20/02/2013 | 1 comments
Replacing a broken spoke is a simple task and one that can save a not insignificant sum paying for the services of a professional.
While it’s possible to break a spoke at any time of the year, winter makes it a more likely occurrence. Corrosion from road salt, obstacles hidden by water and debris, such as a water-filled pothole, and the typical use of heavier equipment all place greater stress on wheels.
This demonstration from Jon Hayes, mechanic at independent bike shop, Ride, covers a broken spoke on the driveside of the rear wheel: the worst case scenario.
A broken spoke is most likely to occur at the ‘elbow’ (the bend that that secures it to the hub flange) or at the nipple. In the case of the latter, the nipple is likely to have failed, rather than spoke.
Additionally, the greater tension placed by the dish of the wheel onto the driveside, and the potential for damage from poorly-aligned gears causing shifts into the wheel, increases the likelihood of spoke damage.
The tools required include a cassette removal tool, a wrench with which to turn it, a chain whip to prevent the cassette from spinning while unscrewing it from the freehub body, tyre levers, and a spoke key.
Step one – remove the cassette
Unscrew the quick release and remove. Insert the cassette removal tool, apply the wrench to it, and apply the chain whip to the cassette.
Apply pressure to the chain whip in a clockwise direction and turn the wrench anti-clockwise.
Step two – remove the broken spoke
Pull the broken spoke from the hub flange. It’s possible, but not essential, to trim the spoke with cutters to reduce the length necessary to pull from the hub.
Step three – remove the tyre
Jon removes the tyre after removing the cassette. “The tyre gives you some purchase when applying pressure to the chain whip and wrench,” he says.
The tyre will absorb the pressure applied when removing the cassette more effectively than the rim, which could be damaged if placed against the workshop floor.
Step four – remove the rim tape
It’s necessary to remove the rim tape to gain access to the spoke nipples.
Rim tape comes in two forms: adhesive, or a stretchable band. Adhesive tape is likely to require replacement once removed. The tape shown here is the stretchable type.
Locate the nipple of the broken spoke. Be sure not to allow the nipple to fall inside the rim, which typically has twin walls and a hollow chamber, in which it will rattle. Attempting to free a nipple from inside a wheel rim by shaking it back through the spoke hole can be a long and arduous process.
Step five – replacing the spoke
Spokes come in different lengths, and the simplest method of obtaining a replacement is to take the wheel to your local bike shop, where the existing spokes can be measured, or a replacement ‘offered’ against it.
Examine the orientation of the unbroken spokes. The wheel in our demonstration follows an alternating pattern of ‘in-bound’ and ‘out-bound’ spokes. The spoke head is visible on the outer edge of the hub flange on ‘in-bound’ spokes; the spoke elbow is visible on the outer edge of the hub flange on ‘out-bound’ spokes.
Thread the spoke through the hub flange. Examine the existing spokes for the lacing pattern and follow it. The wheel used in our demonstration has a three-cross lacing typical on low to mid-range wheels.
Feed the spoke through the rim and carefully drop the nipple over the spoke, ensuring that you do not allow it to fall inside the rim. Tighten the nipple with a screwdriver. Jon is using a ‘nipple driver’. “It’s not an essential tool for a single spoke, but if you’re doing 32, it will be much quicker,” he says.
Step six – tension the spoke
Removing a spoke ‘throws out’ the tension of the entire wheel. In theory, tightening the replacement spoke to the tension of the one replaced will restore the wheel to the degree of trueness experienced before the damage. Use a spoke key to do so.
Spoke tension can be gauged by sound and ‘feel’ (squeezing the spokes to ensure equal tension – ‘feel’ will come with experience). The pitch of the note raises as the spoke is brought up to tension.
Step seven – check the trueness of the wheel by placing it in the bike
If you don’t have a wheel jig, brake pads will serve the same function. Reinstall the quick release, return the wheel to the frame, and use the pads to check for ‘buckle’ in the wheel (‘buckle’ is typically caused by an imbalance of spoke tension).
A wheel with a buckle to the left (touching the left brake pad) will require tension in a spoke or spokes on the right hand side in the same area of the wheel. Be sure not to over-tension and cause a buckle in the opposite direction.
The ‘length’ of the buckle will determine the number of spokes to be tensioned. If the buckle is over one spoke, only one spoke need be tensioned. Apply tension with a spoke key, a quarter of a turn at a time.
In our demonstration, replacing a spoke on the driveside, an over-tightened spoke would cause a buckle towards the right side of the bike; a under-tightened spoke on the driveside would cause a buckle to the left.
A wheel can be trued on two planes; vertical and horizontal. It’s highly unlikely that replacing a single spoke will affect a wheel’s trueness in the vertical plane. This is more likely to be caused by a damaged rim.
Step eight – re-apply rim tape
If the rim tape removed was adhesive, it’s likely a replacement will be required. A stretchable, ‘band’ style tape can be reapplied.
If the stretchable type is used, locate the valve hole in the tape, align it with the hole in the rim, and secure its location by passing a screwdriver through both. Fit the remainder of the tape.
Step nine – refit the tyre
Fully inflate the tyre.
Step 10 – refit the cassette
Remove the quick release, slide the cassette over the freehub body by aligning the grooves (it will only fit in one direction, making it impossible to fit the cassette ‘back to front’). .
Be sure to replace the spacers in the order in which they were removed. Tighten the lock ring. The manufacturer’s website should give a torque rating.
Step 11 – check the brake and gear function
Removing and replacing the cassette could effect the gear alignment. It’s worth checking before heading back out onto the road.
Re-tensioning the brake cable after replacing the wheel is unlikely to have altered braking alignment, but is perhaps worth checking.
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