Re-gearing the Brompton

Second-hand bikes can be a great way to get a good bike at a more affordable price. The downside is that you  get a bike which has been set-up according to the preferences of its previous owner. When I purchased the Brompton back in February, it had been set-up with obscenely high gearing, a 50-tooth chain-ring with a 13-tooth rear sprocket. With the Sturmey Archer S-RF3 rear hub, this gave gears with 3.7, 4.9 & 6.6 metres development respectively. I put up with this for a long time because although it was much too high, it still worked. Eventually, the stresses to the sprocket and chain from starting from stationary in such a high gear were too much, and the chain would no-longer mesh with the chain-ring.

Not having a 24mm socket to remove the left-hand folding pedal, I had a look at the official Brompton chainsets which would allow me to leave my existing left crank in place without a major mismatch. Needless to say, they were excessively expensive. Instead, I was fortunate enough to find a Stronglight chainset which, online at least, looked similar enough to the Brompton one for me to get away with leaving the original left crank in place.

The unused Stronglight left crank, with the original Brompton one. They could almost have been separated at birth.

The fitted Stronglight chainset with the Brompton original below, again they are very similar looking indeed. I also replaced the rear sprocket and chain, resulting in 42 teeth at the front and 14 teeth at the back. This produces 2.9, 3.8 & 5.1 metres development, respectively. This means the Brompton can now much more easily climb hills and accelerate from stationary without busting my knees. It may not be a very flashy upgrade but it makes a significant difference to how useful the bike is. If your gears are too high (or low) don't suffer in silence, do something about it. It can make the difference between a bike you merely tolerate riding in certain circumstances to one you actively want to use.

Servicing a Sturmey Archer AW hub

The Sturmey Archer AW hub is 75 years old this year. The reliability of this design means that there are plenty of these hubs still in service. The ease of serviceability of this design means that returning one of these hubs to its former glory isn't all that difficult. Many minor issues such as resistance to freewheeling, hub seizure, general resistance to rolling and problems accessing certain gears can be fixed by taking the hub apart, cleaning the internals and re-assembling it all with some fresh grease.

Whilst I have written about working on an AW hub previously, the nature of the work means that it is difficult to take pictures whilst cleaning and re-assembling the hub. Thankfully, this time I was able to get a little help with taking pictures. To open up an AW hub (and most other Sturmey Archer hub gears) remove the left-hand (non-drive side) locknut and cone and uncrew the right-hand ball ring using a hammer and a flat screwdriver on the semi-circular cut outs of the ball ring (these are not rounded on the older versions of the AW). This should let you get the internals out, axle and all. This can be further disassembled by removing the right-hand locknut and cone, which allows the rest of the hub mechanism to be taken apart.

One of the notches for unscrewing the right-hand ball ring

Left to right: The left-hand axle nut, non-turn washer, locknut, spacer and cone

Left to right (top): right axle nuts (later integrated into a single piece), non-turn washer, locknut, cone lockwasher & cone. Middle: cone. Bottom: indicator rod (with indicator rod locknut seen above the locknut)

Left to right (top): Dust cap, sprocket snap-ring. Bottom: spacers. Assembled as: Dust cap, spacer, sprocket, spacer, snap-ring.

The driver assembly and clutch spring

Gear ring (left) and right-hand ball ring (right)

Left to right: clutch sleeve, clutch, axle key and thrust ring

Top: Axle (including sun pinion). Bottom (left-to right): Planet-cage, 4 planet pinions (cogs) and 4 pinion pins.

The low-gear pawls in the planet-cage can also be removed if necessary, although when removing these be sure not to lose the tiny pawl springs in the process. The same also goes for the pawls in the gear ring.

Once all this has been disassembled, a good cleaning with some degreaser and a cloth or paper towel should restore the hub to its former glory. Particularly dirty or rusty parts can be soaked overnight or cleaned with wire wool (just make sure to remove any left-over bits of wire wool before re-assembling the hub).

To re-assemble the gear mechanism, hold the axle vertically with the drive-side pointing up (axle hole above the sun pinion).

Add the planet pinions and the pinion pins back into the planet cage and place the assembly over the top of the axle with the planets at the top.

Add a dab of Sturmey Archer hub gear grease to the planet pinions and rotate the planet cage assembly around the axle a few times to distribute the grease around.

Place the clutch sleeve over the axle and line up the hole in the sleeve with the hole in the axle.

Place the clutch over the axle and the clutch sleeve.

Slide the axle key through the hole in the clutch sleeve and axle, with the threaded hole in the axle key lined up with the centre of the axle.

Slide the thrust ring over the axle key and clutch, lining up the grooves in the thrust ring with the protruding parts of the axle key.

Place the gear ring over the planet cage assembly and clutch assembly, being sure to line up the grooves inside the gear ring with the planet pinions.

Place the right-hand ball ring over the gear ring.

Add some lithium grease to the ball bearings within the ball ring (ideally more neatly than this).

