How to add another gear to your 2 speed Brompton (derailleur 3 speed conversion)
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- Опубликовано: 7 сен 2024
- Do you want another gear on your bike? This is a relatively easy way to give your bike more gear range with almost no weight penalty and it keeps most of the stock parts. I have run this on my personal bike for most of the winter and I have had no issues.
FAQ
When researching the conversion I came across a lot of questions so hopefully, I can answer them here.
Q: What shifter can you use.
A: any friction shifter will work, if you want to use an indexed one you need something with the positions. The front derailleur shifter for MTB`s will work and a lot of people use 3 position suspension lockouts. I have used an indexed shifter but the friction is more reliable for me.
Q: Can I add more than three speeds? maybe by using 12-speed cassette parts and chain.
A: You can certainly use 12-speed cogs but you probably will not be able to fit 4 cogs on the freehub without some serious modification. I have never tried so if it's possible let m know.
Q: Is it a hard conversion?
A: It's not extremely difficult but you do need some bike maintenance skills and knowledge. If you are comfortable changing chains, cables and sprockets you can probably do this.
Q: Will this void my warranty?
A: Probably.
Q: Does this add weight?
A: I haven't weighed a bike before and after but I do not think it would add much if any. The chain and sprockets will both be lighter but there is an extra sprocket so it probably cancels out. It probably depends on the shifter you go with.
Q: What cassette and chain do I need?
A: I used Shimano 105 11 speed parts but any 11-speed chain or cassette should work. You could also use a 12-speed chain if you are feeling rich.
Q: What is the biggest sprocket I can fit on the bike?
A: Probably 18 tooth but it depends on the bike. Some frames will fit 19 teeth, some will not fit 17t. Titanium frames max out at 16t most of the time. You could file or cut the corner of the chainstay to add a little clearance. Lots of people have done that and it is not really a structural part of the frame but it can be a little nerve-racking.
Q: How much does this cost?
A: It really depends on what chain, cassette, and shifter you go with. If you buy all the parts I used at full price it would cost about $270AUD ($50 for the chain, $120 for the cassette, about $100 for the shifter and mount, maybe $30 for cable, housing and noodle). If you keep an eye out for sale items and maybe buy second hand you could save a fair amount off of that price. If you use Dura Ace chains and cassettes along with a dropper remote you might end up spending over $400AUD.
If you have any other questions let me know, I'll update this with anything extra as I get it. I made this purely to help answer some questions I have found and some I had myself, it is by no means every answer to every issue you could run into.
If you do try this and it breaks your bike please do not blame me.
Cheers everyone, happy riding and stay safe.
Thanks for the video. I performed this mod thanks to it. I managed to keep the plastic protector by using a thinner circlip, although I had to push the derailer out to avoid touching the chain using a washer.
Thank you Elliot for uploading this simple to follow video, definitely helped inspire me to begin my bike modding journey.
Ended up following your combination of 12-14-18t on the rear. First with a friction shifter, then later with a Shimano 3sp shifter off an old mtb (limit screws to set 1st & 3rd, barrel adjuster to fine tune 2nd). Indexed 3sp is nicer to use, but I agree a friction shifter may prove to be the more reliable/consistent choice.
Initially I had the Litepro chain tensioner + Brompton chain pusher which worked fine with the stock 2sp setup.
After doing to the 3sp setup, the jockey wheels kept binding up due to the geometry of Litepro + Brompton parts not really being designed to work together.
Happy to report the 3sp works perfectly if using Brompton Tensioner + Brompton Chain pusher.
While I decided to run with Brompton parts, someone else might be able to confirm if Litepro tensioner + Litepro chain pusher works with 3sp setup...
The stock Brompton part are honestly really good in a lot of cases.They aren't flashy but they are really reliable and tough. I think there are some aftermarket pulleys that work well for multi gear upgrades but I am not sure what ones exactly.
Wow you made everything looks easy 👍👍
Nice, more Brompton content please!
Wow u made it looks so easy! Great job!
Very useful tutorial👍🏻thank you
Looks nice! Gonna try that too
Thanks for this! Have you noticed any durability issues (increased rate of wear) with using the lighter weight 11-speed components on the Brompton, compared to the beefier stock cogs/chain?
