The Folding Society

Issue 27 - 29 May 1999

There is rather a lot in this issue about gears and gear ratios - apologies to those of you who find this a boring subject, please be reassured that we do not intend to devote as much space to the subject in future issues.


Not content with his much admired modifications to the Brompton, which have included a seven-speed Nexus hub gear and V brakes, Steve Parry has been continuing his experiments. First came a single -speed extra light version; no doubt this would be attractive to some users, but I personally rate multiple gears a necessity, particularly as it is not flat where I live and work.

Hub gears have their advantages and disadvantages compared with derailleurs, the generally agreed main disadvantages being:

The seven speed Nexus has a reasonable range and quite even spacing, though not such a wide range as the seven speed Sachs and Sturmey-Archer hubs (neither of which would fit the Brompton in their current form, and which have rather uneven spacing of the gears). However, the Nexus is rather heavy. The development of the single-speed model showed Steve how he could produce a seven-speed derailleur version without having to spread the forks, and he has now done this. The result is a saving of around two pounds in weight, and with an 11-28 sprocket set the range is slightly wider than the Nexus, while the spacing of the ratios is if anything even better. The down side of the derailleur is of course that it is more vulnerable to damage, more inclined to get dirty, and to be affected by dirt, and consequently more inclined to need attention and adjustment than a hub gear. In the case of small-wheeled bicycles, another drawback of the derailleur is that top gear tends to be limited unless you resort to dinner-plate chainwheels - the 11 tooth sprocket with a 54-tooth chainring would still only give a top gear of just under 80 inches on a Brompton - adequate for most Brompton owners, but not to the taste of some riders. Sprockets of less than 11 teeth are not generally available, but of course you could use other 7-sprocket clusters to give closer ratios and a higher bottom gear with this arrangement if you wanted. It seems likely that on balance those wanting to buy Steve's Brompton-based SP will go along with his change to the lighter and more efficient derailleur.

New modifications are coming from Steve at such a fast rate that we can only suggest that you watch this space for further changes!

Being in Brompton mode after seeing, and ordering, one of Steve Parry's modified machines at Weymouth, I used mine all last week, including a 48 mile ride on Saturday 22nd and a 42 mile ride on Sunday 23rd. Splendid though the front luggage system of the Brompton is, the standard bag certainly increases wind resistance noticeably, and the whole bike feels much more responsive without it. For travel to work during the week, I used a Carradice bar bag mounted to the Brompton luggage block via one of the SP brackets, and for light loads this did improve the ride over the standard Brompton bag which was larger than was needed. Unfortunately on Monday I was working in an office with someone who had a cold, with the inevitable consequences, which curtailed my riding somewhat; by the end of the week I was using the nearest station to work, rather than taking longer rides to and from more distant stations. As usual the Brompton took everything in its stride, and it was particularly welcome when an old class 310 train was substituted for the usual 323 one day, as I could simply take the bike in the carriage with me, whereas owners of cumbersomes were having to find the luggage van and were having difficulty in squeezing in there. On the longer rides, this relatively standard model certainly isn't as fast and as much fun as some of my other bikes, but it performs quite satisfactorily, and with the full 18% gearing reduction on this 5-speed model I only needed bottom gear once on each of the two longer rides.

A Brompton trailer bike

The following article on a novel Brompton modification was kindly supplied by Andrew Holland. Please note the usual warnings and disclaimers about making modifications to your or anybody else's bicycle(s). A picture can be found on our web pages at

With two Bromptons and child seat life was OK. As a 4-year-old became a 5-year-old then a 6-year old boy it got progressively harder getting up the hills. "Daddy why don't you talk to me ?" says Clement "Gasp Gasp" goes Daddy

One of the many good things from the Folder forums was the try other people's bikes out so Clement & I had a test ride on a conventional Trailer Bike. Just the job: Clement can contribute to the pedal power. As Edward and Henry would say "We can do it together!" (Thomas the Tank engine quote no doubt Clement would correct me for getting the wrong engines).

Well there are no ready made folding trailer bikes and I had been considering how to modify the Brompton so we had a folding trailer bike. I didn't want to cannibalise or hack up a Brompton too much, so as Clement grows bigger it can be restored to a normal Brompton.

A series of modifications

Clement having short legs we needed to find short cranks. A quick test showed us there would be no hope of standard cranks. Shortened cranks are not standard items for the bike shop. The folder outing to Uckfield did have a good outcome because Janette Edge had just the job and David put us in contact with High Path Engineering. So we now had the cranks (130mm) and a set of 3 chain rings to chose from.

Folding the handlebars into the horizontal position solved Clement's short arms.