Place the clutch spring over the axle, ensuring the plastic (or metal) ringed-end of the spring pointing upwards.

Place the driver over the axle. The clutch spring will push against the driver until the right-hand cone is added to hold the driver in place.

Add lithium grease the the ball bearings in the driver assembly and screw the right-hand cone onto the axle as with any other cup-and-cone bearing system.

Add the cone lockwasher and locknut.

Add lithium grease to the left-hand bearings.

Add the left-hand cone, spacer and locknut.

On the right-hand side, add the dust-cap, a spacer, sprocket, another spacer and snap ring to the end of the driver assembly.

The wheel may be bolted back into the frame, the indicator rod screwed back into the axle key and to the gear cable and the hub is ready to be tested. With any luck, the hub should perform just fine for another couple of decades. The 'no intermediate gear' (NIG) versions of the hub, such as the current AW hub, the S-RF3 and the gear mechanism in the X-RD3 are fairly similar to this, with minor changes to the clutch assembly and the driver, which has its own pawls in this version. There have also been numerous small revisions throughout the run of the original AW hub, although they should pose little trouble when using this guide as reference. The best advice I can give anyone who wishes to service one of these hubs is to just go for it; when disassembled the hub really isn't as daunting as it may appear from reading this guide (or similar guides).

Punctures

Those of you who follow me on Twitter may have noticed my recent Brompton tyre problems. On Thursday morning I was cycling from Macclesfield to Manchester along the Middlewood Way, when I heard a violent, “Whoosh,” of air leave my back tyre. Thankfully I was very near Rose Hill Marple station so I decided to just fold-up and hop-on. When I took the tube out I found a small spear-shaped piece of glass had managed to pierce the centre of the tyre tread.

A utility bicycle needs to be resistant to punctures; if the frequency of punctures on a bike is too high, it will cease to feel like a viable mode of transport. This was the fist puncture I had on the Brompton which was not due to the poor rim tape, and I decided it would be wise to invest in some Schwalbe Marathon Plus tyres as an upgrade over my Brompton green-label tyres.

This turned out to be a wise choice, on Friday I got a second puncture. At first I expected it would be a piece of the glass which had worked its way through after the repair, but when I pried the tyre off the rim to patch the tube, I found that the puncture was a rather large tear in the sidewall (I had been taking a turn at the time of the puncture. I patched the tyre and the tube and hoped it would hold until my new tyres arrived.

On Saturday I got a third puncture whilst riding down Princess Street in the evening. This was about 1 cm away from the previous sidewall puncture. Again, I patched the tube and put the tyre back on the rim. By this point, the tyre was starting to look like a special effect from Peter Jackson’s seminal masterpiece; Braindead.

The bulging, infected-looking tyre

Some serious warping

I decided that the bike was more of a liability than an asset in its current state, and decided to walk instead on my Sunday train trip to The South.

Today I got my new tyres, which have been fitted to the Brompton. The Marathon Plus tyres were quite challenging to get onto the rim, but their reputation suggests I won’t be taking them off regularly. The tyre-swap also provided me with an opportunity to replace the frankly terrible Brompton rim tape.

The new tyres seem make the Brompton feel a bit more nippy than before, and the ride is a tad harsher, likely due to being 2 mm narrower. Another advantage is the extra clearance between the tyre and the mudguard stays, removing the squeak after a bodged fold which was common with the old tyres. Overall, I am quite pleased with them, as long as I don’t have to take them off for a while.

Bicycle Work Digest

It has been a while since my last post, mainly due to all of my free time being used up with doing bike-related things, leaving me without the time to write about them.

Brompton:

I noticed that in addition to the noise from my folding pedal (which I can live with based on the cost of a replacement), There was some noise coming from the bottom bracket. The Brompton uses a FAG-type cartridge bottom bracket, and the replacement part is relatively expensive. I decided to opt for a cheaper generic bottom bracket cartridge with Shimano-style splined cups.

The standard Brompton bottom bracket, with soft plastic cups

I initially expected that I’d be able to remove the old bottom bracket with a hammer and punch because I didn’t have to worry about damaging it. However, I discovered that the cups on the original bottom bracket are made of a fairly soft resin which simply splits when approached this way. I eventually bought the proper tool and the bottom bracket co-operated with the removal process after that. The bike is quieter now, but there is still a fair bit of noise from the (non user-serviceable) folding pedal.

The new bottom bracket cartridge, sitting in the bike.

In other Brompton news, lovely girlfriend has managed to get hold of a 2000 model L5 (equivalent to an “M5L” in the modern nomenclature). This model comes with the Sturmey Archer 5 speed Sprinter hub, which offers a good gear range with a price, it requires particularly perfect indicator rod adjustment to get all of the gears to work at the same time. I believe that the right-hand cone needs adjusting slightly, as I am only able to consistently get gears 1,3,4,5 or gears 2,3,4,5 to work at the same time.

