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Pulsation while braking... recommendations on a fix or on a source for rotors?

Hey all,

So, after my last track weekend... during which I had to end a session abruptly due to a spin, I now have a non-trivial pulsation when applying the brakes.

I looked at all my rotors (Centric Premiums), they didn't seem too bad looking. I removed the fronts, scuffed them lightly with garnet paper, cleaned everything, reinstalled... didn't work.

I'd sent a message to Stoptech about sanding rotors, and here's what they said:

Unless the vibration you’re experiencing if ever so slight, I believe you’ll be wasting your time attempting to solve the problem by hand with any sort of abrasive paper.



The issue is that it is almost impossible to remove material in an EVEN manner from the rotor surface by hand. If you have an automotive machine shop locally that can take a light cut, that would be best. Try to avoid the chain auto part stores that offer this service as their lathe operators sometimes do more damage than good.

Wish I'd gotten this response *before* I did all this cleaning and sanding! :)

I *hope* it's rotors, because they are easy to replace.

I'm not enthusiastic about having to find a magical, trustworthy, high-quality machine shop that will cut them for me properly.


Any suggestions? Do I buy inexpensive new rotors, replace them, and cross my fingers that it will work?
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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As long as you are sure the rotors are the issues, you need to have then slightly cut or start anew. Given the rotors you are using, cutting may not work out very well unless you have someone who knows what they are doing. Its got to be SLOW cut (not rotor speed, speed the cutter moves across the rotor) and it should not be a deep cut st all. All that said, if seen rotors be worse after a cut than better.
 
I am absolutely not sure it's the rotors :/

Pete, is there a better low-priced rotor that you recommend over the Centric Premiums?

These are $154 shipped for the front two rotors... which is about as inexpensive as I could find.
 
Not that a spin on the track should cause this issue, but worn front hubs could also cause a wobble if I'm not mistaken. I've gone through 2 sets of turned rotors trying to solve my brake wobble problems and I can confirm what Pete said: make sure that your rotors are turned slowly (the movement of the cut, not the rotational speed of the lathe), and don't forget to scuff a layer off your brake pads. You want to introduce a fresh face of brake pad to your turned rotors and re-bed from there.

let us know how it goes.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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Torsion said:
I am absolutely not sure it's the rotors :/

Pete, is there a better low-priced rotor that you recommend over the Centric Premiums?

These are $154 shipped for the front two rotors... which is about as inexpensive as I could find.

I would use stock Ford rotors. Inexpensive and decent iron. IMO you go that route or you move up to the true racing rotors. What's in the middle will just give you heartburn.
 
767
366
I could just be pad deposits. I have had this problem several times following track sessions. Depending on how abrasive your pads are, the buildup will probably wear off over time. Before replacing or resurfacing your rotors, drive the car for a while and see if it goes away.

Steve
 
2012-Boss said:
I could just be pad deposits. I have had this problem several times following track sessions. Depending on how abrasive your pads are, the buildup will probably wear off over time. Before replacing or resurfacing your rotors, drive the car for a while and see if it goes away.

Steve

+1, I had a slight vibration/pulse at the end of a couple of hard track sessions with the PFC08's and they cleanup up quickly during the start of the following session.
 

drano38

Wayne
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What pads are you using on track?
I ran several versions of Carbotechs, and always got pad transfer, which caused a lot of brake shudder. And they wouldn't self-clean.
Went to PFC 01 this summer, and had great luck with them.
So it could be pad transfer.
 
I'm using the Pagid RS-29/RS056 combo that Pete suggests.

I don't see a particularly large amount of material in uneven patterns on the rotors. So I'm not sure if that's it.

I've just realized, like a dummy, that I still have my OEM set of rotors and pads. I'll put them on soon... which should tell me if this problem lies within the rotors/pads... or elsewhere.

Thanks for all the help!
 
767
366
Torsion said:
I'm using the Pagid RS-29/RS056 combo that Pete suggests.

I don't see a particularly large amount of material in uneven patterns on the rotors. So I'm not sure if that's it.

I've just realized, like a dummy, that I still have my OEM set of rotors and pads. I'll put them on soon... which should tell me if this problem lies within the rotors/pads... or elsewhere.

Thanks for all the help!

I have the same pads from Pete and have had pad transfer . This especially occurred early on after first installing the pads. I am still on my original rotors, so I went from the OEM Ferrodo pads to a set of Ferrodo DS2500 and then the Pagids.

I believe that the initial issues were related to running a series of different compounds on the same rotors combined with an inability to bed the Pagids properly on the street prior to track use.

The DS2500 pads also transfered - far worse than the Pagids ever have. I believe the Pagid transfer is directly related to bedding. When I bedded the DS2500 pads on the street, I had smoke pooring out of the front wheels in 30 degree weather. I didn't get the Pagids smoking until the end of a third day at VIR - with Pete as my instructor. Bottom line, when the brakes stopped smoking coming off the track, I stopped getting any transfer.

