Strange braking issue - increased pedal travel
08-12-2011, 04:19 PM
#16
Drifting
Fingers crossed the master is the issue because something would still be wrong if you have to tighten the nut that much to make the problem go away.
Here's a wild thought. If the problem persists and is very predictable, try stopping w/o using the brakes (just use the parking brake) when you're sure you'd have a long pedal. Go around to each wheel and see if the outer brake pad is loose - or - if you can get into your garage without using the brakes, pull the wheels and check everything. It might help you isloate which wheel is causing the problem.
Here's a wild thought. If the problem persists and is very predictable, try stopping w/o using the brakes (just use the parking brake) when you're sure you'd have a long pedal. Go around to each wheel and see if the outer brake pad is loose - or - if you can get into your garage without using the brakes, pull the wheels and check everything. It might help you isloate which wheel is causing the problem.
08-12-2011, 04:32 PM
#17
Nordschleife Master
Thread Starter
Fingers crossed the master is the issue because something would still be wrong if you have to tighten the nut that much to make the problem go away.
Here's a wild thought. If the problem persists and is very predictable, try stopping w/o using the brakes (just use the parking brake) when you're sure you'd have a long pedal. Go around to each wheel and see if the outer brake pad is loose - or - if you can get into your garage without using the brakes, pull the wheels and check everything. It might help you isloate which wheel is causing the problem.
Here's a wild thought. If the problem persists and is very predictable, try stopping w/o using the brakes (just use the parking brake) when you're sure you'd have a long pedal. Go around to each wheel and see if the outer brake pad is loose - or - if you can get into your garage without using the brakes, pull the wheels and check everything. It might help you isloate which wheel is causing the problem.
Now to just figure out how to get the car to stop in my driveway or garage without crashing into anything and NOT hitting the brakes...
08-13-2011, 09:52 AM
#18
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A couple of comments –
Please don’t over tighten the front bearings – that has broken more hubs/spindles that you can imagine. I had one customer break 2 spindles in one weekend at the track because his overzealous pit crew over tightened the bearings. BTW – this failure included the wheel leaving the car at speed!!!
I have a couple of completely different ideas –
Do you have the Phillips head rotor retaining screws on all your rotors? Any rotor run out at all will push the pads back and give you more pedal travel. If you don’t have the retaining screws the rotors may move a little when changing braking direction (forward to reverse).
Did you clean up the rotor mounting surface? (preferably with a rol-loc pad on an angle grinder), especially with the 86 style hub anything between the hub and rotor and the rotor and wheel will cause rotor run out that will push the pads back.
As for stopping the car in the right place on your driveway – get two 2x4 and lay them out 2’ apart. Drive up slowly and roll over the first and the second will stop you. The first one will prevent you from rolling back. Standard practice at the track for stopping after a hot session – you don’t want your pads hard on the rotor when you park with them hot!!
Please don’t over tighten the front bearings – that has broken more hubs/spindles that you can imagine. I had one customer break 2 spindles in one weekend at the track because his overzealous pit crew over tightened the bearings. BTW – this failure included the wheel leaving the car at speed!!!
I have a couple of completely different ideas –
Do you have the Phillips head rotor retaining screws on all your rotors? Any rotor run out at all will push the pads back and give you more pedal travel. If you don’t have the retaining screws the rotors may move a little when changing braking direction (forward to reverse).
Did you clean up the rotor mounting surface? (preferably with a rol-loc pad on an angle grinder), especially with the 86 style hub anything between the hub and rotor and the rotor and wheel will cause rotor run out that will push the pads back.
As for stopping the car in the right place on your driveway – get two 2x4 and lay them out 2’ apart. Drive up slowly and roll over the first and the second will stop you. The first one will prevent you from rolling back. Standard practice at the track for stopping after a hot session – you don’t want your pads hard on the rotor when you park with them hot!!
08-13-2011, 11:23 AM
#19
Nordschleife Master
Thread Starter
A couple of comments –
Please don’t over tighten the front bearings – that has broken more hubs/spindles that you can imagine. I had one customer break 2 spindles in one weekend at the track because his overzealous pit crew over tightened the bearings. BTW – this failure included the wheel leaving the car at speed!!!
I have a couple of completely different ideas –
Do you have the Phillips head rotor retaining screws on all your rotors? Any rotor run out at all will push the pads back and give you more pedal travel. If you don’t have the retaining screws the rotors may move a little when changing braking direction (forward to reverse).
Did you clean up the rotor mounting surface? (preferably with a rol-loc pad on an angle grinder), especially with the 86 style hub anything between the hub and rotor and the rotor and wheel will cause rotor run out that will push the pads back.
As for stopping the car in the right place on your driveway – get two 2x4 and lay them out 2’ apart. Drive up slowly and roll over the first and the second will stop you. The first one will prevent you from rolling back. Standard practice at the track for stopping after a hot session – you don’t want your pads hard on the rotor when you park with them hot!!
Please don’t over tighten the front bearings – that has broken more hubs/spindles that you can imagine. I had one customer break 2 spindles in one weekend at the track because his overzealous pit crew over tightened the bearings. BTW – this failure included the wheel leaving the car at speed!!!
I have a couple of completely different ideas –
Do you have the Phillips head rotor retaining screws on all your rotors? Any rotor run out at all will push the pads back and give you more pedal travel. If you don’t have the retaining screws the rotors may move a little when changing braking direction (forward to reverse).
