Porsche Repair: 993 brakes, power booster unit, power brake booster

Question
I own a 1997 993 C2 with approximately 32,000 miles.  I have owned it for 4 years. I had it lowered to Euro specs shortly after I bought it.  Recently I have noticed that if I have driven much distance (5 miles or so) on the freeway without applying the brakes, the first time that I step on the brakes I get a shake in the steering wheel but it then goes away.  If I step on the brakes a second time I don't get the shake. The brakes seem to be working fine. It feels a little like a warped rotor but it shakes for just the first few seconds.  Could this be a warped rotor or something else?


Answer
Hi Randy...what a beautiful car...you are one fortunate guy.

There are a few things that could cause the brake shudder:

1.  malfunction in the brake power booster unit (like a sticking and gummy vacuum valve...it could work fine after it's activated once...See if there is a vacuum check valve that could be replaced without touching the power brake booster itself.
2.  two brake rotor defects: lateral runout or non-parallelism. (not as likely)
3.  binding brake pedal mechanical mechanism (not as likely).

If it's not in these areas, you may have to pay one of those german speaking Porsche$$$ machanics to fix your baby.

Good luck

Dave