I actually think the 11 speed stuff lasted a bit longer than the stock parts. The newer chains seem to wear really well compared to older 7/8 speed stuff, maybe better metals or coatings? This bike was my regular commuter as well so it was pretty well used. The only real downside of the 11 speed stuff was the increased cost and a somewhat more fiddly set-up.
@@eliotandalcool gonna try my hand at it. Thanks again!
Hi Elliot 2 questions here.
1. Will a 3 speed MTB front derailleur shifter work for this?
2. Will using 10 speed cogs instead of 11 speed work? (11 speed chains work on 10 speed cassettes, so no issues on that front)
These are parts I have on hand and wish to minimize spending
The 3 speed front shifter will work but its tricky to set up, I used that for a while but I found I had to adjust the shifting a lot and it was hard to get it shifting smoothly both up and down the cogs.
I have never tried with 10 speed cogs but it is pretty tight with the 11s ones so I imagine that you couldn't get the snap ring on without modifying something. It would be pretty easy to just try the cogs though, if you do and it works let me know.
A
Hello Elliot, great instructional video! question for you, is it possible to have this 3 cog setup with the 3 speed Sturmey-Archer hub, so as to make it a 9 speed total? Thank you again! MC
A few people have asked this and the short answer is yes it will work, the conversion would be pretty much the same as this. The long answer is you would want to do some maths to find gears that would work, you might end up with gearing overlap (eg 2nd hub and 3rd ext is the same as 3rd hub and 1st ext). It would also give you some awkward gear change as you may have to shift 3 derailleur gears and one hub gear to get to the "next" gear. I think its been done and it will give you more range. Hope that helps!
Where could I buy a thinner circlip? I have been locking everywhere without luck! Thanks. Awesome conversion which I am attempting myself :)
Hey there, a company called Minomods makes a kit. shopee.sg/Brompton-Small-Cloth-Sturmey-Archer-Hubsmith-2-Speed-i.182311758.3779379604
Thanks for the awesome video! I just tried this out and for some reason I can't shift to the smallest cog. If anyone has any thoughts of what to try I'd be keen to have input!
Double check the limit screws on the chain pusher. If that isn't it, check your cable tension. When there is no shifter attached, it should side in the smallest cog. Hope that helps!
Very nice! I am thinking of doing this but not sure if an extra gear is worth having friction shifts
You can also use an indexed shifter, its just a little more work to keep it running smoothly. I have probably put about 2000km on this set up now and it works pretty well. Because you only have three gears to choose from its much easer and smoother to use compared to an old road bike with downtube shifters.
Thanks for the great video. Question: for my C Line. Can I ditch the sturmey archer and set up a 3 speed? Seems like it would work. Buy a new rim, etc. also, is there an indexing 3 speed Brompton shifter? Thanks!
It would work for sure, all C lines (at least up to 2023) have everything to run derailleur gears and/or hub gears. It would need a fair few new parts but everything will work. You can use the stock hub gear shifter but setting up indexing, at least with the stock chain pusher, can be a bit tricky. The middle gear has a bit of play between the chain pusher and upper pulley so it can have a hard time shifting up or down depending on how its set up. I have run my bike with the stock Brompton 3 speed shifter as well as a 3 speed front MTB shifter and both of them do work but they tend to go out of adjustment easily. Hope that helps!
Would you mind sending a link to your friction shifter? I can't seem to find one like yours, it looks great, and I'm not into the indexed fork shifters
The shifter I used was the Velo Orange thumb shifter mount and an old Shimano down tube shifter. There are some other friction shifters out there, Sunrace is a big one. If you are looking to mount it under the bar like I did you will need to get a front (left-hand) shifter and mount it upside down.
velo-orange.com/products/vo-thumb-shifter-mounts-22-2-23-8
The trick is to remove the black plastic disc, so the sprocket remains further away from the frame... But what was the plastic disc for? Chain guide disc
Its just to protect the spokes incase of the chain jumping over the cogs. I have been using mine for ages without and its fine as long as everything is adjusted
Hello! I just tried to put 18T-15T-13T sprockets (from the 12-25 Shimano R7000 cassette, the 12T which is the smallest one of the cassette doesn't fit) and the tip of the teeth of the 18T sprocket slightly touches the frame, but it touches... EDIT: I took courage and filed the frame, very little was enough. The back of the chain tensioner was also filed. 18T-15T-12T sprockets from the 11-32 cassette work great! With 1.8 mm circlip. I would now like to put back the black plastic disc, for this it is definitely necessary to file the frame a little more (but i think it will open the tube wall) and test whether the 1.2 mm circlip fits. The 1.5 mm one not quite but almost.
