Brake upgrades for V8 conversion.

[Doug Crooms]

I've searched the archives and couldn't find what I'm looking for so... I'm needing info on 19mm or LARGER MC. Someone mentioned Mercedes MC but what size, how much, where to buy, maybe a P/N? Will this work with any calipers - Stock, 911, BMW2002, etc?

Doug Crooms

[Dave at Pelican Parts]

The size of the MC and size of the calipers are only somewhat-related. In general, to keep a similar feel to what the car already has, the ratio of the total piston area of all of the pistons in all of the brake calipers to that of the master cylinder should be the same as in the stock system. Yeah, that's a bunch of math... But the calipers don't care what size MC is providing them with pressure, all they care about is the pressure in the brake lines.

A 20mm MC is available; it may have come in some 911SCs, but I am not certain. There is a 21mm one and a 23mm one from Mercedes. I do not know the models.

The larger the diameter of the MC, the harder the brakes will be to push. Conversely, the larger the total diameter of the brake caliper pistons, the easier the pedal will be to push. (And the more fluid you'll need to move.)

I recommend going five-bolt, getting either M or A caliper 911 brakes, and using the 19mm MC. That ought to be enough for any reasonable street use. If you're tracking the car (Big Track, not autoX) then you have different needs and should pay a lot of attention to brake cooling.

--DD

[lmcchesney]

Where do you place the volvo 240 front brakes in the mix. Four piston calipers.
L. McChesney

[Acox914]

or bmw 2002 4 pot calipers?

[Dave at Pelican Parts]

Just the same as the stockers--place them at the end of the front brake lines!!

OK, OK... You have to find the piston diameters for all the pistons in the calipers you want to use. Use those to calculate the total area. (Or you can just square each piston bore measurement, then add all those together--which is very different than adding and then squaring!) Compare that to the same kind of numbers from the stock system.

If you're not willing to do that kind of math, then use 911 brakes and the 911's 19mm MC.

--DD

[AJS]

Dave,

What is the MC piston diamter on the '89 911 Carrera, 19mm?

Thanks,

Andy

[sean_V8_914]

oh yes! I have been flogging my V8 914 for 2 weeks now, it needs more binding power. I am going with the BMW front calipers and 19mm MC. the BMW calipers have bigger pistons and more surface area on teh pad. THANKS SCOTT!!!

[skline]

Originally posted by sean_V8_914
oh yes! I have been flogging my V8 914 for 2 weeks now, it needs more binding power. I am going with the BMW front calipers and 19mm MC. the BMW calipers have bigger pistons and more surface area on teh pad. THANKS SCOTT!!!

No problem Sean, I am glad someone could get some use out of them. I am going with the Volvo brakes on the Chalon and with any luck the the Silver car already has larger brakes. If not, I have a set of M calipers here and can do a 5 lug conversion on it. I should know by this time next week.

[Doug Crooms]

Sean which BMW calipers will you be using - I have the 2002calipers so you think the 19mm will be (not only sufficient) of greatest advantage? I guess I could search the net to see if there was a common upgrade amongst the 2002ti guys.

Doug

[Dave at Pelican Parts]

Originally posted by AJS
What is the MC piston diamter on the '89 911 Carrera, 19mm?

I don't know. (BTW, there were two different 911s in 89, the Carrera with the 3.2 engine and torsion-bar suspension, and the Carrera 4 with the 3.6 engine, AWD, and coil-spring suspension.)

I do know that they both had power-assisted brakes. Not sure how that affects using the MC.

--DD