How to check the compatibility of bicycle parts before buying
The coincidence of the brand and the number of speeds does not guarantee compatibility. You need to check a specific pair of components, and sometimes the entire chain from the manette to the cassette. Make a short bike passport — it will come in handy with the next purchase.
1. Assemble the component passport
Take a photo of the whole bike, markings of the part and adjacent components. Write down the model and year of the frame, shifters, derailleur, cassette, chain, system, bottom bracket, and rear hub. If the build has been changed, the factory specification of the bike may no longer be correct.
In the description of the ad, look for the full model code, not just "105", "XT" or "Force". For Shimano documentation there is official database of instructions, for SRAM — Manufacturer's service section. Look for the compatibility table or the manual of your particular model.
2. Match the cassette and the drum
The drum is a part of the rear sleeve on which the cassette is mounted. You need to know its type before buying. The designations HG, MICRO SPLINE, XD and XDR describe different interfaces; a similar photo does not replace verification.
SRAM's XDR drum is 1.85 mm longer than XD. XD cassette can be installed on XDR with a spacer of 1.85 mm, but this does not imply reverse compatibility of any cassette. Source: clarification of SRAM about XD and XDR.
Shimano LINKGLIDE cassettes are not installed on MICRO SPLINE: this is explicitly stated in LINKGLIDE compatibility table. Therefore, there is no rule "any cassette at 11/12 speeds will do".
3. Check the entire transmission
After landing on the drum, check the cassette range, the maximum large star and the total capacity of the switch. The compatibility of the manette with the switch, the chain line, the standard of the chain and the front sprockets are also important. Mechanical and electronic generations of the same group may differ.
Replacing the cassette with a wider one may require a different chain length and adjustment. Do not buy a rooster extension cord as a universal solution: the admissibility of a particular combination must be confirmed by documentation or by a mechanic.
Transmission Calculator helps to compare transmissions. It does not confirm that the selected parts are physically compatible.
4. The carriage needs two sides
The carriage must fit both the frame and the connecting rod shaft. Write down the standard and width of the carriage cup, the presence of a thread or press fit, the diameter and design of the shaft. The names "threaded" or "under 24 mm" are too general.
Additionally, the spacers, chain line and frame clearances are checked. Do not disassemble the assembly just for the sake of measurement if you do not have the tools and experience: the workshop can determine the standard by the frame model and the installed system.
5. Don't forget the brakes and wheels
- Pads: shape, retainer and acceptable material for a particular rotor.
- Rotor: mounting, diameter, thickness and permitted combination with caliper, plug and adapter.
- The wheel: axle size, bushing width, brake mount and drum type.
- Tire: landing diameter, width, rim compatibility and frame gaps.
For hookless, the tire and rim combinations approved by the manufacturer are especially important. The camera inside does not make the wrong tire compatible. See Schwalbe's explanations about hookless and pressure guide.
6. Send the seller a specific request
Save the response and product specification. If the seller confirms only "in theory it should stand up," uncertainty remains. First eliminate it, then move on to choosing the purchase method.