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.
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 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.
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.
What’s the lowest gear in inches? Mine is a Ti so I’m considering a Schlumpf drive, but I may consider this conversion if the lowest gear is suitable whilst remaining a reasonable high gear.
I haven’t done the calculation but the bottom gear certainly feels very low during my quick test drive. You can find a calculator here.
What size are the chainring and rear sprocket. Need that for the calculator!!
The chainring is a 34 but didn’t check the rear sprocket and I’m traveling for a couple of days so can’t get back to do it. Suggest to ping Ben at Kinetics but if he doesn’t get back to you, I’ll check it out when I get home on Wednesday and let you know.
Okay Bob, I’ll await your return.
I did get a reply from Ben.
He says it’s a 33t chainring and 20t rear sprocket. Which according to the calculator gives 27.3 inches at the bottom. That’s just lower than the 29.1 inches I get with the BWR and 44t reduced range chainring. Unfortunately that’s not low enough for me so it looks like the Schlumpf Mountain Drive for me which is considerably lower. When loaded for touring I need the lower bottom gears so I can continue climbing without walking up the steeper gradients.
I also had a choice between Ben at Kinetics and Graham at Tiller. I plumped for Kinetics and ordered the gear kit to fit it myself. After maybe 6 months of polite enquiries, unanswered emails, lame excuses on the phone, I gave up. I have no idea what Ben’s problem is. Sounds like a very nice guy and very helpful on the phone, but he was simply unable to supply the kit – and more importantly, unable to let me know what was going on.
I ended up ordering it from Tiller – and for slightly cheaper than the Kinetics price had it fitted by Graham as well.
Excellent customer service. Lots of contact, lots of information and consultation and the work done completely on time.
Like chalk and cheese.
Sorry, Kinetics. If you can sort yourselves out, I am sure that your kit is good, but it really wasn’t worth the hassle for me any longer.
Sounds like we should have gone with Tiller. Have not got the Kinetics kit sorted out yet — it rides/works beautifully but the chainline interferes with the fold. And the crankset is so ugly. And I miss the left crank pedal stop. 😦
Hi Bob. I’ve been using your blog as a guide for my own Brompton XRF8 conversion—really useful, thanks. I built my wheel with standard 2 cross pattern and when I try it in the frame, the outbound spokes on the non drive side flange foul on the stay by about 2mm. I wondered if this was anything you had come across? My plan is to rebuild the wheel with all the non drive side spokes inbound, but before I took it all apart, I wondered if you had any words of advice??
I’m glad you found the blog of interest but I’m sorry, I can’t suggest a solution to your current problem.
I did the conversion quite a few years ago and have long since sold the bike.
Good luck with it though!