Monthly Archives: February 2013

A successful improvement to the Kinetics Brompton 8 speed conversion

I’ve now fitted an FSA Vero crankset to the Brompton, removing the outer ring and adding a 3.2mm of washer spacing (2mm + 1.2mm from SJS Cycles) between the spider and the inner 34-tooth chainring to move the latter a little closer in. I used the original chainring bolts and now have a front chainline of about 43mm.

The original Sturmey Archer crankset with 33-tooth fixed chainring

The original Sturmey Archer crankset with 33-tooth fixed chainring

At first, I tried the FSA crankset, that has a JIS square taper, on the original Brompton bottom bracket, which uses an ISO square taper axle. The chainline was out at 50mm or so. I decided that for the modest cost involved it would be better to change the 119mm Brompton bottom bracket (not sure who makes it) for a 118mm Shimano one with JIS taper. It was easy to change and the Shimano BB allows a much greater choice of  cranksets, including those designed for single speed set-ups.

The FSA chainring clears the rear triangle by about 2 – 3mm when folding the bike, so I could probably move it in another mm or two to improve the chainline marginally. The original 100-link chain for the 6-speed Brompton, which I retained intact to use with the 33-tooth Sturmey crankset supplied by Kinetics, works fine with the new 34-tooth FSA one too. 

The new FSA Vero crankset, using the inner ring only from a compact double and mounted on a new Shimano 118mm BB

The new FSA Vero crankset, using just the inner ring from a compact double and mounted on a new Shimano 118mm BB

Despite around 4mm difference between the front and back chainlines, there is no noticeable chain noise and everything feels very smooth. The crankset looks much smarter, the chainring is replaceable, the chainline is adjustable by adding or removing washers under the chainring bolts (either side), and I have a great choice of chainrings if I want to adjust the gearing in future. You can buy chainrings with anything from 33 to 50 teeth that will work with this 110mm BCD crankset. In fact, I think I discovered a chainring with just 30 teeth while researching what to fit to my Brompton, but I haven’t been able to find it again, so maybe I was imagining it! Onto the handlebars…my next target for customisation.


More on the Brompton 8-speed conversion….room for improvement?

I mentioned in my last post about the Kinetics 8-speed conversion kit for the Brompton that the new crankset looks rather cheap and nasty. It is. I’ve discovered that it’s a Sturmey Archer FCS30 model with 33 teeth (why it’s not called the FCS33 is a mystery), which retails for about £16. So we now have a bike that’s cost the best part of £1000, with a somewhat poorly matched crank that’s ugly.

The Sturmey Archer FCS crank - cheap, ugly and no way to change the chainring

The Sturmey Archer FCS crank – cheap, ugly and no way to change the chainring

Worse still, I found that the chainring fouled intermittently on the rear triangle, preventing the bike folding properly. I started looking around for alternatives. The first thing to note is that the Brompton bottom bracket has a 119mm ISO square taper axle. By far the majority of today’s cranksets are JIS taper, so the choice is more limited. The differences are explained most clearly here by Sheldon Brown. According to Sheldon, “if you install a J.I.S. crank on an ISO spindle, it will wind up about 4.5 mm farther in than it would on a J.I.S spindle of the same length.” More about chainline in a moment.

It seems relatively uncommon to find a single-speed chainring with less than 39 teeth, and the most commonly available versions start at 42 teeth or bigger. I need to stay close to 33 teeth to achieve the gear range of the original, which seems ideal for the rather hilly countryside around here. The hub has a 20 tooth sprocket on the back, so according to the online gear calculator, it produces a range from 27.3 to 88.7 gear inches.

Chainline is the next consideration. According to the Sturmey Archer spec, the 8-speed hub with flat 20-tooth sprocket has a chainline of 39.7mm. I measured it and came up with about 38mm, so that checks out. At the FSC30 chainring, I found the chainline to be around 40mm – not perfect but not too bad either. If I’m going to cure the folding problem, the front chainline will need to be bigger at the front, about 41mm. Again, it won’t be perfect, but 3mm difference between front and back doesn’t seem to likely to be much of a problem.

There is no easy way to correct the chainline at the back. You can buy 25-tooth dished sprocket to fit the 8-speed hub. Reversing it would add about 1.5mm. However, the chain tensioner is so close to the sprocket that it’s not possible to use one with more than 20 teeth.

There's not room to fit a sprocket with more than 20 teeth, and you can only get that one in a flat version

There’s not room to fit a sprocket with more than 20 teeth, and you can only get that one in a flat version

The solution at the front may well be to fit a JIS taper compact double crankset and remove the outer chainring – changing the fixing bolts and using washers to adjust the exact position of the inner ring to get the desired 41mm chainline. This will give me a chainring of 34 teeth, rather than 33, so I’ll need one more link in the chain to take it to 101 links. Fitting a new chain at this point seems like a good idea anyway. The gearing will move up very slightly to a range of 28.1 to 91.4 gear inches.

