Stoptech question

[Suck fumes]

Ok my rotors are two piece units and I just noticed that some of the little bolts that hold the center and outer ring together are loose and wiggle while others are tight. I called stop tech and they said that's normal due to a floating disc design??? This scares me to say the least cause I don't want these things flyin apart at 100mph. Plus I would think I would get a vibration in my steering wheel from it?

[michaelmosty]

That sounds normal, part of the "floating" design.
The "street" design keeps the 2-piece rotor solid and does not allow it to float really at all. It has a curved washer in the little hardware that keeps everything tight.
However, on the race setup the washer is flat and allows for movement in the hardware. You can pick up the rotor by the center hat and hear the ring jingle a little with movement.

[Suck fumes]

Weird. Guess ill get used to it. Does it make your steering wheel vibrate under load.

[RichardP]

The floating rotor setup is very much on purpose. It serves multiple functions.

First, when the rotor gets hot, it expands in diamater. On a normal fixed rotor the center is retained and doesn't allow this growth. This forces a rotor into a cone shape. When you apply the brakes to the coned rotor, you have to deflect the calipers to square up the pads. This causes a soft pedal that is hard to modulate. The factory Brembo Cobra rotors have a significant V section at the hub to rotor interface to sort of allow this growth. This V section is subject to fatigue failure on extremely heavy cars because of the next effect:

Significant cornering loads cause the spindle and hubs (and with it, the rotor) to deflect. With a fixed caliper, this rotor deflection would actually push the caliper pistons back. This is called pad knockback and requires you to use up pedal travel to push the pads back into contact with the rotor before any braking happens. This is really annoying and does not inspire confidence. The factory brake setup gets by this to some extent by floating the caliper on sliders. It is sort of effective.

You may notice a little rattling sound when driving around the pits. On the track, all you will notice is a rock hard pedal that is easy to modulate.

Richard P.

[jdlingle]

Some good tech here from Michael and Richard. I wouldn't have known this about the two piece rotors. This will be one less thing for me to freak out over on my next car now.

[marshall_mosty]

I've been very happy with my Stoptech's. The rings seem to never wear. I've been running the same set of rings for 5 years... Just load new pads and keep on running!

[Casey_SS]

Ditto. I was cracking C6 rotors like popcorn (one every 1-2 weekends) and rebuilding calipers twice a season. With the StopTechs, I feed them new pads once in a while and that's pretty much it. I think they were secretly built by Wirlpool or GE. Seriously, it's like owning an appliance. Outright performance isn't THAT much better but the maintenance....night and day difference. Don't expect to outbrake a better driver on lesser brakes but you'll definitely spend less time and money fixing blow'd up brakes.

The loose fit of the ring / hat bolts is normal and desired for the reasons explained above. They're fastened with smallish bolts torqued to just a few INCH lbs and then a couple drops of green Loctite. The green Loctite is the magic ingredient and is pretty amazing stuff. I was also worried about the loose fit at first, got the same advice you see here, raced hard, no issues. And no, I've never had any vibration from it. I still get pad knockback but the source is a GM-specific issue (sh$tty hubs).

[RichardP]

I still get pad knockback but the source is a GM-specific issue (sh$tty hubs).


Do you have Stop Tech super secret Max-Float hardware on your rotors? The regular drive pins that come with the big brake kits don't allow enough float for hub/spindle flex and you will get pad knockback.

Adam and I had dinner with the Stop Tech rep at nationals in Miller a few years back. Adam was trying to get them to stock a CMC legal kit (specifically without slotted rotors). I told the rep that every racer that I knew wasn't happy with their Stop Tech kits because of pad knockback. The rep said there was a fix for that with hardware that was slightly longer. I told him that wasn't relevant if it was a secret pro racer part that wasn't realistically available to the club racer. A few months later, a CMC specific kit was announced with plain rotors, no street pads (which we told him would just get chucked in the trash) and magically, max-float hardware.

Here we are a few years later and I see absolutely no reference to the possible problem or their available fix on their website. Last I heard, a call to Stop Tech complaining about pad knockback will get you a recommendation to flip the spring washer under the nut over to reduce the preload (which doesn't help).

Hopefully you don't already have that hardware, can somehow figure out how to get it, and it helps you...


Richard P.

[Casey_SS]

Do you have Stop Tech super secret Max-Float hardware on your rotors?

Yes. David Donovan helped me acquire the super secret hardware kit a while back. It helps for the first session or two on fresh hubs, after that there's enough play in the hubs to need to tap the brake in the straights. Depending on the track, weather, and how I set the car up, I can lose enough bearing pre-load to cause pad knock back in a single session. Hallett is probably the worst, with TWS a close second. After a while you just get used to tapping the brakes in the straights and learn to live with it.

[marshall_mosty]

The only place I can find MAX FLOAT mentioned is in their trophy kits, but can't find it to buy separately.
http://www.stoptech.com/products/big-brake-kits

Here's the original thread.
http://www.aicmctexas.com/main/archive/index.php?t-3662.html

[rpoz27]

Yes. David Donovan helped me acquire the super secret hardware kit a while back. It helps for the first session or two on fresh hubs, after that there's enough play in the hubs to need to tap the brake in the straights. Depending on the track, weather, and how I set the car up, I can lose enough bearing pre-load to cause pad knock back in a single session. Hallett is probably the worst, with TWS a close second. After a while you just get used to tapping the brakes in the straights and learn to live with it.

flip the washers. BTW...we found the pad knockback was coming from the rear of the car... Front hubs suck but the rear axles get shorter and move around a lot. Camaro hubs suck balls.

[Casey_SS]

flip the washers. BTW...we found the pad knockback was coming from the rear of the car... Front hubs suck but the rear axles get shorter and move around a lot. Camaro hubs suck balls.

The super secret washers are flat. I read an earlier post of yours about new axles helping with the knockback and decided to give it a shot sometime last year. New axles, new C-clips, rebuilt the rear calipers, fresh rear pads, etc. No dice. As you said, Camaro hubs just suck balls. They're great fresh out of the box...for a few laps and then not so much anymore. Timkin has a newer design with less taper in the barrel to presumably house a slightly larger outer bearing. My local Autozone has been stocking them since last summer. They're actually lasting quite a bit longer than the old ones but still aren't anything close to a solution. There are however some interesting things possible with 3rd gen hubs, Vette hubs, and some higher end SKF / Cortex stuff. Most of it would only be legal in AI but it's not an unsolvable problem if I were to make it a priority. For now, it's cheaper to keep throwing free warranty replacements at it and driving around the problem. As long as I'm racing on RA1's. Throw some RR's or Hoosiers on my car and my attitude would probably change pretty quick.