Hi, I have an S-type Brompton (...) if I convert to M type do I need a different stem (I think I know the answer)? Any idea what a stem costs (for some reason I can't find a website that answers the question, challenge also is that my bike is raw lacquer ... Next question, if I was to keep the existing stem and look for a 30-40 mm rise MTB handlebar, has anyone done this and where would they have sourced the right one to accommodate controls? Thanks for your help, Martin
You'd definitively need a new stem to convert to M. You could mount an M bar to an S stem but you would not be able to fold the bike any more then, making this approach a bit useless. A new stem is about 200€ (plus bars and cables), making this expensive plus - depending from the country you are living in - they won't sell it to you but only fit it in their workshop (i.e. Brompton policy for the uk, has changed relatively recently). Looking for a used M-stem in raw laquer would be a bit of a quest therefor I'd recommend just swapping the bars for aftermarket ones. The maximum raise that would fit to an S-stem is 8-10 cm, depending from the width of the bars and if you have a rack or not. The stock bars are 53cm wide. Aftermarket bars are usually wider and can be cut to size as you like them. You would however need bars with a steep raise near the middle to leave a reasonable amount of flat space for grips, brake levers and shifters if you cut them down to Brompton standards and bars like that are not easy to find. Going to something like 56cm width makes it easier, being happy with less than the maximum possible raise does the same.
If you have no rack the maximum raise is 8 cm at 56 cm width of the bar. Been there, done that. If you have a rack with easywheels you can go for 10 cm raise at 56 cm. The Brompton M is about 9cm higher than the S, thus you end up in the same ballpark as the M w/o spending the money for a new stem.
You'll need longer cables if you raise more than maybe 2,5 cm but you can use aftermarket ones, being a bit cheaper. I'd recommend using jagwires as it really makes a difference (they are factory fitted as well since roughly ten years ago). For the 2-speed shifter the easiest is to get a cable for the H-model and cut it down as you need it. Take your time as correct cable length is critical on a Brompton and the wrong length can cause issues, some ob them not too obvious.
I got my riser bars via
ebay from a seller in Germany - the brand name is "Kepu" and the model is "KP-606". Probably some asian stuff that can be found on taobao or such as well and possibly under a bunch of different names and brands (never bothered to look).The good thing about those is that they have a high as well as a steep rise (which is hard to find in combination) - I can recommend them.