Brake shimmy at end of tracks days...
03-31-2017, 04:46 PM
#1
Registered User
Thread Starter
Brake shimmy at end of tracks days...
Ok, read the threads on bedding your pads...
End of last season, usually on the 3rd and 4th sessions of the day car would shimmy with hard braking. Not a lot, just a high frequency wiggle of the steering wheel back and forth when high speed braking...
Didn't do it the first 2 runs of the day...
Switched to PFC 11's. First 2 sessions of the next track day... no issues. By the end of the day, wiggles are back.
Driving home on the high way, no issues. High speed braking on the highway... no issues...
Checked the rotors for runout last week with dial indicator... look good...
So, what am I doing wrong? I do the cool down lap. Do my best not to tap the braked before parking (though you do have to apply some brake--- I do need to stop in the parking spot! Don't use parking brake, etc...
Best I can tell, I must be imprinting somehow?
Its not like my brakes get silly hot, I am in the beginner group.
Was worried about loose tie rods or something, but no such issues seen. And, not sure why it only occurs at the end of the day...
Should I aim to re-bed the pads the morning of every track day?
Thoughts appreciated, first track day set for 3 weeks from now and tying up loose ends...
End of last season, usually on the 3rd and 4th sessions of the day car would shimmy with hard braking. Not a lot, just a high frequency wiggle of the steering wheel back and forth when high speed braking...
Didn't do it the first 2 runs of the day...
Switched to PFC 11's. First 2 sessions of the next track day... no issues. By the end of the day, wiggles are back.
Driving home on the high way, no issues. High speed braking on the highway... no issues...
Checked the rotors for runout last week with dial indicator... look good...
So, what am I doing wrong? I do the cool down lap. Do my best not to tap the braked before parking (though you do have to apply some brake--- I do need to stop in the parking spot! Don't use parking brake, etc...
Best I can tell, I must be imprinting somehow?
Its not like my brakes get silly hot, I am in the beginner group.
Was worried about loose tie rods or something, but no such issues seen. And, not sure why it only occurs at the end of the day...
Should I aim to re-bed the pads the morning of every track day?
Thoughts appreciated, first track day set for 3 weeks from now and tying up loose ends...
03-31-2017, 05:18 PM
#3
Registered User
Thread Starter
That's what I figured...
How do you prevent it?
I do the cool down lap. Drive into the pits, turn into the grass lot or parking lot, gently apply the brakes (I do have to stop!) let the car roll 1-2 feet, shut off, pop into first gear so doesn't roll...
Am I doing something wrong here?
I thought pad deposits were from the pad sitting against the rotor while parked...hot.
How do you prevent it?
I do the cool down lap. Drive into the pits, turn into the grass lot or parking lot, gently apply the brakes (I do have to stop!) let the car roll 1-2 feet, shut off, pop into first gear so doesn't roll...
Am I doing something wrong here?
I thought pad deposits were from the pad sitting against the rotor while parked...hot.
03-31-2017, 05:21 PM
#4
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What type of car? Did you do a break-in procedure when the pads were new?
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Your Porsche Parts Superstore
Parts | Tech-Session | Facebook | Youtube
Jason Burkett
Paragon Products - Porsche Parts & Accessories*- 800.200.9366
Tech Session - Porsche Tech & Info*- 361.289.8834
jason@paragon-products.com
03-31-2017, 05:24 PM
#5
Registered User
Thread Starter
Did to the high speed near stops as recommended...
Should I do it again?
Again, oddly, its fine after a nice high way cruise back home and back to the track... does that wipe the deposits off???
Only occurs when rotors are nice and hot, at the end of the day...
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04-01-2017, 01:15 AM
#8
Being a beginner means nothing. In fact you might abuse brakes more than an experienced guy. In general trackers use too much brake. That said it sounds like you are getting faster as your day progresses. The pads and rotors get hotter too. You are getting pad transfer that is incompatible with the seasoning of the rotor from the 1st set of pads. When you start monitoring and adjusting tire pressures as you get better you will find you start the morning at "x" psi. Then ever session you bleed out air so that your cold temp ends at your target hot temp. This bleed out of air will go on until your day ends at 5pm. Just as your tires grow the heat soak in the car builds. That's why you see the transfer of pad at the end of the day. I think it is a transfer issue because you say after a while everything is back to normal. That's because you are scraping off the transfer layer as you continue to drive home etc. I bet with your next set of rotors when you season them with the pad compound you like to use this problem will disappear.
