Help!: I may be seriously damaging my AWD system, wheel and tire guru's please enter

[ridelikeme]

It was time for new tires last week so i ordered a new set of Pirelli P-Zero Nero M&S tires.
I had them mounted and balanced onto my SLK 55AMG rims, this is where the issues began.

The tires are The rims are
245-40R-18 Rear 18x9
225-40R-18 Front 18x8

Orignally the rims had 245-35R-18s on the rear significantly worn, and there was absolutely no issues

When i got the car back it was vibrating immensely during acceleration, and i could not figure out why. It ends up that they Mounted the passenger side of my car correctly, however on the drivers side they mounted the Rear rim
(18x9) to the front tire (225-40) and put it on the front. At the drivers side rear they mounted the 18x8 with the 245-40. I only drove on these tires for 30 km tops, and had it back at the shop the next day.. needless to say pissed off ... anyways now my car is still vibrating and pulsating during accelerations bad, and starting to get worse. Its even a slight bit rough while off the pedal. Question is, did the shop most likely fuck something up, or is my tire sizing off significantly enough that it is causing issues with my AWD system. If it helps, the probelm is worse while accelerating uphills. Any help would be much appreciated gents.

Regards,
Kidd

[ridelikeme]

Here is the tire size calculation i used, assuming i would be safe



Stock Tire - 225/40R18 Search Tires Tire 1 - 245/40R18
Section Width: 8.85 in 225 mm Section Width: 9.64 in 245 mm
Rim Diameter: 18 in 457.2 mm Rim Diameter: 18 in 457.2 mm
Rim Width Range: 7.5 - 9 in Rim Width Range: 8 - 9.5 in
Overall Diameter: 25.08 in 637.03 mm Overall Diameter: 25.71 in 653.03 mm

Sidewall Height: 3.54 in 89.916 mm Sidewall Height: 3.85 in 97.79 mm
Radius: 12.54 in 318.51 mm Radius: 12.85 in 326.39 mm
Circumference: 78.79 in 2001.2 mm Circumference: 80.77 in 2051.5 mm

Revs per Mile: 829.3 Revs per Mile: 809.0

Actual Speed: 60 mph 100 km/h Speedometer1: 58.5 mph 97.5 km/h
Speedometer Difference: - Speedometer Difference: 2.509% too slow
Diameter Difference: - Diameter Difference: 2.46%

[yung turbo]

if you feel that way then get a tranny, rear diff fluid change and the new fluid should lube it enough to i guess clean up the system.

[heateris]

i'm no guru, but i always belived that quattro likes the same size all around.

[AudiA4Turbo22]

tires and sizes are fine, did they use hubcentric rings if not they cause vibration

[dirtybrd]

As long as you are within 2-3% overall rolling diameter you'll be ok. And you only 2.46% off. Usually a vib on accel is a bad axle, I'm not sure why it would appear after new tires though.

[ridelikeme]

thanks for the help dirtybrd, im going to try to find a set of stock rims to throw on and go for a spin. If that damn shop messed up one of my axles there will be hell to pay. Is there any way to check the axles? will there be excess wheel play or anything like that? and yes i did use hubcentric rings.

[dirtybrd]

Not really.

[bwoy1981]

Off topic: ^^^ By the way Chris... My vibration.... torn boot on the driver's front axle and now I get a knock on a full turn to the right. Should I do boots or axle completely?

[vdubstreets]

the vibration could be from a poorly balanced wheel(s). They could have forgotten or just did a crappy job balancing one or more of your wheels. I would say swap your wheels around see if the vibration happens on any other wheels but i guess you cant. Second thing is do you have any hubcentric rings as mentioned before.

[F16HTON]

Also the tires may be directional and mounted incorrectly.

[GhostSquadGarage]

Off topic: ^^^ By the way Chris... My vibration.... torn boot on the driver's front axle and now I get a knock on a full turn to the right. Should I do boots or axle completely?

Once you hear the clicking\knocking it's too late.. You need to replace both.

[Boosted3.0]

ridelikeme- check your cv boots for tears. Sounds like a bad axle

[dirtybrd]

Off topic: ^^^ By the way Chris... My vibration.... torn boot on the driver's front axle and now I get a knock on a full turn to the right. Should I do boots or axle completely?

Axle.

[A4p]

Have they yet balanced the wheels??

[kbasham03]

I had the same exact problem on my talon, after new rims and tires. I tried putting stockers back on, re-balancing, and even changed my driveshaft and carrier bearings, and It just ended up being an axle.

[ridelikeme]

so is there any way to diagnose the problem? im not going to start randomly replacing axles. there needs to be some additional signs or symptoms. i wish i still had my stock rims, it would make this much easier

[GhostSquadGarage]

Look for leaked fluid all stained under where your CV Boot is.
You should notice a "tar type" gunk as well as the torn or broken CV Boot on the side it's doing it.
That would be the boot and axle you need to replace.

[kbasham03]

Look for this. This one is completely toast but you get the idea.