# 2 to 3 speed



## 12boy (19 Jan 2020)

There have been some posts on converting an S RF3 3 speed SA hub to a six by adding a second sprocket. I have a 2 speed hub with 12 and 17 tooth sprockets and a chain pusher. Is there a way to add another sprocket to that hub, and if so has anyone done it? I really like the lightness of the 2 speed hub and a step between 55 and 78 gear inches would be nice.


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## TheDoctor (19 Jan 2020)

I'm sure it could be done. I'd start by taking a 10 speed cassette to bits, getting three sprockets and two spacers, and fitting instead of the two sprockets you have. Then either modify the existing shift lever by filing an extra notch, or fit an old-skool MTB friction thumbshifter. Three speed conversion kits are around IIRC. Usually sold for fitting to a 6 speed to make a 9 speed, but they should work just as well for your purposes.


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## Schwinnsta (19 Jan 2020)

I have made that mod. I got the Bikegang kit. It came with three cogs, spacer, derailleur mod to clamp the cable end, and clip ring. I also bought a 10 speed chain and a Sunrace 3 speed friction shifter. It works well. I had to add a spacer / washer on the axle on the inside of the drop out as there was a slight interference with out it.


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## berlinonaut (19 Jan 2020)

12boy said:


> There have been some posts on converting an S RF3 3 speed SA hub to a six by adding a second sprocket.


Which - just for the record - does not work w/o using frewheel parts of the BWR, does not add much benefit and thus is a pretty unusual mod. Possible, but more than uncommon.



12boy said:


> I have a 2 speed hub with 12 and 17 tooth sprockets and a chain pusher. Is there a way to add another sprocket to that hub, and if so has anyone done it?


In principle it works the same way as the 9-speed mod that I did to my BWR. I even think many years ago in this very forum was the first mention of a 2-to-3-speed mod that I read of. It was documented as a pdf and it was made on a 2-speed. Could later be found in the (no longer existing) Bromptontalk-wiki as well. I did an extensive write up of my mod over at bikeforums and I think here in the forum are at least a couple of links, possibly in the BSR-thread as well.


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## 12boy (19 Jan 2020)

I will try both ideas...I was thinking that a10 speed chain would be needed. Thanks.


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## berlinonaut (19 Jan 2020)

12boy said:


> I will try both ideas...I was thinking that a10 speed chain would be needed. Thanks.


That's what I used, just to be sure. No idea if it was really necessary. Probably not. 
If you want to go further: You can btw. in the meantime also buy a rear wheel from brommieplus (via their website or via ebay) that is using a Hubsmith hub that is able to take 3 sprockets by default and 4 if wanted, including the benefit of being able to use an 11t sprocket.


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## 12boy (20 Jan 2020)

Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.


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## bikegang (20 Jan 2020)

12boy said:


> Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.



If you can wait, we will have new pilot sample out soon. 11T/14T/17T all in one (CNC machined by KCNC ) for easier installation and more efficient drive, if you like to be our lab rat?


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## 12boy (21 Jan 2020)

Sure would...sweet ratios and an unobtanium 11 tooth!


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## u_i (21 Jan 2020)

bikegang said:


> 11T/14T/17T all in one (CNC machined by KCNC ) for easier installation and more efficient drive



CNC suggests aluminum. Is that correct?


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## 12boy (21 Jan 2020)

Sure hope not..Al sprockets, especially with 11 teeth would wear out PDQ.


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## TheDoctor (21 Jan 2020)

You can CNC mill any material, if you have suitable kit. It's not limited to aluminium.


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## TheDoctor (21 Jan 2020)

12boy said:


> Will be checking that. The Bikegang kit at 25 pounds for 3 sprockets and a C clip seems a bit much.


You do get a shift lever too. The Brompton 2 speed sprocket set costs £10, so an extra 15 for another sprocket and a lever sounds reasonable.


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## u_i (21 Jan 2020)

TheDoctor said:


> You can CNC mill any material, if you have suitable kit. It's not limited to aluminium.



The cost for steel is 4-8 times higher.


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## 12boy (22 Jan 2020)

Be good to check it out.


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## bikegang (23 Jan 2020)

u_i said:


> CNC suggests aluminum. Is that correct?



No. It's some kind of steel. JIS G4105 SCM415 Cr Mo steel ? 
Will know more after they provide the sample and spec. Should be soon after Chinese new year.


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## 12boy (23 Jan 2020)

Looking forward to hearing more...thanks, Ron


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## Kell (23 Jan 2020)

I actually might be interested in this to covert my 6 speed.


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## Tenkaykev (23 Jan 2020)

Me too,

I'm running a 10 speed chain on my 6 speed CHPT3 ( only because the chain is red and black like the bike.)

