2-piece stock size rotors?

[CSG David]

Originally Posted by Guillaume

Well I already run Carbotech XP10s (even with the Porsche brake spoilers http://www.ft86club.com/forums/showp...2&postcount=31 ) and I still have nasty vibrations after trackdays. My understanding is that I overheat them and thus a 2-piece rotor would help dissipate heat thanks to its aluminium hat.

Vibration comes from hot spots and improper bedding. On the topic of hot spots, you can actually cause non-uniform cooling with the improper ducting. In other words, you can cool certain spots of the rotor, yet the rest is hot, causing some weird, inconsistent braking performance.

Another reason is, you already exceed the capabilities of the XP10. Try looking into XP12.

You may also spend some time to change your braking technique as well. We've found many students overusing their brake pedal and forcing the car to engage ABS without them knowing. Many people have this issue when changing from one compound to another as different bite characteristics and how they ramp up the friction coefficient can upset the brake performance when used incorrectly.

2-piece rotors have 2 goals in mind: reduce unsprung weight (great for autocross guys looking to shave as much weight as possible) and provide a disc that can pump more air through the rotors (also good for autocross guys because their brake pad compound will match this characteristic well). Yes they do achieve that, but keep in mind, having too much cooling can also upset where your optimal operating temps should be, which could cause inconsistent braking performance as well

There is a lot more to just changing parts to the car. The factory brakes are quite good and we have to all remember these are the same brakes that help stop the WRX, which is easily 500lbs+ heavier than the BRZ/FRS.

[CSG David]

Originally Posted by Tenament05

I would pick CSG Dave or Mike's brain about why they feels 2 piece rotors aren't good on stock and additionally would also stop being a **** on the internet

They are fine for the use on the street (not so good for places with a lot of salt) and use at the autocross. For tracking, you see nearly zero benefits from it with the exception of a lighter wallet if you do carry it while you're driving on track...-1 lb savings!

But jokes aside, you can only pump so much air through those vanes. More importantly, it's better to have more mass in the stock rotor to dissipate the heat from. This uniformity is what makes the stock brakes pretty good. On top of that, we have seen some 2-piece rotor failures at the mounting tab. If the brake disc company didn't do proper R&D on it, you'll have massive stress concentrations in that location. With improper design and decent metallurgy, you'll have potential failures in those regions. We've cracked a fair share of rotors from el cheapo rotors to uber baller rotors. This is something we can brag about that very few have accomplished or knows how to accomplish.

There is more to it, but hopefully that answers your question. We can bring this to PM if you want to know more otherwise it seems like I'm just pushing you into a buffet of information.

[wparsons]

IMO, the only real benefit to two piece rotors for track use is cheaper consumables. Replacing just the disc is cheaper than replacing the whole thing.

When that becomes important comes down to how often you're replacing rotors. I'm still on my original rotors at ~90k km's with lots of track and autox use, but they'll be replaced before the next track day. In my case, I'm not eating through them nearly fast enough to justify two piece rotors. If you're killing a set of discs every weekend, then it'll be worth it to you.

[Dave-ROR]

Originally Posted by wparsons

IMO, the only real benefit to two piece rotors for track use is cheaper consumables. Replacing just the disc is cheaper than replacing the whole thing.

When that becomes important comes down to how often you're replacing rotors. I'm still on my original rotors at ~90k km's with lots of track and autox use, but they'll be replaced before the next track day. In my case, I'm not eating through them nearly fast enough to justify two piece rotors. If you're killing a set of discs every weekend, then it'll be worth it to you.

More expensive then stock replacements though....


In stock size I see no real benefit.

[stugray]

Wilwood makes one (edit: sorry, not sure if it will fit "stock")



http://www.wilwood.com/BrakeKits/Bra...BRZ&option=All

[justint5387]

This would be good for ppl that runs in STX for auto-x, cheaper way to save weight without having to get the bbk.

[wparsons]

Originally Posted by Dave-ROR

More expensive then stock replacements though....


In stock size I see no real benefit.

100% agreed.