vibration under braking

[2013kAB]

track day cut short

hello, i cut my 1 day track day short today due to a heavy vibration when applying the brakes in the 80-120mph range. brakes are wilwood fnsl6r 14" kit (http://www.wilwood.com/BrakeKits/BrakeKitsProdFront.aspx?itemno=140-9110-R) (it's a long story why these). the vibration was felt in the steering wheel, i could see the vibration in the steering wheel, i could see my drivers side mirror shake.

on the first couple of laps, they seemed OK, but there was a "groan" feeling. then the 3rd lap it started vibrating. it got a little worse the next 2 laps. 2nd session it was there immediately on the first turn and subsequent turns. it didn't get much worse, but it happened every application of brakes. even before this i notice brake fade in the pads right away. so will be going to a more aggressive pad in the future.

a month ago i did a driving school which included several auto-x type laps on a karting track and i did not detect any groan or vibration. speeds were probably never higher than 60mph. 6-10 continuous laps and i know the brakes got very warm can't quantify though.

on my drive home and through town, i did a 60-30mph hard-ER (not hard-EST) stops and no groan or vibration.

initially my braking was pretty abrupt, but according to my accelerometer i was in the .67g's of braking vs 1.03g's when i did that auto-x type lapping.

the pads i currently have on have been on for about 4,000 miles. i switched to them after having about 4,000 miles of a different pad. all city driving, except for the current pad's auto-x type school event.

could this vibration be from slip/grip due to swapping pads without treating the surface of the rotor? could it be simple warped rotor(s) and just not noticeable when "city" driving?

what should my next steps be? just get new rotors and pads?

thanks,

 

[07TGGT]

Warped rotors probably

 

[Arustik]

track day cut short

hello, i cut my 1 day track day short today due to a heavy vibration when applying the brakes in the 80-120mph range. brakes are wilwood fnsl6r 14" kit (http://www.wilwood.com/BrakeKits/BrakeKitsProdFront.aspx?itemno=140-9110-R) (it's a long story why these). the vibration was felt in the steering wheel, i could see the vibration in the steering wheel, i could see my drivers side mirror shake.

on the first couple of laps, they seemed OK, but there was a "groan" feeling. then the 3rd lap it started vibrating. it got a little worse the next 2 laps. 2nd session it was there immediately on the first turn and subsequent turns. it didn't get much worse, but it happened every application of brakes. even before this i notice brake fade in the pads right away. so will be going to a more aggressive pad in the future.

a month ago i did a driving school which included several auto-x type laps on a karting track and i did not detect any groan or vibration. speeds were probably never higher than 60mph. 6-10 continuous laps and i know the brakes got very warm can't quantify though.

on my drive home and through town, i did a 60-30mph hard-ER (not hard-EST) stops and no groan or vibration.

initially my braking was pretty abrupt, but according to my accelerometer i was in the .67g's of braking vs 1.03g's when i did that auto-x type lapping.

the pads i currently have on have been on for about 4,000 miles. i switched to them after having about 4,000 miles of a different pad. all city driving, except for the current pad's auto-x type school event.

could this vibration be from slip/grip due to swapping pads without treating the surface of the rotor? could it be simple warped rotor(s) and just not noticeable when "city" driving?

what should my next steps be? just get new rotors and pads?

thanks,

Are you running Carbotech pads by any chance? If you are then you likely ruined your rotor. The Carbotech pads (and I'm sure some other brands as well) DON'T mix very well with other brands. So if you're running Carbotechs either stick with them, or resurface rotors in between swapping them. Their material just does mix well with any other material. I believe they claim the same on their website. It likely is the case here.

I recently had a track event and swapped over to the Carbotech's, but resurfaced the rotors (thanks to this forum) and all seems OK. I am getting a vibration, but vibrations on the track could be because you're picking up rubber in your wheel wells - thus throwing off the balance of the wheel. I also run non-DOT slicks and don't even balance them when mounting the tire on the wheel since you're going to pick up so much junk on the track anyway.

Long story short if you're running any sort of race pad either have a rotor for that pad or just resurface every time, or just run your race pad all the time like I do (but I don't daily my car).

