Lucy Gets More Gears

I introduced Lucy, my bespoke Brompton, in a previous post, explaining the background to the modifications described here.

All the research on how best to get Lucy some more gears was done last winter and to be honest, I don't remember all the various options that we looked at. In the end, though, we settled on getting a Sturmey-Archer 8-speed conversion kit from Kinetics in Glasgow.

Fitting the conversion kit was essentially a 30-minute job for Adam, even though, until now, he had never worked on a Brompton before -- not even to oil the chain! (So he's not to blame for the state of it!) Basically, everything is supplied by Kinetics to replace the rear wheel and the complete crankset.

The only "old parts" to re-fit are the rim tape+inner tube+tyre and the chain.

Off with the original rear wheel

Fitting the new wheel (with its Internal Geared Hub),
derailleur and chain tensioner unit. 

Removing the original Brompton front chainring and right crank.

The new crankset now fitted

Rear derailleur

Sturmey Archer twist grip shifter fitted, having cut down the
leather-covered handlebar grip. 

Job done!

Or is it?  Uh oh, we seem to have a problem....

The bike would not fold. Not even into the Park position. Hmmm.

It seems the chainline with the conversion parts fitted is very slightly different than it was originally. It catches on the rear triangle. Difficult to see here, but there's simply not enough clearance. Just ~2-3mm too close!!

We phoned up Ben at Kinetics. He said he'd experienced this fouling-on-the-frame problem before on perhaps 3 or 4 bikes, on which he'd fitted the conversion himself (rather than shipping the kit out for the customer to fit). The bikes with this problem ranged widely in age and specification (i.e. they weren't all, for example, 1-year-old 6-speeds). His solution to date had been to fit a spacer or two (depending on what sizes he had available) on the bottom bracket inboard of the right crank. In his experience, this shifted the chainline just enough to clear the rear triangle and permit the bike to be folded as usual.

Unfortunately, this didn't work for us. We got on the Internet to see if anyone else had had a similar problem. It seems Bob in Wiltshire encountered several problems with his Kinetics conversion and has written about it on his Pedalitis blog. His initial problem was different from ours, but in the second post he mentioned having exactly the same problem with the chainline hitting the rear triangle. Solving it (and wanting to improve the aesthetics) led him to make some further modifications -- the end result is quite impressive!

We decided to approach the matter as conservatively as possible, though, to try to fix just the one problem at hand without introducing further changes that may present a myriad more problems! Bob's post did get us thinking a bit more laterally about possible solutions. So we scoured the Internet for various Brompton-compatible bits and pieces.

(I spent a lot of time reading dead-end forum threads too -- why is it people discuss all sorts of problems and possible solutions but then don't post again to say what they tried, in the end, and whether it worked?!)

Our first step was to try a slightly longer bottom bracket. The original one was 119mm; we bought this new 122.5mm Sunrace Sturmey Archer one from Brilliant Bikes.

And you know what... it worked! There is now just enough clearance.  (Phew!!)

I haven't ridden Lucy much yet with the new system, just enough to run through all the gears and confirm that it all seems to work well. Obviously, in addition to more gears, the gearing is now much lower overall with a 33t chainring as opposed to the original 54t one!

I've never been a big fan of twist-grip shifters but I think these will be fine for the kind of distances involved.

The controls are clear and easy to read. And Adam did a tidy job of trimming the handlebar grips.

One thing I have noticed -- which I'm not sure is something I should be concerned about -- is that the chain rests on itself when the bike is folded. I don't recall if it did this before...? (And yes, I know, the chain could use a bit of a clean!)

Another thing: the bicycle now weighs noticeably more... and it's all in the rear wheel so I know it's due to the new hub, not my weakling arms!

Also -- and this is being fussy -- the new crankarms are really ugly. And the left crank doesn't have a 'stop' for the folding pedal.

All minor quibbles though and, in any case, it all works!

And so, without further ado, may I present Lucy to you again... now with EIGHT (count them, EIGHT) gears.

I'm looking forward to seeing how Lucy copes with some of our local hills. The key test is being able to cycle to either Dunstable (local journeys) or Luton (to get the train to London) and then back home again! 

P.S. There is one further modification to be made -- a purely cosmetic one! Although Adam is rather taken with the idea of fitting a compact double crankset now as well...!