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Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

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Old 01-11-12, 02:43 AM   #1
danieledwards
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Brompton 2 to Single Speed Conversion / Gearing

Hi all,

I currently have a 2 speed brompton and after having the cable snag a few times causing me to be stuck in the larger cog (which i never use) i decided just to remove the whole derailleur assembly (keeping the tensioner in place) so it permanently sits in the smallest cog which I'm very happy with but would like to make it look a bit more 'factory planned'.

I've already had the gears off the bike and back on for cleaning but know nothing of bike terms and how to gain measurements, can any one advise what spacer id need to buy in order to remove the larger of the 2 cogs entirely? id also like it to take into account that i didn't want to use (although I'm guessing many will advise against it) the plastic guard that sits nearest the wheel on the freehub.

lastly is it possible to easily fit an even smaller rear cog still (than the 12) or a larger chain ring (than the 54) without too much fuss and cost?

thanks

Dan

Last edited by danieledwards; 01-11-12 at 03:01 AM.
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Old 01-11-12, 10:02 AM   #2
Dynocoaster
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From what I have read the wheels are the same. Here are some choices
http://www.brilliantbikes.co.uk/48-brompton-chainsets

http://www.brilliantbikes.co.uk/56-b...ts-and-spacers
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Old 01-11-12, 10:44 AM   #3
danieledwards
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thanks, i just had a reply back from brompton also confirming that it would be the QRSPRSTACK-BB1 - cheap as it is i didn't really want to buy the sprocket and was hoping to also remove the guard but at least there is a way - thanks!!!

http://www.brilliantbikes.co.uk/brom...bb1-stack.html

dan
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Old 01-11-12, 12:46 PM   #4
jerrysimon
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Not sure if you could fit a larger main. As with all mods on a Brompton maintaining the fold is problematic.

Again not sure if you could run with a smaller rear sprocket, if you could even find one.

A 54T * 12T single speed gives you a 74" gear which I find about right for Cambridge which is flat and for me spins out at about 23mph.

Regards

Jerry
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Old 01-11-12, 02:05 PM   #5
danieledwards
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Quote:
Originally Posted by jerrysimon View Post
Not sure if you could fit a larger main. As with all mods on a Brompton maintaining the fold is problematic.

Again not sure if you could run with a smaller rear sprocket, if you could even find one.

A 54T * 12T single speed gives you a 74" gear which I find about right for Cambridge which is flat and for me spins out at about 23mph.

Regards

Jerry
ah, I can just about get it to spin free on the pedals heading downhill from Picadilly to Marble Arch and then again on the run down to the Royal Mews

still plenty enough to overtake everyone else on the commute (....aswell as the vehicles )

dan
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Old 01-11-12, 03:15 PM   #6
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Putting the 3 speed chain tensioner on will let you exchange the pulleys
to some different ones with sealed bearings .. rather than ,
the unique setup of the 2 speed 2 cog chain tensioner. which is self bushing ,
and has a skosh more friction.
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