The toothed belt has won out. If you scroll through the websites of many bike manufacturers, you’ll struggle to find a bike with in-hub gears that doesn’t feature the low-maintenance belt drive – regardless of the price range. Things were very different just two years ago: The Gates belt was the hallmark of high-quality gear systems such as Alfine 11, Rohloff and Pinion. It was difficult to find a belt-driven bike for less than 1,500 euros. In the lower price range, the classic metal chain was still usually the go-to choice for power transmission.
Cheap and good?
In the 2020 season, the affordable CDN version of the Gates belt is gaining widespread acceptance. In contrast to the more expensive CDX belt made of polyurethane, which is designed for the most demanding conditions, the simpler CDN version is aimed at more moderate uses: It is the more affordable option for everyday cyclists who do not cover 10,000 kilometres a year, and is therefore clearly the better choice for budget bikes. This is because a bike with a low-maintenance CDN belt drive falls into the price range of between 1,000 and 1,500 euros.
The belt itself is made of polymer plastic; as with its more expensive counterpart, carbon fibres embedded lengthways ensure that the belt is completely resistant to tensile stress and does not stretch lengthways. Compared to a chain, manufacturer Gates claims that the CDX drive has a service life two and a half to three times longer, and that the simpler CDN drive has a service life one and a half to twice as long. Even after wear caused by intensive use and under high pedalling loads, a Gates belt – unlike a bicycle chain – does not stretch. This is because, in a chain, friction between the individual metal components inevitably causes wear, which steadily increases the clearance between the rivet, link and sprocket. Many small, worn-out chain links add up to a total elongation of easily 10 millimetres. Yet even chain links that are just a few tenths of a millimetre longer wear down the teeth of their sprockets and cause material loss there too.
With a belt, on the other hand, the compact material ensures there is no internal friction and therefore no internal wear. Even on the outside, where the belt comes into contact with the toothed profiles of the pulleys, abrasion is said to be negligible thanks to the carefully matched material properties of the belt and the drive pulleys. Gates therefore recommends that bicycle manufacturers use a measuring device to adjust a new drive system so that the belt tension lies within the upper green range of the permissible limits. Running-in over the first hundred kilometres causes the surfaces of all drive components to become slightly roughened and to bed in with one another. During the scheduled first service, the specialist retailer can check the belt tension again. Ideally, it should then be in the middle of the green range. And it should never change again after that.
Optimisation of the Riemann drive
However, a drivetrain does not consist solely of the belt. The sprockets on the crankset and rear wheel also contribute to the service life of a drivetrain system. In the CDN system, a ‘chainring’ made of composite plastic has proven its worth here. As the forces are distributed across roughly half of the 46 or 50 teeth, wear remains minimal. The situation is different at the rear wheel: initially, Gates also fitted plastic discs there, which were mounted around a metal support. However, this did not prove successful, as fewer teeth had to bear a significantly greater load and wore out more quickly. For this reason, current CDN sprockets are made of galvanised stainless steel as standard. For the CDX version, designed for maximum durability, Gates uses hardened aluminium on the crank and stainless steel on the rear wheel.
The correct belt tension is crucial
Just like a chain, the belt must run under a specific amount of pre-tension to prevent it from jumping over or coming off. Bike manufacturers solve this on almost all test bikes by using adjustable axle pieces on the rear wheel. It took several model years to develop workable, cost-effective designs for this. The tension only needs to be adjusted once, as the belt does not stretch further once fitted. If there are also adjustment screws on the dropouts, the belt tension can be fine-tuned to the optimum level whilst simultaneously centring the wheel. An eccentric on the bottom bracket and classic dropouts, such as those on bikes from Kalkhoff and Raleigh – both of which are manufactured by Derby Cycles – are also a simple and robust solution. The eccentric should be removed, cleaned and re-greased every one or two years to prevent it from seizing up due to corrosion.
Gears in a can: the pros and cons of hub gears
A key component of durable, low-maintenance drivetrains is the gear hub. Hermetically sealed against moisture and dirt, its complex mechanism operates under consistently optimal conditions, including lubrication. The test line-up is dominated by the affordable Nexus hub and the slightly more expensive Alfine hub, each with eight gears. The inner workings of both models are identical; only the Alfine’s casing is slightly more attractively designed. The internal mechanism should be removed every 5,000 kilometres or once a year and immersed in an oil bath – a task best left to a specialist dealer.
The eight gears are well-balanced, but present some challenges for sporty riders. The T-700 from Fahrradmanufaktur is the only exception, featuring an Alfine 11, combined here with a chain drive. The 11-speed hub has a series of evenly spaced gears overall, but adds its three extra gears at the top end of the range – where very few cyclists actually need them. All hubs share the weakness of offering only a few low gears for longer or steeper climbs. So anyone who has to cycle uphill and downhill every day won’t be happy with Shimano hubs.
Every belt-drive frame requires a belt lock to allow the closed belt to be fitted. Frame manufacturers usually use a split seatstay on the right-hand side, which is bolted into place using stepped connectors. This ensures that the flow of force within the frame structure is hardly disrupted at all; the connection can be opened easily and locked securely again. The steel frame of the T-700 has no belt lock and is therefore chain-driven.
What maintenance still needs to be done
As for maintenance, it is sufficient to clean the belt and sprockets regularly with soap and water and to remove any dirt that has built up in the belt groove. A belt drive may occasionally squeak: a little silicone spray is usually enough to stop it making noise. It is often necessary to make a slight adjustment to the tension of the shift cable using the adjustment screw on the shift lever. On an eight-speed hub, the yellow markings must line up in reference gear 4 (Alfine 11: gear 6). Once everything is optimally adjusted, bikes with low-maintenance hub gears are a breeze to look after – but they always shift crisply.
Gears and gradations – the unfolding
As eight out of nine test bikes are fitted with an eight-speed hub, we took a closer look at these models from Shimano’s Nexus and Alfine ranges. Using the Raleigh Nightflight as an example, we have calculated the gear ratio for each gear in the table below. The bike (tyres: Schwalbe Marathon Supreme 42-622) has a wheel circumference of 222 centimetres; the primary gear ratio is 50 teeth at the front and 22 at the rear. Multiplying this by the internal hub gear ratio for each gear gives the distance covered with one revolution of the crankset in that gear.
It’s clear to see that the gradients are already very steep in first gear: a 3x10 derailleur system would have gradients well below two metres in first gear here – which is useful when tackling longer climbs. The most frequently used gears are spaced at intervals of between about 14 and 18 per cent. You can feel the difference as a distinct shift, but the gears are still close enough together that you can easily maintain your cadence. A large 23 per cent jump between fifth and sixth gears falls right in the middle of the most frequently used range. This throws the cyclist off their rhythm.
An overview of all low-maintenance bikes
- BERGAMONT VITESS N8 BELT
- GIANT ANYTOUR CS 1
- VSF BICYCLE MANUFACTURER T-700
- R RAYMON TOURRAY 6.0 GENT
- RABENEICK TX7C
- RALEIGH NIGHTFLIGHT PREMIUM
- STEVENS COURIER LUXE MEN'S
You can download the full review of the low-maintenance bikes from MYBIKE 02/2020 as a PDF (for a fee) below the article.
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