Caliwild

Hi all,
I didn't see anything too recent on this topic, so here goes...
I have a 2 year-old Brompton S2EX with lots of upgrades (it's down to 20.9 lbs now and the ride is phenomenal). Was thinking of upgrading the last few bits, including the bottom bracket. Is it worth upgrading from the stock Brompton one to the Shimano UN55 (about $40) or would you just go all out and go with the Phil Wood one ($200+)? Would I even feel a difference? The stock bottom bracket feels a little too mushy for me; however, I'm used to nice road bikes... Let's try to avoid the "it's not worth the money" opinions, if possible Thanks in advance...

Jipe

The Brompton bottom bracket is a special one, its asymmetric with the right axle 5mm longer than the left axle to compensate for the frame bottom bracket box asymmetry.

To my knowledge, there are only two possibilities for an asymmetric 118.5mm square taper JIS bottom bracket :
- either the Ti Parts Workshop one made specially for the Brompton (exists with steel bearings or ceramic bearings) it has a titanium axle and save about 100g vs. the original BB.
- either the Phil Wood BB that exists with titanium axle (similar weight saving as for the TPW) or steel axle.

If you want to further reduce the weight of your Brompton, you can also change the crankset, the original one is quite heavy and replace the chainring+cogs+chain with 11s ones that weight less (a KMX X11SL chain last much longer and weight significantly less than the original chain).

If you want to change everything, Ridea has a beautiful low weight crankset with integrated axle and external bearings specially made for the Brompton.

Caliwild

Thanks for the info... I'll look into the Ti Parts Workshop one too.

Caliwild

Reviving my thread from last year... finally about to splurge on a Ti Parts Workshop bottom bracket with stainless steel bearings. Anyone have experience with this bottom bracket?

2_i 

I only have experience with a Ti Parts Ti Tensioner Wheel for Brompton. At 6x the price of OEM it performed miserably, making the bike dysfunctional, and had to be taken off. Phil Wood BB cups provide no sealing. Good luck there!

2_i 

In my measurement, the Brompton's BB spindle sticks out just by 2mm farther on the right side than on the left, something that can be taken care of with a spacer if anyone cares. I think I rode with a symmetric TA Axix Light for a while without any problem. My current spindle is asymmetric, but this has a different background than here at play.

Caliwild

Yikes! Ok, maybe I should just look at the Shimano one... I think it's the UN55, correct? Does anyone know where I can find the one that fits the Brompton?

hopperja

In 2017, when Brompton had the bottom bracket recall*, I replaced my stock bottom bracket with a UN55. The SKU was 4524667778790, and it's listed as part number BBUN55B18. I've been riding it with this bottom bracket for the past 6 years with no issues.

This is a 68 x 118 British thread square taper. I don't recall having to do anything special, such as add a spacer, to make it work.

*I bought it from Clever Cycles in Portland, but live 150 miles from there. I wasn't about to drive it to Portland to have a free replacement installed.

Schwinnsta

Are you saying that you had to take it back to the dealer that you bought it to get the upgrade free?

hopperja

What I recall is that the recall fix had to be done by the dealer. I probably had the option to do it at a local-ish dealer, but that would have been 40 miles away from me and it would have been on their schedule.

The main point is that bottom bracket I mentioned does fit in the Brompton.

Schwinnsta

I just wondered if any Brompton dealer would have done it free? I got mine done on a recall and wondered if any Brompton dealer would do it at their cost. I had to take the Brompton supplied BB they put it in. No issues with it.

2_i 

A real upgrade would be TA Axix Light Pro, in 119mm: https://www.starbike.com/en/speciali...t-bsa-ti-axle/. The bearings are replaceable, so that would be a bottom bracket lasting forever.

ADHDmania

I am using SRAM Dub BSA BB, with SRAM RED AXS crank, with 50TChainring(4mm offset), It works perfectly.