Putting 20" staggered wheels on an AWD coupe...
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2008-2013 Cadillac CTS Appearance Mods Discussion, Putting 20" staggered wheels on an AWD coupe... in Cadillac CTS Second Generation Forum - 2008-2013; Ok so I really would like a set of Vossen wheels for my coupe for summer but the problem is ...
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    MTL_CTS's Avatar
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    Post Putting 20" staggered wheels on an AWD coupe...

    Ok so I really would like a set of Vossen wheels for my coupe for summer but the problem is that since it is AWD this really limits my choices as far as tires. From searching it seems that the best solution is to run same size tires front and rear as much as possible, or, if you run a staggered setup, then the overall circumference front/rear must be either the same, or maintain the same front/rear rev per mile bias as the stock wheels/tires (stock setup has front turning 4 more revs per mile than rear). This is how I understand it but if I'm wrong then someone can chime in and correct me


    I have also spoken to a rep at Vossen Wheels and we have gone over some wheel and tire combos for 20x9's in the front and 20x10.5 in the rear and this is what we've determined:

    Option 1:
    The perfect tire size is 265/35/20 front and 315/30/20 rear imo.
    This keeps the same overall wheel/tire diameter as stock, and same front/rear rev per mile bias, and circumference of the tires is within .15" of stock circumference, and within .5" of each other.
    Problem is, the rep from Vossen says they have never installed 315's on a CTS or V coupe and he thinks they will rub in the rear fenders. He's not sure what mods might be required with putting 315's in the rear the widest they have gone on a coupe is 295's

    Option 2:
    Also ideal would be to run the same tires front and rear regardless of the staggered wheels. It's what I'm doing currently with my stock coupe 18" factory rims I have 245's all around for winter and have not had a problem.
    Problem with this is that with 9" wide in the front and 10.5" wide in the back, there is no tire size that will fit in the front and will not look totally stretched in the rear... 275's might be good on the rear wheel but will definitely rub in the front for example.

    Option 3:
    The only other tire combo I could think of is if I could run 245/35/20 fronts and 285/30/20 rears. This combo has the front and rear wheels/tires at almost the exact same diameter, circumference and revs per mile (the circumference is within .04" of each other ie a difference of only 0.05% !!)
    Only problem with this option is that the overall diameter is about 0.5" smaller than stock, which I'm not sure how that's going to look on a stock height CTS since I'm probably not going to be lowering the car... because of AWD ad the fact that I have to drive my car in winter too. Will the wheels and tires look small?? And will the wheel gap be even more than stock?


    So what do you guys think is my best bet?
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    Re: Putting 20" staggered wheels on an AWD coupe...

    Also there may be another even better option:

    If I go with 245/40/20 front and 285/35/20 rear, this wheel/tire combo will be 0.5" bigger than stock in terms of diameter, however the circumferece of the front tires will be 0.4" smaller than the rear (just like the on the stock tires) and thus the 4 rev per mile front bias is conserved!

    I think this is the best option and I like it best since first I'll probably not be dropping the car and second the higher profile of tires is good b/c we've got some pretty crappy roads around here...

    I'd like some opinions though!! What do you guys think?? Will this be ok with AWD? I don't want to break my transfer case

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Anybody have any opinions? I would like to order the wheels soon but I need to be 100% sure this wheel and tire combo is compatible with my car otherwise it will be a very costly mistake!!

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Ok so I have managed to get in touch with one of the engineers who worked on the AWD system in the CTS, he actually posts here on the forums. Basically he told me that the bottom line is that in any AWD vehicle, the ideal setup is to have same overall diameter on all 4 wheels so that the rev per mile for the front tires is the same as the rear. However in the CTS the design of the transfer case (as far as torque transmittal response time to the front and rear axles) favors the rear overspeeding the front, ie prefers to have slightly bigger tires on the rear, such that the front tires will turn about 4 times more per mile than the rear. If there is too much of a difference between front and rear rev per mile (more than 4), or if the rev per mile bias is transferred to the rear (slightly bigger tires in the front) then this could have adverse effects on the AWD system: clutch heat, noise, excessive driveline wear, poor handling, etc...

    Thus if you look at this case for 20" wheels, the ideal choice according to him would be:

    front 245/35-20 (diameter) 26.8in (revs/mile) 754
    rear 285/30-20 (diameter) 26.7in (revs/mile) 754
    But as you can see this combo is smaller than the stock 27.3" tires so might not
    look good unless you lower the car.

