BGTV8

Advantage of 2-piece rotors is that all the radial expansion that is in the rotor as it cycles from 200DegC to 700DegC and back again many times per track day lap is just that - expansion in a single plane.

When you have a 1-piece rotor, you get differential expansion in the centre of the rotor (the integral "hat" - the hump bit that fits over the hub) and the friction surface which causes stress and eventually the rotor friction surface will crack if the stress gets high enough.

I am a long-term DBA 5000-series user (because they are manufactured in Queensland - well, they were, but now in China but thats almost universal now) - I started in my first WRX Rallye Special in 1996 - and I have never had a rotor failure with them. I now get the rotors cryo-treated as they last longer.

I am also a long-term Endless pad user (TR compound originally, but now have a new one to evaluate), and occasionally use a Ferodo DS2500 for road and track (noisy and a fair bit of dust but good stopping and good temperature tolerance).

I always use a 2-piece front rotor given the extreme level of heat-stress going into them on the track.

Again - my preference has been for slotted rotors simply because they "wipe" the pad and clean any deposits that might build up on the pad surface. Remember - the pad is a sacrificial element in the system - it is designed to generate friction as the rotor abrades it away - so these bits (the "dust") need to go somewhere, and in my opinion, the slot helps "wipe" it away and this promotes braking consistency.

This thread states that F1 don;t use slotted rotors, and that is because F1 brakes are carbon/carbon and the mechanics and chemistry (there is a lot of both in a carbon/carbon braking system) are very different to an iron rotor-based braking system, so IMHO it is not really relevant.

So, to answer your question - I;d always go for a 2-piece rotor to avoid the potential for differnet rates of expansion between the hub and friction surface parts of a single-piece rotor which can only result in friction surface cracks (really big ones).

As for which one - that is up to you - you are in CONUS so you have a much wider choice than us down-under ... for my preference - I use DBA 5000-series, but my guess is that you'll have a much wider choice - so be guided by feedback from users on the forum.

As or cryo-treatment .... I do it as I've got 10+ years of emprical evidence out of my race car that it promotes rotor life - I get 1000klms+ out of my race car per set of rotors but then again - if you are only an occasional track-day user, maybe you're not so concerned at rotor life.

RB