i have mid '80s ('85ish) carrera brakes *on all 4 corners* ...

anyone else running a similar setup and if so, what size/model Master Cylinder are you running ???
what size MC did the '85 911 Carrera have ???

Andy

Isnt the factory size a 23mm for those years?

I thought it was a 23mm for the turbo's and 21mm for the regular cars.

'85s had power brakes, so it's not a completely apples<->apples comparison...
and - those cars ran pressure-limiting brake proportioning valves on the back...

i've got part numbers but i haven't been able to correllate them to sizes...

IIRC, Joe's "914rs" is running a 19mm with 'big reds' at all 4 corners.

I had '85 Carrera brakes on the front and stock brakes on the back of my yellow race car. I was using a 19mm MC and it worked great. The car weighed 1950 lbs if that matters to you.

I had Carerra fronts and SC rears. Used a 19 mm and then upgraded to a 23 mm. The 19 mm gave a much better feel unless you like a real firm pedal. I was trying to solve the problem that I had too much pedal travel when the pads wore to anything less than 75%. The 23 mm fixed that problem but made the brakes harder to modulate. I recently changed out the front Carerra calipers (steel) for Boxster monoblocks (aluminum) and am very happy with the results. Well suited to the 23 mm M/C. I increased the rear about two turns on the proportioning valve and it stops great.

I just had Carrera brakes installed on all four corners of my 914-6 by Deman Motorsports (good high level racing shop). I trust their work.
They installed stock 19 mm. MC. I haven't tracked the car yet, but it feels fine on the road.
David

944t frt and Carrera rears, 19mm works fine still refineng for a stiffer pedal.

I'm running a 19mm on Manfred...Carrera all the way around, alloy calipers up front.

I have '89 Carrera calipers waiting to mount on my car. I had planned on using the 19mm master. From the posts, it looks like the 19mm master will work fine. I suspect that for the street, the 19 may be slightly better suited than the 23 with these calipers. A stiff and slightly higher effort pedal can be annoying for a daily driver, IMO.

Andy

QUOTE (CptTripps @ May 16 2005, 05:11 AM)

IIRC, Joe's "914rs" is running a 19mm with 'big reds' at all 4 corners.

That's correct. I would use a 19mm, if I were you.

QUOTE (914RS @ May 16 2005, 09:11 AM)

QUOTE (CptTripps @ May 16 2005, 05:11 AM) IIRC, Joe's "914rs" is running a 19mm with 'big reds' at all 4 corners. That's correct. I would use a 19mm, if I were you.

Joe..do you have a lot of pedal travel with the 19mm M/C??

if not now, i wonder what it'll be like when your pads are halfway wore down????

QUOTE (Mueller @ May 16 2005, 08:13 AM)

if not now, i wonder what it'll be like when your pads are halfway wore down????

Shouldn't make any difference. The pads always run touching the rotors, so as long as you have fluid in the MC the travel should be the same.

QUOTE (Paul Illick @ May 16 2005, 08:20 AM)

QUOTE (Mueller @ May 16 2005, 08:13 AM) if not now, i wonder what it'll be like when your pads are halfway wore down???? Shouldn't make any difference. The pads always run touching the rotors, so as long as you have fluid in the MC the travel should be the same.

Can't argue with the logic of that but my experience (5 years) with the Carerra caliper and 19 mm combination was always that when the pads wore down the pedal travel would increase dramatically. It didn't matter if the brake fluid was just changed or not. And I use Castrol SRF.

QUOTE (914RS @ May 16 2005, 09:11 AM)

I would use a 19mm, if I were you.

that's what i have right now, 19mm 911 MC. i'm also running a "Tee" instead of the Prop-Valve ...

the pedal used to be very firm (just the way i like it) but after rebuilding all 4 calipers (one had rusty, sticky pistons), now that all 4 calipers move freely, i find the pedal too "mushy" ...

brake system has been flushed completely twice with good fluid, and the brakes work, but the pedal is nowhere near as firm as it used to be ...

any ideas?
Andy

QUOTE (slivel @ May 16 2005, 09:39 AM)

QUOTE (Paul Illick @ May 16 2005, 08:20 AM) QUOTE (Mueller @ May 16 2005, 08:13 AM) if not now, i wonder what it'll be like when your pads are halfway wore down???? Shouldn't make any difference. The pads always run touching the rotors, so as long as you have fluid in the MC the travel should be the same. Can't argue with the logic of that but my experience (5 years) with the Carerra caliper and 19 mm combination was always that when the pads wore down the pedal travel would increase dramatically. It didn't matter if the brake fluid was just changed or not. And I use Castrol SRF.

excactly my point, the pistons have further to travel when the pads are worn down...every single car and truck of mine has less pedal travel after I put in new pads and do nothing else......

