sheshnwoody

I have searched a ton of threads and believe I have a case of pad taper syndrome, but not sure if that's all it. I noticed my brakes feeling a bit of vibration at the end of the last session in my last track day, noticeable difference from early sessions. The front rotors/pads have 4 track days on them...with the last 2 being driven harder than the first two days.

Now, the brakes vibrate when I get on them hard...not really much when I lightly get on the brake pedal..this is street driving now. I thought I had pad taper...which I am pretty sure I have...it was wearing longitudinally and front to back (not as much). I took off the caliper, switched pads from side to side...left outer to right inner and left inner to right outer and opposite. Tried driving...vibration and a noticeable rubbing just from stand still to accelerating. So it seems the swapping of the pads gave me a rubbing and under hard braking...close to same vibration. I tried to take some pictures and illustrate the rotor cracks and pad taper. Not sure if the cracks are that bad...they aren't on edges of rotor, but a few definitely catch your fingernail. I have read some members would love to run these rotors until they split in half and others that would change them. Question is, do you still try to use the pads, as they seem very slanted and having swapped them, are rubbing...shall I say annoyingly.The pads also seem to be wearing differently from inner to outer...guessing that is due to the taper?? I also bedded these in with close to 12 individual 60mph to 10mph stops and they have worked great for 4 track days.

Do I need new pads or can I just try to run them down to equal out the taper? That would drive me nuts with the vibration and or rubbing, but not sure if that isn't due to the rotor cracks as well. They appear to have alot of pad left, so I don't want to spend another $$$ on XP10's just yet, if I don't have to. The rotors are not my only pair...I have a spair set of Centric prem's I can put on, but don't know if I should yet.

Looking for advice, opinions, experiences that are similar with resolutions.

Thanks for your time! Pics in link below.


https://picasaweb.google.com/1054587...eat=directlink

Bill Dearborn

Pads look good and swapping them will equalize the wear the longitudinal taper. The cracks in the rotors aren't bad. Wish mine looked that good. You can get another day or two out of the rotors and maybe the pads as well. The radial pad taper may shorten the life a little. The vibrations/pulsing are probably due to some uneven pad deposits on the rotors although you can get some pulsing when the rotor is getting ready to crack. When that happens you might see a swelling along the line where the crack is getting ready to occur after pulling off the track and once the rotor cools the metal separates. I don't think your rotor is close to cracking so that shouldn't bother you at this time.

Not exactly sure what you mean by rubbing. If you mean the pads are laying against the rotors that is normal. With your tapered pads the whole pad won't be touching the rotor until you apply the brake. If you are getting an alternating rubbing sound it could be due to a wheel bearing having too much run out. Get the wheel in the air and use your hands in the 12 and 6 positions on the tire and see if you can rock it up and down. If you can you may have too much play in the bearing.

Bill

sheshnwoody

Thanks Bill! The rubbing I am trying to explain is some thing like a warped rotor....as I start out from a stop you can hear something rub the rotor, but not a constant rub, more like a rub at 12 o'clock on a revolution of the wheel...it hits every time the wheel hits that point. However, once I get going you don't hear it again. I have since taken it back off and cleaned the rotors and pads again. I just assumed it was because the pads were so tapered and the heavy end or high end of the pad was rubbing on the rotor. I have never swapped the pads before with so much taper.

Does this help or make sense?

Bill Dearborn

Yes. First thing I would check is to see if you have any wheel bearing movement since a loose bearing will give you that symptom. If there isn't any movement in the bearing then check the total run out of the rotor when mounted on the bearing. If you have too much run out then you need to determine if it is a problem with the rotor or the bearing (I have had bad bearings that passed the 12 and 6 shake test but were still bad).

Bill

sheshnwoody

No play in either bearing...feels very tight...to me.

Will check the rotor run out next.

Thanks!

froggy47

Just a couple quick comments, those are not cracks, that's "checking" looks fine to me. Taper is "normal" on pads run hard, when you swap them the pedal will be long until the taper wears out.

Do a few hard threshold stops, like you are breaking in new pads and see if the noise goes away. Get into abs.

JeremyGSU

Not 100% sure what the problem is but I was starting to get rotor shake at the last event and my front pads were shot. I swapped to new pads on used rotors without bedding them in because I didn't have time and had serious rotor shake when I went out the next session. Came in and swapped to new rotors and went back out and had no issues.

My front rotors only had a track day or two versus getting 6 out of them the first time. However, I had a lot more street miles.

Here is what I am noticing from you getting faster.

