Boosterless master suggestions?

[shiboujin]

E30s are apparently 21mm bores. I see stuff for bigger bore sizes (23mm/25mm) but I'm looking for something smaller to make up for the lack of a booster now that I swapped over to manual brakes and killed the vac assist and the hydro assist. I really would just love a master cylinder that bolted in and went. Somehow I doubt that will happen. I see 5 lug people with M3 brakes but I'd like to get away with this for the last cash money.

[e30_302]

Porsche 19mm from a 914.

[shiboujin]

Oh? I think I found a VW rabbit master that will bolt in with 17.5mm. But it needs two holes blocked off and the res is $60 and has no provision to the clutch. It's enough that I'm annoyed.

Any more detail on this 914 master? Can I just bolt in and go?

[burlmays9]

It looks like it probably bolts right on, at least that's what I think from looking at photos.

[e30_302]

Bolts up to the massive booster delete plate I have. Two M10 outlets, one each front and rear. On the Porsche it was a remote reservoir setup so you'll need to do the same. If my car were a street car I'd keep it, but being a track car I'd like a little firmer pedal, so I'm trying a 21mm from a Mustang.

[shiboujin]

I thought 21mm was the factory E30 size.

[e30_302]

21/17, step bore.

PM me if you want the Porsche piece, I'll give you what you need. It's going to have to wait a couple weeks though, gotta see how this 21 feels.

[shiboujin]

oh is it? I just bought the 17mm VW one. What does that mean for feel? I guess the fronts will get stronger but the rears will remain the same? I thought the bias was external to the master.

[e30_302]

There's a pressure reducing valve going to the rears, along with the step bore master. A single bore master will give equal force front/rear. The E30 is lacking in rear brake from the factory, so it's a good thing. Put the 17 on and get rid of the factory prop valve and see what happens. As long as your rears don't lock first, you're good.

A 17mm master should have a very soft feel, with a very long stroke.

[shiboujin]

Heh, I like it soft with a long stroke.

[e30_302]

Then you're in luck. Have you upped the pedal ratio?

[shiboujin]

Yea. I couldn't tell you WHAT the ratio is. It's the sikky kit - https://www.youtube.com/watch?v=Q28U_iDB6Vg (turn on CC for the fun)

[e30_302]

Master cylinder size is really a subjective thing. Some people like stepping on a brick, others not so much. 17 is the smallest I ever found that's dual circuit, so if it's too spongy feeling for you, you can always go bigger in about 2 mm increments until you find something you like. I've been through several.

[Stvstr]

oh is it? I just bought the 17mm VW one. What does that mean for feel? I guess the fronts will get stronger but the rears will remain the same? I thought the bias was external to the master.

Do you have a part # for the VW m/c or know what VW model uses it? I'd like to check it out.

I just installed the 914 17mm m/c on my 5.0 swap with stock brakes and HP+ pads. The braking power is good but the pedal is very soft with too much stroke - however I do like that I can emergency brake with reasonable leg force. The remote reservoir setup was a pain as well.

[shiboujin]

I was on rockauto.com and looked up a 78 VW rabbit. The bore is listed as "11/16" and "non power brakes". I suppose it's 17.5mm and not 17mm like yours?

I actually don't mind too much stroke. It allows me more sensitivity when left foot braking. How did you do your reservoir setup? I'm still completely baffled on that one.