Tyre profiles - Front and Rear

[derekdcosta Lurker Find all posts View Profile Close derekdcosta]

I have hunted everywhere and cannot find a definitive answer to my problem.
I have new BFG 265/65 x 17 tyres on my 2004 Prado (VZJ125)
I also had a tyre blowout with less than 30,000 on the tyres. ( My spare was a Dunlop)
Problem is the BFG dealer has no stocks of the 265/65 tyre.
They do have 265/70.
So I replaced both rear tyres with 265/70 x 17
With a 5% difference in the tyre profile ( translates to 12.5mm increase in diameter) am I risking diff or transmission wind up
Should I also replace the front tyres?



Derek

[Guest Close Guest]

It translates to 26.5mm increase in diameter. All tyres need to be the same size. Is it worththe cost of 2 tyres to find out that there is damage to the driveline down the track?

[Hazza Advanced Member Find all posts View Profile Close Hazza]

Agree with amts. Also keep in mind your vehicle is not road worthy with different size tyres, well at least in some states.

Hazza

[mathewmeldrum Member Find all posts View Profile Close mathewmeldrum]

That is a really common size tyre in Australia, just keep looking around, or replace all tyres so they are the same size.
good luck

[derekdcosta Lurker Find all posts View Profile Close derekdcosta]

I am in East Africa, Kenya
as long as we have tread on our tyres they are legal!
And yes I will get 265/65s eventually, but need to run this vehicle in the meantime

[derekdcosta Lurker Find all posts View Profile Close derekdcosta]

I thought I had posted this earlier, but to recap
New tyres cost US$500 a piece so replacing all four is a very expensive puncture.
Whilst I accept that it makes sense to replace all 4 tyres because we can't be sure what damage may be caused... I can buy a new gearbox or diff for the cost of the 4 tyres!
So thanks for the advice everyone, but I really would still like to know if there is any negative effect to running a 5% higher profile on the rear of an AWD. will the added 26mm diameter wind up the diff or gearbox.
Surely the truth is out there?

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

There are 3 diffs in your Prado, front, rear and centre. The Differential allows wheels to rotate at different speeds, such as going round corners where inside wheels and outside wheels turn at differnent rates and front to rear may also differ. So as long as the Centre diff remains unlocked then at least in the short term it should not be a big deal. The centre diff will have to work hard to allow for the difference and it may fail prematurely but I wouldn't think you will get transmission windup.

If you were to lock the centre diff, then the front and rear wheels need to spin at the same speed, so transmisson windup is highly likely in this case. Something needs to give in this case, if the wheels have too much grip and cant slip then either the trans will wind up or something will break.

So I would think that having all tyres the same is obviously the best bet, if you must drive with different tyres then as long as you dont lock the centre diff it should work, whether this leads to premature failure I don't know as I have not heard of anyone doing what you suggest.

If you lock the centre diff then chances are pretty high that something will go bang.
Thats my take on it anyway

Cheers Andrew

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

As long as you don't lock the centre diff it shouldn't do damage.
But I wouldnt run 2 different size tyres unless it was an emergency.

[Ron.H. Junior Member Find all posts View Profile Close Ron.H.]

The type of road you are driving on may help you, if it is dirt or gravel and bumpy then the wheels can turn back to not give you the wind up but not if you are on a solid surface like bitumen tar or concrete, not sure what you have there.

[derekdcosta Lurker Find all posts View Profile Close derekdcosta]

Thanks guys, I spend about 75% tarmac driving and 25% murram/gravel/sand so the constant even wheel rotation will be quite high.
I will buy 3 tyres - 2 new 265/70s to replace the 265/65s on the front and as soon as the dealer gets stock of the 265/65 I shall buy another to complete the set... so now I have tyres for 6years!!
But I am still keen to have a definitive answer to this.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Maybe he could run the 2 larger tyres on the same side of the car? There is give in the system to allow for different speeds of all wheels when cornering.

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

Maybe he could run the 2 larger tyres on the same side of the car? There is give in the system to allow for different speeds of all wheels when cornering.

I wouldn't do that, on the front the vehicle will pull around when braking, the LSD will steer the vehicle on the rear.
All sorts of funny stuff going on then
It's ok how it is while its unlocked.

[Kitbags Junior Member Find all posts View Profile Close Kitbags]

For a definitive answer start at the logical place:-
1 Your Prado's Owners Manual (only progress to 2 and 3 if you are not completely satisfied with 1)
2 Phone Toyota customer service
3 Phone Toyota Regional Service in your state
Pradopoint forum is a good place to get opinions and the benefit of other members experience. The above threads contain good advice. This info backs up what is in your owners manual. Another real advantage of reading Pradopoint forum info beforehand is that when you do go aftermarket accessories shopping or deal with say Toyota you know what to look for and the questions to ask and also what to avoid in a product or service.