In this episode of the product focus series, we’re going to take a wheelie good look at wheels (hold on to your hats there’s plenty more where that came from). We’ll go round the wheel (I warned you!) looking at spokes (not too much nipple talk though), hubs, rims and the ever elusive freehub.
Spokes hold wheels together, they are responsible for getting and then maintaining the wheels shape. If the spokes are not correctly tensioned, the wheel will become untrue (when you spin it it will be wobbly; not straight) and will gradually break down. So all-in-all, I think we can agree they are pretty important! Spokes are generally made from stainless steel, due to the fact that it is strong, resistant to corrosion and good to work with. Avoid titanium, it is a poor material to make spokes from due to its flexibility and can be a nightmare to work with. Plus from a purely practical point of view, titanium spokes do not retain their tension well, so the wheel will regularly go out of shape.
The spokes are attached to the rim by nipples, which are also the main point of adjustment for spoke tension. Nipples are often made of brass which, while slightly heavier, will not freeze on to a stainless spoke like an alloy nipple. This means you’ll always be able to adjust your spoke tension without risk of the spoke having frozen on to the nipple as can happen with alloy nipples and stainless spokes (they react chemically, effectively welding to each other). Spokes are attached to the hub either with the increasingly popular ‘straight pull’ design where the end of the spoke slots straight in to the hub flange (a bit like a jigsaw), or by the traditional elbow joint which is threaded through the hub flange. The straight pull design saves weight and in theory is stronger, but for some applications (mountain biking for example) a traditional spoke with the elbow is preferred as it can be more secure when the wheel deforms under impact/load.
We’re not going to go in to spoke lacing patterns, because we would be here all day, but spoke counts are worth mentioning. Generally speaking, the more spokes you have then the less tension the individual spokes have to carry. This is a good thing, as you do not want the spokes to be over tensioned as it places more stress on the individual spokes and increases the risk of a spoke breaking.
With the demand for ever lighter wheels, spoke numbers have been cut down to save weight, but you must remember that the fewer spokes you have then the more strain is placed through each spoke. That’s why the pro’s train on wheels with higher spoke counts, they’re much more durable which should be a consideration when choosing a wheel. The weight saved by having fewer spokes is often put back on in the rim because the rims have to be made stronger to counter the lower spoke count!
Finally, a quick look at spoke shapes, butted spokes are a great idea. This is where the spoke diameter is tapered so it is thicker at either end and thinner in the middle. This saves weight where strength isn’t needed (in the middle of the spoke) and keeps strength where it is needed at the end of the spoke. A butted spoke is in fact stronger than a plain gauge spoke because the distribution of material changes where the forces are applied. Bladed spokes are increasingly popular because of the aero advantage they offer. Just watch your fingers in them if you’ve got your bike in the workstand, they’ll make quite a mess!
Wheels tend to use either traditional cup and cone bearings, where the axle has cones on either side which pinch in on a set of loose bearings rolling in the hub cups, or more modern cartridge style bearings. The advantage of the traditional cup and cone bearing is that they are easily adjustable if you know what you are doing, plus you can clean and re-grease or replace the cones and bearings to refresh the hub. The technical bit is getting the tension correct when rebuilding the hub.
Cartridge style bearings tend to run with less resistance as they are a closed system, plus when it comes to replacing them, the old ones are simply knocked out and the new ones pressed in. It is however harder/not always possible to give them a ‘refresh’ clean and re-grease as they may be sealed units and they may not be as durable as cup and cone systems. Cartridge style ceramic bearings are increasingly used on top end wheels from the likes of Zipp and Fulcrum on the Racing Zero. Ceramic bearings are harder and smoother so they roll with less resistance for longer. A great upgrade for any bike!
Rims have come a long way in the last few years. From the 32/36 hole alloy norm that was a top end wheel (and still is a good wheel) , you can now roll around on a full carbon rim with anything from a shallow profile to a deep profile or even a full carbon disc. Full carbon disc wheels like the Reynolds Element offer perhaps the ultimate aero advantage in a stiff, light weight package. Time trial and triathlon types might well use a combination like the Reynolds Sixty-Six 66mm deep carbon front wheel with a Element carbon disc rear wheel. These deep section rims will assist in straight line speed. You would not however choose this wheel combination for a tight, twisty race where manoeuvrability counts. The deep profile rim is aero in a straight line, but has a bigger cross-section when turning increasing resistance felt ultimately slowing you down. Having said that, wheels like the Campagnolo Bora One have a relatively deep 50mm carbon rim, but are very popular for all round use thanks to their solid design, light weight and great price point.
For regular everyday riding, check out the shallower profile wheels like the Fulcrum Racing Zero’s. These mid-profile wheels tend to be the best compromise between the aerodynamic advantage of a deep profile rim and the lightweight, comfortable handling of a shallow rim giving you a fairly aerodynamic yet manoeuvrable wheel.
The demand for light carbon rims has been driven by the advantages to be gained by reducing the rotational mass of a wheel. Rotational weight has one of the most noticeable effects on the performance of a bicycle, the lower the weight then the quicker the bike feels and rides which can give you a noticeable advantage. Therefore one of the first places people often look to save weight is in their wheels, it is often money well spent.
While carbon may be something for us mere mortals to aspire to (or should I say save up for), alloy rims should not be discounted. They are light, strong and roll well which is surely all you want in a rim? Wheels like the Fulcrum Zero, One and Five offer great performance at a much more reasonable price than many carbon wheelsets. They’ll handle training and sportives very nicely indeed.
Finally there is the issue of tubulars and clinchers. Clincher tyres are what most people would probably term a ‘conventional’ tyre, they are U-shaped with a bead which fits with the clincher design rim and they use an inner tube to hold air. Clincher tyres are easy to use, punctures can be repaired easily however there is a slight weight penalty because of the inner tube and also the rim design which has slightly more material in it.
A tubular tyre has no bead, the outer is sown around the inner and the tyre is then glued to the rim. The advantages of tubulars are that both the rim and the tyre are lighter, they are less prone to pinch flats and many believe they offer improved handling. The downside is they are much harder to repair when they puncture, they’re considerably more expensive and if not fitted properly they can come off the rim.
Last but not least – freehubs. You’ll see wheels marked as having either a Shimano/SRAM or a Campagnolo freehub. This is because they use a different profile for the cassette to slot on to.
There are no real advantages or disadvantages to the two designs, it is just a case of different standards and compatibilities between manufacturers. The Shimano and SRAM cassette designs are the same, it is just if you run Campagnolo you’ll have to get a different freehub body.
So there we go, a whistle stop tour of wheels. Where do you stand on the clincher v. tubular debate? Anyone got a particularly bling pair of race wheels they’d like to shout about? Pop a picture up on Facebook and show us your pride and joy! Or perhaps you’ve a favourite pair of old faithful wheels that just keep on rolling? Anyone got a pair of wheels they swear by?
What else would you like to see in the Product Focus series?