OK my MC is leaking at the piston side.
Do most folks go with the $100 19mm MC or pay more for the 17mm one?

I assume you can not get rebuild kits for the 17mm correct?
I kind of like the idea of keeping the 17mm one but am on a tight budget.

Thanks Ken

Both will work but the 19mm requires a stronger leg.
I got the more expensive 17mm one.

i really like the "feel" of the 17mm. i like the modulation and feed back. with that said, i am in the middle of changing my brakes. i am going to the bigger bmw front calipers and replacing the proportioning valve with a T. so i may be forced to go with the 19mm master cylinder to regain what i like about the 17. we'll see.

if the feel of the brakes wasnt important to me, i would probly save the dough and go with the 19mm. if i wasnt making any changes and keeping the stock brake configuration, i would save up for the 17mm.

but if money is tight why not just go for a 19mm and see what you think? if you dont like it, keep your eyes open for a good used 17mm. i might have a 17mm available here pretty soon... i have seen some knock off 19mm on ebay for 65 bucks shipped.

There have been a lot of complaints of internal piston leaks from the chinese 19mm master cylinders. Waiting for the Krusty one to add on his view of the chinese copies...
I wouldn't trust my brakes to a master cylinder with terrible QC. a new ATE 19mm MC isn't that much money, and sometimes good used one's pop up in the classifieds. I personally like the feel of the 19mm over the 17mm, but again, it's all about personal preference.

I'm curious, are you running stock or 320i calipers on your car?

I ran a 19mm master cylinder with stock brakes for 3 years, then recently upgraded to 911 front brakes. The pedal feel really isnt all that different after the upgrade, but i liked the firmness on the 19mm with stock brakes over that of the 17mm master cylinder.

Again, to each their own.

go 19mm you will like the improvement.

The 19 moves a little more fluid, a must for larger calipers. With stock brakes, you might notice a little less travel, but a little more leg pressure required...not much.

If your calipers are stock keep the correct 17mm master cyl.

+1

Well, I'm here and I've read the above. One thing is barely considered. The VERY LAST thing you want to cheap out on is the brakes. After all, if you can't go, you can't go. If you go and you can't stop, a whole world of hurt is apt to descend upon you, physically and financially. Think about it and act responsibly. Some of us like the pedal feel of the 17mm master cylinder, some the 19mm. Nobody likes the feel of no master cylinder as they careen into whatever's in front of them. It CAN happen to YOU.

The Cap'n

I am doing something similiar ....... I have already installed the 911 size 19mm master and will be using the 48mm 911 M calipers up front. I think the 17mm master may allow too much pedal travel, when used with the larger 911 M caliper pistons.

I have contemplated going with a 'T' but since the factory p-valve only regulates pressure after the pressure reaches a certain threshold ........ so I am just gonna leave it in and see how it works. So basically it allows equal pressure on all calipers until that upper pressure level is reached .... then it tapers off the pressure to the rear calipers.

Leaving it in should not throw anything off in the 'wrong' direction (rears locking up) ..... if you are going with larger piston front calipers .......... If anything, one would need to raise that pressure threshold to allow the rear calipers to sqeeze harder. So they can 'catch up' to the higher clamping force of the larger front calipers ................

That said, I have read about others on here going with the rear 'T' when using larger front calipers .......... and ended up with good results.

My thoughts go directly to who made the master cylinders. If made in China, you only seem to get cheapness, not quality and durability. I like OEM brands such as ATE.

Within the above confinements, I think the size depends on your brakes you are running as your preference. Normal 914 brakes I like either the 17mm or 19mm, preferring the 17mm (ran these under normal configuration). When I converted the front brakes to 911 Carrera and normal 914 rear brakes, I used the 19mm. At the time I preferred a strong pedal requiring a strong leg so I was satisfied. These were on a converted Chev V-8 914 and either seemed more than adequate. The most important item relates having your braking system in very good shape.

In building my 914-Sixer (Carrera everything - late model) I opted to use the 23mm which requires a strong leg. It seems to work very well for me at the time being but as I get older I will look at boosting the brakes via hot rod brake technology. Right now it is what I want. I could have used the 19mm which would match better to the early 911 braking system.

Depending on your braking system and its condition, I would use OEM equipment and would be happy with either 17mm or 19mm master cylinders.

Steve

All stock...