Mk 1 coupling

The next problem would be the coupling. I considered the front luggage block upside down and remove all the forks etc. I then hit on cutting of the forks and using the top half as the coupling swivel. At Brompton prices that was a bit excessive for project I was not sure if it would work. The solution was a cheaper set of Mountain Bike forks (1 1/8 inch). The pivot was to place in front of the axle to prevent the front Brompton folding with the weight on the rear carrier. With the forks cut off and a plate on the rear carrier of the front Brompton as a pivot it should be ready for a trail ride

Clement was not so ready for the trial ride. It wobbled excessively and there were a few tears. Future modifications and the use of elastic made a workable proposition but limited the turning circle. The first outing was to Battersea Park for the London folder meeting. The coupling worked but the set up and clear down time was not ideal. The handlebars were independent so could be held all the time, Clement thought it was great to be able to steer and it not affect the direction of the bike.

The Mark 2 coupling

The engineering facilities at home are limited to cutting and drilling. Some steel was procured, buying wood is easy but small quantities of steel seemed a problem. This time the steering was linked by using the brake bolt hole in the cut-down forks as the pivot coupling. The pivot is a High Tensile Bolt in the slot so if the bolt breaks then the coupling does not fall apart but becomes slack.

Clement's next test ride ended in protests because on the start of the ride the folded down handlebars went out of reach on tight corners. Other considerations were the ability to get over the humps for road calming thus a plus and minus 10-degree movement are necessary to keep all three wheels on the road without stressing the coupling.

It took a week of me thinking if there were an alternative solution to the handlebars and Clement deciding that perhaps roads were not all very sharp bends to compromise and have another try but starting on a straight piece of road. Cutting a longer slot in the socket end of the coupling solved the speed hump problem. Once confidence had been established there was no problem apart from the over confidence from Clement let's go faster.

Folding the trailer is easy and the package is held together with a luggage fastener. The handlebars are left sticking out to save wear on the centre joint. If there was a compactness problem these could be folded also.

Folding the front Brompton, the folding is OK but because the coupling is mounted on the rear carrier the folded bike is not so compact. The coupling can be removed by removing 4 bolts. The biggest disadvantage is that with the coupling in place the Brompton does not stand on its own but falls on its side.

Mk 3 requirements

The coupling arrangement stands proud of the rear carrier so the compactness of folding is compromised and it adds 700g to the weight so the plans are afoot for a Mk3 coupling but this will need some welding or epoxy resin work. More of that later. We will probable do some more riding to gain some experience before moving onto build the Mk3 coupling. The ride for me on the front is quite hard because of the wobbly nature of the rider at the back, the usual tandem problem. With Clement looking back to see where Jane is this doesn't help stability. Clement does quite enjoy this new arrangement. It makes a great difference on the uphills to have a contribution of effort.

Parts needed

50mm of 6mm internal dia thick wall tube. Or 12mm round drilled with 6mm on its axis. 12mm * 3mm steel strip to make a new rear carrier ? or 2 more pieces of tube and a lot of epoxy resin and mat

We are still getting to grips with who uses which gears and to keep Clement from pedalling too fast. The best so far is me in 1st and Clement in 2nd for all but the worst uphills. Moderate hills me in 2nd and Clement in 3rd. On the flat 3/3 is the answer.

Some modifications to a Pocket Rocket

Despite my cold, the weather was so superb here this morning (Saturday 29th) that I felt that I had to go out for a ride, although I decided on one of under 30 miles. During the week I had made some modifications to the gearing of my Pocket Rocket, so this was the bike chosen for today's outing.

My Rocket has (or rather, had) an 8-speed Campag Mirage gear set, with 53/39 chainwheel and 12-23 sprockets. Overall I have found the bottom gear rather on the high side for my taste (33.9 inches), but with a relatively low top gear - typical Campag, close ratios, and no large sprockets. At the front, the changer does not seem to like changing except when in a mid-ratio on the sprockets, and does not seem happy at other times as well, with the chain sometimes jamming across the two chainwheels. At the back, apart from the limited range of the gearing, there seems some backlash at the two extreme gear settings, requiring a bit more than normal movement of the shifters to start moving back through the gears.

As I'm planning a number of 100 km day rides on the various folders/separables as part of an extended test programme (reports will follow over the next few months), and the Rocket is scheduled for the first of these, I decided to make some gearing alterations. The main aim was to give the equivalent of one extra gear at the bottom, without lowering the top, and to retain as much of the existing system as was practical. This is not easy, given the limited range of Campag sprockets available (no really large ones) and the capacity constraints of the changer mechanism - 27 teeth, with a maximum sprocket size of 28. In the end I made a decision to go for a 52/42 chainring combination and 12-28 tooth sprockets. As Campag do not currently have a 28 tooth sprocket, I made use of the service offered by Chris Bell of Highpath Engineering, who can supply sprockets of all sorts to enable changes to be made to clusters, or he can supply clusters to your requirements. These are based on Marchisio sprockets, which have their own fitting and come with adapter and spacer rings to suit various Campag and Shimano freehubs. Literature and then the necessary parts were sent with commendable speed, and fitting was quite straightforward.

