wise erring on the reliability side for a couple of reasons. I also didn't want the expense of changing the rims.
What I REALLY would have liked is a 215/85R16 tire size in Load Range G! Had they been available, I would have run Load Range G tires in the 215/85R16 size, but at Load Range E pressures -> but then would have had the increased construction ruggedness of Load Range G. You do not have to run Load Range G tires at Load Range G pressures in order to take advantage of their heavier duty construction.
By the way, I have been doing this on my 4X4 PU for years for maximum wear and reliability (...and improved gas mileage due to making overdrive really tall). I run two tire sizes over stock but use only the stock tire pressures.
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