Need help curing Repetitive Brake Vibration Syndrome

[SoundGuyDave]

If you DO go there, drop a line to Capaldi Racing, they have them in stock, with the ARP studs pressed in, for less than the dealer wants for a bare hub.

 

[neema]

Stock sized apr replacement studs or the 3/8" studs?

 

[Department Of Boost]

Stock sized apr replacement studs or the 3/8" studs?

Stock studs are 1/2-20. Why would you go 3/8?

Do you mean 5/8?

 

[neema]

Stock studs are 1/2-20. Why would you go 3/8?

Do you mean 5/8?

Sorry that's what I meant

 

[DusterRT]

Does it do this at all temperatures (street, out lap, cooldown..), or only once things have warmed up after a couple laps?

 

[SoundGuyDave]

Stock diameter, but quite a bit longer! Yes, 1/2-20.

 

[Department Of Boost]

Stock diameter, but quite a bit longer! Yes, 1/2-20.

Like This:

 

[DUFUS]

What's the advantage of longer studs? Not that it would be a big deal $-wise, but additionally I'd have to get open lug nuts. And I guess I'd want both 3/4" for my TSW track wheels and 13/16" for my DD GT500 wheels.

Does it do this at all temperatures (street, out lap, cooldown..), or only once things have warmed up after a couple laps?

Street speeds/temps are fine, no vibration. High/track speeds is where I have the issue. And it doesn't take long for the problem to develop, and once there it ain't going away.

 

[SoundGuyDave]

Length means an easy start to the nut, the little tip is perfectly sized to help prevent cross-threading, the studs are diamond-hard, so they don't wear like the stock studs...

All in all, a far superior fastener. If you get hubs from the dealer, you'll have to press out the stockers and press them into the new hubs. At that point, why not upgrade to something better? FYI, raw parts cost on the ARP studs is right at $100 per axle.

Honestly, based on the high-speed, won't go away comment, it still sounds like uneven pad deposits. I also use DTC-60 with stock rotors, and don't get the shimmy, AND I don't bed them "properly." I just go out for a session, and pound on the brakes until I get the first hint of fade, then park the car.

Are you keeping your race and street sets of pads and rotors segregated, or are you just changing pads for the track? Not all compounds are compatible with each other, so for a dual-purpose car, I would keep a "street set" and a "race set."

Also, what did you think of the ST43 pads? How did they compare to the DTC-60's in terms of initial bite, linearity through the braking zone, release and wear?

 

[DUFUS]

Length means an easy start to the nut, the little tip is perfectly sized to help prevent cross-threading, the studs are diamond-hard, so they don't wear like the stock studs...

All in all, a far superior fastener. If you get hubs from the dealer, you'll have to press out the stockers and press them into the new hubs. At that point, why not upgrade to something better? FYI, raw parts cost on the ARP studs is right at $100 per axle.

Honestly, based on the high-speed, won't go away comment, it still sounds like uneven pad deposits. I also use DTC-60 with stock rotors, and don't get the shimmy, AND I don't bed them "properly." I just go out for a session, and pound on the brakes until I get the first hint of fade, then park the car.

Are you keeping your race and street sets of pads and rotors segregated, or are you just changing pads for the track? Not all compounds are compatible with each other, so for a dual-purpose car, I would keep a "street set" and a "race set."

Also, what did you think of the ST43 pads? How did they compare to the DTC-60's in terms of initial bite, linearity through the braking zone, release and wear?

Ahhh, excellent, thanks Dave. I had come close to cross-threading the stock studs on a couple of occasions. I think I'll step up.
I hadn't been segregating/dedicating rotors, but... on one occasion I did slap on new rotors at the track so the only pad they saw were the race pads, and, yep, nasty vibration by the end of the 2nd day.
I use a Raybestos semi-metallic pad for the street in hopes of not cross-breeding compounds/manufacturers too much, but maybe it is time for track only rotors.
I do like the ST43 pads. Being a newbie, and somewhat unobservant at times, I can probably only comment on the wear with any intelligence, and that has been fine. I sent you a PM. If we find each other at the same event, you're welcome to drive my car to get your own impression of the ST43's performance, and the different suspension bits I've thrown together.

 

[neema]

Like This:

is the hub considered this whole assembly?

 

[Department Of Boost]

is the hub considered this whole assembly?

Those are stock hubs with ARP studs.

Not sure what you get if you buy hubs with studs already in them.

 

[SoundGuyDave]

Ignore the big lump of cast iron, though, that's the knuckle. The hubs are the part starting with the ABS cog-wheel, and running outboard from there.

 

[neema]

Ignore the big lump of cast iron, though, that's the knuckle. The hubs are the part starting with the ABS cog-wheel, and running outboard from there.

That's what I was wondering. Thanks. I may need to call up capaldi--I have gnarly brake shuddering as well. We'll see how bad it is after rotor/pad replacement.

 

[SoundGuyDave]

I'm not saying that new hubs will cure anything, but it is a place to look... We've all seen the "stress shot" videos: Tire carcass shifting back and forth on the rim in corners, Griggs' knuckle flex video showing force transmission under braking, etc. ALL of those forces are transmitted through the bearings in the hub. If you add in a nice, heavy wheel and tire package, it only gets worse.

Any amount of play in there is going to cause the rotor to "wobble" and can cause shudder with floating calipers, or knock-back with fixed calipers.

 

[JAJ]

Well, all that said, I had solid braking with no knock-back or other issues until the brakes got hot. Two-piece floating rotors fixed it. All the discussion about what "should work" is interesting, but I have a solution that "works".

 

[SoundGuyDave]

I have no doubt that 2-piece floaters solved the issues you were having, which is most likely a belling of the rotor from heat differential. That said, however, not all brake shudder has the same cause, therefore not all have the same solution that "works." 2-piece rotors won't do a thing for you if you have a bad hub, or pad deposits.

 

[JAJ]

I agree, but the original post pretty much ruled out issues with bearings, pad bedding, compound mismatches, uneven deposits and so on. The poster came across as thorough and as analytical as I was and to top it off, the problem sounded exactly like the problem I was having.

Hoping for a cheap solution to an expensive problem just makes it more expensive.

I expect that the problem I was having was from either belling or other uneven expansion of the rotors. That the Brembo factory (actually made in Italy) rotors would distort was hard to believe, but the floaters fixed it, so it must be true.

 

[jymontoya]

I've had wonderful experiences with my 1 piece Brembo rotors. The only time I've had any brake shudder with these ST43's was when it was cooler than 70* and I kept the front ducts open. When I closed the ducts, all was well, even below 50! I now keep them closed until I feel the slightest fade, usually above 80* ambient. These pads like it HOT! But can still drive anywhere on them... With some minor noise of course.

 

[DUFUS]

Well, I've diligently cleaned the hubs, and measured runout with new rotors installed at .001", so that shouldn't be a concern. I will burnish pads/rotors as recommended, bleed the brakes, and not drive the car until a track day this Saturday. I don't usually block the ducts at this track (Blackhawk Farms, it's a brake beast), but I'll try that too as it should be somewhat cool out.
If I experience the same shudder, I might have to go the route of new hubs and/or 2-pc rotors before the next event (last of the year for me).
BTW, what's the theory behind bleeding in the order we've all grown accustomed to (RR, LR, RF, LF)? Could it really be all that bad to bleed in any order?