Hey guys.... Yet another newbie question spewing from my.... keyboard. Anyways, I was looking for a master cylinder rebuild kit and I found two for my car (1970 914-4). One was 19mm and the other was 17mm... Pause..








While writing this post I found saw something on Pelican, but I'm still confused. They sell 19mm UPGRADE master cylinders. However, they also sell Genuine Porsche 19 rebuild kits... My question is, what master cylinder should my car be, and how do I know? Thanks for putting up with me.
Mark D.

Get a brand new 19 mm. 17 mm was stock, but for the price, you can't beat the 19 mm. Bolts right in. While you're in there (famous last words) get a rebuilt pedal cluster from Eric Shea.

Another Mark D!

17mm was stock, but 19mm was a popular "upgrade". The only way to tell what you've currently got is to look for numbers on the top side of the MC casting. Yes, the side you can't see with the thing installed in the car. Dig out a mirror or two and a flashlight and you may be able to tell.

Or just buy a new MC. Most shops won't rebuild 'em any more; the liability is just too high and the profit is too low.

The only real difference between the 17mm and the 19mm is that you have to press 25% harder to get the same braking effect with the larger one. But the pedal moves 25% less distance. (You're changing your "effective leverage" that way.) The pedal feels harder, but you have to press harder to get the same effect.

Some people like the feel with the 19mm one, some don't.

--DD

Serious question:

What is the advantage of going to the 19mm MC?

I run the 17mm and have fantastic brakes

I can't believe I haven't asked this sooner...


KT

IMHO, it's only advantage is $.

19mm is usa\ually cheaper....

The funny thing is that the 219 is $35 cheaper than the 217. I like tight, racey feeling brakes anyway, so I may just do that. I've already got the steal lines that I'll put in at the same time. Thanks for the help. By the way MC, you're the second other Mark D I've run into on this site. A guy name Mark Durnil sold me my shift linkage last week. I guess 'Mark D's just have good taste in cars... Anyways, thanks for the help. This forum rules because I can post a question and get it answered by three different people quicker than it would've taken to call somebody. GTG.
Mark DEE.

With stock brakes, I much prefer the 17mm.

Yeah, it usually costs more, but I think it's worth it.

The last thing that stock, unassisted 914 brakes is LESS leverage on the pedal and 25% MORE pedal effort required to get the same braking.

I do a ton of squats to build up my brake-pedal-muscles.

I like the 19mm, yes it is a firmer peddle and it takes more effort to get the same

responce but I never submarined a passenger before I got the 19mm M/C. You

just have to stomp it harder.

The 19mm is a standard 911 part I think so more volume, lower price?

Yup, DaveE.

Thanks for all the info and perspective guys. I got a 19mm from AZbill last night that's new; still in the box. He sold it me for only $175, so I'm set now. I should be going to 5-lug and 911 brakes eventually anyways, so 19mm probably the right way to go for the long run. We'll find out I guess. I'll shut up now.
Mark D.