    Also acceptable would be:
    front: 245/40-20 (diameter) 27.7in (revs/mile) 728
    rear: 285/35-20 (diameter) 27.9in (revs/mile) 724

    Since in this case the front is still only turning 4 more times per mile than rear


    Hopefully this post comes in handy to anyone searching for info on aftermarket wheels/tires with AWD!!
    doozmlk, doozmlk, soku and 10 others like this.

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    Re: Putting 20" staggered wheels on an AWD coupe...

    What about for 22" rims? Thoughts on tire selection for '09 AWD?

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    Re: Putting 20" staggered wheels on an AWD coupe...

    lynk,

    Go here: http://www.miata.net/garage/tirecalc.html

    Basically as I said, you want ideally perfect split between front and rear in terms of rev/mile.

    If you have a 09, then you have a sedan and should have no problem running same wheels front/rear so there is no need for you to even have to worry about running a staggered setup. If for whatever reason you WANT to go with staggered wheels and tires then you can go up to +4 rev/mile to the fronts!

    HTH.

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    lynk2098 is offline Cadillac Owners Member
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    Quote Originally Posted by MTL_CTS
    lynk,

    Go here: http://www.miata.net/garage/tirecalc.html

    Basically as I said, you want ideally perfect split between front and rear in terms of rev/mile.

    If you have a 09, then you have a sedan and should have no problem running same wheels front/rear so there is no need for you to even have to worry about running a staggered setup. If for whatever reason you WANT to go with staggered wheels and tires then you can go up to +4 rev/mile to the fronts!

    HTH.
    Thx, now to just decide on wheels!

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Ok so yet another problem has arisen... In 245/40 frt and 285/35 rear there is only one matched tire choice available and that is pirelli pzero. Problem is the fronts are 470$ each and rears 505$ each, which is almost as much as the wheels cost LOL... Apparently this is a stock ferrari size

    So I'm wondering how bad is it to go with mismatched tires front/rear, beacause there are obviously many more and cheaper choices in this case. What if I stay in the same brand but just different model tire?

    My other option is to go with the "ideal" 245/35 frt and 285/30 rear (alot of choices at around 200-250$ per tire) but then I must also get a set of lowering springs for sure.

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    Did you figure it out??

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Well as of right now I'm leaning towards going with 245/35 frt, 285/30 rr, since this would be perfect split for the AWD system and I will likely lower the ride height with D3 or H&R springs (0.75"-1.00")it will look nice. Only drawback is that because of lowered stance and lower profile tires It will be more likely that I'll damage a rim or my front CTS-V bumper/lip since the roads around here aren't exactly perfect (in fact they are shit).

    Unless if someone chimes in and tells me that it would be no problem to run different tires front and rear I run mismatched tires on my other car for summer but it is RWD and pretty low tech compared to my CTS

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    Where are you located, I'm in Michigan and haven't had much luck finding anyone willing to deal with the AWD. Your information is the best I have found so far, about ready to just get a V.

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Any update i have an AWD 09 3.6DI and i'm looking to go 20" staggered!! Please help i have to go 20x9 in the front and 20x10 in the back.

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    Re: Putting 20" staggered wheels on an AWD coupe...

    Ok so I have found a set of (relatively) inexpensive tires 245/40-20 fronts and 285/35-20 rears... Yokohama advan sports are 330$ each for fronts and 360$ each rear... Gonna give it a shot the load rating is higher than stock so my wheel/tire guy has told me the ride will be harsher but should not be too bad
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    Quote Originally Posted by MTL_CTS
    Ok so I have found a set of (relatively) inexpensive tires 245/40-20 fronts and 285/35-20 rears... Yokohama advan sports are 330$ each for fronts and 360$ each rear... Gonna give it a shot the load rating is higher than stock so my wheel/tire guy has told me the ride will be harsher but should not be too bad
    Very useful info my friend, do you think this set up can work on a sedan RWD ? Im in the market for a set of wheels ans love the stagered look. Im even willing to do 19's for this matter

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    Re: Putting 20" staggered wheels on an AWD coupe...

    With RWD you don't even need to worry about rev per mile bias and overall diameter of the wheel and tire combo you have many many more choices available to you... In your position I would just run any tire size that is reasonably close to stock wheel/tire diameter so as to not affect speedometer/odometer... But even that can be reprogrmmed in the ECM through a recalibration by trifecta for example...

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