Drive the car . If it is transfer, the RS-29s will clean the rotors back up. If you haven't seen any smoke coming from your brakes, they probably aren't fully bedded.

Steve
 
Allright, this evening I put my OEM pads and rotors back on the fronts and I'm happy to report that the pulsation-under-braking is now gone.

I don't think it was a matter of improper bedding, since I was pretty careful during my rotor prep and I'd had three track days on this setup.

So, check out this crack in my rotor, think this is the cause?

P1040348.JPG
 
Update: I took my rotors to O'Riley and they turned them both for $30. Took about an hour.

Now they look like this, and the crack seems to be gone.

If these don't wobble then I'm a happy guy.

P1040359.JPG
 
I don't think so..that's a minor stress/heat fracture and you'll get many more as time goes on.

This is the best two videos I've found on the subject: http://www.essexparts.com/learning-center/cat/brake-rotors/post/Bed-in

I have severe shudder as time goes on at almost every event...it's driven me crazy, tried 3 different rotors brands, and 3 different pads (but all from CarboTech). I've decided to go away from Carbotech for the next set and see how it goes.
However, I get by right now by using an old set of Hawk DTC60s I have to wear off the pad deposits the CarboTechs leave (see video on the Essex site). Definitely works as the shudder was erased immediately after using the Hawks to scrape it off.

CarboTech's claim (to fame?) is that since all of their compounds are the basic same makeup of material, you can switch between race/street pads and not have it scrape off the transfer layer from bedding...however I think over time that ends up being worse in the end. Layers spread unevenly over time make the judder worse...but if you use a harsh compound like Hawks DTCs it scrapes off the old transfer layer soon as you start using cold pads again. (Which of course has the negative effect of wearing your rotors out quicker).

In short:
-Bed them in as properly and evenly as you can on a highway in the middle of the night before an event
-Don't touch your brakes if you can help it on cool down laps and DEFINITELY don't put you brakes on while standing still while they're hot
-Even after being careful with the above, you can still develop judder after one event (like I have been) but you can use a harsh compound pad to scrape off the pad deposits after the event.
-Pads that are too harsh (like Hawk DTCs) will eat your rotors apart, but will scrape off pad deposits to avoid judder. Pads that are too soft (like Carbotechs) I think leave pad deposits very easily causing judder, but are kinder to your rotors.
-Don't ask me if there's a happy medium out there...but I shall keep my abrasive pads around until I find them.
 
Reading these posts have me confused somewhat. I've got a slight pulse in the pedal with the same Pagid pad setup on OEM rotors. Brought them to O'Reilys who said they turn rotors but when they looked it up on the computer it told them (NS) non-serviceable.

I'd rather not buy new rotors but looking to solve the problem. Could anyone shed some light on the issue for me? I'd much appreciate the info.
 
Now that I have some perspective on the situation, here's what I've learned:

I like Carbotech pads better than Pagid. My current usage is XP20/XP10 for the track with NT01 tires, and 1521/XP10 for the street with Pilot Super Sport tires, and I'm pretty happy.

With the Pagid pads, after some track time I got uneven transfer layer caused *severe* shuddering under heavy braking, and it didn't go away with repeated use.

The Pagids are more expensive than the Carbotechs, and I don't think they necessarily would have worn longer. So I'm out on Pagid pads for our cars.

Regarding SUPRMN's question of "how do I fix this"... I feel your pain bro. I don't think resurfacing your rotors but using the same pads will really fix your problem for long. Everyone agrees that the OEM rotors are okay. So I'd try another set of pads with fresh (or resurfaced) rotors.

Another note: when I had O'Reilly resurface my rotors, the cut they did was quite rough. Meaning they took more off than I'd hoped, and I was afraid the new surface would chew the shiznit out of my expensive race pads. I hope one day to find someone who can "grind" my rotors next time I need them done. Maybe you have someone near you.
 

TMSBOSS

Spending my pension on car parts and track fees.
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SUPRMN said:
Reading these posts have me confused somewhat. I've got a slight pulse in the pedal with the same Pagid pad setup on OEM rotors. Brought them to O'Reilys who said they turn rotors but when they looked it up on the computer it told them (NS) non-serviceable.

I'd rather not buy new rotors but looking to solve the problem. Could anyone shed some light on the issue for me? I'd much appreciate the info.

I had the same problem after my first track day Pagid pads. Turns out I did not properly bed the pads. I went through the steps on the Pagid web page but did not block off the brake cooling ducts. Pad and rotor temps were too low. Build up and pulsation from same was horrible.

The fix was to sand the rotors removing all buildup, sanding the surface of the pads and rebutting the pads. Be sure to get the pads hot.

Two track days and several hundred road mile and smooth as silk.

Best part is... Zero Cost!!
 

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