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Discussion Starter · #1 ·
Given that there's almost no way between front and rear to perfectly match overall diameter (though you can get within 2-3mm) and load when using staggered wheels, is there any issues with possibly prematurely wearing the clutches in the center diff since Quattro is full-time?

-Ray
 

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Discussion Starter · #2 ·
Since nobody has responded, I'll just point out that this is a prevalent issue with the BMW 3xi owners and IS250 AWD, etc.

I'm going to venture to say that you can stagger the offsets to get that aggressive look, but if you don't match the widths, you're eventually going to wear out the center diff / transfer case. Anybody hoping to keep their A5/S5 Quattro for the long haul should keep this in mind.

I posted my ideal sizes a while back coming from a RWD background, but in light of this, I'll revise this and say my recommendation would be 20x9.5 all around, ET30 in the front, ET23 in the rear. The 20x9.5 +23 is equivalent in terms of fender clearance as my previous calculation of 20x10 +27 --- and really you don't need the extra half-inch of width, the car has plenty of traction.

-Ray
 

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Since nobody has responded, I'll just point out that this is a prevalent issue with the BMW 3xi owners and IS250 AWD, etc.

I'm going to venture to say that you can stagger the offsets to get that aggressive look, but if you don't match the widths, you're eventually going to wear out the center diff / transfer case. Anybody hoping to keep their A5/S5 Quattro for the long haul should keep this in mind.

I posted my ideal sizes a while back coming from a RWD background, but in light of this, I'll revise this and say my recommendation would be 20x9.5 all around, ET30 in the front, ET23 in the rear. The 20x9.5 +23 is equivalent in terms of fender clearance as my previous calculation of 20x10 +27 --- and really you don't need the extra half-inch of width, the car has plenty of traction.

-Ray
'
+1 for everything you've written.

Ian.
 

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That makes me happy about my 19x9's all around I ordered, and the fact that the Professor gave you a plus 1!:D:rolleyes:
 

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I'm going to venture to say that you can stagger the offsets to get that aggressive look, but if you don't match the widths, you're eventually going to wear out the center diff / transfer case. Anybody hoping to keep their A5/S5 Quattro for the long haul should keep this in mind.
But I wonder how much of an issue this would be for those folks who don't really drive their cars hard. In other words, if you get a staggered setup and just drive the car in a "leisurely" manner the majority of the time, would this potential issue be as likely to occur?

BTW, it's possible to maintain an overall diameter difference of only 0.5mm (0.02") between front and rear if you go with 255/30/20 front and 305/25/20 rear on a 9" and 11" wheel setup.
 

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Discussion Starter · #6 ·
But I wonder how much of an issue this would be for those folks who don't really drive their cars hard. In other words, if you get a staggered setup and just drive the car in a "leisurely" manner the majority of the time, would this potential issue be as likely to occur?
Even further research indicates that the Quattro system is a torsen type-3 which is naturally designed to continuously balance an uneven load (making the 60/40 torque split possible), and doesn't have a clutch pack or any other wear out item. It is designed to last the life of the vehicle.

BTW, it's possible to maintain an overall diameter difference of only 0.5mm (0.02") between front and rear if you go with 255/30/20 front and 305/25/20 rear on a 9" and 11" wheel setup.
I agree. There's more variation than that just from different tire pressure or even payload. It still stands that staggered widths are absolutely unnecessary for this application, and may alter vehicle dynamics. However, it's far easier to find a staggered width set of wheels than it is to find identically-widthed staggered offsets, especially if you are not ordering custom-made wheels. With that in mind, of course just do your best to match overalls by calculating the profile ratio as you have done.

-Ray
 

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Even further research indicates that the Quattro system is a torsen type-3 which is naturally designed to continuously balance an uneven load (making the 60/40 torque split possible), and doesn't have a clutch pack or any other wear out item. It is designed to last the life of the vehicle.
Well great! That's a good thing!
 

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Well, I can't say that the diff' will wear out, but there's no doubt, that staggering the wheel diameters will affect how it is operating during driving - any driving, not just hard driving. I think for high milers, a few percent difference may well affect the life of the diff'.

In the 90s there was a spate of Jeep Cherokees with failed diffs because they were being driven around town in 4wd and over-working the diff, which was designed for off-road conditions (or on US roads which do not have corners!) where there's more give between the road and tyres, so it just shows that things should be used as designed.

It may well be absolutely fine and well within the design life of the components and i would not expect any problems from such relatively small differences in wheel diameter until many tens of thousands of miles, bearing ('scuse the pun) in mind that they are design to do a few hundred thousand miles. Having said that, it's not a modification I would consider doing for a car that wasn't designed in transmission, suspension and dynamics terms... But that's just me.
 
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