Transmission Overhaul Question

Bromptonaut

Rohan Man
Location
Bugbrooke UK
My Brompton is a 2009 M6R. It still has the original standard transmission so presumably 50T chainwheel and 13/16 rear sprockets. They and the chain, although still just about in 'mesh', are well worn. I've enough experience to know I need to replace the lot.

As it's the old 'fixed' chainwheel it looks as though I'll have to upgrade to the new spider version QCRANKSET-SPI-50.

Do I have to replace the Bottom Bracket as well?

If so, and it would probably be good practice anyway, is QBBCART-119-JIS the right part?

100 link chain too.

Looks like around £120 altogether.

Would appreciate confirmation that the assumptions above are correct and any other observations from those who've been there and done that.

Thanks in anticipation....
 

Shreds

Active Member
I had my S2L crankset replaced on day one. Why? The standard one was too flimsy and a carbon fibre one also offered significant weight saving.

What a difference that made.

The beautiful rigidity and power transmission made having two gears almost unnecessary.

Obviously dumped the Brompton pedals too for small clipless.

BB altered to outside cups too.

The ‘fold’ is now unique and requires care in positioning the cranks but what a difference.

Its yet another “mod” that Brompton seem to fail to recognise could improve the bike. A decade of very intensive use have proved it to be a good decision.
 

cheys03

Senior Member
Yep, you're right - the spider cranksets require the newer bottom bracket. It's worth confirming a few things though. Do you have a SACHS/SRAM rear hub or Sturmey Archer? 2009 should be Sturmey according to Wikipedia (changed from SRAM in 2008) but worth double-checking as the the rear sprockets are different for each manufacturer and have a different number of teeth.

Also best to count and confirm the chainring teeth, confirm the rear hub manufacturer and decide chain length from there.

Brilliant Bike are (as the name suggests!) brilliant for this sort of thing and have good descriptions for each part
https://brilliantbikes.co.uk/43-brompton-transmission
 
OP
Bromptonaut

Bromptonaut

Rohan Man
Location
Bugbrooke UK
Yep, you're right - the spider cranksets require the newer bottom bracket. It's worth confirming a few things though. Do you have a SACHS/SRAM rear hub or Sturmey Archer? 2009 should be Sturmey according to Wikipedia (changed from SRAM in 2008) but worth double-checking as the the rear sprockets are different for each manufacturer and have a different number of teeth.

Brilliant Bike are (as the name suggests!) brilliant for this sort of thing and have good descriptions for each part
https://brilliantbikes.co.uk/43-brompton-transmission
Thanks for confirming as above.

It's a Sturmey hub (BWR) and all standard; there's a 50 stamp on the chainring.

Brilliant bikes have been my go to since Simpson's in Camden/Kentish Town closed their doors.
 

shingwell

Active Member
If you are doing it yourself you will also need the bottom bracket tool - again I think the Brilliant Bikes web site will point you in the right direction. I did this on my Brompton because I wanted a 44-tooth chain wheel - pretty straightforward, no complications.
 
OP
Bromptonaut

Bromptonaut

Rohan Man
Location
Bugbrooke UK
I've got a 'standard' Shimano style BB tool. Some suggestion I may need a different one to remove the old BB but as I'm chucking it anyway a Mole wrench may do the job.
 

chriscross1966

Über Member
Location
Swindon
You could take the opportunity to significantly upgrade the crank. If you want a bit of bling with an easy life then a 68/73 dual-purpose Hollowtech2 BB goes in easily (get the LBS to face the bracket tube square) and there are plenty of decent secondhand 130 bcd cranks that will fit that, if you fancy a challenge and have the tools then Campagnolo Ultratorque cranks can be fitted and they are truly joyous things to pedal around on..... and massively offensive to hardcore roadies too... which is nice...
 

rogerzilla

Legendary Member
Mine has a Stronglight XD2 RH crank and a 112mm Dura-Ace cup-and-cone BB, so you can do what you like.

The two things to watch are that curved cranks can hit the folded rear triangle (put the ring inside the spider and use a longer BB) and the folding left pedal will not go over the end of some cranks. I have a Brompton LH crank for that reason.
 

12boy

Veteran
Location
Casper WY USA
The old style cranks were ISO and the new JIS. ISO will go on a JIS spindle but not the other was around. I replaced my ISO bottom bracket with a Shimano 119 JIS and many thousands of miles later no problems. I now run 2 chainrings, a 58 and a 38 on a 110 bcc crankarms, but I have the ISO original on another bike with a JIS spindle without problems.
 

Pale Rider

Legendary Member
Obviously dumped the Brompton pedals too for small clipless.
I doubt Mr or Mrs London office commuter wants to wear cycling shoes to work.

The cage pedals on my Brompton were very grippy, to the point I nearly had a couple of 'clipless moments' when coming to rest.

Some of the finishing kit on Bromptons is poor for a £1k+ bike, but at least a lot of it can be customised.
 

Shreds

Active Member
I am a London commuter who visits top notch clients all over the capital on a Brompton and have done so for a decade. From Fulham & Chelsea through to The City not only is the Brompton welcomed but the black shoes for the clipless pedals are never noticed or commented on. All about a positive attitude that works.
 

Pale Rider

Legendary Member
I am a London commuter who visits top notch clients all over the capital on a Brompton and have done so for a decade. From Fulham & Chelsea through to The City not only is the Brompton welcomed but the black shoes for the clipless pedals are never noticed or commented on. All about a positive attitude that works.
I'd expect no less, this being an internet forum.

But are you seriously saying Brompton should offer the bike with clipless pedals as standard?

If you like them, great, but very few owners, even those with other bikes with clipless, would want them on a Brompton.
 

12boy

Veteran
Location
Casper WY USA
I've used the Shimano combo pedals for years...clipless on one side and flat on the other. I can wear flipflops, Crocs, insulated hiking boots, clipless shoes or whatever.
 

Kell

Über Member
I've used the Shimano combo pedals for years...clipless on one side and flat on the other. I can wear flipflops, Crocs, insulated hiking boots, clipless shoes or whatever.
Genuine question - how easy are those to use in practice?

Might be quite useful to just be able to hop on a bike in normal shoes. All of my bikes have SPDs.
 
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