turbogrill Posted September 19, 2021 Report Share Posted September 19, 2021 Hi, What are the benefits with 2 piece rotors besides weight? Do the discs last for ever? You can buy "drop-in" 2 piece rotors for our car, its pretty pricey but saves some weight. Currently we run cheap rotors and replace them often. Quote Link to comment Share on other sites More sharing options...
petawawarace Posted September 19, 2021 Report Share Posted September 19, 2021 There are 2 types of 2 piece rotors. Fixed and floating. Fixed generally just offer a weight savings. Floating have a few more benefits. The biggest one is eliminated stresses in the rotor which can cause warping. The steel rotor and aluminum hat expand at different rates and can cause the runout to be less than perfect. The floating mechanism allows them to be separate and the rotor will spin perfectly true. Quote Link to comment Share on other sites More sharing options...
Ian Posted September 19, 2021 Report Share Posted September 19, 2021 Cost. If you can build your brake system around an off the shelf race designed rotor ring, they last longer, and are generally cheaper to replace vs good rotors. If your car works well with cheap rotors, there's no major benefit. Our old car had excellent braking power and almost never warped rotors. They were $13 each and we just replaced every race weekend. Our new car has gotten a terrible pulsation within a few hours every time we try cheaper rotors. Now we only use true Brembo blanks at like $75 each which has me exploring 2 piece options for the off season, just need to find someone to cut me hats at a reasonable cost. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 19, 2021 Author Report Share Posted September 19, 2021 Thanks! That makes sense. For our car Good Win Racing sells the "discs" for $85 a piece, not sure if that is a marked up Wilwood rotor or a good price. This race we are trying $17/$25 rotors, cheapest from rock auto. Let see how it goes. I think we went semi fancy last race, don't remember... Good Win racing also sells fancy 1 piece rotors for $125 a piece. Do you know what your 2 piece would cost? I wouldn't mind paying a little extra for the weight reduction, but currently it's a little step. Quote Link to comment Share on other sites More sharing options...
Grant Posted September 20, 2021 Report Share Posted September 20, 2021 We ran the cheapest RX8 rotors we could find for a while. They lasted ~2 race weekends and they're cheaper than replacement rings for a 2-piece setup. However if your rings are directional, as our Wilwoods now are, cooling will improve. Meaning they'll last longer. We've got idk 20 hours on our set of Wilwood fronts and there's not a heat crack in sight. So it's looking like they'll last longer. We don't run brake ducts, just removed dust shields. If you run ducts forcing air into the rotors I'd imagine directional veins provide less benefit. Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 20, 2021 Author Report Share Posted September 20, 2021 (edited) 1 hour ago, Grant said: We ran the cheapest RX8 rotors we could find for a while. They lasted ~2 race weekends and they're cheaper than replacement rings for a 2-piece setup. However if your rings are directional, as our Wilwoods now are, cooling will improve. Meaning they'll last longer. We've got idk 20 hours on our set of Wilwood fronts and there's not a heat crack in sight. So it's looking like they'll last longer. We don't run brake ducts, just removed dust shields. If you run ducts forcing air into the rotors I'd imagine directional veins provide less benefit. Why would you run the RX8 brakes in the first place? I thought they where heavier? Or is this so you could use of the shelf RX8 2piece rotors? Did you pick a rotor from Wilwoods catalog and build something from that? They seem to have a lot! Found a kit, that uses the Ultralite32. https://www.wilwood.com/Rotors/RotorProd?itemno=160-0471 $44, not too bad! Edited September 20, 2021 by turbogrill Quote Link to comment Share on other sites More sharing options...
Grant Posted September 20, 2021 Report Share Posted September 20, 2021 (edited) 3 hours ago, turbogrill said: Why would you run the RX8 brakes in the first place? I thought they where heavier? Or is this so you could use of the shelf RX8 2piece rotors? Did you pick a rotor from Wilwoods catalog and build something from that? They seem to have a lot! The RX8 stuff is bigger and lasts longer. I also knew I didn't want to run a solid rear rotor (cooks wheel bearings and breaks hubs), and only upgrading the rear to RX8 would throw off the brake bias even more than the full RX8 stuff does. They are very heavy but in 2020 the Wilwood stuff would have cost a bunch of points. Yes I have a Wilwood kit pieced together using their 12.88x0.81 rotors (160-9960 and 160-9959, 10.2 lbs) front and rear, with narrow superlite 4s. I'm sure the 11.75" stuff could be plenty for single races, but bigger brakes last quite a bit longer. The 11x1.25 straight veined stuff is $45 each and 8.8 lbs but I'm sure won't last nearly as long as my bigger rotors. Back then I was also building the car thinking it would later compete in WRL GP1, and eventually GTO. Sadly the off the shelf kits that fit my 17x10 Konig Hypergram wheels were all 6-pot. So I had to spend more money to do 4s... I'd also look at Coleman rotor rings. They'll make you some in almost any size, and their curved vein stuff is IME a lot cheaper than the competition. Edited September 20, 2021 by Grant Quote Link to comment Share on other sites More sharing options...
turbogrill Posted September 20, 2021 Author Report Share Posted September 20, 2021 6 hours ago, Grant said: The RX8 stuff is bigger and lasts longer. I also knew I didn't want to run a solid rear rotor (cooks wheel bearings and breaks hubs), and only upgrading the rear to RX8 would throw off the brake bias even more than the full RX8 stuff does. They are very heavy but in 2020 the Wilwood stuff would have cost a bunch of points. Yes I have a Wilwood kit pieced together using their 12.88x0.81 rotors (160-9960 and 160-9959, 10.2 lbs) front and rear, with narrow superlite 4s. I'm sure the 11.75" stuff could be plenty for single races, but bigger brakes last quite a bit longer. The 11x1.25 straight veined stuff is $45 each and 8.8 lbs but I'm sure won't last nearly as long as my bigger rotors. Back then I was also building the car thinking it would later compete in WRL GP1, and eventually GTO. Sadly the off the shelf kits that fit my 17x10 Konig Hypergram wheels were all 6-pot. So I had to spend more money to do 4s... I'd also look at Coleman rotor rings. They'll make you some in almost any size, and their curved vein stuff is IME a lot cheaper than the competition. Why does a solid rear cook the bearings? Less air around the hub? Quote Link to comment Share on other sites More sharing options...
Grant Posted September 20, 2021 Report Share Posted September 20, 2021 9 hours ago, turbogrill said: Why does a solid rear cook the bearings? Less air around the hub? The rotor gets far hotter than a vented one, and that heat gets transferred to the hub. Though S2000 guys have told me simply ducting air to the back side of their solid rear rotors helps a lot. My thought was the solid rear rotor contributed to the hub failures seen in the Global MX5 Cup cars. Quote Link to comment Share on other sites More sharing options...
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