Normal brake pedal feel???

[gilach]

hello everybody,


i have stock brakes on my 78 930, they're the 4 piston 917 jobbies i believe. i have started to drive the car harder and have noticed the following when braking:

the brake pedal is firm. it does require a little muscle compared to power brakes, but basically-the harder you push, the quicker you stop-which i like, much more mechanical. Now, i've noticed when i really get on the brakes, the pedal feels like it 'hits' or reaches bottom, i'm guestimating 3 inches from top brake pedal position. it just doesn't feel right and as a result, i haven't really pushed them too much/hard. i have a feeling that the fluid has not been changed in a couple of years, due to the car having very little mileage put on it. Is this normal brake pedal travel for p-car---any suggestions welcomed.

best, paul.

[Noney]

If your brake fluid is a couple of YEARS old, then you are more than ready for some fresh stuff. Some folks, myself included, flush the brakes before every DE event (may be overkill or not, see past discussions....). The point being, p-cars are renowned for their braking ability. If you feel you are having issues with only 3 or so inches of brake travel, then a great place to begin troubleshooting is with some fresh fluid. It's a very easy DIY project, albeit a messy one, but that will at least give you a baseline to work with.

Good luck.

[Craig 930 RS]

Don't screw around - use a pressure bleeder with NO fluid in it.
Fill and check reservoir level often and bleed all with ATE or Motul and enjoy.

[Bill Verburg]

You should have a high hard pedal w/ less travel, sounds like the m/c is stroking out, probably bad seals in there, a new m/c would cure it.

You do have a power booster, it's an 8" vac can w/ ~3:1 boost ratio.

you can check for fluid leaks before buying a new m/c by checking for fluid inside the vacuum can

[Bullet Bob]

I agree. 3" sounds like a lot of pedal travel. My pedal gets firm after .5" or so and I would probably lock them up if I went another inch.

[2.7RACER]

gilach,
High performance car needs high performance brakes.
You've got 'em, now you need some maintenence.
Change the fluid once a year. Use the good stuff like ATE Blue.
Get some decent pads, Pagid, Ferrado, Hawk.
Others may have more suggestions for pads.
Check and replace your rotors as necessary. Don't run old worn out rotors.
Replace the brake lines if they are original.
If you still have issues look into the master cylinder.
This stuff isn't cheap, high performance costs money.
Your life may depend upon your brakes.

[randywebb]

take the carpet up and look in the pedal cluster area - what do you see?

get under the car and look around right below that also

[Natog]

Originally posted by Craig911
Don't screw around - use a pressure bleeder with NO fluid in it.

I always put the fluid in the pressure bleeder. Is this a big no no?

Sorry to hijack, I hope a fluid change fixes your brakes.

[Craig 930 RS]

It attracts water like nobuddies bidness. What essentially works out to be 'air on top of the reservoir fluid' is a much better idea and most of my customers use this method.

I used fluid in my bleeder wished I didn't, what a mess.

[randywebb]

and it is water that makes the brake fluid "go bad"

[dean]

Like Bill said high and hard is correct. I think my brakes have a total travel of 1". One good way to check if your master is bad is put a ton of pressure on the pedal and hold it there. If the pedal goes down at all it is usually a bad master. You should bleed the brakes at least every 2 years. I use a vacume bleeder. They are nice and clean and work great except for on some clutches.

[gilach]

ok great...thanks for the advice guys...i will start with testing the pedal as suggested by dean. I just put in a new stereo, so i've had the carpets out and all looked clean.
If no dice, i'll swithch out the fluid. i'll use the pressure bleeder, and then get back to you guys and let you know what i find...how much ATE will i need? is one liter enough?
best, paul.

[Gunter]

Paul:
All of the above AND: Make sure that the pistons are not frozen (Rusted) in the calipers. Push the pistons back (Large channel-lock pliers between pads/calipers) and press them out a few times with the pedal.
When pistons are not exercised, they rust in the calipers.

[gilach]

ok...i will try to get to this tonight/tomorrow and report back.

paul.

[Navaros911]

Not much I can add... but one liter is enough. As suggested, get the ATE stuff as in our host's catalog.

First find the source, then report back and you will get tons of tips on how to solve it.

I did my entire brake system one year ago and it wasn't that difficult (rebuild calipers, replace lines, replace MC and MC feed lines and pressure bleed it three times). We'll guide you through the process.

Don't use the fluid in the pressure bleeder, doing this makes a mess (as said before). Bleeding like this takes less than an hour or so for me, including putting the 911 on stands.

[dean]

I just drove my car and checked the brake travel. It is between 1" and 1.25" to rock hard. More on the 1" side I think.

[gilach]

ok, i'm gonna check travel and pedals and such tonight.