I was told there would be problems shifting, I twiddled the adjuster and it shifts OK, although I do have to hold the shifter for a few seconds when changing up, changing down is immediate.


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## bikegang (13 Feb 2020)

12boy said:


> Sure would...sweet ratios and an unobtanium 11 tooth!


Sorry about the wait, it's into surface treatment stage now... should have it soon.


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## 12boy (13 Feb 2020)

I am waiting eagerly.


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## bikegang (13 Feb 2020)

12boy said:


> I am waiting eagerly.



After laser engraving label and we are done ...


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## Nufab (13 Feb 2020)

That looks awesome... will that fit without having to file or bend the rear triangle? Will it come with a shifter, or can the 2-speed Brompton one be modified to 3-speed?


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## Tenkaykev (13 Feb 2020)

bikegang said:


> After laser engraving label and we are done ...
> 
> View attachment 504337



Looks great, I'm certainly interested 👍


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## u_i (13 Feb 2020)

Cogs wear off together with the chain. The question will be of the cost and durability. On a bike used regularly the cassette will need to be changed at least every 2 years and maybe every year.


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## 12boy (13 Feb 2020)

Bromptons and other small wheeled bikes run through sprockets, especially small sprockets much faster than 700c bikes. It would be good to be able to replace them individually.


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## bikegang (13 Feb 2020)

Nufab said:


> That looks awesome... will that fit without having to file or bend the rear triangle? Will it come with a shifter, or can the 2-speed Brompton one be modified to 3-speed?



Yes, the idea is plug and play. Compatible with all exisitng stock parts (Frame, hub, tensioner, jockey wheels ...) Not chain though as this set is better with 10 speed and up chain. And you need a 3 speed thumb shifter.


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## 12boy (14 Feb 2020)

I'm thinking any decent friction shifter would do.


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## u_i (14 Feb 2020)

bikegang said:


> Yes, the idea is plug and play. Compatible with all exisitng stock parts (Frame, hub, tensioner, jockey wheels ...)



So what about the chain guide disc? Depending whether I keep it or not I use different spacers between the cogs and if I use the disc I must trim it. If the disc is not there, it is easy for the chain to get stuck between the largest cog and hub on a folded bike. Somehow the reality I see is not as bright and clear as yours .


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## ukoldschool (14 Feb 2020)

What? why are you over complicating this. Nothing on the front chainring will change.


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## u_i (14 Feb 2020)

Chain Guide Disc

Spacer for tensioner?


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## bikegang (17 Feb 2020)

12boy said:


> Bromptons and other small wheeled bikes run through sprockets, especially small sprockets much faster than 700c bikes. It would be good to be able to replace them individually.



Just learned that it is not possible to produce single cog 11t for stock brompton hub, too small the remaing steel rim, will break easily. Only if it is attached to another cog ... (It is possible for 3rd party hub that uses screw in cap? instead of C clip type fastener)
Confirmed material is SCM440H heat treated steel. _ED_-Electrophoresis deposition surface processed black.
will pm (conversation) you shipping address, please check.


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## 12boy (17 Feb 2020)

I've sent you my address today.


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## u_i (17 Feb 2020)

What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?


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## 12boy (17 Feb 2020)

I like the 11 because I would enjoy having the higher gear inches. With my 58/38 chain ring setup, I get 85, 67 and 55 GI on the large chain ring and 56, 44 36 on the small, good for around here. If more climbing was in store a 32 chain ring would get me down to a low of 31. I've done ok here with the 38, though. The 67 GI on the big chain ring would be a treat for level ground with 20 mph headwinds or moderate grades. I am an inveterate grinder though and rarely peddle much over 70 rpm.


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## 12boy (17 Feb 2020)

I should have read your post more carefully. My current set up is a 2 speed hub, with 12/18 sprockets. Were this to work well on post my BSR I could get by with just one chain ring.


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## Schwinnsta (17 Feb 2020)

u_i said:


> What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?



I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.


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## u_i (17 Feb 2020)

Schwinnsta said:


> I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.



If the 3 sprockets yield your only gears, sure you want to spread them out. If you piggyback them on the gears that are already spread out, you want to fill the gaps and limit the overlaps. Optimal jumps are 12% or so, but this is hard to do on a Brompton, 15% or 16% is a compromise and you go with 25% if you have no choice.


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## bikegang (18 Feb 2020)

Schwinnsta said:


> I have 12-14 -17. So just a 3 speed. I like having a low for climbing. I may replace 17 with a 19. Once your over a hill you can go directly to high. You don't need the in between gears.


