I tried a search and read lots of threads, but any matching threads I found were left unresolved.

I changed the front brake pads on my 968 (similar to 951), and now the pedal is soft and goes down farther than before. I didn't drive the car very far, and didn't test the stopping power, since the pedal going down farther got me worried. I got the impression the stopping power is weaker than before, though.

I put in a set of used pads from another car I had. They're just regular pads, Jurid or something like that. All I did was push the calipers' pistons back in with a big screwdriver (prying between rotor and old pad) and slipped in the new pads.

I tried pushing the pedal in short strokes to get the pistons to come back out without blowing the MC, but on the very first touch I could feel the pedal was soft and wanted to go down farther than before.

I'm thinking either the MC or a caliper (or both) is messed up. Is there any way to determine?

 

Pump the brakes without the engine running.

Once the pedal gets hard, start the engine.. the pedal should drop aprox 1/2 inch and stop.

If it does this your booster, master, and I would suspece calipers are fine!

I bet once you do this, the pedal feel is MUCH better as well!

 

If you didn't change the rotors the pads will take a while to bed in and will feel spongey. Do the test John suggests first then bed them in using the manufacturer's recommendations.

 

I sometimes get this when changing back and forth between street pads and track pads. My theory is that when squeezing back the pistons, somehow a little bubble of air gets in there. It seems to happen less when I do it slowly.

The solution is to bleed the brakes. It always seems to be either the right rear or right front that gets the bubble.

The different pad material can also be a contributing factor as mentioned. I have to be careful when going from track to street. It takes a while for them to bed in again.

 

OK, I'll start with bleeding since my feeling is that it's a hydraulic issue.

If the rotors are used (were used with regular Mintex street pads, which I just took out), and the replacement pads are used (used with basic rotors, from the rear of a 968, still have like 90% life), shouldn't it behave as though they've already been broken in? I mean the pads were broken in on the last car, and the rotors are already broken in with a similar pad. Is it because the brands are different? I didn't think it would matter - street pad is a street pad.

 

If the existing rotors and pads have "mated" to each other, meaning any grooves in the rotor now match the pad, changing pads would result in a lower percentage of contact until the pad countours itself to the rotor. Obviously the rotors shouldn't have grooves, but thats my take.

 

Bleed and bed the brakes and you will be good to go. You do not have to change rotors when you change pads, if you did most of us 944 racers would be broke.

 

If you push the pistons too far (or too fast?), you can introduce air into the system somehow (just from what I've read).

It'd be silly to start by bleeding when JKW gave you a 30 second solution. Try that first. If it's bad, then go ahead and bleed.

Did you remove the cap from the reservoir before pushing the pistons back into the caliper?

 

Since you're using used pads it is very possible that the pads have some taper to them and some of the pedal travel you're noticing as an increase is the added travel necessary to seat the entire pad surface to the rotor. If this is the case then driving the car and using the brakes will wear the pads such that the pedal should improve over time. I notice this in my racecar when I swap my used from pads to the rear. It takes a few laps to seat the pads (wear the taper to the new axle) and the pedal improves.

 

Sorry, I did see JKW's post and I forgot to say that I tried it and it didn't change anything. Thanks for the suggestion JKW.

A lot of good ideas here. I'll have some time this weekend so I'll try everything and report back!