Nobody

From what I understand the S2000s (or any other relatively current) ABS system uses wheel sensors that measure the rotation of each wheel and sends the information to the ABS computer. When the computer determines that a wheel is approching lockup, it sends a signal to a hydraulic modulator to reduce pressure momentarily only to the wheel that's locking up.

Assuming this is correct, can the electronics be tweaked/retuned/reflashed to increase stopping effectiveness? Can things like the amount of pressure released be modified? Can the duration of the lockup be extended before ABS kicks in? Also, it seems as though ABS continues to pulse for a few seconds after it senses lockup even though the thing that caused the lockup (railroad track for instance) is long gone.

Also, are brake bias valves made obsolete by modern ABS systems?

Gregg Lee

The pulse you feel in the pedal is from the recovery pump, not the ABS action. Pump comes on as soon as the ABS is activated, and stays on briefly after release.

Basically yes to bias valves, which don't really change the mechanical bias, but put a pressure limiter set at a fixed value in the rear brake circuit. ABS is also a pressure limiting valve but with a smart controller that decides how much and how long. "Bias valves" were normally used for one purpose: to assure that the rears never lock first.

However, ABS does not cure the broader issue of correct front/rear bias. In the S2000 for example, front ABS activates long before the rear brakes do much work, because imo the brakes are biased too much to the front. Once front ABS is on, steering goes to heavy understeer, so pushing the pedal harder to get the rears to work is no longer the main concern. You could nstall race type parallel master cylinders with T linkage, but the easiest method to crudely adjust bias is to install different pad compounds front and rear. This does work. You could also install calipers with a different piston size, but that's a much more expensive experiment.

Gregg