If it's possible to get a reasonable chainline, the inner ring of this compact double would be a much more attractive and flexible  alternative to the Sturmey crank

If it’s possible to get a reasonable chainline, the inner ring of this compact double would be a much more attractive and flexible alternative to the Sturmey crank

It may even make sense to change the bottom bracket for a JIS taper version at some point – Shimano sells them in 118mm and 122.5mm axle widths, so it’s likely I can achieve a fit one way or the other. The FSA Vero compact crankset looks infinitely better than the Sturmey one, so it’s on order and I’ll know if it’s going to work later this week.

Incidentally, the 6-speed parts taken from my Brompton fetched over £100 on eBay, after deducting the costs and PayPal commission, so the final cost of the upgrade will be £200 plus whatever I end up spending on the crankset and/or bottom bracket.

Kinetics Brompton 8-speed conversion kit

I’ve not done many miles on my 6-speed Brompton, despite owning it for several years. It’s not that I don’t like it; I simply don’t do many of the sort of miles for which it’s designed – short commutes around the city. Nevertheless, I had two niggles with the bike from new – the cheap and grotty handlebar grips and the rather ugly and fiddly gear shifters. If you don’t know the Brompton, the 6-speed version has a Sachs 3 speed hub to which a pair of sprockets is attached. The left hand shifter selects the sprocket and the right hand one the  internal gear. To go up and down the gears one by one, you use the shifters alternately.

The 8-speed Brompton chainset and tensioner installed. Note the much smaller front chainring

The 8-speed Brompton chainset and tensioner installed. Note the much smaller front chainring

While on holiday over Christmas, I found out about the possibility of converting the Brompton to an 8-speed bike with just one twist grip shifter. A kit is offered by Edinburgh-based Kinetics and, in a slightly cheaper form, by Tiller Cylces. Both firms offer other hub options, but I decided on the Sturmey Archer X-RF8(W) 8-speed kit. I ordered it from Kinetics over the Christmas period, paid my £300 plus postage, and waited for the 2-week delivery stated on the web site. By the middle of the 3rd week of January I’d had no acknowledgement of my order and nothing had arrived. I called Ben, the owner of Kinetics, and he explained that he was just building up a batch of wheels with the hubs and my kit would be despatched later in the week. It wasn’t. I emailed and got a quick reply and apology, saying that it would be sent the following week. During the last week of January it arrived.

The Sturmey Archer 8-speed hub at the centre of the new wheel

The Sturmey Archer 8-speed hub at the centre of the new wheel

The web site stated that the conversion takes about 30 minutes. The Kinetic instructions were reasonably clear so I set about the conversion. I’m not quick, but not that slow either…you might do your 100th conversion in 30 minutes, but I challenge anyone to do their first one in that time. It took me several hours, but I was not too familiar with the peculiarities of the Brompton, having never worked on it before. You take off the existing wheel and tensioner, plus all cables and other parts associated with the drivetrain. Then you remove the chainset and replace it with the new, smaller one.

I followed the Kinetics directions to the letter but the tensioner jockey wheels were about 5mm out of line with the sprocket on the hub, so the chain wouldn’t stay on. I emailed Ben at 10pm on a Saturday evening and got a reply within minutes. One of the changes during the conversion is to replace the tabbed washers on the wheel axles with thicker ones from the kit. Ben suggested I revert to one of the original thinner ones in order to move the tensioner closer to the frame. It was bad advice because it caused the tensioner to press against the edge of the hub, preventing the gears from changing. I went back to the original washers and packed out the jockey wheel fixing bolts with some washers to move them the required 5mm. All was well and the gears change smoothly.

The new gripshift if much neater than the original Brompton shifters - just need to find some new grips to go with it now.

The new gripshift if much neater than the original Brompton shifters – just need to find some new grips to go with it now.

SUMMARY: This is a nice conversion and, if you don’t mind the extra weight (perhaps a kg or so?) it makes for a more rideable bike with a slightly wider range of gears. The bike looks neater, has cleaner lines and is not quite so quirky, although quirkiness is something that few Brompton riders will worry about. I was disappointed in the service, the hassle of having to modify parts to get the conversion to work, and the rather cheap and nasty looking drive side crank and chainring supplied with the kit. In my view the latter is nowhere near as nice as the one shown on the converted bike on the Kinetics web site. At £300 plus postage, enough to buy a reasonable bike, the kit is expensive, but I’m hoping to raise £100 by selling the original parts, so that eases the pain a little.

Cold mornings, warm days….a neat solution to the ‘what to wear’ question

You know the problem. You’re setting off for a long day ride at 6am, when it’s going to be cold, but later in the day, it’s going to warm up. What to wear? Is it worth suffering the chilly morning for a couple of hours to be more more comfortable later, or do you end up doing most of the ride carrying a spare jacket, maybe a bulky one, that you don’t need. The solution is a device that works in conjunction with your normal cycling clothes but gives you a continuously variable way to control your levels of insulation. This great innovation was first demonstrated to me by my father when he used it during his winter commutes by motorcycle…it’s called a newspaper…stuffed up the front of your jersey or jacket.

