Hub Gears for Bicycles

It is several years ago now since the "Mountain Bike" first appeared in Britain. The concept was a good one, a rugged bicycle that could be ridden anywhere - although mountains will probably always be best tackled with climbing boots.

More recently the "Mountain Bike" has become known as the "All Terrain Bicycle" (ATB). Neither title is really suitable.

As I have already said, the concept is a good one. A rugged frame with wide wheels makes a stronger bicycle. The problem lies in the rear wheel and the transmission.

Some History

Roller chains have been used in engineering since the industrial revolution. As the bicycle developed it was soon evident that the roller chain was the best method of transmission. This chain has stayed with us to the present day and is used on virtually every bicycle including the ATB. The principle of the roller chain is excellent engineering and it's use is to be commended.

As soon as bicycles were invented people started racing them. The famous penny-farthing was in fact designed to be a racing cycle, possibly the first purpose built racing bicycle. Racing cyclists where also responsible for the development of chain driven bicycles which allowed higher gearing.

In the late 1930s and early 1940s everyday bicycles had just a single gear or one of the beautifully engineered hub gears made by such firms as BSA and Sturmey Archer. Racing cyclists were looking for a lightweight alternative to hub gearing and so the derailleur gear system was developed.

The dérailleur system brakes the basic engineering principle that a roller chain should always run perfectly in line. Running a chain out of line causes increased wear in all of the transmission components. Further wear is encouraged by the components being out in the elements picking up dirt and water.

As the dérailleur system was developed for racing this wasn't a great problem as the increased wear was acceptable if it helped the rider to victory. Racing cyclists were happy to strip down, clean, lubricate and replace any components as necessary.

The dérailleur manufacturers soon realised they had a potential market and offered the general public a lighter gearing system than hub gears and (eventually) more selectable gears. The manufacturers benefited hugely as did cycle repair shops (including my own).

Manufacturers offered more selectable gears by adding more sprockets to the rear sprocket cluster. The only way this could be accommodated is by making the rear hub narrower and moving the hub off centre, both of which weaken the rear wheel considerably.

I must point out that I don't totally disapprove of dérailleur gears, but they really are only suitable for cycling enthusiasts who have an interest in bicycle maintenance.

Derailleur gears certainly do not belong on any bicycle that professes to be "All Terrain". The situation is not helped as the difficulties are increased by the incredibly long rear changers required to get the gear ratios which the manufacturers erroneously believe are necessary.

The main reason for the current design of the ATB is a commercial one. Numbers sell. Who would want a bicycle with 3 or 5 gears when you can buy one with 18 or 21 gears. Isn't it obvious that if there are more gears then it's a better bike? It might appear so but let's have a look at these gears.

A typical ATB has 3 chain rings and 6 rear sprockets giving a total of 18 gears.

A possible combination might be:

Chain rings - 28T 38T 48T
Sprockets - 32T 28T 25T 22T 19T 16T

That would give the following gears:
Smallest Chain ring 22.75 26 29 33.09 38.31 45.5
Middle chain ring 30.87 35.28 39.52 44.91 52 61.75
Largest Chain ring 39 44.57 49.92 56.72 65.68 78

In order and rounded to the nearest whole number we get:
23 26 29 31 33 35 38 39 40 45 45 46 50 52 57 62 66 78

Most people find gears below 30 to be too low to ride comfortably so we now have:
31 33 35 38 39 40 45 45 46 50 52 57 62 66 78

Gears which are less than 3 apart are not usually different enough to make any perceivable difference to ease of riding,
If we eliminate this duplication we are left with something like this:
31 35 40 45 50 57 62 66 78

We now have only half the gears we started with.

I have found that many commuters who use an ATB will stay on the largest chain ring for there entire journey to work, and even then are only using three or four of the six gears available to them on that ring.

Why do manufacturers insist on putting two extra chain rings onto bicycles when most riders won't use them? As I already said earlier, numbers sell.

Usually when I put forward an argument for hub gearing I am told that hub gears are far heavier than dérailleurs. When you compare the weight of a hub gear with a competition dérailleur set this is true and I am fully in favour of using dérailleur gears for competitive events. However most ATBs are not competition bikes.

