Whats causing my brake rotor shudder? (Page 1 of 2)

Uneven pad deposits cause shudder. You need brake cooling. Bedding them in really well helps out too.

If they still have issues after brake cooling, then you'll want a better compound.

what pads are you using?

We learned 2 things about brakes at our first race this past weekend in our heavyish Mercedes E Class.

1. Cooling ducts are a must
2. You have to brake properly. Late, hard, and short. If you start braking too early and just drag them they won't last.

And once a rotor is warped there is nothing you can do to fix it. Good luck!

Did you actually measure runout and confirm it's warpage that's causing the shake?

As others have mentioned, uneven pad transfer usually causes the "warped rotor" feeling.

Another (less common)  thing is hard spots on the rotor. They'll leave a bump as rotor material erodes around them.

A wire brush isn't going to remove pad material. (ed: oops. You said wire wheel. A power wheel might get it done...)
Use 60 or 80 grit emery cloth and cross hatch the heck out of them. Rough them up good and get all the shine off.

...I'm guessing the uneven transfer comes from racing around getting the brakes all toasty, then stopping for a yellow, or traffic, or something. The melty hot pads sit in one spot on the rotor and leave a blob there.

Beenthere, I can go on for several paragraphs detailing our learning curve through this issue but I simply do not have the energy to conjure all the details, bad memories not to mention people are likely tired of hearing it again
We ran RP2 for  two years of hell then XP24 three yrs of love then in a pinch back to a old set of RP2. Even with a well developed proven package the problem immediately went back to hell.

Short story, you love those Rp2 pads, they work! they last! They stop like nothing else .................They are the issue............ if you heed this advice you will be free...

You are over-temping the compounds recommended,it is pad transfer, the brake guys do not understand what some of us are asking of their products, add cooling and ORDER XP24
then
literally throw out all old pads as to be never tempted to go back. Results will go from being intimate with the 5 gal paint shaker @ home depo to a casual stroll through a china shop.

Or give these guys a call, http://www.g-locbrakes.com/ tell them you want xp24 and they will give you their equivalent, apparently half of carbotech didn't get along with the other half and they split up, have yet to try em but their price was excellent in comparison.

Oh mention Infiniti it may help us both

Final straw was rotors with no run out that shook so bad the nut holding the valve to strut piston unscrewed.

Note: we have tried carbotech xp8 xp10 proterfield ST43 and ST47

Q: Would an underperforming/undersized brake master cyl cause this issue?

I read an article once about upgrade options for fox body tbirds and remember seeing something about needing a larger master cyl when you upgrade calipers. Since you mentioned already having upgraded to calipers for 13" rotors, is the master cyl sized appropriately?

What he said.

The Super G-Rover has willwood calipers Up front with Chevy Astro van rotors.
By the last stint at NJMP the rotor warp was pushing back the pads so far, the initial pedal push had no pressure.
The second pedal push sent you through the windshield.
Our calipers were contacting the rotor edge when hot, destroying the caliper. the growth from heat was incredible!
Ducting and clearancing the calipers my be our fix.
Just letting you know,
You are not alone.

I'll also add that the uneven pad wear/heat can also eat the rotor unevenly making this issue compounded, no pun intended. I went through numerous rotors and pad combinations before finally adding ducting to my track car.

You end up with a pad that is overheating, but unevenly. That is eating the rotor, unevenly. So it just gets worse and worse.

I've done the ct xp24's...my suggestion is try the st43 first

Another vote for pad deposits causing the problem. Even with ducting our team MX3s had this issue with Carbotech pads (small OE rotors and calipers). ST43 pads not only minimized the problem but last longer also with no loss of braking power.

Figured I'd post an update since I used most of your suggestions at CMP a couple weeks ago. I went for broke, fashioned a set of brake ducts and ordered some XP24s. Spent some time on the highway on Friday to make sure they were properly bedded. The result was smooth, consistent braking all weekend long and more than enough pad/rotor to go at least another weekend.

While I'm not sure how much can be attributed to each the ducts and/or compound, I'm happy to report our issue seems sorted for now. If they can survive in a big heavy car at CMP...

I went with the XP24s over the ST43s only because I had a credit with Carbotech that made them cheaper this time around. I'll continue the experiment with the Raybestos' only because the XP24s are so damn expensive, but I'm excited I have a combination that works. Thanks again for the suggestions everyone.