We like to provide as wide gear range as possible yet compatible with as many stock parts as possible
Need to file off frame end or clamp it in order to fit 19T. But not major issue. 19T is the biggest cog the stock tensioner can take.


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## bikegang (18 Feb 2020)

12boy said:


> Be good to check it out.


Looks nice with hub  40g


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## 12boy (18 Feb 2020)

u_i said:


> What is the point of choosing 11-14-17 cogs? What is this combination supposed to achieve? I am using 12-14-16 which gives 16% of gear jump optimal for BWR as 1.57^(1/3)=1.16. With 14/11=1.27, i.e. 27%, it is just as bad as with 2 sprockets. I do not see this choice doing anything either for BSR. Am I missing something?


I don't think this will work on the BSR because even 2 sprockets won't work. The driver on the BWR is made for 2 so it should be ok for that


bikegang said:


> Looks nice with hub  40g
> 
> View attachment 505078
> 
> ...


That does look nice.


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## u_i (18 Feb 2020)

12boy said:


> I don't think this will work on the BSR because even 2 sprockets won't work. The driver on the BWR is made for 2 so it should be ok for that



I missed the fact that its premise is to increase the speed number without a gear hub. While it might be possible to put it on BWR, the choice of cogs is not the best for such purpose. Sorry for the confusion


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## 12boy (18 Feb 2020)

I actually called my favorite Brompton shop to see if the two sprocket driver that comes on BWR hubs could be bought separately for my BSR and they said they couldn't get the driver that way and had to buy the whole hub. I assume Sturmey Archer makes the Brompton 1/2 speed hub but don't know for sure. Anyone know who makes it?


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## u_i (18 Feb 2020)

I lack a direct experience with BSR, but my understanding is that it takes Sturmey-Archer specific cogs (3-spline), not Shimano type (9-spilne) like BWR. The simplest conversion is to get 2 such cogs and put a spacer in-between. There is a long thread on BSR conversion and this is the best way I can summarize it:

https://www.cyclechat.net/threads/brompton-3-or-6-gears.251949/


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## bikegang (18 Feb 2020)

12boy said:


> I actually called my favorite Brompton shop to see if the two sprocket driver that comes on BWR hubs could be bought separately for my BSR and they said they couldn't get the driver that way and had to buy the whole hub. I assume Sturmey Archer makes the Brompton 1/2 speed hub but don't know for sure. Anyone know who makes it?


They are made in Sturmey Archer (now in Taiwan / SunRace) , My impression is you can change the free hub body to the shimano 9 splines spec. Let me check. 
It will be something like this ==>


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## 12boy (19 Feb 2020)

I understand the BWR has the 9 spline system and you are right about the BSR.


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## berlinonaut (19 Feb 2020)

12boy said:


> I actually called my favorite Brompton shop to see if the two sprocket driver that comes on BWR hubs could be bought separately for my BSR and they said they couldn't get the driver that way and had to buy the whole hub.


That's wrong. You can buy the BSR driver and other parts i.e. at SJS and this way convert a BSR to take two sprockets. Just that it is a bit of a pointless conversion and so nobody does it. If you want two sprockets on a BSR style hub just buy one of the older SRAM 3/6 speed hubs for the Brompton. The older Brompton 6-speed solution based on the SRAM hub is exactly what you would get with upgrading a BSR with BWR parts. 9 speeds on the basis of a BSR hub would even be more pointless due to overlapping gears. I'd recommend checking this thread where the topic has been discussed extensively.


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## ukoldschool (20 Feb 2020)

@bikegang is this available to buy yet?


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## bikegang (20 Feb 2020)

ukoldschool said:


> @bikegang is this available to buy yet?


Testing phase.. @12boy will have a sample next week. Lets see how it performs.


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## ukoldschool (20 Feb 2020)

@bikegang Im happy to test on BWR hub


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## 12boy (28 Feb 2020)

At the moment I am about 750 miles from home, having gone to New Mexico to help my sister and BIL since he is just finishing radiation therapy for throat cancer and he is totally exhausted and in despair. Hope to get home by Monday, if not Sunday, and my wife says there is little package from Taiwan with my Bikegang triple gear set up inside. Something to look forward to. Thanks, Bikegang..


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## Schwinnsta (28 Feb 2020)

What is the advantage to the new Bikegang triple over existing 3 cog system?


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## 12boy (29 Feb 2020)

The advantage to me is comparing to a 2 speed. Higher high and a nice medium are the advantages to me. Compared to a Sturmey Archer three speed it's primarily weight.


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## Schwinnsta (29 Feb 2020)

I have the Bikegang 12 - 14 - 17 now so I was wondering why the triple compared to that.


