I've got a '97 S500 sedan. I just bought a set of 19" rims with 235/35's all around as part of the package. It was immediately apparent that the car needed more meat in the rear. I picked up a hardly used set of Michelin Pilots, size 275/35's. This would give me a 4% difference in circumference front to rear. Before I put the 275's on my car, is the difference enough that it's going to screw with my ABS?

 

No affect on ABS.

Each wheel has its own speed sensor and slippage at each wheel is controlled individually.

You'll have bigger problems, such as clearance issues and generally totally screwing up your car's handling.