Cobra Caliper brackets

[clindahl]

So at the 2007 convention, the third or forth time I got to run, I got noted after the run that I had what sounded like metal on metal contact when turning / braking. Today I pulled the caliper, brakets and rotors off to see what was going on ( yeah I' ve been busy!!). Take a look at the attached pictures and brake brackets specifical the circuled areas.

It appeas that the rotors would flex hard and wear somewhat against the caliper bracket. Where should I start looking?? I'm clueless on this one....

 

[greenbeanmtx]

Id be more inclined to say the brackets are what flexed, not the rotors.... Im not expert though

 

[NWGRN94MTX]

Known issue, it even happens on the Mustangs. Grid a bit where it's making contact or let it wear in until it stops chaffing.

 

[Storm-Chaser]

Yeap - bracket issue.

Actually quite a few cars could be heard making the caliper bracket/rotor grinding noise through some of the harder turns.

 

[K-Dawg]

Yep, mine was making the noise too.

 

[gmorrell]

Actually, it's hub flex. Draw yourself a little diagram of the knuckle, brake caliper bracket, and hub with a brake rotor and wheel. The caliper bracket is bolted fast to the knuckle, so these two move as one, and there are no bending forces (normal to the axle) on the caliper bracket of any significance. High lateral loads from the tire will try to bend the hub, which will cause the rotor to move in the caliper bracket slot.

Make sure the slot in the caliper bracket is centered about the rotor substrate, you may have to shim or machine the mounting faces on the caliper pads to get the opening centered.

This problem on Mustangs caused more then an occasional complete rotor failure - the side loading on the rotor substrate weakens the area where the rotor substrate connects to the rotor hat, cracking this interface. The result was complete separation of the rotor substrate from the hat - consider this an ugly, catastrophic failure.

Gary M.

 

[SHOZ123]

Never noticed it on my '97. Maybe the aluminum hub is more resistant to flexing?

 

[gmorrell]

Never noticed it on my '97. Maybe the aluminum hub is more resistant to flexing?

Wheel hub, not knuckle. The hubs are steel in all applications.

The '96-up Aluminum knuckles are rather stout parts, which is why they're barely lighter then their earlier nodular Iron counterparts. It's my belief that the Gen III Aluminum knuckles have a far superior bearing and hub design compared to the Iron-knuckled Gen I and II parts.

Gary M.

 

[Storm-Chaser]

The wear/contact is occuring on the outer portion of the caliper bracket.

clindahl - is the rubbing occuring on both ends of the caliper bracket, or just one end; and if just one end, the leading or trailing end of the caliper bracket?

Were the pads wearing straight, or was there any angled wear (lateral or vertical) to the pads?

 

[Ishodu]

Wheel hub, not knuckle. The hubs are steel in all applications.

The '96-up Aluminum knuckles are rather stout parts, which is why they're barely lighter then their earlier nodular Iron counterparts. It's my belief that the Gen III Aluminum knuckles have a far superior bearing and hub design compared to the Iron-knuckled Gen I and II parts.

Gary M.

I am running the gen 3 subframe and knuckles. Just watch this video, it squeals like crazy in the hard turns.
http://www.youtube.com/watch?v=NrMYtnK30Kc

 

[clindahl]

Storm-Chaser and all -

- the contact is on the leading end of the bracket only
- the contact is on both brackets (left and right)
- the contact is only on the outer side of the bracket on each side, i.e away from the engine
- Pads wore straight and even - top to bottom and front to back.


FWIW - I'm glad I'm not the only one with the noise. First time I heard it I thought it was the power steering pulley slipping, but the belt was tight enough it should have.

SO - where to go from here? I had the rotors turned and new pads should be here this week. I will see how well things line up when I go to put it all back togather and see if I need to do some more clearancing of the bracket.

Ishodu - I'm surprised your car squeeled louder than mine even w/ Gen III knuckles.

 

[shopartsnw]

We have always had the problem on track cars (high lateral load). I just ground out the offending part of the caliper bracket a bit (about 1/8").

Mike

 

[SolidState]

Mine do it too. Sounds wonderful.

EDIT: YOWZA!

 

[Ishodu]

Where did you dig that pic up from Teg?

 

[SolidState]

a mustang forum. It was a thread on the exact failure mode.

seems as though it can happen on the Cobra-R Brembo set up as well.

 

[Ishodu]

Damn. I filed mine down last weekend for clearance where the rotor was rubbing on it. It may not be enough yet. I will see when I get to play with it again.

 

[SASHO91]

Should the guys running Cobra's on 11.6'' rotors need to be concerned? I don't think it would apply, given the way the Cobra bracket is modified/mounted for the use of 11.6's.

But then again.....

 

[SolidState]

maybe, maybe not. Depends on the shape of the hubs (wheel bearings) and how much the rotor deflects in hard cornering.

As for the rotor fracturing, I would imagine that the edge of the rotor wouldn't deflect as much anyways, as it is smaller in diameter to begin with, therefore less stress put on the hat.

 

[JEM]

It's worse on the Cobra R Brembos because there's no room for the caliper to move; with a sliding caliper the bracket can and probably should be clearanced. Rotors flopping around also cause pad knockback in fixed-mount calipers.

IIRC there was a fatality in an '00 Cobra R that suffered that kind of rotor failure not long after the car was introduced, a massively nose-heavy car with two aboard on a rough track that created big transient loads on the outboard front wheel (Nelson Ledges???)

Apparently the 'pleated' hat design of the Brembo rotor is quite intolerant of side loading like that. Ford was for a while recommending use of the earlier Kelsey-Hayes rotor with the conical hat in situations where rotor-caliper contact was possible. Probably more data over on Corral or corner-carvers.

 

[SolidState]

this should be stickied. this is a large safety concern for all using or considering upgrading to the cobra brakes.