Warped rotors probably

Do you even track your car? The most unhelpful post ...

 

[ddd4114]

How do the rotor surfaces look? How did you bed in your pads before the track event?

6-10 autocross runs might not be enough even if the brakes got warm. To properly bed in race pads, you have to get them hot and keep them hot to create a transfer layer on the rotors. If I bed in pads during a track session, I'll sometimes notice vibration for a few laps (unless the rotor is brand new), but it's never enough to make the mirrors shake.

When you drove the car home, how did the brakes feel? If you noticed fade right away during your second session, I'm wondering if you have a partially seized piston. I don't have any experience with Wilwood products, but I haven't gotten a good vibe from friends who do. I think it's unlikely, but it wouldn't hurt to jack up each wheel and see how much drag there is when you spin it.

A cracked rotor will also produce similar symptoms (except for the fade), but I assume you've already checked for that.

 

[07TGGT]

Are you running Carbotech pads by any chance? If you are then you likely ruined your rotor. The Carbotech pads (and I'm sure some other brands as well) DON'T mix very well with other brands. So if you're running Carbotechs either stick with them, or resurface rotors in between swapping them. Their material just does mix well with any other material. I believe they claim the same on their website. It likely is the case here.



I recently had a track event and swapped over to the Carbotech's, but resurfaced the rotors (thanks to this forum) and all seems OK. I am getting a vibration, but vibrations on the track could be because you're picking up rubber in your wheel wells - thus throwing off the balance of the wheel. I also run non-DOT slicks and don't even balance them when mounting the tire on the wheel since you're going to pick up so much junk on the track anyway.



Long story short if you're running any sort of race pad either have a rotor for that pad or just resurface every time, or just run your race pad all the time like I do (but I don't daily my car).







Do you even track your car? The most unhelpful post ...

Y u mad

 

[2013kAB]

the 1st set of pads i used where wilwood bp10 that came with the kit. they don't advertise them as track pads but they bit harder in than my current pad, ebc green stuffs. the wilwood pads had about 2000 street miles and then 1 track day in the rain (slow speeds) and they seemed pretty smooth and good. then winter weather hit and they didn't do well at all. the next pad i tried was the green stuff which worked a lot better in the cold wet slush. they have been OK since winter and that auto-x went well so i figured hey they might hold up for me.

it's that switch between the wilwoods and green stuffs that made me think of the grip-n'-slip - if the bp10s were bedded in pretty well, and if they are way more track orientated then the green stuff then going to the green stuffs without rotor treatment may be the culprit.

does that still apply if you dailly drive for 4,000 miles?

 

[Arustik]

I would assume that if the pads never got hot after driving 4000 miles they wouldn't have the pads material transfer onto the rotor (thus not cause a vibration). That's my educated guess.

PS - You don't NEED to bed track pads in on the street, you can do it in a few warm up laps at the track, it's easy enough.

 

[Arustik]

Try to get the rotors resurfaced and see if you can save them. It's unlikely, but worth a shot. Worse case you can keep them as backups if they are saved.

 

[2013kAB]

the root cause could be because i did not properly resurface before i switched pads and then did street driving for many miles on the new pads followed by really getting the rotors and new pads hot via that school and this track day?

Sent from my Nexus 7 using Tapatalk

 

[STEVE_POE]

probably not rotors at all . check your front hubs or Ball joints . that is what it sounds like to me

 

[TheKurgan]

Or tie rod ends. Mine were done at 50k.

 

[AndrewNagle]

probably not rotors at all ....check your front hubs............

Hmmm I have had similar vibration and I stupidly pounded out my wheel studs with a hammer instead of pressing them out.

 

[2013kAB]

well i'm starting over and we'll see how it goes. new pads and new rotors.. i'm going to go with carbotech since it seems they have no problem with me switching from their 1521 compound to xp compound for TD. i'm also going to see if the rings i have are salvageable, the shop has never resurfaced slotted rotors.

yeah, i'm one of those that learns the hard way, expensive way

i kind of know now to properly bed stuff in, track pads for track and street pads for street, swap rotors... like i said though seems i can switch compounds with CT. so that's a positive.

