minho78

I have an 1986 Turbo, and and for some reason any of my other cars brake better that the 951 specialy at High speed. The calipers were rebuilt 3 years ago. Could this be the master cylinder?
TIA

alxdgr8

When was the last time you replaced/bled the fluid?

minho78

Alex that was 3 years ago. I noticed that my brakes never really braked that well. THat's why I rebuilt the calipers. After that I didn't have the time, But I'm thinking could this be the MC?

Lemming

What pads are your running?

How does the pedal feel? Normal, abbynormal?

User 52121

Ditto to what Lemming posted. I think you're going to need to go into a little more detail about your other cars "braking better" than this one.

Is the pedal firm? Does it sink to the floor when you hit it? If the pedal sinks to the floor (won't stay firm), or if you can pump the pedal to make it firm... then yes, I'd say it's possibly the master. If you haven't bled it in 3 years, you might also have air in the system (and/or possibly never got all the air out in the first place).

Pads also make a big difference. Run a cheap pad and you get what you pay for... low initial bite, and no real "power" when pressing hard on the pedal.

Stock '86 951 brakes aren't the best, but the only time I've found them lacking was after repeated hard braking at the track (like coming into T12 at Road America after 4-5 laps at 135mph). On the street, or at autocrosses, I've never had an issue. Pedal is always firm, pads (OE Porsche for street/AX use) always bite nice and offer lots of brake torque (and require modulation to keep from locking up tires).

Tedro951

Yep, pads/rotor surface made the difference on mine. I had no idea what pads were used by the PO, and the rotors were in rough shape. I was really disappointed with what I had, compared to the stories I'd heard about 951s.

Then I installed PBR ultimates, new caliper seals, super blue flush, braided brake hoses, and new rotors on and the result is exactly what I'd hoped for. The pedal is now firm as you were on prom night. The ability to lock the pilot sports is easy, but modulation just before lock-up is great, at least from 80 or more to 0. From 60 or less it doesn't much matter, at least to me.

reno808

there is air in your system

minho78

Tim I'm running PBR's deluxe. The pedal feel feels normal but, when I try to brake at 30 and above it looks like the pads are not grabing enough. These pads work fine on my Jetta turbo.

minho78

Uhmm, maybe I should get porsche OEM. Thanks

minho78

I tried to brake hard but it doesn't lock. I have the PBR deluxe, Rebuilt calipers, new Zimmerman rotors. I think the brak booster maight have problems, or the MC is to old and is not applying enough pressure.

minho78

Carlos no air in the system. If there was air the brakes would be soft. The brake feel seems fine, but it doesn't have a brake bite.

Dougs951S

My stock baby brembos with good pads easily lock up my tires if I brake hard. Sounds like you do have air in your system. Go under your dash and look for a pleated rubber boot that is behind the clutch pedal; check for fluid. If there is of fluid seeping in around that boot, replace the master cylinder. Do the same inspection on the slave cylinder which is behind the starter. Replace and bleed if they are leaking. buy a motive power bleeder and bleed the brakes, its almost mandatory if you're at all serious about working on your own car, and it makes brakes and clutch bleeding an no brainer. Seriously one of the best tools I've ever purchased. Also I don't think it has anything to do with your brake booster- I have no power assist in my 951 and if I lay into the brakes too hard they just lock. Bite on them feels great with great modulation at high speed.

http://www.motiveproducts.com/

Lemming

First bleed the brakes, if that does not fix it, then your flex lines may be old and bulging under pressure.

User 52121

The previous owner to my car sold it to me with Performance Friction PF97's mounted up, but included a box of PBR pads. I didn't like the excessive dusting or squealing from the PF's so I swapped in the PBR's. I don't know what kind of PBR, they just said "PBR" on the backing plates. They were awful.... no amount of pedal effort could get the tires to lock. Thinking perhaps it had to do with an improper "transfer layer" on the rotors (or the fact that I was using new pads on used rotors and perhaps I wasn't getting 100% pad engagement) I swapped in brand new rotors, and also switched to the Hawk HP-S pads. I run the HP-S pads on my wife's VW GTI and they work great. But I still had the same problem... no matter how hard I squeezed down on the pedal, I couldn't lock the tires. The pedal was firm, the car just didn't want to stop. Fluid flushes, bleeding, nothing helped. Was already on braided lines. Rebuilt all 4 calipers - still didn't make a difference. For a while, I just assumed that what I'd heard here ("Stock 951 brakes suck") is what I was experiencing, and just lived with it.

After owning the car for a year and a half, I signed up for a DE. I switched the PF97's back in (as they are much more appropriate for track use than street), went out for a quick ride to bed the pads in... and promptly flat-spotted my tires. That right there proved to me that it was indeed a pad issue and had nothing to do with my braking hardware.

Did a bit more research - wound up switching to OE Porsche pads, and that solved it. Now the car brakes like I'd expect a Porsche to brake.

Assuming the rest of your system is up to snuff (bled properly, lines themselves are in good shape), I'd try OE pads. I think I paid $115 for a box through Sunset.

ehall

I have an 87, with ABS, and I HAD an 86 without ABS. If you are used to ABS, then I "guess" the 86 brakes suck, but until I had the 87, I had no problem betting my life on my 86 brakes. Those brakes are outstanding, straight from the factory. IF you are now used to madern day stuff, then we're now in the apples to oranges zone. Somehwere you have a problem. Thoise brakes should lock up and launch the umbrella, in the hatch, through the windshield, if they are working right. I'm with the guys who say look for leaks/old lines/pads and air. Something is amiss.