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Hard shakes under braking.

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Running stop tech slotted rotors with HP Plus pads all around. Noticed after two track days, well during the second track day at Watkins glen under hard braking from 120MPH area, coming down get very violent front end shake. Is it likely I warped and ruined the rotors after a couple sessions? I'm at my 4th track day now and shake is there and just as bad. Can't really get aggressive on braking because the front feels like the wheels are going to shake off.
 

ArizonaBOSS

Because racecar.
Moderator
8,730
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Arizona, USA
HP Plus pads probably melted/deposited an unwanted layer on your rotors and/or maybe front hub failure.

Try having the rotors turned and see if it goes away; also check your front wheels/hubs for play when the front end is in the air.
 
Checked wheels hubs bushings bearings last night, all seems to be good there. The slots in the rotors are still very defined, no build up. I just find it hard to believe I warped them pretty much within 6 sessions, 4 at limerock and two at Watkins glen. But stoping from like 120 hard on the brakes I can hardly hang onto the wheel.
 
Cool. I'll try that out, thank you. Pilot super sports are about done also so today has just been kind of a mess. August is too hot for track time so will start again in September.
 
1,022
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It's most likely just deposits on the rotors from the pads. Most people mis-diagnose and think they are warping the rotors which is almost never the case. There is a really good article about this you can find on the web if you do a search. Try rebeding the rotors when everything is cool and you may be able to clean that layer off or if you have a set of more aggressive pads they should do the trick. If not pull the rotors and sand them down. I have never turned my rotors because they were either too thin to turn and most don't recommend turning a rotor used on a track car. I wouldn't compromise the integrity of the rotor, just get some new ones. The OEM's are super cheap
 
Flyboygsxr said:
It's most likely just deposits on the rotors from the pads. Most people mis-diagnose and think they are warping the rotors which is almost never the case. There is a really good article about this you can find on the web if you do a search. Try rebeding the rotors when everything is cool and you may be able to clean that layer off or if you have a set of more aggressive pads they should do the trick. If not pull the rotors and sand them down. I have never turned my rotors because they were either too thin to turn and most don't recommend turning a rotor used on a track car. I wouldn't compromise the integrity of the rotor, just get some new ones. The OEM's are super cheap
+1
Slotted rotors are typically not "turnable" due to the slots that can cause chip out or skipping on a brake lath - blanchard grinding (google it) is the only way to turn slotted or drilled rotors safely, but like Flyboygsxr stated not recommended for track rotors - rotors are just part the consumable cost of tracking your car.
If you read the Stoptech white paper on warping rotors you'll come away thinking it has to be pad build up, well it may be true but I have warped 3+ sets of Stoptech rotors (Audi S4 w/ST40 calipers), one set that was replaced by Stoptech. Take them off, run them down to a quality brake garage and have them check the run out - if they're out it's time for new rotors, if not try the sandpaper! My2Cents
 

Grant 302

basic and well known psychic
I'd also double check alignment. Could also have been wheel balance since the tires are almost done.

Agree with the others that a warped rotor is unlikely. For most track use, I think the rotors are pretty evenly heated.
 

drano38

Wayne
1,130
318
Been there, done that, changed to more aggressive brand of pad.
See photo below. This was a rotor-friendly brand. Shiny and smooth on the inner part of the rotor face. But towards the edge, you'll see brake pad deposits. Than makes the brakes shudder like you described.
I switched to PFC 01 and 08 pads for the front. They are not quite as rotor friendly, so they keep the rotor clean.
Brands that say their pads are very rotor friendly can leave deposits if you don't bed them just right. Not sure what I was doing wrong with the other brand, but PFC are easy to bed, don't deposit, and don't eat rotors. Hawk DTC 70 and 60 will keep a clean rotor, but are a little more aggressive at wearing the rotor itself.
You may have warped the rotors, but I think not unless you're driving 10/10 all the time. A friend drives his '12 GT almost as hard as cloud9, without brake cooling kit, and he doesn't warp his rotors (and I tell him he's crazy for not installing a cooling kit every time I see him).
Good luck on your solution, and keep us posted.

2012-04-09%2007.57.36_zpsyrqs4lha.jpg
 

576

Same experience with Stoptech slotted & 5.0 Hawk pads. After a day at Laguna, front rotors looked like I was trying to stop my car, a race trailer, an Airstream and a Z/28. HEAVILY warped & heat scored. AND I felt I was braking maybe 5-6/10ths! Went back to basics: Stock rotors with a slightly more aggressive pad. No problems.
 
My rotors look very similar to the one above. Almost like a white streak all around the fronts. I really leaned on them the last session of the day and in the 3 big braking zones from about a 120mph, 100mph and 80mph stop it was going into ABS every time but it clearly left the deposits on the rotors. I don't mind switching to a more aggressive pad but I'm not changing them out after every track day. I drive the car a couple times a week on the street and I just don't want to do all the swapping. I honestly chose the stop techs and Hawks because I can get them for about 40% off list price and I read a lot about these rotors being better than DBA's.
 

drano38

Wayne
1,130
318
I've never ran those pads, but being a heavy duty street/light track pad, they most likely are not aggressive enough to clean deposits off rotors. So even your heavy braking at/close to ABS on your last sessions most likely won't clean it off. And you're probably driving harder than the pads can handle.
Changing pads is generally the way of life for a dual use car.
I run PFC 01 or 08 on track, and switch to PFC Z-rated pads for the street. They're compatible, so don't change rotors. Front pad swap is actually pretty simple.
Rears I run Carbotech XP-8 street and track. Keeps a clean rotor, and last a long time (~10 weekends) with traction control off.
Some people have had good luck with Pagid pads for dual use. They are kind to rotors, so some people got deposits during track use, and switched to different brands.
Individual driving styles dictate what pads work for us. Just like certain brands of blue jeans fit better. YMMV.
 
Flyboygsxr said:
It's most likely just deposits on the rotors from the pads. Most people mis-diagnose and think they are warping the rotors which is almost never the case. There is a really good article about this you can find on the web if you do a search. Try rebeding the rotors when everything is cool and you may be able to clean that layer off or if you have a set of more aggressive pads they should do the trick. If not pull the rotors and sand them down. I have never turned my rotors because they were either too thin to turn and most don't recommend turning a rotor used on a track car. I wouldn't compromise the integrity of the rotor, just get some new ones. The OEM's are super cheap
This.

I actually turned my fastest lap time ever at Road America a few weeks ago with severe shudder coming down from 150 mph to 50. If the video on my GoPro was shaking as bad as my head it would have been unwatchable. I just power through it and they either rebed themselves or once you change rotors its gone. Of course I was going through a set of front pads a day and rotors don't last long there either :p
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
cloud9 said:
This.

I actually turned my fastest lap time ever at Road America a few weeks ago with severe shudder coming down from 150 mph to 50. If the video on my GoPro was shaking as bad as my head it would have been unwatchable. I just power through it and they either rebed themselves or once you change rotors its gone. Of course I was going through a set of front pads a day and rotors don't last long there either :p

If you weren't getting that 350 I'd say it's time for a Brembo Pro-Kit upgrade.
 
Check out your front ball joints. I chased down a brake shudder for months (years?) only to find that steeda ball joints were the wiggling component.

Here's what it looks like under the car:
http://youtu.be/9dLmev5pUP8
 
neema said:
Check out your front ball joints. I chased down a brake shudder for months (years?) only to find that steeda ball joints were the wiggling component.

Just to add on that...It probably wouldn't hurt to also check the rearward FLCA bushing (fliud filled one) for any play or slop. Its my understanding that this bushing plays a big role under braking conditions
 

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