 

[barbaro]

I have run into this problem and I am not sure if the solution should be so radical. 1st I imagine that your traction and stability control were off. I had huge repeated brake shudder going into turn three at willow. That is the fastest turn and makes you get on the brakes hard from above 100 mph. Had no problems before and have had no problem since. I kept my rotors and pads but I changed my front camber which was previously at 2.5 to 1.5. Voila, the break shudder disappeared on the next track day and have not had it since. I theorized that the combination of radical camber change and grippier race pads confused the anti-lock system and caused the heavy vibration that could be felt throughout the entire car and especially in the steering wheel. Of course ten people will get on here and tell you 1) that I am full of shit, 2) I don't know what I am talking about and 3) I am a democrat. Which may all be true, however, I can say that I no longer have brake shudder. Now fuel starvation in some steady state corners. That problem I still have.

 

[dontlifttoshift]

I had a shudder at high speeds, too. Hard braking from 90 mph or more. When I slowed down it went away. Normal driving it is not a problem.

I don't worry about it. I wouldn't trade the camber for a little vibration, but that's me.

Barbaro......

1. Sometimes you are
2. Sometimes you don't
3. That's your problem

The poor me attitude is very old already, we have all gotten over it, you should too.

 

[2013kAB]

Edit: nevermind.

 

[barbaro]

Thank you Donny for the peptalk. And what you said about me applies to virtually everyone here. so since I am among such good friends, I will act accordingly. Not.

 

[2013kAB]

new rotors and pads apparently did not solve the problem. installer did somewhat of a bed in, but said as soon as they braked from 70mph the vibration was there. kind of wish i could have done the bed in myself. they were braking fairly hard but not into abs. i did a bed-in in myself but didn't get up to over 65mph and things seemed OK.

i do hear a "wa wa" sound which i've heard for a while now, thought it was from switch from snow tires/wheels to my all seasons. but they did a wheel balance too and apparently felt the vibration after. along with the "wa wa" i hear a really low-frequency "wo wo". changes with speed. does not change when going about 50 and acting like i'm warming up my tires (left-right left-right).

slow speed driving for the last week the brakes do feel better than the old rotors/pads. i did notice a difference with the wheel balance too. but the sound and vibration continues.

another thing i realized is the car wash i used to go to, the track they have on the self-serve wash would hit something "clunk" by my left front wheel. the control arm i think is the lowest. i've been going there for a couple years, once every 3 months or so. but then going through the self serve, i never noticed it until the last 2 times.

going to find a shop and see if they can have a look. bearing, tie rods, maybe the control arm? lots of things more knowledgeable peeps should be able to look at.

 

[JPC]

check your front control arm bushing (the big one)
read posting number #46
http://www.s197forum.com/forum/showthread.php?t=96978&page=3

I had the front bushing replaced. Terry told me he has seen the OEM bushing defect under hard braking on many Mustangs.

 

[2008 V6]

track day cut short

,

Wilwood –

BP-10 pads (Very Rotor friendly) are very good street pads but will melt in ¾ to 1 lap of medium braking. Good for Auto Cross
BP-20 pads (Very rotor friendly) old compound will last (4-5) 20min sessions with 12 to 15 minutes each of medium braking. They have a newer BP-20 compound out that is suppose to be more efficient at medium temps.
BP-30 – not street friendly even driving to track - work reasonably well but will eat your rotors – replace rotors with second set of pads. These work well when up to temp and last a bit.
Poly Matrix B would be a better pad choice for track work. (Work very well when up to temp) Install and bed at track.
You must prep your rotors before BP-30 or Poly Matrix B.
Installation to remove old material – Sand / clean up your rotor perpendicular to the rotation with 80 grit paper to remove prior compound. Take a short drive & bed in pads.

I have 3" ducting to the front rotors but will be upgrading after I solve other issues

Wilwood has very good pricing if you are licensed – They are very friendly & relatively local to me. I am not affiliated.

Your vibration – Check A-arms, bearings, ball joints