ca993twin

I'm getting a set of used GT1 brakes, and one of the hats is rattling a bit on the rotor. I'm told that this is addressed by replacing the "bobbins". I've never heard this term and wonder if anyone can describe them. Is this something simple that a machine shop can just copy? Thnaks for any help.

brucegre

I'm guessing they are floating rotors, but in any case, the bobbins are the fasteners that hold the hat to the rotor. On Brembos, it's a T-bolt, others have allen head bolts, it shouldn't be too hard to get a replacement fastener kit. If they are floating rotors, the noise is normal, they all rattle after a few miles.

Bruce

ca993twin

Bruce,

Thanks. Gulp... what is a floating rotor? I assume it means that its not bolted firmly to the hat, but can move for... ahhh... thermal expansion?

Can you tell from this picture what the GT1 brakes are?

pole position

Go to www.vehiclecraft.com and floating rotors are explained in great detail.

ca993twin

Pole,

Thanks, but I can't see any description on that site. I can see that I sold my Big Reds way too cheap!

pole position

Go to the 930 brake upgrade and click on floatong or non floating. You should also check with Brembo if the McLaren rotor hardware is applicable for your new brakes . This specific hardware will stop common floating rotor noise.(Came from the McLaren F1). For the regular fasteners they should be able to help you as well.

pole position

BTW, Brembo is www.racetechnologies.com in Costa Mesa.

ca993twin

Pole,

Great info. Thanks for that. I left a call at Brembo to ask about the GT1 brakes (are they floaters?) and the fastener parts. Porsche Motor Sports is another source for these.

tar6day

Steve,

Try CDOC. Ask for Mark Francias in customer service. If he doesn't know than he can find out and you can buy everything from him. I had him research custom floating rotors for my 993 RSR. Tell him Tim Rooney sent you.

Tim

ca993twin

Tim,

Dang... I'm such a doofus. I googled "CDOC" and its best hit was "Colorado Dept of Corrections". The guy that answered the phone there didn't know anything about brakes, but wanted to meet my wife. I dunno. Can you give me better details?

Mike Buck

http://www.cdoc.com/


Probably didn't want to order from Mark last Friday morning, but in a better mood by now I'm sure. Hope you aren't a Louisville grad lol

ca993twin

I finally saw my new (to me) brakes this evening for the first time. Definetly floating rotors. So now the question is "how much play is too much, and what is normal?" The drivers side shows a bit more wear than the pass side, and the seller said that the driver's side was rattling in a most annoying fashion. I thing that new bobbins would help, at least for a while. I'll check with CDOC tomorrow and see what Mark has to advise.

Thnaks for the help.

SundayDriver

Floating rotors (at least all of them I have seen) rattle. There should be definite movement between the rotor and hat. I would tend to be more concerned about the quiet one than the noisy one. This is why most people abandon them after installing on street cars.

chris walrod

Radial slop is bad, axial float of .010" is typical for floating rotors. Any more than that can lead to pad knockback. I would be more concerned with radial float or slop due to wear that axial float.

Sent you a PM Steve..

ca993twin

Thanks everyone for the help. I have learned a lot about my new-to-me brakes. Now that its daylight and I have the two fronts side-by-side, I can see that the driver's side hat is totally worn beyond redemption. This will have to be replaced. I'm working on that now. It seems odd, however, that the car this came off of has only 32k miles, was never tracked, and only one of the hats is worn. Anybody have any thoughts? I can only think that the fastener HW was not properly tightened down in the past (they seem to be tight now). What else could do this?