Excellent post. Thanks for taking the time to make things so clear and provide so many pictures. Top Notch! I second the sticky idea.
Will

 

Brake bias will be WAY forward with a XR2/SpecVR setup.

The XR series is the new carbon/ceramic compound. The XR2 is for GT race applications (Speed challenge, Koni Challenge,...). The XR1 is for NASCAR and the XRT is for "heavy downforce application". The XR2's torque figures where described to me as "Much higher than the SpecVR's, with the same curve profile".

I'll be running a XR2/XR3 combo on my next track day. I have the pads already and they are hot !

 

Thanks, Kolia for clarifying that. I forgot to explain the characteristics of the new XR2s. The folks I spoke with at Cobalt thought the XR/VR combo would work okay. Do you think it might be too front heavy?

 

Too front heavy ? I don't think so. The EBD will just send as much pressure to the rear as it can. The car will brake fine, with the rear end more "civilized" at turn in with less rear brake bias.

You'r brake distance will probably be a bit longer than with a XR2/XR3 combo, but still shorter than with an all SpecVR setup. (All speculations of really...)

We're not racing, so let's just have fun driving. All I ask from my brakes and tires is to last a whole session with no fade. The rest is just extra stuff.

 

Are you sure you're not confusing the Spec VR with the GT Sport? The SpecVR's are rated with a mu=0.64, and it was Cobalts 'aggressive' stuff last year. Although I don't have the torque curve data, the SpecVR friction coeff seems kind of high to be eclipsed by the new XR2 compound. Isn't 0.64 pretty damn high?

On another note, the 355 mm Stoptech kit does move bias towards the rear as compared to the OE Brembo and 332mm Stoptech kit. So, I have to run a low friction compound in the rear, or end up with premature rear ABS actuation.

I agree that the new Cobalt line of brakes do look hot!

 

No mistake there. XR2 = more torque than SpecVR.

Got that from Glenn at Cobalt Friction. Call him if you want ! His exact words when I asked if they had similar torque to the Spec VR were "No no no. The XR2 have much more torque, with the same profile as the Spec VR."

 

That's really good news for me then...Hopefully, I'll get brake bias moved more forward. On another note, I heard the new Sport GT's also have more friction than the old formula. Apparently, some folks are having bias issues with the new Sport GT's when they expected similar characteristics to the old version.

Seems that Cobalt is taking forever getting their torque curves published online.

 

I should have some decceleration curves when I go to MidOhio. It'll give us an idea.

My first time on an all SpecVR setup was very interresting. Braking wasn't simply about hitting the brake pedal. I had to balance the car too! Much more fun!

 

James, do you remember the part number for the replacement seals ?

I ordered a "standard" seal rebuild package online, plus I now have the anti-knock back seals from the HRP web site. And no two seals are the same size ?!?

By any chance, did you measure the seal diameter ?

 

I don't still have the part numbers handy, although you could check with Dave Zeckhausen. According to his Web site, the part numbers are:

143.99040 (rears, one kit)
143.99038 (fronts, one kit)
143.99044 (fronts, one kit)

The last two digits are the piston size in millimeters.

 

Very informative. Nice write-up!

 

Good stuff, even though I own a Z and its not a 350z, but a Z4 BMW its still good news. Might be able to apply this to my car. Bookmark and thanks for taking the time to write this up.

 

Oh...

The P/N on one of the Brembo seal kit I have is 44124-12U00

 

Sorry, I forgot to mention that my kits were Stop-Tech, so the part numbers are probably different from Brembo OEM numbers. But the 44 looks right.

 

Yeah. But that's where the fun starts !

That seal has an ID of 41mm and OD of 44mm. I was expecting an ID a bit smaller than 44mm

On the other hand, the anti-knock back seal I have are 38mm ID and 44mm ID respectively. With no documentation provided, just the seals in a bag...

I'll have a few phone calls to make I'm affraid...

 

Great thread.

Thanks.

 

Great Thread all and to the OP. Kolia keep us updated about how it works out for you.

 

I have to take these pictures!

I haven't changed the seals yet. Confusion in seal sizes... But it's interresting to see the inner race of each seal. The regular one are smooth, almost mirror like, while the AKB are much rougher.

 

brake guru? i think so. excellent write up

 

The final touch, weeks later than I expected: painting the Brembo logos.

Not really much to tell: I had my local sign shop make the stencils in vinyl, I applied them, masked off the area, and sprayed them with three coats of red High Heat Duplicolor paint. After the paint dried for an hour, I removed the stencil, and there you go: a custom, one-of-a-kind Track caliper paint job.