I had a conversation with Shane on Sunday about ABS options for the GTM. He has a customer car that needs an ABS system. I'm interested in a better option than the C5 brick.
The C5 ABS/EBCM is generally regarded as a crappy system that is prone to what C5 guys and girls call "ice-mode" (EBCM freaks out and brake pedal goes hard, you have no brakes! -on the track primarily-). Lots of stories of C5 track cars blowing through a corner on the track because the EBCM got confused and blocked flow to the calipers, no brakes and a rock hard pedal.

So one option I've talked to Shane about is the M3 system, which is able to operate independently of a PCM. Bulletproof and much 'smarter' than the GM system, proven as a swap into countless track cars.

The 1st issue with it is that the components are very expensive even used. Figure 1500-2000 just for the components, plus wiring etc. The second issue is that the C5 wheel sensors are incompatible with the BMW ABS unit. This requires replacement of the hubs with ZR1 hubs with the yellow pigtail connectors. This is not inexpensive, but additionally, as Shane pointed out, the spline count on the rears is different from the stock C5 rear hub spline count. This requires custom axles at $600-1000 and I believe different outer CVs? So were getting in the $4k-$5k dollar range just to get the BMW up and running.

One option I recently became aware of is the late model Mustang s197 ABS unit, out of 2005-2014 Mustangs. Dirt cheap, robust, and my understanding is that it will operate independently of a PCM. I recently became aware that Vorshlag has this system up and running in one of their C5 track cars, and it is light years ahead of the GM unit. But they had to do the changes above, same requirements as the BMW units so lots of peripheral costs to make this work in the GTM.

So my question is this-
I believe the C5 has passive hub sensors for the ABS, vs more modern active sensors which are compatible with the BMW and Mustang ABS units. Is this terminology correct? or maybe Hall sensor vs AC sensor?

For you electronic wizards, is there a converter that could interpret the C5 hub sensor into something that the newer ABS units could function with?

My other idea is, can the rear vss tone ring that we install at the gearbox flange feed a sensor that is compatible with the newer units? This would let us keep our rear hub, CVs, axles, etc which is a huge cost savings. Still would have to swap out the front hubs but that is peanuts in comparison to revamping the rear. Just run a tone ring on both axles to feed a signal to the ABS unit.

Who wants to be a GTM hero?