Quick and Important Tire Size question

[seafish]

I need to order only a PAIR of tires for my truck (2005, 4WD).

I have a pair of Toyo Open Country AT 285/75/17 LRE on the front that have ONLY 3k on them.
I now need to buy a pair of tires for the rear axle, but want to try the new Cooper AT/3 tire, the largest size of which is a 285/70/17 LRE.

Among other things, I though it would be great way to compare wear on these 2 popular tires. The Coopers come with a 55k treadwear warranty, while the Toyos have only a 40k warranty.

MORE IMPORTANTLY--

The Toyos new have a tire diameter of 33. 8" and turn 614 rev per mile
The Coopers have a new tire diameter of 32. 76 and turn 638 rev per mile.

Sooooooooo... my question is--

Will I damage anything in the transmission/transfer case by running tires that are approximately 1" difference in diameter on each axle??

TIA

 

[HBarlow]

If you engage four wheel drive on dry pavement or any surface with good traction you will create a stress. I don't know if it will cause damage but on paper your tires will be trying to force your differentials to spin at different road speeds. Probably not good.

 

[seafish]

Thanks Harvey... I do sometimes use 4wd around my ranch in the winter, but only rarely, and in slick conditions.



Anyone else ??

 

[GaryOwen]

I think your Toyos are 33. 8" from what I could find. Since they are 75's instead of 70's, they should be taller than the Coopers.

 

[seafish]

I think your Toyos are 33. 8" from what I could find. Since they are 75's instead of 70's, they should be taller than the Coopers.

OOOPS you're right. . typo in the first post, corrected!!

But what I would like to definitevely know if running the 2 diffrent sizes on each axle will negatively affect the transfer case or anything else while driving in 2wd OR 4wd.

 

[rscurtis]

It shouldn't matter in 2WD. However, I would fit the taller tire to the front axle so that in 4WD, it tends to pull the truck as opposed to having the rear try to push it.

 

[goodguys75]

I would not do that, why

 

[S.Morris]

If you only use 4wd off road in slick conditions you might be okay.



In anything but these conditions you will be putting a bind on your driveline at all times that you use 4wd.



The transfer case will probably take the brunt but all ujoints and etc will suffer.



I would not recommend doing this for any length of time.

 

[04blackcherry]

You would effectively be changing the gear ratio of your vehicle; front to back.

 

[MChrist]

Doesn't one inch diameter equal 3. 14" circumference? So every revolution would be over 3" difference. I would think that would stress things a bit.

 

[seafish]

Doesn't one inch diameter equal 3. 14" circumference? So every revolution would be over 3" difference. I would think that would stress things a bit.

Well when you put it THAT way, it does sound like alot of diffrence if the front of the truck is trying to drive 3" farther then the back of the truck... ,

Does that mean I'll get there faster too?? :-laf:-laf

But seriously, this is NOT looking like a good idea, BUT I would like to clarify that this stress will ONLY happen it 4WD when the transfer case locks things together, or will stress ALSO happen in 2WD... . I am NOT really sure about that given the newer transfer case design.

AGAIN... thanks for all of the input!!

 

[Dieselnerd]

It will be fine in 2WD. Front driveshaft spins, but from the rotation of the front wheels only. It is not connected to the transfer case unless you are in 4WD.

 

[d6c]

Shift on the fly will be a bad idea also... full stop to engage 4wd... . then the binding SHALL begin.....

 

[rscurtis]

That's the main downside of the whole idea, probably worse than using two different tires even if they were the same size.

 

[BigPapa]

Just put the Cooper's on one side and the Toyo's on the other. If you make a lot of left hand turns, put the Toyo's on the right.





































:-laf

Scott

 

[AH64ID]

I would not do it if you ever plan to put it in 4wd. Unless there is zero traction you will create binding and excessive wear on your u-joint, axle shafts, and transfer case.

 

[seafish]

Just put the Cooper's on one side and the Toyo's on the other. If you make a lot of left hand turns, put the Toyo's on the right.

:-laf

Scott

:-laf:-laf





Thanks guys... I get it now, probably WON"T do it... Likely I'll get another pair of Toyos, run the full set out, and THEN switch tire sizes.





Thanks Again!!!

 

[AABEN]

If it was me I would NOT do it. Repair will be a lot more tham jest a little Money.

 

[RPosey]

BigPapa, you made me laugh, thanks.

 

[SRay]

Run the toyos on the front and the Coopers on the rear, measure from the ground to middle of hub with coopers on, and adjust air pressure in the front until the measurements are the are the same front to rear. This is the best way to equalize the front to rear.



The front will be heavier due to the weight of the Cummins and will push down more on the tires and will look flatter than rear of the same pressure. I run 35 psi front and 20-25 psi rear to equalize them out. When I add a load, I air up the rear to compensate. This way there isn't much binding at all. Plus I've done different sizes front and rear already.



Just in case everyone ask why my air pressure is very low, the tires are large in size and has a large volume of air inside. The more air, the more lift. Also at 40 psi only 4-5" of the tread touches the ground instead of the actual 12. 5", so I lowered to get the entire width on the road.



Shawn