How to mount your bike on a trainer: axles, cassettes and adapters

Identify the trainer type and generation

A direct-drive trainer replaces the rear wheel; the chain runs on its cassette or compatible single-sprocket system. A wheel-on trainer retains the rear wheel, with the tyre against a roller. Mounting hardware and procedures differ, so a brand name without a model and generation is not enough.

Find the manual for your trainer generation and its frame compatibility list. Some bikes require revised adapters or have restrictions; see the example of Wahoo's updated adapters. Matching axle dimensions does not replace the frame check.

Write down the rear axle standard

You need the attachment type, diameter and spacing between the supports. Examples include QR 130/135 and 12×142 or 12×148 thru-axles; these are not a support list for every trainer. Select end caps according to its manual. Do not spread the stays or use axle tension to pull mismatched spacing together.

Direct-drive trainers often use the bike's thru-axle with trainer adapters. A wheel-on trainer may require a dedicated axle with protruding ends for its clamp; axle length and thread pitch also matter. Confirm the kit for the exact model rather than buying any adapter labelled 12 mm.

Match the cassette and freehub

For conventional shifting, the trainer cassette must work with the bike's shifters, derailleur and chain. The same cassette model as your rear wheel is a useful starting point, provided the trainer supports it. Equal speed counts do not guarantee the same freehub fitting or chain compatibility.

HG, XD/XDR and Micro Spline are different interfaces. Check available freehubs and model-specific restrictions in the manufacturer's compatibility documentation. Spacers depend on the cassette and freehub combination: “one ring for every ten-speed cassette” is too broad a rule.

If the trainer has a single sprocket

A single-sprocket virtual-shifting setup must be checked together with its app and controller. A compatible chain and mount do not establish that your chosen software can shift virtual gears on that trainer.

Before buying, find an explicitly supported combination of trainer generation, firmware, sprocket system, controls and app. Check each service separately if you plan to use several. Displaying power or running ERG does not establish virtual-shifting support.

Your first mounting checklist

1. Place the trainer on a stable, level surface and fit its supports as instructed.
2. Confirm the cassette, spacers and end caps are fitted according to the manual, without play.
3. For direct-drive, shift to the smallest rear sprocket, remove the wheel and lower the frame carefully onto the adapters while guiding the chain onto the cassette.
4. Check the dropout contact points: the trainer must not press against an unintended carbon surface, brake caliper or derailleur.
5. Secure the axle or quick release using the manufacturer's specified method and force. With a disc-brake wheel removed, fit a suitable transport spacer in the brake.

The KICKR CORE setup manualillustrates one common device. It is an example; its adapter labels do not apply to another trainer.

Test the mechanics before the app

Begin by pedalling gently and checking several gears without hard efforts. The cassette should not wobble, the chain should not fall beyond it, and the frame should not move in the mounting points. If it is noisy, check cassette and adapter installation before changing derailleur limit screws.

For wheel-on trainers, complete any specified roller-tension and tyre-pressure setup before calibration. Once the mechanics are checked, continue to connecting the trainer. Use the first short, easy session to check mounting and control rather than test maximum power.