You can salvage a used rotor by taking them to a pepboys and doing a very light "turn" of the rotors. Or you can use a more aggressive pad and see if that will not smear on your rotors when hot.
I actually don't think bedding pad or seasoning a rotor makes you faster or brake better or have consumables last longer if the right pad is chosen for the heat range it will be used for. That's just my experience. I have bed pads and seasoned rotors before and it seems like a waste of time. People get issues like yours then become preachers of "the good of bedding pads." I really think the problem is improper pad selection for the job.
You can better choose a pad with some data. Something as simple as caliper paint from pegasus racing can give you an idea of your operating temps. Then you can choose an appropriate pad and test it. Some systems like carbotech are really simple they go xp8-xp24. Lets say you pick xp10. You test it and you want a little more you go xp12. Other makers are not so easy in how they do their compounds.
You can salvage a used rotor by taking them to a pepboys and doing a very light "turn" of the rotors. Or you can use a more aggressive pad and see if that will not smear on your rotors when hot.
I actually don't think bedding pad or seasoning a rotor makes you faster or brake better or have consumables last longer if the right pad is chosen for the heat range it will be used for. That's just my experience. I have bed pads and seasoned rotors before and it seems like a waste of time. People get issues like yours then become preachers of "the good of bedding pads." I really think the problem is improper pad selection for the job.
You can better choose a pad with some data. Something as simple as caliper paint from pegasus racing can give you an idea of your operating temps. Then you can choose an appropriate pad and test it. Some systems like carbotech are really simple they go xp8-xp24. Lets say you pick xp10. You test it and you want a little more you go xp12. Other makers are not so easy in how they do their compounds.
04-01-2017, 10:14 AM
#9
Registered User
Thread Starter
Being a beginner means nothing. In fact you might abuse brakes more than an experienced guy. In general trackers use too much brake. That said it sounds like you are getting faster as your day progresses. The pads and rotors get hotter too. You are getting pad transfer that is incompatible with the seasoning of the rotor from the 1st set of pads. When you start monitoring and adjusting tire pressures as you get better you will find you start the morning at "x" psi. Then ever session you bleed out air so that your cold temp ends at your target hot temp. This bleed out of air will go on until your day ends at 5pm. Just as your tires grow the heat soak in the car builds. That's why you see the transfer of pad at the end of the day. I think it is a transfer issue because you say after a while everything is back to normal. That's because you are scraping off the transfer layer as you continue to drive home etc. I bet with your next set of rotors when you season them with the pad compound you like to use this problem will disappear.
You can salvage a used rotor by taking them to a pepboys and doing a very light "turn" of the rotors. Or you can use a more aggressive pad and see if that will not smear on your rotors when hot.
I actually don't think bedding pad or seasoning a rotor makes you faster or brake better or have consumables last longer if the right pad is chosen for the heat range it will be used for. That's just my experience. I have bed pads and seasoned rotors before and it seems like a waste of time. People get issues like yours then become preachers of "the good of bedding pads." I really think the problem is improper pad selection for the job.
You can better choose a pad with some data. Something as simple as caliper paint from pegasus racing can give you an idea of your operating temps. Then you can choose an appropriate pad and test it. Some systems like carbotech are really simple they go xp8-xp24. Lets say you pick xp10. You test it and you want a little more you go xp12. Other makers are not so easy in how they do their compounds.
You can salvage a used rotor by taking them to a pepboys and doing a very light "turn" of the rotors. Or you can use a more aggressive pad and see if that will not smear on your rotors when hot.
I actually don't think bedding pad or seasoning a rotor makes you faster or brake better or have consumables last longer if the right pad is chosen for the heat range it will be used for. That's just my experience. I have bed pads and seasoned rotors before and it seems like a waste of time. People get issues like yours then become preachers of "the good of bedding pads." I really think the problem is improper pad selection for the job.
You can better choose a pad with some data. Something as simple as caliper paint from pegasus racing can give you an idea of your operating temps. Then you can choose an appropriate pad and test it. Some systems like carbotech are really simple they go xp8-xp24. Lets say you pick xp10. You test it and you want a little more you go xp12. Other makers are not so easy in how they do their compounds.
Will try a harder pad next time also...
The bearing races are press fit into the rotors, hard to take off and get skimmed... Cant find any places that do it on the car, but will look...
Any chance this gets better with use? Can it resolve as the prior pad layer wears down? Would adding more brake duct cooling solve it?
