Unfortunately, Shimano’s sports hub dynamos have a problem: condensation inside the hub can lead to severe rusting, which means the dynamo is a write-off. In another article, we explain the background to this and which models are affected. Here is the step-by-step guide to servicing a hub dynamo.
Tool
Shimano dynamo housings can be opened using a 32 mm headset spanner. However, the manufacturer also supplies a special ring spanner, the TL-DH10, for this purpose.
Open the axle
First, open the axle on the non-contact side (left): use a 15 or 17 mm cone spanner and a 17 mm open-ended spanner to release the lock nut. Leave the right-hand bearing untouched.
Losing weight
Unscrew the lock nut and the axle cone. The ball bearing is covered by a sealing ring: gently pry it out of its housing. Make a note of its installation position.
Open the casing
Now turn the wheel round, carefully slide the ring spanner over the contact tab on the right-hand side of the axle and place it on the hexagon of the dynamo cover.
Loosen the screw connection
Hold the wheel firmly and turn the spanner anti-clockwise. The housing cover, together with the internal components and the axle, will now slowly unscrew from the hub sleeve.
Dismantling the dynamo
Carefully pull the dynamo unit out of the housing by its axle. Take care not to lose any balls from the open bearing opposite.
Clean the internal unit
Allow the dynamo unit to dry thoroughly if you notice any damp on it (use a hairdryer). Then spray the unit carefully with WD40 or spray wax to protect it from rust.
Clean the sleeve
Wipe the inside of the hub dry as well, if it is damp. Spray on a coat of spray wax or WD40 to protect against rust.
Lubricate the thread
Apply assembly paste to the hub thread before assembly. This will make the cap easier to turn during fitting and prevent it from seizing up due to corrosion, even after a long period of time.
Close the case
Fit the housing cover whilst turning it anticlockwise to ensure it engages with the start of the flat thread without jamming. Finally, tighten the cover to approximately 35 Nm.
Grease the axle bearings
Fill the left-hand axle bearing with thick bearing grease, then press the bearing cap into place correctly. Screw the axle cone and nut onto the axle and tighten them so that the axle has no play.
Check the run
Finally, try spinning the wheel by hand to check it: there must be no play in the axle, nor should the axle run roughly due to excessive tension.
The article appeared in issue 6/2014 of *Trekkingbike*. You can also download the individual article as a PDF here.
