Cassette bodies can be replaced really easily. First of all you will need to remove the cassette (yes we will cover this too, check back soon…) and you need to order the appropriate cassette body for the Shimano hub you have.

1. Tools for the job

1 — Tools for the job
The tools required for stripping and servicing hubs as follows:
2 x 15mm Cone spanners (a Shimano rear hub has 15mm cones, however these can vary in size)
Torque wrench
17mm open ended spanner
10mm Allen key
Waterproof synthetic grease (NOT white Lithium stuff)
www.finishlineusa.com
Axle vice and bench mounted vice

2. An axle vice secures the wheel

2 — Use an axle vice for holding the hub securely and safely. This one has aluminium jaws so it does not damage the threads. You can do this job without a vice, but having the axle ‘locked’ does make it a lot less of a fiddle.

2a. Park Tools AV-1 Axle vice

Place the hub driveside down into the jaws because you will undo the cones from this side.

3. Use a 17mm spanner and a 15mm cone spanner

3 — Hold the cone with a cone spanner and release the lockring with a 17mm spanner. Remove the cone, spacers, washers and (very carefully) the wheel, leaving the axle in the vice. Clean each item and lay these components out in the order they go back onto the axle.

4. leave the drive side cone intact

4 — By leaving the drive side cone assembly complete on the axle, you will simplify re-assembly because it means that the gap is preset. This picture also shows the bearings at the edge of the cassette body, the races on the drive and non-drive sides are spaced as far apart as possible for strength. At this point the bearings may fall out onto the floor, so be careful to do this over a workbench.

5. Thoroughly clean the inside of the hub

5 — Clean the inside of the bearing surfaces and inspect for damage. Pitting to the bearing surfaces and cones will require replacement of either the cones or the hub assembly. New cones and bearings will help if the hub is running rough and they shouldn’t be re-used if they are damaged.

6. remove the cassette body bolt

6 — Once the hub is cleaned the cassette body can be removed with a 10mm Allen key, this is usually factory fitted and tight so use an appropriate Allen key (i.e. a very long one)The bolt is recessed into the hub. There may be washers behind the body so be careful to keep these to replce with the new unit.

7. Tighten the cassette body to approx 50Nm

7 — The cassette body can be replaced if necessary, set the torque wrench to 34.3—49 Nm (Newton Metres) and tighten the bolt. Cassette bodies can be soaked in release agent (parrafin or diesel fuel) overnight to rejuvenate the internals, this will not cure long term problems but shifts some of the muck from the mechanism.

8. new bearings and fresh synthetic grease

8 — Grease and reset the bearings into the hub, 9 x 1/4″ bearings are required either side. It is impossible to detect slight damage to the surface, so new ones should be used to ensure smooth running.

9. Use a 17mm spanner and a 15mm cone spanner

REASSEMBLY…
Restore all the bearings into the hub bearing faces, smear some extra grease on top so they stay stuck in place. Insert the axle from the drive side (reverse of step 4) then finger tighten the cone onto the axle so the bearings run smoothly and freely. Then fit any washers and spacers. Hold the cone in place and tighten the locknut onto the stack, this is where you have to take care to get the adjustment just right. If you use a axle vice this job is quite straightforward. If you can’t use a vice then using two cone spanners on either side of the hub can help back them off a little, against each other, if they are too tight.
Once you are happy there is no play in the hub have one last check that both lock nuts on either side are tight.

Shimano Ultegra service instructions at www.shimano-europe.com

Shimano Ultegra spares diagram at www.shimano-europe.com