A hub gear is a shell filled with metal components and so is naturally somewhat heavy. However all bicycles need to have a rear hub so if we are going to put the hub gear on one side of the scales you need to put the rear hub from the dérailleur bicycle on the other side.

Also on the dérailleur side there is a cluster of sprockets which is usually a very heavy item. We then have to add the rear dérailleur mechanism and the front dérailleur mechanism and two extra chain rings (which on a budget ATB are usually made of steel).

On all but the most expensive of bicycles the dérailleur system by now has usually equaled or exceeded the weight of the hub gear. To fully compare you would also add the controls and cables of each system to the scales.

Another argument which is often raised is that the hub gear is a turning weight. However in the dérailleur system the hub, sprocket cluster, pulley wheels and extra chain rings all have to be turned.

For your average street bike if there is a weight advantage for either system then it is an insignificant one.

As a big fan of hub gears I would love to be able to say yes, but in reality hub gears are not perfect.

In the late 1960s almost all of the classic hub gears were discontinued leaving only the AW wide ratio 3 speed which was fitted mainly to commuter bicycles.

The AW was the simplest of the hub gears produced by Sturmey Archer and is very reliable and robust. Unfortunately the ratios are really a little too wide. Having said that, in my early teens I used to ride an AW all over Surrey and Sussex and thoroughly enjoyed it.

In the 1980s Sturmey Archer produced a 5 speed hub. The hub was excellent but the controls were a problem. The choice was between a simple two-control system, which made gear selection complicated, or a complicated single control, which was very unreliable. Not surprisingly the 5 speed was not a commercial success.

In 2000 Sturmey Archer was sold to the Japanese company SunRace. The AW and 5 speed were discontinued and a new range of Sturmey Archer hub gears is now available. These new hubs cost more than most commuters spend on a complete bicycle. Once bought they need to be fitted to the bicycle which is not a job for a novice.

The conversion from derailleur to Sturmey Archer AW is not a task to be undertaken by the novice cycle mechanic. Here are the steps involved.

STRIP DOWN
1. Remove the rear wheel (save)
2. Remove the rear derailleur mechanism and cable
3. Remove the front derailleur mechanism and cable
4. Remove the chainset and bottom bracket (save)
5. Remove the gear levers
6. Remove the chain

FRAME
7. Retrack the frame to the correct width for the new hub - this is particularly heavy work on an ATB and may require heat

REAR WHEEL
8. Remove the sprocket cluster
9. Remove the tyre, tube and rimtape (save)
10. Remove the rim (save)
11. Build the saved rim onto the AW hub - it is usually possible to cut and rethread the existing spokes if desired
12. Fit saved rimtape, tyre and tube

CHAINSET
13. Remove surplus chain rings - on budget chainsets this may involve drilling out rivets, on more expensive chainsets this may involve grinding down retaining bolts

REBUILD
14. Refit bottom bracket and chainset
15. Refit rear wheel
16. Check and adjust chainline
17, Fit chain
18. Fit trigger
19. Fit toggle chain and cable
20. Adjust gear
21. Road test

I was riding this bike as single speed fixed for many years.

It currently has a 1950s Sturmey Archer AM gear in a 1980s alloy AW shell. The shell change was necessary so that it could take the 36 hole rim, the original shell is 40 hole. The gear is controlled with a top-tube mounted quadrant lever.

When I bought the AM hub from eBay it came complete with the correct 2-part indicator (toggle chain). However if this is missing from an AM, the hub can still be used after a relatively simple conversion.

This is a lovely bike to ride. Much better than the AW. It's a pity these hubs were discontinued.

When I was given this bike it had 18 gears.

The conversion gave me a small surprise. The 4 speed trigger wouldn't change to the lowest position due to the straight handlebars. I found a more suitable set of bars on a bike I have put aside for my daughter. She now has a nice set of perfectly straight handlebars. :)

It now has a 1968 Sturmey Archer FW 4 speed gear.