It’s been a while since I posted – a busy few months – but I did say I would give un update on how my B75 conversion went, and whether I could convert a B75 to an Alfine 8 hub, and upgrade its components to those of a regular M6L Brompton, for less than the price of a six-speed. At the time, the cheapest M6L was £1275. (Now its equivalent, the C-Line Explore, is upwards of £1350)

Let’s see how I got on…

The B75 is a great value Brompton, at £850 (even better when it was £750!). It has been succeeded by the Brompton A-Line which, apart from sounding like a frumpy skirt, is basically the same bike but in white. The price is the same, although I’m struggling to find one for sale online!

So my task was to take the B75 as my base, and see if it could be upgraded to standard M6L Brompton, AND converted to an 8-speed hub.

A reminder of the compromises made by the B75 (which I reviewed more fully here.)

  • saddle – more generic, but still with Brompton name on it
  • the saddle pentaclip has gone, replaced with a clunky old steel bracket
  • no mudguards
  • three speed only
  • no folding left pedal.
  • older-style brake levers.
  • hard rubber bar grips, rather than the soft foam version
  • no carrier block
  • 44t chainwheel – you don’t get any choice.
  • no choice of stem height or handlebar shape.

So to convert this to the spec of an M6L, (but 8 speed) I needed a new

  • saddle
  • pentaclip
  • mudguards
  • folding pedal
  • newer brake levers
  • decent bar grips
  • carrier block

In addition, to facilitate the 8-speed conversion, I needed:

  • Shimano Alfine 8 speed hub, lock ring, chain guard
  • wider bottom bracket
  • rim
  • spokes
  • smaller 16T Rear sprocket 3/32
  • Small parts kit CJ-8S20
  • derailleur style chain tensioner + washer (longer arms)
  • axle nuts
  • 8 speed shifter + cable
  • new jockey wheels

Once complete, this left various items I could sell:

  • Sale of 3-speed gear lever and cable
  • chain tensioner
  • gear cable pulley
  • rear wheel and gear parts
  • B75 Saddle
  • brake levers

There were one or two bits I would have had to replace, selling the removed part, but already had in stock, e.g. a larger (54t) chain wheel.

At the end of this process, the final cost to me was eerily close to my target price of £1275. All in, with spare parts sold off, this conversion cost me £1274.13.

Here’s the breakdown of the costs, with the places I purchased the bits from:

Bike Halfords 850
Saddle Edinb Bike 37.5
Carrier block Edinb Bike 17
Bottom bracket Amazon 18.99
Rim sjs 34.99
Spokes yourspokes 18.15
16T Rear sprocket 3/32 sjs 6.99
Shimano Alfine 8, lock ring, chain guard eBay 173.98
Small parts kit CJ-8S20 sjs 16.99
Chain tensioner + washer Edinb Bikes 27.5
Axle nut sjs 3
8 speed shifter + cable Bike parts 24.99
Brake levers Edinb Bike 47.5
Handlebar grips GP2 Tredz 29.99
Pentaclip Ed Bike 32.5
Folding pedal Ed Bike 42.5
Stays front and back Condor 42.5
Front Mudguard Ebay 15.24
Rear Mudguard Bike Trax 10
Jockey wheels pair Brilliant Bikes 4
Sale of 3-speed gear lever and cable -14
Sale of chain tensioner -14.5
Sale of gear cable pulley -6
Sale of rear wheel and gear system -159
Sale of B75 Saddle -10
Sale of brake levers -9
Ebay fees on sales 32.32
TOTAL 1274.13

So there you have it – an 8 speed Brompton for the price of 6! I could have shaved off another £20 if I had not gone for the Ergon Grips, but I think these are really worth it. Also, although I have recorded full-price brake levers above, in fact I had to buy an older pair second hand (for £30). This is because the current style of brake ever has (frustratingly) filled in the space between the bar and the lever which used to allow the gear trigger clamp to fit snugly underneath. If I am doing this again, I may need to abandon Brompton levers altogether. 🙁



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