21 vs 24mm master cylinders...

[flatlander757]

So I've seen that when going front drum/disc to 4 wheel disc people say you need to upgrade to the 24mm master cylinder.

I know that a large master cylinder piston will = a harder pedal. I was wondering out of curiosity if doing this on a stock disc/drum setup would make it impossible to stop. I like the feeling of a very firm brake pedal, I just wanted to make sure that it would have enough power to lock up the brakes without requiring the incredible hulk to do so. I figure this could also be a step towards 4 wheel discs as well.

Would it require a different proportioning valve or no? I think since it's still stock at the brakes themselves the answer would be no by my logic.

Reason I ask is my MC blew out on my 1990 Sundance RS. Need a new one... might as well "upgrade" right?

[turbovanman²]

24mm is the way to go.

[iangoround]

I just put a 24mm master on my car with shelby z front brakes and early TINY TINY drums on the back. stock prop. valve. The pedal is INCREDIBLY firm. It took a little getting used to in order to brake properly now. Pretty sensitive. I can fully lock my brakes up and still have about 2/3 reserve on the pedal. Granted my tires aren't the best, but still.

I would say go with the larger MC. I got mine brand new with the reservoir attached from Advance Auto for about $40. Its found it listed under an 89 daytona ES as an option.

[turbovanman²]

Or to save any confusion, just order a 89/90 Minivan, they all got 24mm MC's. And yes, buy new or don't bother.

[Vigo]

i had a rebuilt mc that let go about 200ft out of the driveway, good thing i wasnt hauling --- (yet). thats in addition to the many other problems ive had with rebuilts. so definitely buy new, especially since new ones for these cars are so cheap.. if our MCs cost what some other cars do, you'd see a lot of us junking our cars over it.. we should consider ourselves lucky to buy new at 40-50$.

[4cefedomni]

don't bother going anything more than 24mm i put a 33mm one on my car with 4 wheel discs and the pedal was like a rock i could only make it move about an inch and a half no matter how hard a pushed, and you would have to be hurcules to actualy lock up my wheels. in case you are wondering the 33mm came off a 1 ton van.

[turbovanman²]

don't bother going anything more than 24mm i put a 33mm one on my car with 4 wheel discs and the pedal was like a rock i could only make it move about an inch and a half no matter how hard a pushed, and you would have to be hurcules to actualy lock up my wheels. in case you are wondering the 33mm came off a 1 ton van.

I guess it depends on the car, I have the 1 1/8 off a B250 van and my pedal is a bit hard but DAMN, it will stop NOW.

[Vigo]

hmm, making me want to upgrade. i have the r/t brakes on the 24mm mc on my dynasty and i like it just fine, EXCEPT it seems to be a bit slow to respond in panic type stops, like the pedal goes about halfway down before you've got max braking.. maybe i should get that b250 one..

[4cefedomni]

i think the 33mm is 1 1/4 inches it was off a b350 van and the pedal has no feel to it whatsoever its just rock hard. i would rather a slightly longer pedal travel and more feel. i will put on the 24mm one i just bought and see if i like it if not maybe i will try the b250 van one

[turbovanman²]

i think the 33mm is 1 1/4 inches it was off a b350 van and the pedal has no feel to it whatsoever its just rock hard. i would rather a slightly longer pedal travel and more feel. i will put on the 24mm one i just bought and see if i like it if not maybe i will try the b250 van one

HOLY CRAP, 1 1/4", well no wonder you can't stop it,

[4cefedomni]

yeah i know its way overkill, thats why i keep complaining about how hard my pedal is.

[TurboJerry]

The FWD vans have a bigger brake booster. That's why they stop good with a bigger MC. My 3/4 ton truck has the 1 1/4" master on it and it's got really good brakes. Also the aluminum MC's have a hard anodized bore surface. Honing them would be a fatal mistake. The seals will quickly destroy a "bare" aluminum surface. I just clean the MC, and put new seals in as long as the anodize is still good. I've put many miles/years of use on them like that......

[4cefedomni]

yeah i'm still using my stock omni booster cause thats all that will fit behind the shock tower.

[Anonymous_User]

Did the '88 Shelby Z come with 21 mm or 24 mm? I think it's 21, right?

OK, I have THAT master cylinder in my drag car. Had it laying around when I scrapped my Z. It is running 4-wheel disc brakes without a booster. Fully manual. The car originally had manual 4-wheel drum with a single resevoir m/c so it stops incredibly better now, but it does require quite a bit of pedal movement. If the 24mm would be an upgrade for this, I may want to go buy one.

[Vigo]

Also the aluminum MC's have a hard anodized bore surface. Honing them would be a fatal mistake. The seals will quickly destroy a "bare" aluminum surface.

thats part of the reason why REMAN BLOWS!! you CANT do a decent job and then turn around and sell the thing for 19.99. its BS, they suck and they WILL fail.