Awd Different Tire Sizes.

[04CHASE]

im looking at changing rims to somethine with different rim widths and different tire sizes,

 

the overall height is what counts , the tired im going to use are going to have a difference of as much as .6 of an inch . im wondering if everything will be ok , or should i run exact same tires. i know the stock spare tire is a bit smaller than the stock 20 inch diameter and since they provide that with the truck id assume its ok to run that but probably not meant for long term use.

 

any ideas ?

[12'SROCK]

i think you would be fine cuz you are changing all 4 tires so there shouldnt be an issue

[evallejo]

I'm no expert at this man, but for an AWD, you should try and match your tires' OD as close as possible. It is my understanding that width is not too big a deal, but a difference in OD as much as .6" can wear out your awd drivetrain components considerably fast in the long run, and as you noted yourself, the spare is not meant for long term use. You want to match the number of revolutions per mile for each tire.

 

Like I said I'm no expert, but I would try to get the OD closer if possible to being the same all around. This sounds like it will be pretty cool, though, I'm guessing you're going with Asanti's? Either way, whatever you decide, good luck.

 

EDIT: Never mind the question I just saw your poll on the wheels.

Edited February 20, 2008 by E-man (see edit history)

[kelleyperformance]

you might get some cel codes, since the front and rear speed sensors are gunna be seeing different revs per mile. but im not sure if that small of a difference will set anything off.

[12'SROCK]

EDIT: oops i forgot your runing different tires in the back than the front. . . . . .i would keep them the same for all 4 corners

[usabodyguard]

wider i dont see an y issue, taller yea... they wont spin at the same rate and im thinking that could play tricks on the transfer case / pcm but thats only from a common sense point of view... i could be wrong.

[AUTOGUY]

You might want to look into this before buying tires. I was always sunder the impression on an AWD or 4wd vehicle the tire sizes needed to be the same. Since your AWD is running ALL the time, it might be even harder on the drivetrain components. On the other hand, since the AWD transfer case acts as a differential as well, it might not be as much of an issue. I would check with an EXPERIENCED Tech at a local GM Dealer before making the committment.

 

I was talking to a frind that runs a tire shop last week about a Magnum AWD that a customer wants to run 20's on, and he did mention that the BMW X5 and some other AWD SUV's come with staggered tires and AWD. I would assume that since it comems from the factory this way, this was factored in during the initial desing of the vehicle.

[montanass]

I'm no expert at this man, but for an AWD, you should try and match your tires' OD as close as possible. It is my understanding that width is not too big a deal, but a difference in OD as much as .6" can wear out your awd drivetrain components considerably fast in the long run, and as you noted yourself, the spare is not meant for long term use. You want to match the number of revolutions per mile for each tire.

 

Like I said I'm no expert, but I would try to get the OD closer if possible to being the same all around. This sounds like it will be pretty cool, though, I'm guessing you're going with Asanti's? Either way, whatever you decide, good luck.

 

 

[2004Denali]

OD does make a huge difference, you will put undo wear and tear on you T-case, nothing to do with the computer, these unit are completely mechanical. but if one set of tires are a different size it will think one is loosing traction and start shifting power to the other set, which in turn would cause your transfer case to work harder.

Mark

Edited February 20, 2008 by 2004Denali (see edit history)

[JF-03-SS]

AWD should have same tire all the way around (something to do w/ the clutch packs inside transfer case)

[Justin Lamanna]

stay with the same size all around, more functional.

 

IMO though

[bobwrench]

Way I understood original post, he plans to keep all four the same as each other, just go to different diameter for all four. This should be perfectly acceptable, other than speedo won't be correct. Most later computers allow you to change tire diameter in their programing to compensate for this, don't know about one in SS though.

 

As long as all four corners are the same, no real problems. Different size front to rear and better grab your wallet! This will even come into play if one tire in a 1/2 worn set is damaged and must be replaced with a new one,,better buy all 4.

 

Bob

[AUTOGUY]

Way I understood original post, he plans to keep all four the same as each other, just go to different diameter for all four. This should be perfectly acceptable, other than speedo won't be correct. Most later computers allow you to change tire diameter in their programing to compensate for this, don't know about one in SS though.

 

As long as all four corners are the same, no real problems. Different size front to rear and better grab your wallet! This will even come into play if one tire in a 1/2 worn set is damaged and must be replaced with a new one,,better buy all 4.

 

Bob

 

No, he is talking about going a bit taller in the rear than in the front.

[2004Denali]

AWD should have same tire all the way around (something to do w/ the clutch packs inside transfer case)

there are no clutch packs.

it is the Viscous Coupling you will over work

http://www.denalitrucks.com/documents/serv...-149%20view.htm

Edited February 20, 2008 by 2004Denali (see edit history)

[Black2003SS]

#1 You will destroy the differentials as they do their job, slipping. It will create more heat in the diff and I would seriously estimate life expectancy to be less than 5k miles per diff (both front and rear). It slips now, but will have to slip more as the rear wheels will be spinning slower than the fronts if you go taller in the rear. I'm not 100% sure this can play into the transmission itself, but I would imagine its a possibility.

 

#2. You will lose your abs, it will disable itself and throw a constant ABS light. The ABS relies on the speed sensors to tell if any wheels are slipping or not. The ABS is designed to read all four wheels are going the same speed and when one slips, it tells because that wheels speed changes from the others, so it will activate the ABS. When it is constant, it throws a trouble code and deactivates. I personally would not want to live without ABS, even if it is AWD and you live in Cali. If you need to slam on the brakes on a low mu surface in the rain, you could end up backasswards and shiny side down in a ditch real fast, no matter how good of a driver we all think we are. I used to program ABS, TC, and VSC on GM vehicles for TRW, so this is how I know what I am talking about.

 

#3 You can recalobrate your speedometer to be correct as the speedo only relies on the rear two wheels for vehicle speed. That wont be an issue.