Hi, great video, please can you advise what year model your Brompton is that you are doing the 2 to 3 speed mod on please?
Hey there, the bike in the video is a 2020/2021 model. Pretty much all the parts will be the same (so this mod should work) on all bikes from 2017 till today.
Hi and thanks for the great video! I've converted my B from 2 to 10 speeds long time ago with 5-speed gear hub and 2 sprockets. Hub is wear out already (non-repairable) so I'd like to come back to stock rear 2-sprockets hub but add 3rd gear to it. What do you think Shimano HG700 11-34 fit to my needs? It has 11-13-15-17 sprockets and I'd like to use 11-13-17. Thanks in advance. Also I'd like to keep stock 2-speed shifter but drill additional hole in slider to make it 3-speed
That cassette will work, I think it was what I used but the 11 tooth will not work with the Brompton hub. The lockring design on the Brompton 2 and 6 speed hubs is such that a 12 tooth is the smallest you can use. I ended up using 12-15-18 for my little cassette and it has worked pretty well. Hope that helps.
@@eliotandal thanks a lot it helped so much, will do the same
Does anyone happened to watch 3 external gear setup with 3 speed internal Brompton shifter (right hand side)? Would you share with me please? Thanks in advance
Hello Elliot! Thank you for your great videos! Question for you, I'd like to have that 3 sprocket conversion, but can you tell me if the Brompton frame (present model year) has the clearance for a 12-15-18 sprocket combination? and if the derailleur can handle it? I've already done the Sheldon Brown Gear Calculator and there isn't really any overlap. Thank you for your help! MC
The derailleur can handle it for sure, the only way to be sure if a 18t will fit is to try it on the hub. Some bikes will be OK, it seems a little random
Hey there, great vid...just wondering if the conversion would work with a Sunrace 3-speed friction shifter. And also, do you think that there is enough space to do the conversion on a 6-speed Brompton with Stermy Archer hub?
Hey there, the answer to both questions is yes but there are some catches.
For the shifter it would work with no problems, the H and M bars have a little bit less room but there is still more than enough room for the shifter. You should also be able to use a right or a left shifter as they both have enough throw.
As for the 3 cogs on a 6-speed hub, it will work, there is enough room on the hub and enough clearance everywhere else but it will end up with some awkward gear changes. The BWR hub is designed to have the two cogs fill the gap so adding more range to the cogs could end up with overlapping gears (ea 1st hub gear and 3rd derailleur gear might be the same as 2nd hub gear and 1st derailleur gear). it may also end up that to get to the next gear up (or down) you need to shift three gears on one side and one on the other. It might work fine in practice but I haven't tried it yet.
Sorry for the long response, hope it helped
LIKE SUB DING DONG BELL - excellent video, i will do this to my brommie thumbs up!
Can i do that on a regular single speed?
Another question. Can we use the 3 speed hub shifter on the left side as well? I mean two of the 3 speed shifters (one for the hub itself and the other for the 3 cogs). Will the indexing and shifting work fine?
The newer style shifters (under bar) are right and left specific so no. If you have the older, over bar, shifters you could use one on the left, it would just be flipped around.
How come you don't use Brompton's anti torque washers with tabs on to lock into the frame above the drop out to stop the rear axle moving out of the drop out under load? Brompton state they must be used in their assembly instructions when fitting a rear wheel as it is for safety. Conventional round washers that you use are not sufficient.
The anti rotation/torque washers are only needed on internal gear hubs. On the 2 speed wheels there is no torque on the axle so the only load is the chain pull and vertical weight but the shape of the dropout manages both well. The are necessary on 3 and 6 speed bikes because the axle could spin and cause issues.
