Eric, they do, but few have a vacuum pump, they simply steal it from a tap on the intake manifold. When you get to turbos, it gets trickier, GM used hydroboost on the 80s Grand Nationals, a hydraulic system derived from their medium duty diesel trucks; that powered the steering and braking. They used no vacuum at all.

 

FYI- The TyrolSport Brake Caliper stiffening kit for R53s doesn't really fit the rear calipers. The bushings are about 3/16" too long so they move in the caliper instead of sliding on the stainless steel bolts.

 

From reading a few posts about R53 vs. R56 brake feel on the same R56 S calipers, it seems some feel the R56 has too much of a grabby on-off feel vs. the longer pedal travel and smooth progression of the R53. Some prefer the R56.

I don't like a mushy pedal, but I don't want an on-off switch. The pedal feels pretty good in my R53 with stoptech pads so as long as it doesn't get noticeably worse I'd be happy when I switch to R56 calipers.

I'm still interested in seeing what sort of changes you feel if you swap MCs.

- drew