Brompton Modifications

[berlinonaut]

I've set myself a £100 budget
I have a Ti Brompton (ie genuine brompton with Ti fork and rear triangle. It is 2007 model with 2 speed. Does anyone know of a 4 or 5 derailleur gear conversion within my budget which doesn't involve changing to an expensive narrow chain?

I don't know of any and I would go as fas as to say: doesn't exist. Not with a "thick" chain and clearly not for that budget. As others have mentioned converting to three sprockets is possible, cheap and easy (but needs a 10-speed chain, so possibly ruled out already), converting to four sprockets is possible but not within your budget. Converting to five sprockets is possible in principle but lightyears outside your budget.

 

[Tenkaykev]

I don't know of any and I would go as fas as to say: doesn't exist. Not with a "thick" chain and clearly not for that budget. As others have mentioned converting to three sprockets is possible, cheap and easy (but needs a 10-speed chain, so possibly ruled out already), converting to four sprockets is possible but within your budget. Converting to five sprockets is possible in principle but lightyears outside your budget.

Just as a matter of interest I run one of my Brommies with a 10 speed chainI was advised that it probably wouldn’t shift properly but I tweaked the limit screws on the pusher and it’s fine ( I have to hold the shifter engaged momentarily when changing up )

 

[LittleWheelsandBig]

Last century, there were a few folk fitting derailleur gears to Bromptons. The ones I’ve seen involved cutting and narrowing Shimano hubs (getting flanges closer together) with obsolete 5sp freehub bodies. They were always finicky and undergeared. Stick with easier options.

 

[Fastpedaller]

I've noticed some folk have mentioned elsewhere about Shimano's press release (CUES) - also about LInkglide which has been around a couple of years as the transmission of E-bikes. It is stated as having higher profile sprocket teeth which last longer (Hmm - just like BITD?). I wonder if this is my affordable route to a 4-speed (or 3?) on my 2-speed Brompton?
https://bike.shimano.com/en-US/technologies/component/details/linkglide.html

 

[Fastpedaller]

I've updated the above post by adding the link to ......er linkglide.
It appears this may be an affordable way into 11 speed chains, and if the separate sprockets are available it may be possible to fit them to the Brompton 2 speed freehub to gain an extra gear. If only Brompton had used a freehub utilising the Shimano lockring rather than the groove and clip, it would have made a bit more space!.