Anybody installed a modified 3rd gear to a BWR hub?

[ukoldschool]

Have left my brommie alone for a while, but I'm inkling for some tinkering...

Of late I have been reading up about 6 to 9 speed conversions, that use either expensive thinner titanium gears to get 3 cogs on the rear, or break up a set of cogs to get 3 thin enough to fit on with either a thinner circlip, or garden wire (sounds very 'unusual'...) . They all need a new thinner 10 speed chain.

Heres the Ti parts expensive option:
https://www.sjscycles.co.uk/gear-sp...um-rear-cassette-sprocket-set-w-chain-pusher/

and how it looks mounted up:
https://clevercycles.com/blog/2017/...rompton-the-ti-parts-workshop-triple-cog-kit/

Heres the DIY alternative:
http://thebromptonman.blogspot.com/2018/12/custom-drive-chain-options.html

Now the question I have is has anybody done this? any real world experience? what size sprockets did you use?

If i'm going to attempt this I cant work out if it will be easier to modify the existing left hand up/down gear change to work with a 3rd position (middle I presume) or if its better to purchase a new right hand side 3 speed change and modify that you use on the left?
https://brilliantbikes.co.uk/brompt...3-speed-and-integrated-brake-lever-black.html

Thanks!

 

[Cycleops]

I think @chriscross1966 might be the man to ask.

 

[ukoldschool]

thanks, but I dont think he has done this particular conversion

 

[chriscross1966]

No I haven't, my loathing of the hybrid shift system would prevent me even considering it :-). One obvious issue is that the six speed is setup to introduce a mid ratio gear between each major ratio on the hub, so your choice would be closer ratios (good idea on a six speed system that runs 300%+ gear range) or to have a weird over or under drive, compounded by a need to modify frame and chain tensioner to accomodate sprockets outside the normal range. The closer ratios thing sounds more realistic, another reason i would advocate an 8-speed Sturmey kit over Bromptons 6-speed is that you get slightly closer shift ratios as well as a slightly higher overall range. I do have a vague interest in using a multispeed chain pushing kit, but that would be to build a really lightweight three or four speed. You might look at the possibility of swapping the BWR for a five speed, ive seen them rigged with 9-spline sprocket carriers to build ten speed systems that have slightly more range than the six but much closer ratios... though with a shift system that sets my teeth on edge...

 

[ukoldschool]

I understand your frustration at the system, but I am now used to it, so for me being able to have an extra one in the mix seems very attractive, certainly more attractive than having to buy a new 5 or 8 speed hub and then getting the wheel laced etc.

Standard brompton low/high gears on the BWR hub are 13t and 16T, I quite like the idea of a slightly lower option and a slightly higher one so 12/15/18 as per the ti workshop kit.... hmmmm.....

maybe I should just try to change the standard 50t front ring with the 54t and see if that gives me what I need first...

 

[bikegang]

[QUOTE=" ...
Standard brompton low/high gears on the BWR hub are 13t and 16T, I quite like the idea of a slightly lower option and a slightly higher one so 12/15/18 as per the ti workshop kit.... hmmmm.....

maybe I should just try to change the standard 50t front ring with the 54t and see if that gives me what I need first...[/QUOTE]

We have more affordable option

12-15-17 or
12-14-17

and choice of 3 speed shifter from Sturmey Archer

This also works on standard 2 speed hub

 

[ukoldschool]

wow thanks that is good! and works on BWR hub?

 

[bikegang]

wow thanks that is good! and works on BWR hub?

Yes, Shimano 9 splines spec.

 

[BromptonFan]

What are the ratios of the stock 2 speed gears?

 

[bikegang]

12 and 16T, I think.

 

[BromptonFan]

12 and 16T, I think.

Thank you. So the 12-15-17 mod would significantly reduce the gearing of a stock 2 speed? Do I understand that correctly?

 

[u_i]

Yes, Shimano 9 splines spec.

So what is the the widest chain chain that can be used in practice with those 3 cogs? 9-speed? 11-speed? Thanks.

 

[berlinonaut]

Now the question I have is has anybody done this? any real world experience? what size sprockets did you use?

I have. Works flawlessly. I did a writeup in another forum: https://www.bikeforums.net/20170010-post8.html

 

[12boy]

Berlinonaut, thanks for that. Being slow I need to confirm...
The spacer between the derailleur and frame is actually the tensioner and the frame?
Are you dremelling the lip on the 12 tooth? I take it the standard 12 tooth that comes with the hub won't work?
Can a 17 or 18 tooth sprocket work in lieu of the 16?
Thanks again for the good work in the BF folding post.

 

[BromptonFan]

I'm dense so help me out. Does this 3 gear set up result in a 6% lower gear ratio on the low end compared to the stock 2 speed?