differential binding?

Folks, I need your input. My 07 CS in the AM or whenever it's cold, when backing up and turning (backing out of a garqge and into the street) has an unusual sensation. It feels as if the rear differential or the rear universal joints bind up and the let go. There is a shudder like sensation as if something had to break free to move smoothly. After that, I drive off and as long as the car is warm or has been moving-no problem. It only happens in reverse. Any thoughts? The dealership wants to look at it, obviously thinking it may be normal or not. Problem is the dealership is 250 miles away and it'll be some time before I'll get to them. Thanks for any ideas. Bill

From your description of when it happens (cold, backing up and turning), it's probably your front end. The steering is optimized for going forward, and when the car is cold, the front tires lose compliance -- this causes them to build up and release tension when backing up and turning. It's a side effect of low-profile, high-performance tires, and is completely normal (annoying, but normal). If it ever happens when backing up and going straight or when going forward, then you should take it to the dealer.

You live in Oregon, I see... has it been wet lately? I'll bet almost for certain, it is your brake pads sticking slightly to your slightly rusted brake rotors... when they get wet and dry out, the brake rotors can get a very thin layer of rust on them - only takes a few hours, then the pads stick to them... this happens to those of us in dry climates who wash and dry the car, then put it in the garage... the next time you drive the car, it binds a little bit, then they break free - it feels like a mechanical thing, but it's not... there's been several threads on this if you do a search. This is normal, and the rust comes off after a couple of blocks... no big deal brad

I second that as the cause. Happens to me all too frequently after it rains.

thanks guys. bill

Bill - Be sure to use the brakes a bit for a couple of blocks to get the rust off... otherwise if you have to hit them in an emergency in the first couple of blocks, your stopping power might not be what you're used to... You'll be able to hear the rust coming off for the first few rpms of the rotors, then it will stop and they'll be clean... brad

Thanks you guys, I live in California and while it doesn't get cold, when its cold this happens to me. Sorta worried me, but now that you mention it, its always cold and I'm always backing up and turning to get down the end of my driveway and onto the road. Now, if I can only get over the feeling thats there's something wrong with my brakes.................. (I don't think there is, its just that I don't drive my CS as much as I used to and switching between my GTI whose brakes are quite grabby and the CS whose brakes are much more progressive takes a while to get your head around...I hope!) Thks. G.

I'm with BillC on this - I'm pretty sure it's the combination of wide tyres & sports steering geometry. I notice it too in chilly English mornings on full lock when reversing out of my drive. My Audi TT used to do the same. If you look at the wheels on full lock they tend to roll on the outside shoulder of the tyre - my theory is that when the rubber is cold and hard and the road is slightly damp, the tyres skid ever so slightly until straight. I do also get the brake pad clunk that others have described, when the car has been left with the disks wet overnight, but that only happens once when the wheels initially move. The 'reverse judder' that I experience happens throughout a few revolutions of the wheel. By the way, I checked my tyre presures and found they were all 3 or 4 psi down. After adding air, the judder is less noticeable. Marco

+2 for brake pads. The first time it happened it nearly scared me to death.

I'm with billC. I noticed that for a while, it is a very noticable and disconcerting jerking of the car but I didn't worry about it. In my car anyway, you can tell it's from the front end so I took it at wheel scrub. But it does seem to be worst now that it's colder and yea, I guess it only does happen first thing I'm with billC. I noticed that for a while, it is a very noticeable and disconcerting jerking of the car but I didn't worry about it. In my car anyway, you can tell it's from the front end so I took it at wheel scrub. But it does seem to be worst now that it's colder and yea, I guess it only does happen first thing in the morning so it all makes sense now. Besides, BillC is a supergenious.in the morning so it all makes sense now. Besides, BillC is a supergenious.

See also this thread posted today in the main forum. Maybe the answer is twofold: One-off clunk = brake pad freeing from rusty disk Juddering from front on full lock in reverse for a few wheel revolutions = cold tyres & wheel slip on cold/damp road Marco