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Sherborne Times September 2018

Spinning Hoops

wheel truing outside workshop

As I wrote this Geraint Thomas aka “G”, coasts across the line in Paris to win the Tour de France; bicycle makers and sponsors names will get the limelight, but without a good set of “hoops” the result would be different. Around the course you see wheels held aloft at strategic places and carried on cars, these are neutral service wheels which riders can access if they have a failure. I found so much to share on the subject that it needs two articles, so I will discuss wheels this month and tyres next.

The bicycle wheel is an impressive piece of engineering design. Each rotation a spoke changes from pulling to pushing; at 400 rpm, that is 24,000 squeeze and stretches per hour. A wheel may weigh 1 kg or less, but a pair will support a load of 100kg or more.

Wheel Types

Our store above the workshop is full of many wheels, there are many types varying in application, size and material.

Most modern rims are aluminium. They do not rust and improve brake grip. The downside is braking surface wear which riders may not notice until the rim is so thin it splits. To extend the rim’s life wash the bike or wipe road grit from the rims and pads, also better quality pads are less abrasive.

Carbon fibre (CF) is seen as a wonder material for bicycles, but requires caution. Under hard braking  rims heat up, the combination of softened rim and increased tyre pressure can be catastrophic. My opinion is that carbon wheels are best reserved for disc brakes where the brake is separate from the rim. disc brakes also avoid rim wear.

Steel wheels still have their place especially for vintage bikes, but the wheels that pique my interest have wood rims as made for generations by the Ghisallo family in Italy.

Free speed

In a previous career I worked on product development in wind tunnels, I learned about aerodynamics and saw early drag reducing skin suits and helmets tested for skiers and cyclists. In the quest for speed, bicycle manufacturers realised drag becomes the dominant resistance at relatively low speed, so concluded drag from wheels should be reduced. Bladed spokes, shaped, deep rim sections help the rider seeking performance gains. However, the real world is not a wind tunnel and a side gust from a gap in a hedge can push a rider with deep rims across the road, so they are best kept for suitable conditions.

The route home included a big hill on the South Downs and I learned there the benefits of good hub bearings. Tucking elbows in and freewheeling downhill I overtook other cyclists who were pedalling. So how did I gain this speed boost? The answer is balls of steel – ball bearings are graded and at Campagnolo’s factory where my hubs came from, they selected the best of the highest grade to use. So when servicing vintage Campag hubs we don’t replace ball bearings automatically, but carefully clean and inspect the originals because they are best of the best.

Many modern wheels use sealed cartridge bearings and the quality of these can also affect the ride. We choose replacement bearings with good seals to keep the dirt and wet out and the grease in.

Servicing hubs is advisable especially if ridden regularly in the wet, they last years if cared for, but when a hub bearing surface is wrecked by lack of grease the wheel is written off.

The Wheel Builders Art

Building wheels takes patience and concentration or lacing can be messed up. That is why I let retired friend Paul do any complete rebuilds. We replace broken spokes and true wheels in the workshop, more than that is impractical as we have to stop when interrupted. Mass produced wheels laced by machines have reduced wheel costs, but the human touch is used to tension and true the best wheels.

Repairs and Truing

Truing involves adjusting spoke tensions so the wheel spins without deflection. It is a skill developed through experience. We have an ancient truing jig and a modern one with dial gauges, but it is interesting that results with the old jig are pretty good, because the “feel” of the mechanic is an important factor.

I was chuffed recently when asked to true a steel wheel.  I had kept an old rim setting tool despite others telling me to get rid of it, thinking it would be useful, it worked a treat to fix a ding in the rim. The old jig I am using in the picture was easy to move outside for the photo and houses a stock of spokes and tools; on top is a spoke cutter and threading tool so it is a handy item to keep. Don’t think we would work on your modern high performance carbon wheels with this though, in the workshop is a modern Park tools jig bristling with dial gauges and a tension tool.

Looking after your Wheels

It is surprising how people are often unaware they have a wheel problem, a quick inspection will tell if something is failing. Before a ride, while static, grasp parallel spoke pairs and squeeze to feel the tension, work your way round and you will feel any slack spokes, look at the spokes to spot damage, grasp the wheel at the top and wiggle side to side, if there is slack then hubs need adjusting. With the wheel off the ground, spin and listen for noises, a rumble indicates bearings need attention, visually check for a buckled rim by watching for deflection by the brake blocks.

A common problem occurs if rear gears are incorrectly adjusted and the chain comes off by the spokes. The rider is unaware the chain has partially cut the spokes and some miles later a spoke will break.

As I finish this article, I am reminded it is 5 years since I took over the cycle shop and I am grateful for the customers who have supported me over the years and also for Peter’s help with the previous cycling articles in this excellent magazine.