Brompton bottom bracket
 

Do the long time Brompton users here stick with the *** BB or use something similar such as a Shimano UN54 118mm (I wonder if that 1mm difference might matter as the clearance between rear hinge and chain is very tight, i.e. a slightly off-centre chainwheel would rub)?

Hmmm, the forum censorship isn't particularly helpful here. Eff Aye Gee.

The stock BB is quite light, quite cheap and lasts reasonably well. In nearly a decade of B ownership, I've not felt the need to use anything else, except when fitting a different crank.

How long do you find it lasts?

My Mk2 has a loose ball BB, the cartridge BB currently used is probably fine.

I installed a Schlumpf Mountain drive crank, it is a whole thing,
Includes the Arms, chainring , trouser guard ring and BB.
made to fit in without frame mods.
[though I think the left side could be faced a bit shorter,
to fully access the fixing and adjustment lockrings]

I'm wondering if I'd actually prefer a cotterless type. I used to assume they were for cheapo bikes only, but I'm wondering if actually they're superior for those who don't mind servicing their own bikes.

If there's any easy way to shave a bit of weigh during mandatory component changes then that's worth the effort of research, I think, and I certainly don't want to add any weight through poor component choice.

A shimano UN54 is around 300g and slightly cheaper than the Brompton BB. I'm guessing that's about the same as a cotterless cup and cone type.

Anyone know the weight of the Brompton BB? If it's around 270g or less then I'll certainly stick with it.

I've got a ti phil wood on order to help with my 8 speed conversion. I let you know how it works :D

8 speed. . . you've given up on the 5? Which hub are you going for?

I need more gears for hauling my kid. I just mounted it. It's a lot heavier than the 5, but has a bit more range.

Phil Wood Campagnolo (read ISO) taper 120mm spindle+British cups = set for a LONG time.

I wore out the stock bottom bracket in 2 winters and about ~5000km. It was getting a littlerough way before that, at that point the play was just too much. I am by no means small (6'7" 94kg (205lbs)) however, I do take very good care of my equipment. Also with the Phil Wood you can get +/- 5mm adjustment. I had to buy the tools to take out the F_A_G cartridge and by the looks of it I will not be using them ever again, unless I ever run into an old Campagnolo BB....who knows.

I will be careful with +/-1mm on a Brompton since everything there just fits. Although a Shimano cartridge is pretty cheap and will not be an expensive experiment. There is a TA (TA Axix Light) bottom bracket that also comes into 119mm spindle, however, the price is the same as PW if not more expensive. PW just gives me a peace of mind =)

-Carcinogent

About 4 years.

Phil Wood Co. as specified, has a close tolerance fit between ID of the bearing and OD of the axle,
the axle has no shoulder. the offset can be anything you need ,
you just press the axle further thru the bearings.

http://www.youtube.com/watch?v=50L5yRZ7icc

The axle has a shoulder. The way you adjust a PW BB is by screwing in one of the cups and unscrewing the opposite one.

-Carcinogent

The BB cartridge has a shoulder, the mounting ring sits against,
the OD of the bearing.
O is for Outside in this English language case, D for diameter.
I'm referring to the axle itself it's 17mm ,
there are no interior shoulders on the axle,
It is a Press Fit. [a precise term in a machinist's glossary]

I have shifted the axle within the bearing cartridge, myself,
pulling the axle thru the bearings with the crank fixing bolt,
as the applied force.

Hmm interesting. That movie showed that the axle has a sleeve on the drive side. I suppose you can move the axle towards the non-drive side since there is nothing to support it. In any case i would highly recommend a PW to the OP if he wants an upgrade when he wears out the stock bearings. Shimano BBs have JIS taper while the Brompton crank is ISO so the chainring would align differently. Just something to keep in mind. :)

-Carcinogent

I expect that ring is pressed off next, Phil sells 17mm axles,
to use in sealed bearings with a 17mm ID.