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Posted by: SirAndy Apr 23 2004, 02:28 PM

so, i got some helpful tips and hints on the previous brake question post,
but the main question is still unanswered ....

- what exactly is the difference between the early (pre '78) 911 MC and the later model ('78 and onward) MC ???


also, anyone out there who runs mid '80s carrera brakes all around and got the brakes balanced OK? if so, what MC are you using? what else did you have to do to get it balanced?

sooo many questions ...
Andy

Posted by: davep Apr 23 2004, 03:03 PM

I'm not sure how relevant it is because the 911's went to boosted brakes about 1977. The cars with "S" calipers got 20mm masters as early as 1969. So as brakes got bigger, master cylinders followed suit and the forces required increased as well. People complained about the forces required, and we got boosted brakes as a result. I have only seen one 914 with a boost MC setup.

Posted by: brant Apr 23 2004, 04:52 PM

yeah.. what dave said..

the other thing is that the size of the MC should effect pedal pressure but really should not effect the proportioning rates for front and rear.....

I doubt that any MC's (other than dual MC set up) will fix your lock up problem

b

Posted by: lapuwali Apr 23 2004, 05:44 PM

The other way to fix this is to increase the front weight proportion. Either moving the weight statically or raising the ride height (esp at the back) to get more weight transfer under braking. Neither one is without side effects, of course.

Posted by: TimT Apr 23 2004, 05:52 PM

Andy I have carerra brakes on all 4 corners... 19mm MC... Strangely enough I had the opposite problem you have... My rear brakes locked up early... this is not fun when approaching the bus stop at the glen at 140mph!!

I installed a wilwood adjustable bias valve in the rear circuit... and have dialed it pretty much in...

I can get on the brakes really hard now and all four wheels seem to be locking at pretty much the same time..

carrera calipers,drilled and slotted carrera rotors, hawk blue pads all around, 19mm MC, ATE blue fluid, braided teflon brake lines (just the flexible part)

Posted by: TimT Apr 23 2004, 05:53 PM

BTW getting the brakes dialed in required some "butt clenching" moments at the track

Posted by: Jeroen Apr 23 2004, 06:58 PM

The trouble TimT is mentioning is what you'd expect with full carrera brakes on a 914
After all, a carrera has much more weight in the back, sitting right over the rear wheels, which creates more rear wheel grip/friction, which in turn would allow bigger brakes without having them locking up

And yeah... locking rear wheels will give you sweaty palms

Other things that can upset the brake bias is the difference in front/rear spring weight
If your front is sprung harder than the rear, the fronts would lock easier/earlier

cheers,

Jeroen

Posted by: SirAndy Apr 23 2004, 07:20 PM

i actually need to go stiffer in the back, i was thinking 225 lbs instead of 180 ...

i'll give the pads in the rear some time to settle in, the rotors were used but looked brand new (no wear). the front is well used ...

we'll see how this works out on sunday
Andy