Tabloid is about the right size for most people. Just wear one under your top layer and peel off a few pages at a time as it gets warmer, disposing of them in an environmentally responsible fashion along the way. If you’re really hard up, you could even fold up the pages and keep them for the next trip. Push them up the back of your jersey, rather than the front, and you won’t notice the insulating affect.

City traders favour the FT, school teachers The Guardian, Tories The Telegraph and Liberal Democrats The Independent. Your own choice is  an opportunity to make a little statement about yourself.

Of course if you’ve money to spare, I can provide you with an old newspaper of your choice,  trimmed to your size (S, M, L, XL) and complete with Pedalitis logo sticker on the front page for just £20……plus P&P.


The bike lane reclaimed….

Just a quick update to yesterday’s post. I didn’t get a reply to my e-mail to M. J. Church when I wrote to the company about one of its vehicles blocking a cycleway near Bath. However, driving past this evening (I couldn’t cycle with two 10-year olds on the crossbar) I noticed that the vehicle was parked a good 20m further up the hill, no longer blocking the cycleway. I hope it’s not coincidental or worse, a temporary change, but I’m happy to give the company the benefit of the doubt.

FOOTNOTE: 2 days later an email arrives from the Chairman’s assistant apologising for the inconvenience caused by their truck. Thanks M. J. Church!

Another cycle lane defeated by thoughtless parking

I think this is the first time I’ve posted an outright grumble. Forgive me, but I can’t see the point of cycle lanes that are a free for all. Cars can rarely park on pavements, pedestrians can’t sit in roads, but it appears that cycle lanes are fair game for everyone. They have no legal status.

A couple of years ago I was on holiday in Weybridge, Cornwall. Gonvenna Hill descends into the town from the B3314 and has cycle lanes on both sides. These cycle lanes are primarily used by pupils of Wadebridge School, a secondary school towards the top of the hill. During my visit, builders’ trucks and vans were parked all along the cycle lane on the descent side of the road. I took some photographs, attracting abuse and derision from the charming workmen, who took great delight in pointing out that they were legally parked. The fact that every pupil from the school who cycled home along that route was now forced to ride in the main traffic flow didn’t concern them in the least. I checked out the situation online and the builders were right. The vehicles were legally parked. Of course, that didn’t mean that their drivers weren’t being inconsiderate, selfish and ignorant of the risks to children that they were creating.

A dysfunctional cycle lane caused by an inconsiderate driver on Bathford Hill, near Bath, UK

A dysfunctional cycle lane caused by an inconsiderate driver on Bathford Hill, near Bath, UK

It’s two years on and my commute to work takes me up a 2-mile climb just outside of Bath. In a couple of places, it has traffic calming measures where the road narrows and signs give priority to traffic travelling in one direction or the other. A very inconsiderate driver now uses the end of the cycle lane alongside one of the traffic calming sections to park his large van. This is not a one-off incident. This is his regular parking spot.

I’ve written a very polite note to M.J. Church, asking the company if it might speak to the van driver to ask him if he’d mind parking a few metres up the hill. I’ll post the response, if I get one.

It seems that cycle lines are a free-for-all, with no penalties for those that block or constrict them. They rely on drivers being considerate and, in my experience, that’s the exception, rather than the rule.

What to do with a ‘perfect’ vintage bike?

Last year I bought a 1982 Merican custom racing bike from its original owner. The man was a perfectionist, having even sent the metal bottle cage over to Mercian to get it sprayed to match the frame. The original (bum cleaving) saddle, which is not the one in the photograph, even came boxed with the bike. The appearance of the bike, which boasts a first generation Dura-Ace EX drive chain, is as near to perfection as you’re likely the find in a 30 year-old, unrestored machine. Why so? Well, the owner rode it two or three times, covering “less than 100 miles” and then decided it was too nice a bicycle to get chipped or worn out, so he kept it indoors for 30 years. I was the lucky beneficiary of his caution.

Mercian custom road bike

This 30-year old Mercian is almost like new. Now I don’t know whether to ride it or keep it that way.

I can’t decide whether to ride it regularly or keep it in its present superb condition – it would be a real challenge to do both, even if I restrict its use to summer riding. Of course, it would make a great bike for L’Eroica in October. (I registered for this year’s ride earlier today.) But should I risk such a lovely bike to baggage handlers at Bristol and Pisa airports?

My instinct is to ride it, and maybe use it for the classic ride in Italy. I don’t want to damage it – and if anything will make parts fall off, the strada bianche of L’Eroica will do the job nicely – but I can’t help thinking about the craftsman that made the frame, and perhaps assembled the bike too. Would he have wanted it to languish in a garage or shed, or would he have wanted the results of his labours to be tested, exploited and enjoyed? I think the latter, don’t you?