Brake Rotors
Used road brake rotors are the wear surface your pads grip, typically 140mm rear and 160mm front — lighter and more aerodynamic than MTB sizes. Shimano's Ice Tech and RT-CL series dominate, with SRAM Centerline and Paceline the equivalents. Rotors are consumables: they wear thin and need replacing, so check thickness and mounting standard before you buy.
What size rotor should I run?
140mm is the standard road rear rotor — light and sufficient for most riders — while 160mm front provides more stopping power for heavier riders, loaded touring or steep descents, and some riders run 160mm front and rear for maximum braking. Larger rotors offer more leverage and better heat dissipation but add weight and can affect aerodynamics. For flat criterium racing, 140mm front and rear is fine; for alpine descents or riders over 85kg, 160mm front is recommended.
One-piece or two-piece rotors?
One-piece stamped rotors are cheapest — they work, but can warp from heat on long descents. Two-piece rotors such as Shimano RT-CL800 and RT-CL900 use an alloy carrier with a steel braking surface for better heat management and lower weight, and SRAM Paceline rotors use a similar two-piece design. Ice Tech rotors sandwich an aluminium heat-dissipation layer between steel braking surfaces — the best heat management available and essential for mountain descents. Hope and Galfer make high-performance third-party options for road disc brakes.
Centre Lock or 6-bolt?
Centre Lock uses a splined interface and lockring — faster to install and remove, and the standard on most road hubs. 6-bolt uses six Torx bolts, is more common on MTB and budget road hubs, and appears on some frames and third-party options. Adaptors exist to run 6-bolt rotors on Centre Lock hubs, but not the reverse, so verify which mounting standard your hubs use. Centre Lock lockrings come in external (Shimano standard) and internal types — check which your hub requires.
When is a rotor worn out?
Minimum thickness is stamped on the rotor, typically 1.5mm. Measure with callipers at several points around the disc rather than at a single spot, because wear is rarely even.
What should I check buying used rotors?
Check for warping by spinning the wheel and watching for disc rub against the pads; light warping can be straightened with a rotor truing tool, but severe warping means replacement. Inspect the braking surface for deep scoring — light surface marks are normal, while deep grooves indicate contaminated pads have been used. Never use rotors contaminated with oil: they will never brake cleanly again.