1 - you need brake ducting

2 - you need to upgrade to SKF front hubs to reduce the brake pedal and pad problem or get a BBK. You'll be complaning about that next like I did if you don't make those upgrades. You're getting too fast now where you need those components if you want to stay happy with your system.

The uneven pad wear is most likely from pad taper because you need the hubs.

sperkins

I've had a bad front hub cause that issue and it was not loose when I checked it. The problem would worsen as the brake temps went up.

sheshnwoody

Thanks to all responses!

What about pad material on the rotor? Jeremy: From your experience above, could that have been your issue and potentially mine?

I plan on taking some sanding discs to the hub portion where rotors go over and make sure it's a solid seating...I'd hate to think one lug area was a bit higher than other 4, but I am reading that could also cause the runout.

sheshnwoody

Update: I tested for runout and these are still very solid rotors with almost no movement side to side. I took everything apart again and reinstalled. I was wrong about the rubbing at 12 oclock...it's more like after a good (moderate to hard stop), the brakes are still on..slightly. The 'rubbing' is just the brakes are still engaged and rubbing pad to rotor...I am wondering if i need to rebleed the system or push the pistons all the way back in and try again. It's a tight fit when I put the caliper back on with the pads swapped, but I am wondering if the pistons need to go back in further to keep from the brakes staying engaged. That addresses or potentially addresses the 'rubbing'.

The vibration under hard braking is still there, but seemed less than yesterday. I didn't get the brakes very hot today, so perhaps that was difference. I was trying to take it easy and clean rotor off with colder pads.

Thoughts?

JeremyGSU

Very possible. Based on my rotor wear I didn't see a point in trying to rebed them only to go back out the next session and have them shake violently again. I elected to just put the new rotors on.

Bill Dearborn

I just let them violently shake. Don't replace the rotors until they are cracked or close to cracking. Thumping rotors still work so I use them thumping or not.

Bill

sheshnwoody

I put the original rotors from Brazil back on the car to test with...the vibration and rubbing is gone. Go figure. I am guessing those little cracks and pad material deposits made for an unpleasant experience!

Thanks for the help diagnosing everyone who contributed to this thread!

I am getting pretty good at taking calipers off...if I only had impact wrenches and a lift!!!!!

JeremyGSU

True but it's annoying as hell.

Dirty Howie

Mine were thumping bad. I sanded them down. Will drive a few days with lots of squealing to remove any deposits I missed. Then will the same pads again. Should be nice and smooth again for this saturday. I have run several (including) last track day with thumping. You feel like something is going to come apart .........


DH

JeremyGSU

The other issue I have with the rotors shaking that much when you're braking is it makes it hard to catch other issues you might have with your car or suspension because you are getting so much vibration it may mask it.

ktlspider

Pad taper is a function of not having differential sized pistons in the caliper, or the pistons not having a step in their surface. So basically it's unavoidable if you stick with the OEM style (awful) floating caliper. An abomination of a brake caliper design in my opinion that works like crap even in simple light duty street use.

The uneven pad wear from inboard to outboard side of the brake disc is also a function of the floating caliper. Fixed calipers with floating rotors (either floating on bobbins or elongated mounting holes which account for thermal expansion) are the way to go. Not for the faint of heart in terms of cost though.

Those pads are near done IMO. When the pad gets as thick as the backing plate, you need to consider getting new pads ASAP. Keep in mind that the pad, in addition to being a sacrificial friction source, is also an insulator. The pad insulates the caliper pistons from heat. The thinner the pad gets, the less it can insulate the caliper. That means higher fluid temps and potentially softer pedal.

I agree rotor "checking" is common but its certainly not desireable and can be minimized. Getting some cooling into the brakes is key. Any sort of cooling you can get in there is going to help. Doesn't have to be true pro-style ducts. Even some simple scoops like these make a big difference (scoops mounted a customer's Porsche 911 A-arm)



Thumping rotors may continue to let you brake but they're certainly not letting you brake effectively or improve your driving ability. Big brake kits do solve a lot of this but they are of course a bit expensive. You have to think long term to rationalize the brake costs. The initial cost is quite a lot but over time it pays for itself in parts savings, less time spent tending to the brakes (fluid, pads, rotors) and considerably improved driving. I know from experience that an imbalanced or problematic brake setup really takes away from your performance. Once I got my brakes dialed in on my racecar, my competiveness increased substantially. When you can reduce you braking time (which is a HUGE component of going fast on track) AND have more confidence + consistency in using your brakes, it's really surprising how your times and the car behavior improves.

Alcon C5 Front Brake Kit