Is the thickness of these brake pads ok?

DelPico · 07-31-2007, 04:49 PM

Front pads from a 77 911 C3. I just pulled out and they measure .9 cm and .8 cm. My brakes went soft on a long road trip. I bleed the brakes and they seemed fine for a short period of time. I figured I would check the thickness before I bled again. Any thoughts?

Thanks,

David

DelPico · 07-31-2007, 04:50 PM

Oh these are both from the front right side. Not two sides.

DelPico · 07-31-2007, 06:13 PM

No one?

frogger · 07-31-2007, 06:20 PM

That should be OK for street use. How worn are your rotors? How clean / fresh is your brake fluid and what fluid are you using?

tonythetarga · 07-31-2007, 06:21 PM

can you still see the groove in the center of the pad? If you can then the pads are still above 50% and are certainly usable for normal street use. Track rule of thumb is replace when they get thinned than 50% pad left.

DelPico · 08-01-2007, 03:04 AM

There is no groove in either pad.

I bled the brakes a few weeks ago. I don't think I got out all the old stuff though. Maybe I should bleed again. I was told when I bled the brakes that the rotors looked good.

David

GothingNC · 08-01-2007, 04:01 AM

I would replace them now while your in there.

Why spend the time cleaning everthing up and then doing the same job over again in a few thousand miles.

tonythetarga · 08-01-2007, 05:11 AM

Quote:

Originally Posted by GothingNC

I would replace them now while your in there.

Why spend the time cleaning everthing up and then doing the same job over again in a few thousand miles.

+1. It will give you a chance to inspect the rubber boots around the pistons as well. Make sure they aren't baked crisp and that there are no tears in the rubber that will let brake dust and rust collect on the pistons. Work them back and forth several times as well but be aware that if your pads are now worn and your fluid reservoir is full, when you back the pistons back in the caliper you might push fluid out the overflow tube and on the ground. It will drop to the inside front of the front left wheel.

KTL · 08-01-2007, 08:05 AM

I believe the brake fade problem is not the pad thickness. .8 or .9cm is about 50+ % of original thickness, which is fine. Typical new thickness is 12, 15, 17mm for the A caliper pad, depending on pad type or manufacturer.

Were you riding the brakes alot and how old, what type is the fluid that was in there? But it sounds like the problem's returned. I would bet on air in the system like others said. Street use should not cause brakes to fade.

Could be a problem with the master cylinder too. Depending on ambient temperature and age of the master, the operation of it can be intermittant. I've seen it happen on a handful of street cars where the brakes are fine one day and then the pedal goes away, only to be fine again. Turned out be the master in those instances

tonythetarga · 08-01-2007, 05:28 PM

Quote:

Originally Posted by KTL

Could be a problem with the master cylinder too. Depending on ambient temperature and age of the master, the operation of it can be intermittant. I've seen it happen on a handful of street cars where the brakes are fine one day and then the pedal goes away, only to be fine again. Turned out be the master in those instances

Good point here. The other question is how you are bleeding. If you are manually bleeding by pushing on the pedal, and if you push the pedal to the floor, it will be out of its normal "range of travel" and it could cause damage to the O-ring seal which could account for the soft pedal. With the car off, pump the pedal until it gets good and firm. Hold the pressure on the pedal and if you feel it start to sink, then there is a good chance that the seal in the M/C is damaged or worn out.