The L5 also needed a new front brake cable, indicator rod and rear mudflap, which have all since been fitted and the bike is currently working very well. The Marathon Plus tyres it has make the bike feel noticeably smoother and faster than my Brompton, and the wider gears range is pleasant too. Hopefully Brompton will see sense and start speccing the X-RF8 hub as an option in the near future. It also came with the special Brompton version of the Brooks B17 saddle, a luggage block and an older version of the Touring Pannier (now T-bag) from back when they were made by Carradice.

DL-1:

After fitting the anti-rotation washers to the back wheel last week, I rotated the reaction arm slightly to compensate for the re-positioning of the axle in the frame. In the process of doing this, I inadvertently over-tightened the left-hand cone making the ride feel “draggy.” Thankfully this was an easy fix once the wheel was out thanks to the two grooves on the “washer” which locks into the cone on the other side of the drum brake. This allowed me to adjust the brake position and re-tighten the locknut without it tightening the cone at the same time.

Taken from the X-RD3 manual, the special washer (31) which sits between the cone (not shown) and locknut (29) is highlighted in red.

because this job was non-urgent, I put it off for quite a while. Now the bike is back to normal I really appreciate just how wonderful it is to ride.

Kona Africa Bike:

After giving this bike to lovely girlfriend, she never really felt safe in start-stop traffic because of the coaster brake preventing her being able to rotate the pedals into an ideal position to set off. In the end, we decided that replacing the 3 speed Nexus hub with a roller-brake version would be best. I disassembled the wheel and intended to use the old spokes with the new hub, only to find out the flange diameter of the new hub was slightly bigger and the old spokes were too long. After ordering some new spokes which were a few mm shorter, I built the wheel up without too much trouble (no severe dishing required as with derailleur gears).

The new wheel, before the cable had been installed. Note the brake arm with the hold for the cable clamp to sit in.

The roller brake idea is particularly good, unlike Sturmey’s drum brakes, the roller brake is a completely separate module which sits on some splines on the left hand side of the hub. If the brake fails, or you want to fit a better version, it can simply be replaced without re-building the wheel. The brake slots onto the splines and is held in with a simple locknut. Other than that, the mechanism is similar to Sturmey Archer drum brakes, except they don’t need a special brake cable, the barrel adjuster and cable clamp come with the brake, all you need to use is a standard brake cable. Upon testing the bike, the roller brake provided an impressive amount of stopping power for a low-maintenance, non-performance-oriented component. This is one of the most basic model roller brake Shimano makes

Raleigh Twentys:

I recently acquired a pair of Raleigh Twentys which I am reconditioning on behalf of a few friends. One is a 1974 “Shopper,” the other is a 1980 model with a rear Dynohub. I tested the Dynohub with my Brompton lights and it was perfectly able to power the front and rear LED lights despite its lower official power rating than modern dynamo hubs.

The Dynohub AWG on from the 1980 Twenty

A previous owner has attempted to fit road bike caliper brakes and drop bar brake levers to the 1980 Twenty, which will have to be swapped out for the appropriate brakes. The rear wheel had a broken spoke, but I happened to have some spokes of the right length already due to a mistake made when ordering spokes for a Twenty wheel last year. Other than that, both bikes only need a bit of de-rusting, new chains and new tyres and they will be ready for their new owners. So far I have only serviced the rear wheels of each bike.

The 1974 AW hub, after disassembly, cleaning and re-assembly.

Universal Folding Bike:

This is another bike I am servicing for a friend, a Universal folding bike with a Shimano “333” 3-speed hub and 20 inch (406 mm) wheels. The riding position is quite comfortable and upright, making the bike an ideal runaround machine. The 333 hub is in good condition, although the cable has rusted seized. 333 hubs were a lot less popular than Sturmey Archer hubs, meaning a replacement cable was not forthcoming. Thankfully, I should be able to come up with a suitable bodge using a cable clamp nut/bolt and a Sturmey Archer gear cable. Other than that it just needs a bit of rust removal, new tyres and a new chain.

The 333 hub shifts via a bell-crank and push-rod mechanism in a similar way to modern Nexus 3-speed hubs.

He’s Dead Jim

In response to CycleA2B’s Jim, I thought I’d present my damaged X-RD3 hub parts. Sturmey’s 3 speed hubs are usually tremendously durable and long-lasting, which makes the fact that I’ve managed to destroy part of one quite interesting & impressive. The hub has always felt a bit off, and as the DL-1 is second-hand. I imagine that a small amount of damage occurred to the internals of the hub before I bought it, which was made worse through use and led to this failure:

The planets which rotate around the axle were also similarly damaged:

The stripped off parts loose in the hub will have no doubt made things worse:

I’ve ordered new planets and a new axle from SJS Cycles, and I hope they are a bit less lethargic about getting it dispatched than they usually seem to be. Until then it’s Brompton or Yuba only…