Brompton 13-17 tooth sprocket set for 6 speed.

[ExBrit]

I want to replace my 13-16 sprockets with 13-17 next time I change my chain. For some reason my local hills are getting steeper.
Can anyone recommend a source for them? My usual suppliers have come up short.
Thanks

 

[Tenkaykev]

I want to replace my 13-16 sprockets with 13-17 next time I change my chain. For some reason my local hills are getting steeper.
Can anyone recommend a source for them? My usual suppliers have come up short.
Thanks

It’s not just your hills, ours are definitely feeling steeper and I too was pondering swapping a 16 for a 17.

 

[Kell]

Can’t recommend anywhere to get one, but I would say that when I ordered a new set of sprockets a while back they accidentally sent the 12-16 from the two speed.

I thought that might prove useful to have a slightly taller 6th. And it was. But it obviously also meant a taller 2nd and 4th.

The problem was that it made changing from 4>5 really short and then going from 5>6 really long.

It doesn’t feel like it would make that much of a difference, but I was glad to swap them back to ‘normal’ when I next changed them.

Interesting experiment, but it ruined the ratios IME.

 

[rogerzilla]

They're not fussy about ramps and cutouts, so any 3/32" sprocket with the right spline pattern will do. You may need spacers if the original sprocket incorporated a bit of a flange (oo-er).

 

[berlinonaut]

On your bike with the BWR I'd rather change the chainring from 50 to 44 than increasing the spread of the sprockets if you want to go shorter. Going from 13/16 to 13/17 makes jumps between gears pretty uneven. If with 44 you lack development in the highest gear I can from experience recommend switching to 3 sprochetes / 9gear setup: 44:12/14/16
You can use any shimano-compatible sprockets, i.e. either by butchering a casette or by buying them separately.

 

[rogerzilla]

My 2-speed has a Zimo 13T and a Shimano Dura-Ace 15T. 12T/16T wouldn't suit me at all.

 

[12boy]

Sprockets are a lot cheaper than chain rings. The Shimano free hub oneswork well and because they are narrower it is possible to have 3. Sheldon Brown's gear inch calculator is good to figure out what chainring/ sprocket combos will work for you. If you have the JIS 130 BCD cranks it is easy to add another chainring as well.

 

[rogerzilla]

What do you use to shift between 3? A friction thumbshifter?

 

[ExBrit]

I found a 17 tooth sprocket at BrommiePlus in Taiwan and placed my order. I have a good feeling about this. But I'm keeping the 16 just in case.

 

[Kell]

Be interesting to see how you get on.

I recently changed my 50T Chainring for a non-OEM 48T and I think I like it. Especially now I've shortened the chain and it's no longer jumping off every time I hit a bump.

I didn't like the 44T as I spun out too easily in 6th.

 

[u_i]

On your bike with the BWR I'd rather change the chainring from 50 to 44 than increasing the spread of the sprockets if you want to go shorter. Going from 13/16 to 13/17 makes jumps between gears pretty uneven. If with 44 you lack development in the highest gear I can from experience recommend switching to 3 sprochetes / 9gear setup: 44:12/14/16
You can use any shimano-compatible sprockets, i.e. either by butchering a casette or by buying them separately.

Indeed, 13->17 makes a pretty large jump, 17/13=1.31. Optimally, the cog ratio should be as close to the square root of the BWR jump as possible, sqrt(1.57)=1.25. With this, rather than changing only 16T to 17T, it may be better to change 13T to 14T at the same time too.

 

[ExBrit]

Indeed, 13->17 makes a pretty large jump, 17/13=1.31. Optimally, the cog ratio should be as close to the square root of the BWR jump as possible, sqrt(1.57)=1.25. With this, rather than changing only 16T to 17T, it may be better to change 13T to 14T at the same time too.

That's not a bad idea. I'll see how the 13-17 feels and snag a 14 if the jump is too much.

 

[berlinonaut]

What do you use to shift between 3? A friction thumbshifter?

In my case a Sunrace M90, also sold as M96. You can also modify the original older version of the Brompton Shifter. Brommiplus is selling a mod for the newer Brompton-2-speed shifter. I assume gripshift 3-speed grips could also work. Here's an older post about my mod: https://www.bikeforums.net/20170010-post8.html In the meantime several enhancements have been developed, i.e. no dremeling but using an old spoke to create a slimmer ring to hold the sprockets and to buy single sprockets instead of finding a cassette and butchering it. Nonthelast using the post 2017 dogleg enables mounting the derailleur cable the normal way. With the older dogleg you have to mount it the "wrong way round" and need a clamping thingy on the shifter side. No problem (get one of a cheap nipple set for motorbikes) but looks ugly.

 

[berlinonaut]

Indeed, 13->17 makes a pretty large jump, 17/13=1.31. Optimally, the cog ratio should be as close to the square root of the BWR jump as possible, sqrt(1.57)=1.25. With this, rather than changing only 16T to 17T, it may be better to change 13T to 14T at the same time too.

Jupp. With the BWR and two sprockets a 3t difference between the sprockets creates the best result. With 3 sprockets as well as with the SRAM hub it is 2t difference.

 

[ExBrit]

I found a 17 tooth sprocket at BrommiePlus in Taiwan and placed my order. I have a good feeling about this. But I'm keeping the 16 just in case.

I just received a 44 tooth chainring and 17 tooth sprocket from BrommiePlus and I'm very impressed. They seem to be a new store, still getting set up. The packaging was excellent, they delivered on time, for a low price, and the product looks very good. I would buy from them again.