Why 944 Mcyl vs 911?

[DORIGTT]

Why does everyone seem to use the 944 mcyl versus the 911? I would think the 911 would have the proportioning 'right' for our rear weight biased vehicles over the 944 which was more 50/50 if I recall correctly.

[Humble]

Actually that didn't make much sense to me either, until I sat down and looked at it. My 944 stuff came with the mc but i didn't use it at first. Instead I went with the beetle mc, which was a mistake, and soon swapped in the 944 mc. The 944 part was better (and I already had it) but still locked up the front tires pretty early. Recently I ponied up the cash to buy a new porsche 930 turbo mc (it shares brakes with the 944 turbo but the mc is split differently) and it's worked great ever since. Fronts still lock up first but I think that is a tire issue not a brake issue since I have to push it damn hard for this to happen.

[DORIGTT]

To make sure I understand you correctly..

Both worked, but the 930 version worked better than the 944 m/cyl for your application?

Was the install the same for both units?

[Humble]

Install was the same for both, I just bolted in the mc in place of the beetle part. Now I'm using 87 944 turbo disks, and 4 pot calipers all around so I'm not sure how well this setup would work with n/a brakes. The porsche 930 of the same year used the same brakes as the 944 so the mc matches the calipers. The 930 mc with 944 brakes is like hitting a wall if you jump on the brakes. The 930 mc also has dual brake light switches that connect exactly like a beetle mc (the 930 mc I bought even came with new switches).

[Steve C]

Hi

Do you know the bore of the 944 and 930 m/c? I don't think that the 930 used a brake booster.

Steve

[Jeza]

Because it works with the brake callipers as a system. The Beetle mc does not have enough volume to work well with the single piston sliding FRONT callipers from the early 944.

The 944 has a split bore mc, 23.?? for the front, and 19.06(?) for the rear. The rears work fine with the Beetle mc because the rear portion of the 944mc is the same diameter as the Beetle mc.

If you sit down and work out the front to rear ratio, you will be surprised, the 944 is not as bad as you think.

If you use a 911 mc, then use it with 911 callipers. You need to compare the mc volume and the calliper volume between the models, not just the master cylinder.
http://www.germanlook.com/Forums/showthread.php?t=2183

The later 944 4 pot setups are a different kettle of fish, and guys here have found the Beetle MC works with those callipers. I can't comment on this setup.


Cheers
Jeremy

[Humble]

I don't know the bore off hand but it is printed on the mc. I want to say it's 26mm and 20mm but I'll have to double check the mc to be certain.

[DORIGTT]

I've got the 4 piston 968 calipers that I plan to use.

[Humble]

If you know the caliper piston bores for front and rear i can tell you if it'll work with the 930 mc or not. I'd have to dig up the numbers for the 944t calipers again as well.

[Bugnutz]

the 944 master cylinder (thru 86, p/n 944.355.011.01) is 23mm front and 19mm rear.

[flat_iv]

Humble, what is the part # of the 930 master cylinder?

[Humble]

The part # I have is 930-355-011-03 and when I did a search I found it on pelican parts which is where I bought it

http://www.pelicanparts.com/cgi-bin/...911%20(1978-89)

As an update to my previous statements, I can lock up the front tires first with staggered rims and street tires. But when I toss on the race rubber it throws you against the belts and stops the car incredibly fast with hardly a peep from the tires.

[evilC]

The Porsche 930 M/C is a 23mm diameter (both pistons) model. The beetle standard one is 19mm diameter (both pistons) so it should be more 'powerful'. However, M/C piston size selection is very often down to the preference of the individual driver - power verses length of stroke.

Clive

[Humble]

What are the markings on the MC then? I thought those were the bore sizes

[effvee]

Hi, I have a 1302 that I am going to use the early 944 1985 single piston setup on. However I choose to use the front calipers on the rear also. So I will have all four wheels stopping with front calipers. Can you suggest a MC for me. I also have a 1971 Porsche book where the front calipers and rear are very close in sizing. I believe I need more than 19mm mc.