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## 12boy (29 Feb 2020)

Sorry, I misunderstood. The advantage would be a high gear about 7 gear inches higher, at least with a 58 tooth chain ring.


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## 12boy (6 Mar 2020)

Got back from my trip and found both the 3 sprocket part and a thinner retaining ring waiting for me. Pulling the rear wheel is fairly quick and taking off the 2 speed sprockets is also quick and easy. Putting the 3 speed sprocket on is also about as simple as it could be.
However, getting it to work was a little more problematic. I did have a new SRAM 10 speed chain cut to the same length as the KMC chain which I was using with my 12/18 two speed. I couldn't get the three speed set up to run and shift well, and as I have 2 chainrings, 58 and 38 tooth, was surprised to see it autoshift onto the small chainring. I read back through the posts, and someone, I believe Schwinnsta, added a washer between the frame and the 15 mm nut holding the wheel on the drive side which essentially pushed the tensioner out a little. I learned the second washer must be the same size as the original washer to allow the tensioner to seat properly. Once I got the washers right it worked well, and that was with a friction shifter. There was also a little loosening of the shifter cable to allow the shifter to go far enough to hit the 11 tooth sprocket easily.
Today was my first opportunity to try this out. I rode about 16 miles, some downhill at 29 mph, most of it fairly level and half with 18 mph headwinds. The 3 sprockets, 11, 14 and 17 gave rounded off gear inches of 85, 67 and 55. I appreciated the 85 for downhill and level with no headwind or a tailwind , the 67 for level or a short rise with a headwind, and the 55 for long grades with a headwind. I had a few gear skips with the 14 and 11 tooth sprockets but also managed to grind up some short grades standing on the pedals with the 11 and 14 with no skips. Might just be getting the friction shifter exactly right. Pretty much a very satisfactory experience from my point of view. Having a high gear 7 gear inches above the 12 tooth sprocket (78 gear inches) and something in between the high and low was very nice.
I would suggest including a washer of exactly the right diameter and thickness with the kit to avoid having to experiment with finding the right one. Then swapping the 3 speed setup for the 2 would be a 15 minute job, plus a little tweaking of the cable length. I will post again after I get some more miles on it.


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## bikegang (8 Mar 2020)

12boy said:


> Got back from my trip and found both the 3 sprocket part and a thinner retaining ring waiting....


Thanks for the review and the tip of tensioner washer.
So this is why H&H has produced washers for tensioner to fine tune the shifting, but they are inside the tensioner.


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## 12boy (8 Mar 2020)

Thanks for giving me the opportunity.


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## u_i (8 Mar 2020)

This is the type of washer that needs to be put on the axle under the tensioner







I cut one myself out an alu sheet, but I have seen these also on AliExpress, $6 apiece though


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## 12boy (8 Mar 2020)

I just used a washer the same size as the original. Had I thought more I would have used the washer from the non drive side and used a regular axle washer for that.


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## ukoldschool (10 Mar 2020)

No offence to 12 boy, but it seems kind of pointless to me to have feedback from somebody that has a dual chainring setup, especially odd ones (58 and 38). All talk about gear inches is completely redundant when you aren't even using a chainring that 80% of people would use IMO.

Id like to hear experience from somebody that has changed from a normal 2 speed or 3/6 speed Sturmey hub to this, with a 'normal' Brompton chainring (44/50/54)


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## bikegang (7 May 2020)

The Unibody cog set can easily be the base of 4 speed mod (11-14-17T + 21T).
Need a longer 4 speed free hub body though.


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## bikegang (7 May 2020)

Still snap ring (circlip) type, but you can see what they did to the end section
in order to squeeze in one more cog.


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## Gunk (9 May 2020)

A mint complete 2018 3 speed wheel just sold on Gumtree for only £80 this week including a new Schwalbe Marathon tyre, three speed shifter, cable and the chain tensioner. If you want to swap to 3 speed then a good used rear wheel is probably the way to go.


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## 12boy (9 May 2020)

I have a 3 speed 177% ratio SA wheel. Wotks very well. But thehub alone weighs a little over 1000 grams. The chaIn pusher solution is much lighter although the range is less. Guess it is whatever your tastes run to.


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## rogerzilla (9 May 2020)

In t'olden days there was a simple 2-sprocket converter for a Sturmey threaded driver. The threaded driver isn't any good for an SRF3, which is a totally different design to the old AW, but AWs are two a penny and this might offer an easier solution.


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## Gunk (9 May 2020)

The Sturmey Archer 3 speed hub is a tried and tested piece of kit. reliable and needs very little maintenance, for a commuter bike it does the job very well once paired with a front chain wheel which makes the gearing comfortable.


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