930 Master Cylinder Needed for Boxster Brake Upgrade?

[utbeamer]

I'm getting a set of Boxster (non-S) brakes for my '79 SC. It is suggested in the adapter description to upgrade the master cylinder to the Turbo version (part no. 930.355.011.03). Has anyone with a bigger brake kit run the stock MC? Thoughts? I'm curious to know if this is more of a nice to have or a must have for the upgrade.

The car will be used 80% street and 20% DE & autocross events.

Thanks!

[scottrx7tt]

I am running the stock MC, and I have a nice firm pedal

[Rodsrsr]

When you say set, do you mean all four? If so, I'd go with the larger mc.

[speedster911]

Another option and a few dollars less is the ATE 23mm MC. I think some places label it as Mercedes Benz MC. I am doing all four corners with Boxster calipers on my 75 and doing a MC upgrade.

[Bill Verburg]

Originally Posted by utbeamer

I'm getting a set of Boxster (non-S) brakes for my '79 SC. It is suggested in the adapter description to upgrade the master cylinder to the Turbo version (part no. 930.355.011.03). Has anyone with a bigger brake kit run the stock MC? Thoughts? I'm curious to know if this is more of a nice to have or a must have for the upgrade.

The car will be used 80% street and 20% DE & autocross events.

Thanks!

There's a range of m/c sizing that works. Its just a matter of choosing the one that fit your particular situation.

if changing all 4 calipers to Boxster(I still don't fully understand the attraction of this) you can use the stock 20.6 or the 930 23.8.

The difference is use will be pedal feel. For performance use the lower the ratio the better the feel but more leg will be needed.

the ratios w/ 4 Boxster calipers
20.6 => 43.17
23.8 => 32.34

[Bill Verburg]

Originally Posted by speedster911

Another option and a few dollars less is the ATE 23mm MC. I think some places label it as Mercedes Benz MC. I am doing all four corners with Boxster calipers on my 75 and doing a MC upgrade.

Up through '76 911 used unboosted brakes, from '77 on they use boosted brakes.

Though some of the m/c bore sizes are the same the boosted and non boosted m/c are not interchangeable

for boosted brakes the '78 up 930 m/c(23.8mm) is a bolt on

for non boosted brakes the ATE (ports face left) # 03-2123-3402.3 also 23.8mm. There is also a version w/ right facing ports.

It's best to buy a kit which includes the correct actuating rod, angled fluid feeds and flex hose to connect to the reservoir.

[speedster911]

Thank you Bill, very helpful info.

[utbeamer]

Very good info, thanks guys. Bill, thanks for the calculation.