I have a medium amount of pedal travel and I'm running 20 (yes, 20) total pistons.

Always remember that increasing the size of your MC DECREASES your mechanical advantage over the calipers. I'll take a soft, effective pedal over a 'firm' pedal any day of the week. Modulation of lock-up is far easier with a pedal that moves.

As for travel vs wear, we'll have to see. My brakes are still relatively new.

QUOTE (914RS @ May 16 2005, 09:49 AM)

I'll take a soft, effective pedal over a 'firm' pedal any day of the week. Modulation of lock-up is far easier with a pedal that moves.

well, but that's just a personal preference ....
i like the brake pedal firm and i have no problem with modulating it.


so, guys, please help me to get my thing back to firm!
Andy

QUOTE (SirAndy @ May 16 2005, 08:44 AM)

QUOTE (914RS @ May 16 2005, 09:11 AM) I would use a 19mm, if I were you. that's what i have right now, 19mm 911 MC. i'm also running a "Tee" instead of the Prop-Valve ... the pedal used to be very firm (just the way i like it) but after rebuilding all 4 calipers (one had rusty, sticky pistons), now that all 4 calipers move freely, i find the pedal too "mushy" ... brake system has been flushed completely twice with good fluid, and the brakes work, but the pedal is nowhere near as firm as it used to be ... any ideas? Andy

Andy,

If you are sure that you have bled all of the air out of the system and still have a mushy pedal, then I would look at these two areas:
1. Replace all of your flex lines. Aging rubber lines will balloon under pressure giving you a mushy pedal.
2. Look at the firewall flexing where the M/C mounts. If so brace like Brant did or weld in a stiffining plate on the bulkhead.

so Andy, did you find those parts you called me about??

did those studs work for you??

got pictures of the new wheels on your car???

QUOTE (Mueller @ May 16 2005, 08:48 AM)

QUOTE (slivel @ May 16 2005, 09:39 AM) QUOTE (Paul Illick @ May 16 2005, 08:20 AM) QUOTE (Mueller @ May 16 2005, 08:13 AM) if not now, i wonder what it'll be like when your pads are halfway wore down???? Shouldn't make any difference. The pads always run touching the rotors, so as long as you have fluid in the MC the travel should be the same. Can't argue with the logic of that but my experience (5 years) with the Carerra caliper and 19 mm combination was always that when the pads wore down the pedal travel would increase dramatically. It didn't matter if the brake fluid was just changed or not. And I use Castrol SRF. excactly my point, the pistons have further to travel when the pads are worn down...every single car and truck of mine has less pedal travel after I put in new pads and do nothing else......

That's true in a car or truck with drum or disc/drum brakes, but shouldn't happen with all discs. You should get more fluid into the pistons as the pads wear, but as long as there's friction material on the pads and the M/C stays full of fluid the cups should be working in the same range inside the cylinder. If your experience is different I'd sure be curious to find out why.

QUOTE (Mueller @ May 16 2005, 10:05 AM)

so Andy, did you find those parts you called me about?? did those studs work for you?? got pictures of the new wheels on your car???

don't get me started ...
nope, parts are lost in space. thus no new wheels for me.

i did end up using the studs however.
i pressed them into the old hubs, just to see how they work and they're perfect!

i am so pissed that that box has disappeared and now i have a set of brand new trailing arms with your roller bearings in them sitting here collecting dust ...

anyone got a set of original 914-6 stub axles for sale? and some new 911 carrera hubs? and a whole assortement of aluminium spacers in various thickness? and a full set of 70mm wheel studs?
Andy

Andy,

did you try the trick of removing the pads and getting the pistons of the calipers to come out just a tad so that you have to tap the pads back into place with a mallet? that actually worked for me and it firmed up the brake pedal a lot after I rebuilt my front calipers. the issue is that the pads don't drag against the rotors at all if the calipers were just rebuilt and the pistons forced all the way back into the caliper. you want some minimal drag so that the brake engagement is immediate.