soft brake pedal with Big Reds
02-17-2009, 02:12 PM
#32
Burning Brakes
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One thing I'm picking up here is most have used a power bleeder. My 86 has the stock MC, 5/33 bias valve, ATE blue, and big reds with good pedal pressure.
When I first intalled them they were mushy and it would lock-up too easily. I rebled them (motive bleeder) three or four times to no avail. On the last bleed, with the bleeder pressurized and the valves open, I pumped the pedal through the full range of motion a few times and the pedal stiffened up to the point where it's pretty close to stock.
Now if I can only stop it from squealing under light-moderate pedal pressure...........
When I first intalled them they were mushy and it would lock-up too easily. I rebled them (motive bleeder) three or four times to no avail. On the last bleed, with the bleeder pressurized and the valves open, I pumped the pedal through the full range of motion a few times and the pedal stiffened up to the point where it's pretty close to stock.
Now if I can only stop it from squealing under light-moderate pedal pressure...........
Jeremy, the squeal can be eliminated by changing pads, my pfc 01s squealed badly on light pedal, the pfc z-power (IIRC) street pads don't and still have strong stopping power.
02-17-2009, 03:48 PM
#33
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Street pads and the vibration dampers on the brake pads will stop the squeal. With race pads on, they will squeal under light braking.
02-17-2009, 03:55 PM
#34
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02-17-2009, 05:27 PM
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I have the porsche pad ant-squeal shims (all 8 of them) and am running a Hawk HP + pad. I've ran these pads for years with minimal noise until I fitted them in the big red. The rears are dead quiet.
I attribute the brake noise due to the fitment of the calipers on the spindle which leaves the pad ever so slightly exposed above the rotor. While braking into a turn, regardless of pressure, it get's pretty significant and I beleive based on the pad height any rotor deflection makes it worse.
I'm using the lindsey adaptor and 993TT rotors. Problem I've seen, on my 86, is the base the caliper, when using the lindsey adaptor, rides to high and the caliper actually touches the spindle caliper mounting ear, which I clearanced a bit to get somewhat of a flush fit.
02-17-2009, 05:43 PM
#36
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I'm using the lindsey adaptor and 993TT rotors. Problem I've seen, on my 86, is the base the caliper, when using the lindsey adaptor, rides to high and the caliper actually touches the spindle caliper mounting ear, which I clearanced a bit to get somewhat of a flush fit.
02-17-2009, 06:14 PM
#39
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02-17-2009, 06:34 PM
#40
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When I first intalled them they were mushy and it would lock-up too easily. I rebled them (motive bleeder) three or four times to no avail. On the last bleed, with the bleeder pressurized and the valves open, I pumped the pedal through the full range of motion a few times and the pedal stiffened up to the point where it's pretty close to stock.
Now if I can only stop it from squealing under light-moderate pedal pressure...........
Now if I can only stop it from squealing under light-moderate pedal pressure...........
As for your squealing, that is the rust on your rotors.
How are the new digs?
02-17-2009, 06:37 PM
#41
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I was thinking there is air in the master behind some of the seals and what you did may have equated to a "bench bleeding." Some masters have a bleed valve on the master and ours do have a bolt and crush washer on the bottom. Has anyone messed with that bolt?
As for your squealing, that is the rust on your rotors.
How are the new digs?
As for your squealing, that is the rust on your rotors.
How are the new digs?
02-17-2009, 06:48 PM
#42
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I found this article very useful when I did mine: 944 Big Brake Instalation
I guess they liked what Dave wrote since they didn't change a word.
I guess they liked what Dave wrote since they didn't change a word.
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Mike or Dave Lindsey
www.lindseyracing.com
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Other 1-405-947-0137
Mike or Dave Lindsey
www.lindseyracing.com
U.S. 1-877-943-3565
Other 1-405-947-0137
02-17-2009, 07:47 PM
#43
If the brakes feel spongy or soft then the odds are that you have some air in the system. Proper bleeding should fix this. If the pedal travel is excessive and you have upgraded your brakes, then the odds are that you have an incorrectly sized master cylinder. Brakes are a highly engineered system - change one thing and it affects another. Going to larger calipers (with probably larger pistons or even more pistons) without a corresponding increase in master cylinder piston size will result in more pedal travel - just about guaranteed.
Short story: I had 911 Carrera brakes front and rear on my 914 /6 racecar and a 19 mm master cylinder. With new pads I would have full pedal travel but after a couple of track sessions the travel was excessive. Brake modulation was always good but too much travel when the pads had any wear.
I upgraded to Boxster front calipers and went to a 23 mm master cylinder. Now the brake pedal travel is always full no matter what the pad wear is, but brake modulation has changed a lot. Pedal always feels hard and more difficult to modulate. I've gotten used to it but ideally I should have a master cylinder piston size of about 21 mm. Wish I could find one for my application.
Short story: I had 911 Carrera brakes front and rear on my 914 /6 racecar and a 19 mm master cylinder. With new pads I would have full pedal travel but after a couple of track sessions the travel was excessive. Brake modulation was always good but too much travel when the pads had any wear.
I upgraded to Boxster front calipers and went to a 23 mm master cylinder. Now the brake pedal travel is always full no matter what the pad wear is, but brake modulation has changed a lot. Pedal always feels hard and more difficult to modulate. I've gotten used to it but ideally I should have a master cylinder piston size of about 21 mm. Wish I could find one for my application.
02-17-2009, 08:21 PM
#44
Nordschleife Master
Interesting some have problems with pad squeal also. My friends car squeals aswell, we used those adhesive backed antisqueal pads (4x on each caliper) that snap into the piston centers. I will double check and see if the pad sits over the rotor at all this weekend. We used RacersEdge adapters.
02-17-2009, 08:46 PM
#45
Nordschleife Master
I just want to add that using a power bleeder with mdoerate pressure (8-10psi) AND manually moving the pedals will achieve optimum purging of air from the lines.