different size tires, effect awd system?

fandizzle

fandizzle

Forum Member
Joined
Sep 14, 2008
Messages
221
Location
brissy
Car Model
XT
Hay guys I currently have 215,75,15 sized tires and was wondering if i get a puncture and put my standard 205,70,15 sized tire on will i run into any trouble with the awd system?

Thanks, Mitch
 
The OD of a 215/75/15 is 712mm and a 205/70/15 is 669 so that is a fairly large difference. 43mm. I would suggest for as short a time/distance as possible.
 
For a short time it should be fine, just make sure the smaller one is one the front where there is no lsd. Long periods of time will start wearing things out though.
 
thanks for the replys. 2jz929 I dont have an LSD, so it should be sweet?
 
fandizzle said:
thanks for the replys. 2jz929 I dont have an LSD, so it should be sweet?
Click to expand...

That's what a differential is for, it evens out the drive in corners etc, so one wheel can be doing different (faster/slower) speed to it's opposite number. In this case the the wheels are rotating at different speeds and the differential is equalizing all this for you.

You will find that there will be no difference in the tyre wear as the original wheel will be rotating at its "factory" RPM at any given speed and the larger tyre will be rotating slower at that speed.

What is a problem is that it's illegal to fit 75 profile tires to your Foz (in QLD) and uneven profile tires, so if a cop pulls you up for one he'll book your for both :madred: not that i mind either way, just thought i should mention it :iconwink:
 
Not quite correct. If you have a tyre with a larger OD on one side and a smaller OD on the other the tyre with the smaller OD will wear out quicker than the one with the larger OD because it has to rotate more to travel the same distance.
It is not good for the car to do this and should only be done for emergencies. It will affect the handling,the ride and the mechanics.
It is not necessarily the profile of the tyre that is illegal but the OD of the tyre.
There are a few of issues here. One relates to compliance plates (speed and load ratings),one to state laws (you can only vary the OD by X amount) and one to insurance,both 3rd party compulsory and comprehensive.If you have an accident with illegal tyres and they investigate they WILL cancel you comprehensive and it can lead to you being sued by any injured third party as the insurance company can say that the modification,which it is, contributed to the accident, lets say 30% , therefore will pay 70% of a determined claim and the injured person can sue you for 30% of the claim.
 
Not quite correct. If you have a tyre with a larger OD on one side and a smaller OD on the other the tyre with the smaller OD will wear out quicker than the one with the larger OD because it has to rotate more to travel the same distance.

We are talking about the same thing, the difference is you are relating it to the larger tyre and I'm relating it to the factory tyre, and in fact the rotation of the tail-shaft in a straight line at a given speed is the same, the differential will compensate for the different tyre sizes, averaging the rotation of both the small and large tyre, the large tyre will be rotating at a slightly lower RPM then it would do normally and the small tyre slightly faster than normal.
The wear would not be noticeable in the short term. What is, as you stated, an issue is the uneven loads placed on the the tires/suspension and your points/wallet.

It is not good for the car to do this and should only be done for emergencies. It will affect the handling,the ride and the mechanics.
It is not necessarily the profile of the tyre that is illegal but the OD of the tyre.

I.E a space saver

There are a few of issues here. One relates to compliance plates (speed and load ratings),one to state laws (you can only vary the OD by X amount)

Try getting your car compliant for a different profile tyre on a standard rim, have fun and let me know if you succeed :ebiggrin:

And yes the overall tyre rotational distance is the regulation, i stated that the 215,75,15 tyre is illegal on Mitch's Foz and it is, this was for Mitch's general education, as i was unsure if he new, what he does with info is up to him.

and one to insurance,both 3rd party compulsory and comprehensive.If you have an accident with illegal tyres and they investigate they WILL cancel you comprehensive and it can lead to you being sued by any injured third party as the insurance company can say that the modification,which it is, contributed to the accident, lets say 30% , therefore will pay 70% of a determined claim and the injured person can sue you for 30% of the claim.

Insurance sucks, but i gotta have it :raz:

As for profiles, the 15" Foz is illegal with a 65 profile (in QLD), in theory :iconwink: although my 60 profile Yoko tires have a greater measured rotational distance and as such a greater height than the standard tyre and the regulations allow, so in theory should be illegal, but because it is printed in black on the tyre 215-60-15 it's ok, go figure :lol:

Rod
 
Last edited:
If you are auto non-lsd, put it on the rear and plug in the FWD fuse; otherwise as stated, put it on an open diff (emergency only)
 
Fandizzle. Not sure where that was going.
I think the message is don't do unless you have to and be aware that there could be insurance issues if something goes wrong.
That said, when i go on my trip i will be using Bridgestone 693's which are a 215/65/16 because that is what i want to use!!!:)
 
Last edited:
You must log in or register to reply here.
Back
Top