Replace, rebuild or upgrade master cylinder?
 

My stock master cylinder was sucking air for an unknown length of time while stored by the previous owner. Should I ...

rebuild it?

replace with NOS or rebuilt MC?

or

upgrade to 19mm?

Also, if I go with the 320 caliper upgrade, does this require the use of a 19mm MC?

Any and all knowlegable input would be appreciated - stopping effectively is high on my list of things that matter.

Thanks

Don't bother rebuilding it. It's a whole lot easier to buy a rebuilt one, and while it's somewhat more expensive it isn't hugely so.

The 19mm MC will make the pedal "feel" harder, but you will have to press about 25% harder on the pedal to get the same braking feel.

The BMW calipers will reverse this effect; if you get them with the stock MC they will "feel" softer and have a longer pedal travel, but you won't have to push as hard on the pedal to get the same braking effect. Going to the 19mm MC goes back to just about the factory balance between MC and caliper piston sizes.

--DD

I have used the 19mm on all of the 914 I have owned, when replacing the master cylinder.

isn't the 19mm cheaper? I prefer the power brakes feel of teh 17mm with the bmw calipers. the 19mm with stock brakes requires ALOT of foot power to stop

I had the 19mm MC with a stock brake setup, and just recently put on 320i calipers up front and replaced the proportioning valve with a T fitting while leaving the rear calipers alone. I have to say it's a great improvement, because the pedal was harder to push down (but by no means difficult to depress) before I did the upgrade, but having it there from when I rebuilt the entire car several years ago made switching out the calipers quite easy. As the car currently is, the pedal feels great, powerfully stops the car, and is perfectly safe as the fronts readily lock before the rears (as tested in the parking lot). As always, it's a lot of personal preference how one likes the pedal to feel but I feel that it's a great setup on a relatively stock 914. Steve

I went with the 19mm, and still have stock calipers. It is a little hard, but not bad.

19mm

Upgraded front brake pads - with low cost pads there will be more braking effort.

Ken

the 23mm is cheaper than the 19mm, but if your not going to 4 piston calipers all around, its not worth the hassel of plumbing the 23mm (i know this first hand). Stick with the 19mm, even if you keep the brakes stock. Its a world of difference.