Greetings All,

Just bought a 2005 A4 last month. Noticed the car was pulling to the right. The Audi dealership first told me it was a combination of road crowning and my 18" wheels. Had a technician drive it - he noticed it was not just that. They adjusted my alignment and tow angle - and the car still pulled to the right. He switched the left and right front tires and now it pulls to the left!

Can tire condition (assuing pressure is proper and even on both sides) make the car pull like that? I want to get some expert advice before I blow a bunch of duckets on new tires if it is something much more sinister...

Cheers!

 

I know the grip of the tires can pull from side to side.....when I had drag radials on my old teg, it would do that.

 

That's really bizzare. I'm degreed in chassis engineering and I can't say that I can conceive of many things that would cause that except a tire/wheel defect. Have you weighed both of the wheels? If they are markedly different it will result in different forces associated with caster angle and self centering force. Are you sure they are geometrically identical? if you have one 225/40 and one 225/45 it will pull too.

BTW if its the same tire, the side to side "grip" mentioned with the teg won't occur with an audi. What quattrosedan is talking about is torque steer, it occurs due to a combination of things during launch - the aforementioned available friction force, amount of compliance in the tire, and amount of compliance in the half shafts (most front drivers have unequal length half shafts so one shaft will twist more than the other, causing the other wheel to turn more times and transmit more power to that side of the car)

 

Wohho:

Thanks for the explanation. I have wondered about that torque force causing the drifting because I have never driven a passenger car with 4 wheel drive/traction before. I checked the tires and they are identical on both sides - Continental SportContact 2's (235/40 ZR18 95Y), but I haven't really a way to check the weight. I have pretty even wear on my rears so I thought I would rotate them up front to see what happens. My current fronts are both pretty worn on the outside 1/3 of the width.

Looking at TireRack.com, I noticed that the customer feedback on the SportContact 2's was that they rated low on tire wear. I wonder if anyone else has experienced something similar.

Thanks again for your detailed explanation. Unfortunately I am a Structural Engineer and not a Mechanical. I deal in statics and not dynamics! : )

Cheers

 

Try rotating front to back.

 

if they are worn on the outside that could mean a couple of things.

1) the camber is off too positive, this would cause instability in straight line performance
2) both tires are either toed in or toed out. its not 100% on which one it would be because of other suspension settings, but generally if the outer third is worn, it would be toe in.
3) you corner like a maniac

Aside... mmmmmmm statically indeterminate problem sets. Sadly, though I'm degreed in something that could be fun, I work quotes for Ford and Nissan all day. blah

 

Wohho:

Statiscally indeterminate problem sets! Please don't remind me - it has taken many years of therapy to get over that stuff!

The Audi tech did perform a toe adjustment yesterday - probably because he made an identically observation to yours - that the outer edges were worn. So I think I am good with respect to toe angle and alignment - I am guessing that it is a tire issue causing the pulling. Hard for me to contemplate, since both look identically worn, and the pull is to one side. But it seems like the only thing left that it could be.

Hang in there on the profession thing. At least you do something related to automobiles. I push paper on the program management side of things - no design work unfortunately.

Cheers

 

No actually, it would do it. Put a set of drag radials on and every time you hit an imperfection in the road, the car will slightly pull to one side or the other. This didn't happen when I launched the car because I had a type r diff in the tranny. I know what torque steer is, and that is not what I am talking about. I am just talking about daily driving down the highway at 60mph, not accelerating, just cruising, it will pull to one side or the other, which ever is gripping better.

 

yes they can i believe that after having aftermarket rims with aftermarket tires. they are totaly diffrent , my stock ones are kinda oval shaped and it rides fine on the road. but the after market one is like flat it sits on the road better but depends on the road if the road has like dent(i dunno how to say it) like road line or sumthing then it starts to pull to either left or right.

 

Well, I got you covered there, I am almost done with my ME degree.