87lc2

Just got this car and the front inner tires are chopped pretty good. Vibrates around 45-55 mph. Alignment is ok, what else would cause this? Dont want to put new tires on just to ruin them. Also, how can I tell what gears I have? Is there an identification tag anywhere? I pretty sure theyre stock, its a 94 Formula A4

WhyHelloOfficer

iTrader: (5)

A vibration from the tires is commonly caused by them being out of balance. We'll assume that is the culprit and not bad front-end parts. If you continue to drive on tires that are out of balance, you can eventually do some damage to the front-end.

Be sure the alignment is correct and within spec (not just the toe adjustment, but camber and caster too) and purchase some new tires and have them correctly balanced. If you can, look into road force balancing. Its slightly overkill, and more expensive -- but its the best way to get it done.

To know what gears you have, I'd say the easiest way (yet not very accurate) is what RPM you are at, at 60mph. The only other way would be to decode your VIN (which I can't find right now) and find out whether you have a regular axle or the 'performance rear option' with the car. My car has the factory 'performance rear' with 3.23s. At 60mph I am right around 2000 rpms.

dhdenney

iTrader: (53)

Be sure to tell him which transmission you have.

urbanhunter44

iTrader: (1)

The VIN won't help, RPO codes will though.

To find your gear ratio put your trans into it's 1:1 gear, for an auto its 3rd gear, for a stick it's 4th.

Then drive 70mph with you foot slightly on the gas (not coasting). If your RPMs read 2,730, then you have 2.73s, if they say 3,230, then you have 3.23s, and 3,420 for 3.42s. This method works with any gear ratio.

Sounds like you need an alignment and some new tires.

LT1Falcon

iTrader: (3)

another way is to twist your driveshaft by hand and however many driveshaft rotations it takes to make the rear wheel turn 360 degrees is the gear u have. example: if it takes about 3 and 1 quarter driveshaft turns, then you have 3.23's

87lc2

Im at about 3500 on the highway at 70....were 3.42 gears an option as Im sure they were never changed in the car As far as the front tires, what CAUSES them to get chopped on the insides. I know I need new tires, but I want to know what causes this before I do to prevent it from happening again
thanks

Ralls

iTrader: (32)

Can you get a picture of the tires? Looking at the type of wear pattern will somewhat determine what's wrong. If the wear seems to be at an angle and the tread has a lip on it, then you probably need toe adjustment. If it's a straight even wear, then it's probably a camber issue. Run your hand along the tread to feel the pattern too.

the_merv

iTrader: (88)

Is that in OD..cause with my 3.73's, I am about 3000 at 80 mph..

87lc2

Urbanhunter44 said to check out my rpm in 3rd (1:1) with an A4. In OD, im at 2400 at 70 mph...

LT1Falcon

iTrader: (3)

ide say less than 3.23 in that case. im at about 3000 in 3rd at 70 mph, although my tires are a little smaller than yours, ide say you have 2.73's. isnt there some rule like if you have the option of putting your car in 1st gear in the stock console, you have 3.23 and if you are locked out you have 273's?

urbanhunter44

iTrader: (1)

one thing to remember too is that the stock tachometers are NOT accurate in these cars. I bought an aftermarket one after verifying that mine was off by almost 200 rpm.

LT1Falcon

iTrader: (3)

that is true, mine is off by about 200 rpms also, and my speedometer is off by about 3 at 70 mph

87lc2

yea, I figured the factory tach wasnt the best to start with...What about decoding the VIN? Someone mentioned that before, what digit verifies the rear?