Author Topic: Brompton Mk 2 - advice needed  (Read 878 times)

Brompton Mk 2 - advice needed
« on: September 24, 2020, 05:56:15 pm »
I've got an early Mk 2, late 1991 that I'm restoring, (well taking to bits and pitting back together), I need a few bits and pieces and maybe the Forum can help - I've typed the queries on the following images.

Also the bike has the SA 5 star hub, (the one with two SA triggers on the bars), - I'd like to take it out clean it and re-grease etc., it - has anyone done this, is it difficult, (I've taken the Sachs 3 speed hub to bits and back and that was relatively easy).

Thanks in advance










Re: Brompto Mk 2 - advice needed
« Reply #1 on: September 24, 2020, 06:28:27 pm »
Sturmey hubs of that era are easy enough but the RH ball cup will be very tight when you come to unscrew it.

That is a cup and cone bottom bracket!  It can be cleaned and regreased if water hasn't got in and pitted the races.  10 to 1 this has happened, so get a cartridge unit with the same RH spindle protrusion.  Measure the flat at the end of the taper: 12.7mm is JIS, less is ISO.

Not sure about the rivets but pop rivets would work ok.

Brompton will send you FREE screws if you tell them yours are loose.  However, the old ones will be turbo-nutter-tight.  Tey an impact driver, a heat gun to soften the threadlock and the proper *imperial* allen key but you may end up drilljng the heads off.  When you've done that, get the rear hinge done as the hard part is over!
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompto Mk 2 - advice needed
« Reply #2 on: September 24, 2020, 06:36:24 pm »
Thanks Roger - I'd like to keep the BB original if possible


Re: Brompton Mk 2 - advice needed
« Reply #3 on: September 24, 2020, 06:57:21 pm »
You can find NOS or good used cup and cone BBs but if it's ISO it gets trickier.
And Darkness and Decay and the Coronavirus held illimitable dominion over all.

Re: Brompton Mk 2 - advice needed
« Reply #4 on: September 24, 2020, 07:02:08 pm »
You can find NOS or good used cup and cone BBs but if it's ISO it gets trickier.

Thanks Roger

here it is

I need an original seat, seat post is rusty and mudguards are poor plus a new chain, agin rusty- but the paintwork is great as are the wheels and hub - saved by being "greasy"

smaller headstock and stem seems smaller - sachs/huret "jocky" wheels - un-named brakes - solida chainwheel

David Henshaw's book describes the BB as "forged"?





Re: Brompton Mk 2 - advice needed
« Reply #5 on: September 24, 2020, 07:24:47 pm »
Is it the whole BB you want to replace, or just the lock ring?

It's most likely to be British/ISO 24 tpi and they are easy to find on ebay. Complete BBs are often of dubious quality though.

If for some bizarre reason Brompton used Raleigh 26 tpi (and I wouldn't put it past them) these are very hard to find.
Quote from: tiermat
that's not science, it's semantics.

Re: Brompton Mk 2 - advice needed
« Reply #6 on: September 24, 2020, 07:41:07 pm »
Is it the whole BB you want to replace, or just the lock ring?

It's most likely to be British/ISO 24 tpi and they are easy to find on ebay. Complete BBs are often of dubious quality though.

If for some bizarre reason Brompton used Raleigh 26 tpi (and I wouldn't put it past them) these are very hard to find.

Yep, it's just the lock-ring, (for now), for cosmetic purposes - it's rusty and flaked and just spoils the rest of the Bike

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton Mk 2 - advice needed
« Reply #7 on: September 24, 2020, 07:45:57 pm »
Brompton never used Raleigh threading.

Good luck finding an original seat in decent condition. From memory, it was a cheap and nasty but light foam thing. Many riders replaced them quite quickly.

Bromptons of that vintage used a 1” headset and matching stem.

A modern B seatpost is interchangeable (and unchanged).
Wheel meet again, don't know where, don't know when...

Re: Brompton Mk 2 - advice needed
« Reply #8 on: September 24, 2020, 09:06:14 pm »
Brompton never used Raleigh threading.

Good luck finding an original seat in decent condition. From memory, it was a cheap and nasty but light foam thing. Many riders replaced them quite quickly.

Bromptons of that vintage used a 1” headset and matching stem.

A modern B seatpost is interchangeable (and unchanged).

Thanks

It's also surprising how the fittings on the mudguards have not changed apart from two small allen's replacing the older screws

The mudguards aren't great and the PO had sprayed them silver without taking them off the bike - so I spent a couple of hours cleaning it off the guards and parts of the frame - but I think I'll just change over the fittings from some more modern guards that I have and they will look a bit like a feature


Re: Brompton Mk 2 - advice needed
« Reply #9 on: September 24, 2020, 10:33:52 pm »
You need to strip the bottom bracket out to find out whether the innards are in a better state than that ring. If it's just the ring, I for one have some lying around, and could let you have one. You can loosen and tighten lockrings with a hammer and punch or similar, but a lockring spanner is better, especially if you want the replacement ring to look good. There are lots around; Park Tools and Hozan are good, but a cheaper one may do you.

If you need a full BB, decent cup and cone ones are hard to find now. I'd probably try SJS Cycles, but even theirs are nothing special. You need an exact match for the BB spindle - measurements vary. Although, if it were me, I'd be putting a sealed unit in instead.

I've mended loads of mudguards with an ordinary hand-held pop rivet gun. The rivets tend to sit slightly more proud of the guard than the originals, but unless clearances are tiny it should be fine.