7 replies to this topic

[carld]

In the spring of 2014 I purchased two LT265/75R16 E rated tires to replace only the back the stock P245/70R16 tires and kept the stock tires on the front.  I drove about 7000 miles in 2014 and realized I had made a big mistake (can't put it in 4 wheel drive with different size tires).  So in 2015 I got three more  LT265/75R16 E tires for the back and the spare.  Since then I've driven another 10000 miles.  The tires have very little wear on the order 0.1 inch in tread depth. Bottom line is I have the following situation:

 

17kmi (front) 45 psi

10k mi (back) 50 psi

 0 mi (spare) 50 psi

 

Doing the math, I can equalize the miles in 4 rotations after driving 17k mi twice and 10k mi twice.  Starting out I switched the 10k pair to the front and 17k to the back and then switched the 0 mi spare with the drivers side 17k, since the camper weight is mostly on the rear driver side.  

 

Miles Driven:    0     17k    17k    10k    10k

Drivers Front: 10k   27k    34k    44k    54k

Pasngr Front: 10k   27k    34k    44k    54k

Drivers Back:   0     17k    34k    44k    54k

Pasngr Back: 17k   17k    44k    44k    54k

Spare:            17k   34k    44k    54k    54k

 

I’m at 0 miles driven and headed to Alaska on May 1, a round trip 10k miles.  I put 45 psi in the two front tires, and then to help equalize the rolling diameters for the mismatched rear tires,  I put 50 psi in the 17k and 45 psi in the 0.   A test drive on the highway feels very stable. 

 

[Mickey Bitsko]

Not sure if I would EVER be capable of figuring all that out..

 

Have a safe trip, sounds fun.

[Foy]

I'm not sure I see an issue here.  Even with the mismatched front/rears after replacing the rears, it's not a "can't put it in 4WD" situation for the simple reason that when on a non-paved surface, be it a graded gravel road or a two-track trail, there's enough slippage between the tread and the ground to preclude drive train "wind up".  No, I would not want to go flying down a graded gravel road in 4WD at 45 mph on those mismatched tires, but judicious use of 4WD on an as-needed basis would not be a problem, IMHO.

 

And certainly there is no problem with the slightly uneven wear on the now matched set, though your efforts to equalize wear are admirable.

 

Foy

[carld]

Yes, but with a change in tire pressure you can change the rotational radius for tires.  The 0 mi tire tread depth was on the order of 0.1" more than the 17k mi tire, which is not much.  Changing the pressure in the 0 mi tire will help.  Makes you think if you have a 4x4 with a camper and run uneven pressure due to the camper loading the back tires.

[Durango1]

With respect I will say this thread is the definition of "OCD"!

[PaulT]

With respect I will say this thread is the definition of "OCD"!

That's CDO. Must have letters in alphabetic order.

Paul

[Kolockum]

I notice that the tires on the back of my truck wear a lot faster than the tires on the front. It was the same way with my jeep wrangler. I just accepted that the tires are going to be different sizes. The drive wheels wear relatively fast. I just make sure I rotate the wheels when necessary.

 

The only time slightly mismatched tires cause problems are with locking differentials on pavement (always bad) or if there is an actual size difference i.e. 31" matched with a 32" tire and driven on for a long period of time. 

[carld]

So when I noticed that I had made a mistake with the 265/70  front and 265/75 back, I  engaged 4WD to get out of a parking area onto the paved rode.  Once on the pave road I tried to shift out, but no go.  I drove 1/4 mile to the trail head to pick up my friends and was back on to the dirt.  Still no go.  So when this is a problem you need to put it in reverse and back up a little.  Finally it shifted back into 2WD.  Now I just want to keep the ware even so there is less stress on the system. Which includes the spare.  By rotating the tires with the spare you can get 20% more out out of the tires. I've already put about $1000 into the 5 tires, although I got 16000 mi on the 265/70 and traded them in for two /75 at an net $200.