Did you clean up the rotor mounting surface? (preferably with a rol-loc pad on an angle grinder), especially with the 86 style hub anything between the hub and rotor and the rotor and wheel will cause rotor run out that will push the pads back.
As for stopping the car in the right place on your driveway – get two 2x4 and lay them out 2’ apart. Drive up slowly and roll over the first and the second will stop you. The first one will prevent you from rolling back. Standard practice at the track for stopping after a hot session – you don’t want your pads hard on the rotor when you park with them hot!!
Excellent idea on using the wood blocks - thanks. I will do exactly that
And no worries about tightening the bearings - it will be not much more than a trip around the block. I live in the suburbs, it's a very small block. Probably 1/4 mile all the way around.
08-15-2011, 12:22 PM
#20
Nordschleife Master
Thread Starter
Ok - so still didn't get anywhere.
Over-tightened wheel bearings didn't fix it.
A new (used) master also didn't fix it.
Took Jerome's and Chris's suggestions and got the car up into the garage without hitting the brakes. Raised the car up. No one single wheel had any more or less resistance than the others. Spun the wheels (with help from my dad and the neighbors) and had my wife hit the brake pedal slowly, to see if perhaps one caliper was late to grab (suggesting that just that one caliper was having its pistons sucked back) and still reached no conclusion. Each wheel seemed to bite right around the same time.
To ensure that I'd get the sinking pedal I did a series of aggressive sways on the street similar to a slalom in an autocross. So it's plausible that all the pistons were being pulled back as I did a pretty even amount of right/left sweeps with the wheel.
At this point, all I can figure is that the pistons are getting pushed back in their bores due to G-forces. That or I have a collapsed brake line. The lines don't have many miles on them (braided lines installed by previous owner) but it's really the only part of the brake system I haven't touched myself. That or the far-left-field idea that, since the strut bearings are going, maybe that tiny little clunk I feel is juuuust enough extra force to knock the pads back? Yeah, I know... I'm *really* reaching here.
To band-aid the issue I adjusted the brake pedal such that the pedal, when it sinks, is still above the gas pedal, as going for a heel-toe downshift when the pedal fell below the throttle pedal was the most alarming and distracting. It made the AX yesterday a bit more liveable.
Thanks everybody for the help.
Over-tightened wheel bearings didn't fix it.
A new (used) master also didn't fix it.
Took Jerome's and Chris's suggestions and got the car up into the garage without hitting the brakes. Raised the car up. No one single wheel had any more or less resistance than the others. Spun the wheels (with help from my dad and the neighbors) and had my wife hit the brake pedal slowly, to see if perhaps one caliper was late to grab (suggesting that just that one caliper was having its pistons sucked back) and still reached no conclusion. Each wheel seemed to bite right around the same time.
To ensure that I'd get the sinking pedal I did a series of aggressive sways on the street similar to a slalom in an autocross. So it's plausible that all the pistons were being pulled back as I did a pretty even amount of right/left sweeps with the wheel.
At this point, all I can figure is that the pistons are getting pushed back in their bores due to G-forces. That or I have a collapsed brake line. The lines don't have many miles on them (braided lines installed by previous owner) but it's really the only part of the brake system I haven't touched myself. That or the far-left-field idea that, since the strut bearings are going, maybe that tiny little clunk I feel is juuuust enough extra force to knock the pads back? Yeah, I know... I'm *really* reaching here.
To band-aid the issue I adjusted the brake pedal such that the pedal, when it sinks, is still above the gas pedal, as going for a heel-toe downshift when the pedal fell below the throttle pedal was the most alarming and distracting. It made the AX yesterday a bit more liveable.
Thanks everybody for the help.
11-15-2011, 03:12 PM
#21
Nordschleife Master
Thread Starter
Just to close the loop on this one too for future searchers....
It seems I have finally rectified the issue. This past weekend I had my spare set of calipers rebuilt - this time by a professional, rather than me doing it. Installed them, along with a brand new master cylinder, and it seems the problem has gone away.
As I tried swapping masters before (from mine to a borrowed used one) with no change, I don't think the master fixed it. I just installed a brand new one for good measure. Must've been the caliper rebuild that did it.
I can still get the pads to kick back a teeeny tiny bit if I really zig zag back and forth hard (like an AX slalom) but it's NOTHING like it was before. IMO I think that is probably "normal." Might even be placebo, or me being overly-critical. Hard turns, on-ramps, etc. that previously caused my pedal to sink, no longer cause the problem.
It seems I have finally rectified the issue. This past weekend I had my spare set of calipers rebuilt - this time by a professional, rather than me doing it. Installed them, along with a brand new master cylinder, and it seems the problem has gone away.
As I tried swapping masters before (from mine to a borrowed used one) with no change, I don't think the master fixed it. I just installed a brand new one for good measure. Must've been the caliper rebuild that did it.
I can still get the pads to kick back a teeeny tiny bit if I really zig zag back and forth hard (like an AX slalom) but it's NOTHING like it was before. IMO I think that is probably "normal." Might even be placebo, or me being overly-critical. Hard turns, on-ramps, etc. that previously caused my pedal to sink, no longer cause the problem.
11-16-2011, 11:09 AM
#24
Nordschleife Master
Thread Starter
