So I recently replaced two of my tires. I was running 205/60/15 all around and due to not having a job at the moment, am unable to purchase a full set of new tires. That being said, I did have a full set of 195/65/15 tires that were on Audrey when I bought her. Only problem is, two of those tires were no longer fit for use (down to the wear bars). So enterprising me decided to put the two 195's that were good on my wheels. My dad and I put them on and hand balanced them, no digital nothing around here. I now have the 195/65/15 on the rear two wheels and the 205/60/15 on the front two wheels. I took Audrey out to the courthouse to pay a speeding ticket and noticed an intermittent vibration when I'm doing anywhere between 45 and 75 miles an hour. It'll start, last for maybe a minute, and then disappear. I noticed a sweet spot around 80, but I don't feel comfortable doing 80mph all day long especially considering I just paid a ticket. Anybody out there have any ideas as to what is causing this? Pretty sure it's something in the suspension and not my drivetrain (motor mounts, transmission mounts, etc...) because the vibration is still there whether I have the clutch in or out. Any input is appreciated as always.

 

The prevailing opinion is to always match tire sizes by their rolling diameter when you have Quattro. If the tires arent within a few percent of each other, you'll end up smoking the diff. It sounds like you didn't do this math beforehand but you're in luck - those two sizes are 1.2% different so I would say the diff is safe.

Check all of your ball joints and suspension bushings, and make sure the CV joints aren't messed up. Honestly though, I'd take a trip to someone who can actually balance the tires - hand balancing isn't gonna do it.

 

Thanks Devil! I actually had posted earlier about tire sizes before I put the 195/65/15's on Audrey just to be on the safe side.

I was thinking the vibration had something to do with the balancing of the tires, but the newer tires that I put on Audrey are on the rear, not the front where the vibration seems to be coming from. Should I switch the fronts and rears and see if that makes any difference? If the vibration is still there after switching the tires (from 205 up front and 195 in back to 195 up front and 205 in back) then I should look into the front suspension? I'm not driving very frequently right now but would be able to take her out for a test.

 

Exactly right. You may have some abnormal front tire wear causing it, and that'd be revealed by swapping front to rear. If no change, look at everything in the front wheel wells - arms, axles, brakes, everything.