Today's ride of 48 miles (well, I was enjoying it so much that I went considerably further than planned) provided a reasonable first test of the modified system, and after a little adjustment a number of advantages are evident. The smaller gap between the chainwheels (in terms of teeth) seems to make changing much cleaner, without any jamming (so far) and with no apparent problems changing when the rear system is not in one of the mid gears. At the rear, there is no improvement in changing, but the mixed system of some Campag and some Marchisio sprockets seems to be working perfectly. Overall the change in the range from 34-88" to 30-87" is an advantage, and has the very useful side effect that I can manage many hills now without having to change down on the chainwheel, which makes life much simpler. Although the overall change in ratios is not all that great, so far I judge it a worthwhile modification.

If you are looking for odd gearing changes of this kind - or shortened cranks as described in the item on the trailer bike - you can contact Highpath on 01570 470035 - I am also using some of their sprockets to reduce the huge gap in the middle of the gear range on my Moulton AM7 (now running as an AM8, but with a jump of 13 to 17 teeth, over 30%, right in the middle of the range!). Incidentally, while on the subject of Moultons, we are promised an issue of the Moulton Flyer (or possibly a Moultoneer?) Real Soon Now - the last one was dated January February 1999.

More folder/separable tests

As mentioned earlier, I am intending to do some further extended tests of a number of folders over the next few months. The tests will have several parts, one of which will be a 100 km day ride; I shan't follow the same route with all the bikes, but will instead use them on a number of Brevet Populaire events. The Bike Friday Pocket Rocket is due to be the first to be subjected to this treatment, and others to be tested include the AM Moulton, Birdy and Brompton (or more probably the SP modified Brompton). I very much doubt that I will use the Micro or single-speed Moulton Stowaway for these longer rides! Reports on these tests will appear on our web pages in due course.


Saturday 5th June - Mud Dock
Meet at the Mud Dock Cafe in Bristol from about 10.30am. Further details from Gary Lovell, Tel: 0117 932 4633.

Sunday 6th June - New York Folding Bike Ride
The first ever New York Folding Bike ride will take place on Sunday, June 6 at noon. Meet at City Hall (Park Row side opposite Pace University) for a leisurely 10 mile bike ride to Coney Island. (People without folding bikes are also welcome to attend.) If interested, email - or just show up.

Saturday 12th June - Origami Ride
The usual arrangement is to meet at the Tearooms in Meriden from 10.30 for an 11.00am start, but the location occasionally changes to suit special rides. Watch the web page for more details, at contact John Pinkerton on 0121 350 0685 to confirm arrangements for this month's ride. John tells me he expects to be attending the ride himself this month!

National Bike Week is from 12th to 20th June, and there are local events in many parts of the country, so look out for things in your own area. We have mentioned a number of the larger local events already, but details of the Birmingham Bike Bonanza weren't available for the last issue. I'll concentrate on that event here as it is local for me, and member John Pinkerton is intending not only to have a display of veteran cycles at the event, but also folders as well - though that depends to some extent on we take along! The event is on Sunday 20th June between 11am and 4 pm at Cannon Hill Park, which is fairly close to the centre of Birmingham. The programme includes, apart from the display of veteran and folding cycles, a display of bikes of the future, a cycle jumble, trade stalls and a demonstration of bike polo. If you are in the Birmingham area, do try and come - if you need information on how to get to Cannon Hill Park, contact us. If you are coming with a folder or separable, and can include it in the display, it would be helpful if you could let us know, so that we can try to provide as many different types as possible. There are some more details of the event on the web site at

Sunday 20th June - London Ride
Meet at the cafe in Battersea Park at about 2.00pm. For more details contact Rob Cope at

PPP Rides. We have received information on some monthly rides intended for parents with young children. These will take place on the last Sunday of every month from April to September, starting at 10.30am from either Wimbledon station or Richmond Park (Star Garter gate). The rides are not too long (10/15 miles or so) with plenty of appropriate child-friendly stops. Kids of all ages welcome, in bike seats, trailers or on their own bike. Turn up and go - no need to book, no charge. Telephone 0181 946 0912 for further details. Dates - May 30th, June 27th, July 25th, August 29th, September 26th. [Information provided by Richard Evans; this is not a Folding Society event.]

Contributing material for FSN

We would very much welcome articles, photographs or any other material for inclusion in future issues of FSN, or on our web pages. Please send any material to The Folding Society at the address given below.

The Folding Society
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Last updated: 29 May 1999