Pad knock back - due to driving style?
03-12-2013, 09:11 AM
#16
Drifting
If your track location data feed is precise enough, check the lines through the turns preceeding where you were experiencing knockback. Is the other driver taking the same line and using the same amound of curbing that you do?
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
03-12-2013, 09:41 AM
#17
Rennlist Member
I've had some form of knockback in every race car I've ever had. The gt3r is the best, probably due to the very stiff uprights and brembo anti knockback seals, but I still habitually left foot tap before brake zones. My e36 with stoptechs is the worst. Wish I could find a cure....
A quick look at the data reveals some interesting things. I looked at two average laps that were within 0.05 seconds of each other (and about 1.5sec slower than qualifying times). In all of the braking zones I'm on the brakes a lot harder, by an average of about 0.3G. I'm also on the brakes for a shorter period of time, by as much as ~0.5 sec and as far as 100 feet. I'm probably slowing the car too much, and I saw a couple of spots where I could carry a few more MPH through the turns. The other driver may not have been as heavy on the brakes because it was his first time in the car and he didn't know the limits before lock-up. My lap should have been faster but I lost all of my margin in one tricky high speed turn. So it looks like he was spending a lot more time on the brakes and not braking as hard.
If your track location data feed is precise enough, check the lines through the turns preceeding where you were experiencing knockback. Is the other driver taking the same line and using the same amound of curbing that you do?
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
03-12-2013, 09:57 AM
#18
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If the knockback is caused by the rotor pushing the pads back (from caliper, rotor, upright, etc flex), how does applying the brakes differently stop that?
03-12-2013, 10:02 AM
#19
They are simply springs that start around the size of your piston then get smaller. They simply fit behind the piston. They are very light. I was surprised to see that they would move the piston at all, but on the bench they appeared to work.
I also got a new set of dust boots/rings from paragon to complete the rebuild, and some red rattle can to make things look good
03-12-2013, 10:02 AM
#20
Rennlist Member
Less force input in the system means less force having to be dissipated.
03-12-2013, 10:50 AM
#21
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03-12-2013, 11:01 AM
#22
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The rotor pushes the pad back due to caliper flex, rotor flex, upright flex, etc. Some of that flex can be reduced by using less dramatic inputs.
03-12-2013, 12:09 PM
#23
Drifting
Thread Starter
That could be part of it. He's not very sensitive to suspension changes in the car and doesn't provide very detailed feedback. Maybe since he was starting his braking earlier than me and not braking as hard he never felt the "oh s#it" moment when the pedal goes way past where you expect it to engage.
03-12-2013, 12:15 PM
#24
Drifting
Thread Starter
If your track location data feed is precise enough, check the lines through the turns preceeding where you were experiencing knockback. Is the other driver taking the same line and using the same amound of curbing that you do?
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
There could be bumps in the track on the loaded side of the car that the other driver is missing, or he's using less (or no) curb at track out.
03-12-2013, 01:39 PM
#25
Rennlist Member
I have the same issue in my car when I use a lot of rough curbing.
The springs sound like a good idea but it seems the spring would result in the pad pushing against the rotor continuously ever so slightly which would scrub speed and wear out pads/rotors faster?
The springs sound like a good idea but it seems the spring would result in the pad pushing against the rotor continuously ever so slightly which would scrub speed and wear out pads/rotors faster?
03-12-2013, 02:04 PM
#26
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Heck, in some series, those "helper" springs are illegal. Don't know why...
If there is "knock back," it's a mechanical issue. For whatever reason (lateral shock loading or hydraulics), the rotor is moving side to side in relation to the caliper. Even floating pin calipers (as well as bolt-on versions) are attached to the upright and the stub axle and hub assemblies have to move to make this happen.
Still have questions regarding VR's "soft, long" brakes theory. This idea is not supported by Brembo, PFC or any of the braking manufacturers for proper thermal operation of the braking systems using their components.
That "soft, longer" braking is also not a skills execution goal that I've seen any of the top pros use, but that's another discussion because I don't think this is a thermal issue. It's a mechanical one and should be treated that way.
I do understand the idea and agree with VR's goal of higher entry speed achieved by earlier release, but this covers the last few car lengths of slowing and should not be over the whole braking episode. My experience and opinion, only.
If there is "knock back," it's a mechanical issue. For whatever reason (lateral shock loading or hydraulics), the rotor is moving side to side in relation to the caliper. Even floating pin calipers (as well as bolt-on versions) are attached to the upright and the stub axle and hub assemblies have to move to make this happen.
Still have questions regarding VR's "soft, long" brakes theory. This idea is not supported by Brembo, PFC or any of the braking manufacturers for proper thermal operation of the braking systems using their components.
That "soft, longer" braking is also not a skills execution goal that I've seen any of the top pros use, but that's another discussion because I don't think this is a thermal issue. It's a mechanical one and should be treated that way.
I do understand the idea and agree with VR's goal of higher entry speed achieved by earlier release, but this covers the last few car lengths of slowing and should not be over the whole braking episode. My experience and opinion, only.
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03-12-2013, 02:08 PM
#28
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Heck, in some series, those "helper" springs are illegal. Don't know why...
If there is "knock back," it's a mechanical issue. For whatever reason (lateral shock loading or hydraulics), the rotor is moving side to side in relation to the caliper. Even floating pin calipers (as well as bolt-on versions) are attached to the upright and the stub axle and hub assemblies have to move to make this happen.
Still have questions regarding VR's "soft, long" brakes theory. This idea is not supported by Brembo, PFC or any of the braking manufacturers for proper thermal operation of the braking systems using their components.
That "soft, longer" braking is also not a skills execution goal that I've seen any of the top pros use, but that's another discussion because I don't think this is a thermal issue. It's a mechanical one and should be treated that way.
I do understand the idea and agree with VR's goal of higher entry speed achieved by earlier release, but this covers the last few car lengths of slowing and should not be over the whole braking episode. My experience and opinion, only.
If there is "knock back," it's a mechanical issue. For whatever reason (lateral shock loading or hydraulics), the rotor is moving side to side in relation to the caliper. Even floating pin calipers (as well as bolt-on versions) are attached to the upright and the stub axle and hub assemblies have to move to make this happen.
Still have questions regarding VR's "soft, long" brakes theory. This idea is not supported by Brembo, PFC or any of the braking manufacturers for proper thermal operation of the braking systems using their components.
That "soft, longer" braking is also not a skills execution goal that I've seen any of the top pros use, but that's another discussion because I don't think this is a thermal issue. It's a mechanical one and should be treated that way.
I do understand the idea and agree with VR's goal of higher entry speed achieved by earlier release, but this covers the last few car lengths of slowing and should not be over the whole braking episode. My experience and opinion, only.
03-12-2013, 02:22 PM
#30
Rennlist Member
"I think what you will find is a combination of both your styles works best in many cases: on the brakes more softly AND for less duration. Not only does this reduce the opportunity for your car's brakes to experience knockback...but it is also way faster! "
Not softer longer...softer & short.