Mis Matched tires....think I messed up the Quattro

[WJolly]

Hey Guys,

Before everyone tells me what I did was wrong I will admit it, I ran different size tires in the front than in the back...not thinking about quattro or the % difference.
I realize now what my mistake was all I am asking is where I can go from here...Car feels funny under acceleration.....almost shaky/vibrating the same feeling you get when you cut the wheel hard over and push the gas.

What needs to be replaced...we talking an entire transmission/drivetrain? does anyone have any pictures of under the car so I can see what I need to replace or be able to maybe check?
right now the car is sitting in my driveway until 4 matching size tires come in the mail and I have them thrown on...What I am trying to find is whether I made irreversible damage by putting the 50 or so miles on my car and it will go back to normal when I put matching tires or whether I just need to throw them on and get rid of the car...

any help would be appreciated, not too pumped up so try not to be so negative

[dbens]

First of all it all comes down to rolling diameter. What size were the the tires you ran? I beleive within 3% should be fine

[torquesteer]

How much mismatched are we talking about here? (width? rolling diameter? both?) Which torsen system version do you have? How long did you drive with the mismatch?

[dparm]

Front to back mismatch is not as bad as side-to-side.

[Tropicgreena4]

if anything would need to be replaced, I would think the center diff would have taken a brunt of the damage... but like the others said, if you're within 3% overall rolling diameter, you should be fine.

[ilko]

What tire sizes were you running? You may be in the clear. Generally you should get ABS/ESP lights coming on when you have significantly different rolling diameters between the tires.

[WJolly]

Hey thanks for all the quick responses and not being dicks about it

235/35/19 in the front
255/35/19 in the rear...


im doing all 255 all the way around


but the stocks back on and didnt notice a significant vibration so hopefully all is well???

lolololol

[rollerton]

You're fine. Don't worry about it. You were just feeling the ABS fight you. Think about all the Audi's (and Vw's) in history that were sold with TEMP spare tires, THOSE are tiny and never hurt anyone. Do you think Audi would design a drive-train that could be wrecked just by driving a while with mismatched tires?
No sweat, just get closer sized rubber.

[b spot]

Front to back mismatch is not as bad as side-to-side.

Not saying you're wrong, but that makes no sense to me. Aren't the front and rear diffs essentially open, with brakes acting as the "electronic locking differential", and the front back constantly coupled via Torsen diff? I thought front/rear would be much worse.

[ilko]

What are the wheel widths? Aspect ratio might be negated depending on the width of the wheel.

[torquesteer]

Not saying you're wrong, but that makes no sense to me. Aren't the front and rear diffs essentially open, with brakes acting as the "electronic locking differential", and the front back constantly coupled via Torsen diff? I thought front/rear would be much worse.

Essentially what this means is that tires on the same axle should be the same size and tires on different axles can have different diameters. In this case, front and rear diffs are locked since they are the same, respectively, but the center diff is slipping (or open). It doesn't make sense until you think about it since only an utter idiot would run different diameters or widths from one side to another.

[WJolly]

for reference

[Tech/Sales@JHM]

Hey Guys,

Before everyone tells me what I did was wrong I will admit it, I ran different size tires in the front than in the back...not thinking about quattro or the % difference.
I realize now what my mistake was all I am asking is where I can go from here...Car feels funny under acceleration.....almost shaky/vibrating the same feeling you get when you cut the wheel hard over and push the gas.

What needs to be replaced...we talking an entire transmission/drivetrain? does anyone have any pictures of under the car so I can see what I need to replace or be able to maybe check?
right now the car is sitting in my driveway until 4 matching size tires come in the mail and I have them thrown on...What I am trying to find is whether I made irreversible damage by putting the 50 or so miles on my car and it will go back to normal when I put matching tires or whether I just need to throw them on and get rid of the car...

any help would be appreciated, not too pumped up so try not to be so negative

WJolly-

By running two different over diameter wheels in the front and rear, you have a chance of ruining your Center Differential. If you would like, you can send in your Center Differential to us and we will take a look at if for free and let you know if your Center Differential is in good condition or toast.

Give us a call if you are interested and we will be more than happy help!

[simplesedan99]

^ and this is one of the many reasons why we love you guys

[dylanbike1]

^ and this is one of the many reasons why we love you guys

+1

[Silversrfa18T]

I noticed that as soon as i saw it. But it seems everytime i wave or try to say hello it's like you have an attitude. So i didn't even bother to say anything to you bout it. If you are wondering who i am, i'm in the 2005 b6 s4. Windows are not tinted. It's a few guys on post with S4's. My buddy has a white b6 s4, and 2 others has the b8 s4. Maybe now that i'm speaking to you we can all meet on post and kick it, share info ect... But i know a few things about our cars. My friend knows much about these platforms.