On A 4x4 Can You Run 31.9" Front & 32" Rear Wheels?

[Morepower]

I have a dually and wanted to run a wider tire in the front that has a little different diameter height than the rear. Is . 1" anything to worry about?

 

[rspinks]

Before I did this I would check the loaded radius measurement for each tire, or better yet see how many revolutions each tire makes in X yards to get an actual measurement of loaded radius. I wouldn't trust the specified tire height dimensions for something this critical. Any difference in front/rear diameter will load the drivetrain in 4x4 and must be taken up by tire slip.



Assuming the actual difference is in the order of . 1" then I wouldn't hesitate. Consider that the difference in tread depth between front and rear tires can be much more than . 1" after several months of normal abuse .

 

[Blakers]

Measure as rspinks says, but if the difference is only that much, I wouldn't worry too much about it. You should not be using 4 wheel drive on hard surfaces anyway and turning a slight curve on hard road - even if the front and rear tires exactly the same size - will cause binding. Some vehicles even run slightly different ratios front and rear.



Blake

 

[Morepower]

The spec sheet shows a SLR and RSCS is fronts 14. 2 and rear 14. 9. Is this what you meant.



The full story is I would like a wider tires but don't want to change to rear dually spacer and studs. I can by a Toyo M55 Front tire with the following spec.

LT265/75/R16 (LI)123m, (SW)10-E, (1/32")18, (O. D. )31. 9", (SW)10. 8", (SLR)14. 2", (RV per KM)404, (Rim Width)7. 5", (Rim Range) 7. 00-8. 00"

Rear Tire.

LT235/85R16 (LI)119/116m, (SW)10-E, (1/32")18, (O. D. )32. 0", (SW)9. 3", (SLR)14. 9", (RV per KM)403, (Rim Width)6. 5", (Rim Range) 6. 00-7. 00"



This will give me and increase width Front width 10. 8" vs. Rear of 9. 3" and hopefully use the standard rims on the rear with a bone stock setup and purchase new fronts rims with plenty of clearance.

 

[Blakers]

Morepower...



Sounds like a plan! I think it will work just fine.



When you're in 4x4 they'll be some slipping between front and rear anyway. Just so you take it out of 4x4 when you get to the hard roads.



Blake

 

[Morepower]

Thanks for the quick reply. I think it will work for the same reason you mentioned that 4x4 mode is for loose surfaces.

 

[nickleinonen]

good idea. . sudo super single steer. . nice... i've had the idea kicking around if i had a training wheel equipped truck [aka dually lol] i would want to run some 305/70/16's in front, and 255/85/16's in rear. . mmm, that could be fun. . !

 

[willyslover]

any quality tire dealer or tire Mfg. would advise not to do this... you will have different tread patterns and handling characteristics ... potential of front end to rear end swap in rain or snow conditions and or in 4X4 mode

 

[rspinks]

Personally I'd be concerned about 14. 2 vs 14. 9 loaded radius. That's a 5% difference in front/rear wheel speeds in 4wd. Do you really want to be skidding your tires for 1/2 yard for every 10yards you travel in 4wd?



It's true that axle ratio's differ slightly front to rear sometimes, this is because they can't always get the exact same ratio of pinion teeth to ring gear teeth in different model axles. However 5% difference in tire diameter is almost like running 3. 55 in one end and 3. 73 in the other .

 

[RustyJC]

Do you have 4 wheel anti-lock brakes? If so, I would find out how much variance the computer allows between wheel speeds before invoking the anti-lock system.



Rusty

 

[tcourse]

Why not 18" wide MT's on Weld wheels on the back and match up the front? Had them on chev dually but it was 2wd.

 

[BV]

MHO - I could see this being okay if the fronts are bigger and therefore would turn faster than the rears and pull the truck instead of being pushed by the rears. I know the difference doesn't seem like much but I see a picture like willyslover pointed out.



I due know that with 3. 50 gears in the rear and 4. 10's in the front that a jeep cherokee gets very scary in the sand which is what my dad found out with a used rig he bought - Glad he didn't hit 4x4 mode on dry pavement

 

[jerryrigg]

1/10th of an inch is nothing. If your really worried about it you can compenstate the difference through air pressure. After all think about why there is such a difference in your recommended tire pressures listed inside your drivers door.



If your put 85psi front and rear especially on a 3500 you have changed the gear ratio's. The rear tires do not compress as much as the fronts as the weight of the truck is spread across 4 tires thus the fronts are shorter. But if you run the recommended psi and drop a 5vr on the back depending on the weight of the 5vr the rear may be shorter than the front, so air up the rear.



-Matt



Oh. . Assuming 32" is the orginal tire and a 3. 54 ratio, adding a 31. 9" to the front axle would have an effective ratio of 3. 551

 

[work2muchplay2little]

No problemo - a decent burnout would even them right up

 

[Morepower]

I do have anti lock brakes and 32" tires with 3. 54 gears are standard.



I never realized that load radius was so important compared to overall diameters. After thinking about it, maybe that’s all that really matters rather than diameters. I know that when I am in soft stuff the front end really sinks in ground because the front end is so heavy. That is why I was trying to add some surface width by changing to wider tires but am limited for the rears with a dually. If I were to match the rear with the front would require spacers, which another member pointed out leverage characteristics on the rear axels and spacer run out could be a concern with heavy loads.



It sound like with the heavy load on the front reducing the load radius even more, and the overall diameter being smaller, that I could end up with quite a bit more difference that originally imagined.

 

[willyslover]

might I suggest a call to Michelin tire teck line... we might be two years from now and still not have an answer you'll be comfortable with... and you could get the answer from the horse's mouth that way... . if you do call please fill us in on the conversation

 

[Morepower]

Isn't revolutions per minute verse diameter height and load radius all that matters?

Isn't revolutions per minute verse diameter height and load radius all that matters? The difference between both of these is 1 revolution per Km. The diameter height is . 1" but the load radius is 14. 2 vs 14. 9, how can that be so different? I know it is a static load test. Does that mean if it has a higher load capacity it probably will increase the load radius because the tire is flatter closing in the distance to centerline?

 

[rspinks]

I would expect that the rev/km would be directly related to loaded radius. If 14. 2 vs. 14. 9 is 5% different then I'd expect 5% difference in rev/km between these 2 tires .

 

[Morepower]

Surprising just the opposite

The 14. 2 load radius has 404 rpm per Km and the 14. 9 has 403 rpm per Km. I have checked the stats twice. See the specs on page 1.

 

[Morepower]

Toyo M55 http://www.toyocanada.com/products/sizesLT.asp?Sizes=m55&Submit800=Get+Data

Tire Size LI SW 1/32" O. D. SW SLR RV Rim Widths

M-55 1/32” O. D. WIDTH S. L. R. PER LARGEURS

DIMENSION D. H. T. G. B. R. S. C. S. KM DE JANTES



LT265/75R16 123M 10-E 18 31. 9" 10. 8" 14. 2" 404 7. 50 7. 00~8. 00



LT235/85R16 119/116M 10-E 18 32. 0" 9. 3" 14. 9" 403 6. 50 6. 00-7. 00