Where can I get the 1.8mm curculio! My original one will not go on man 🤯
Ill leave a link at the bottom but a few people have told me that they have ground down the stock circlip on one side using sandpaper laid flat on something. It only needs a little taken off.
bikegang.ecwid.com/Brompton-External-Cog-Sprocket-Mod-Misc-Fine-tune-Components-Washer-Spacer-Circlip-p197926678
Anyone thought about a double clanger chain wheel and create 6 speeds?
It could be done but it would be pretty complicated and would require some interesting engineering to deal with the front derailleur/chain issue when the bikes folds. It would probably be easier to do 3 cogs on a 3 speed Brompton hub for a 9 speed bike.
Hi and thank you for the amazing video! I find that in the 4 speed Brompton P Line the 163% range is quite narrow - I feel it is very slow on wide roads (especially declining ones) and I can't take advantage of the downhill to go faster. Do you think it could be possible to add gears to the P Line without adding much weight (lightweight was the main reason I went for this model). If not possible, do you think I could expand the range by choosing different sprockets than the default ones?
I was thinking that even turning it into a 5 speed (6 speed or higher would be even better), with a good sprocket size selection I could have a decent range. What do you think?
Thanks!
Hey Alexandros, I think the P/T line drivetrain has a lot of potential to modify but I haven't been able to try anything so far. I am almost certain you could add a larger big cog and increase the gear range but I am not sure how big the max is without modifying the derailleur. The P line uses 10-speed sprockets and chain spacing so it would be pretty easy to get a 10-speed cassette and try some different cogs from it. Because it uses 10-speed parts it should be possible to use 11 or 12-speed cassette parts and make it into a 5-speed but I have yet to try this. You would also have to sort out a shifter, but there seem to be some options for those.
HI, Great video. So does that mean, that with a 3 speed Sturmey archer and a 3 cog, we are effectively looking at a 9 speed brompton.
Is this possible?
It is completely possible and I think some people have done it but you end up with some overlapping gears and shifting would be a little confusing. It could give you an extra gear on either end of the range though.
@@eliotandal what if I use a derailleur from a 3 speed Brompton on a 6 speed steamy archer hub? Would that alleviate the overlapping gear slot issue?
Great tutorial! Is it possible to use the 11t sprocket from the casette?
Not with the stock Brompton freehub. The 11 tooth is thicker than the others so it can engage with the lockring. You can get some aftermarket freehubs with use a lockring, I think Wheelsmith makes one.
Could you let me know how can I order a thiner circlip? Thank you!
A company called Wheelsmith makes a set but you could probably stop by an industrial bearing type shop and find something
shopee.sg/Brompton-Small-Cloth-Sturmey-Archer-Hubsmith-2-Speed-i.182311758.3779379604
@@eliotandal Thank you so much!
👌👍
So what cog sizes do you use ?
What front chainring size you use?
And what’s the speediest cog you think is reasonable to put?
Do you know what 6 speed Brampton’s 5th gear equals to in terms of cog size?
I have 6 speed gear hub and I hate it for the friction and resistance.. hope to convert to outer gears and still be able to rip 😁
I have 12, 14, and 18 tooth cogs on my bike, this gives me about a 150% gear range. The Brompton 6 speed has about 300% range and the 3 speed has 178%(?). It doesn't have as much range as either of those options but I have no issues using it around town and on some longer rides. I like hub gears, but the Brompton hubs are heavy and lose a bit of efficiency, As for the top speed, it will completely depend on the front chairing. Have a look at www.bikecalc.com/gear_inches if you want to compare different setups.
@@eliotandal hey man, thanks for deep dive! Appreciate it
Where can one order then thinner circlips online? I've google and looked all over. Any help please Elliot?
Sorry, I should have included a link.
shopee.sg/Brompton-Small-Cloth-Sturmey-Archer-Hubsmith-2-Speed-i.182311758.3779379604
That is a few different sized ones in the kit so you should be able to pick the right one for your hub.
Depending on where you are you can also go to most shops that sells bearing and bring the old one with you.
You can also try your local bike shop, some older coaster brake hubs used thinner clips so they may have something that works.
Hope that helps!
Hi, what brand is your friction shifter?
Hey there, the shifter is an old Shimano downtube shifter mounted to a Velo Orange thumb shifter mount. Any old MTB thumb shifter would work though
velo-orange.com/products/vo-thumb-shifter-mounts-22-2-23-8
Do you have any idea when i am shifting down to from big cog to middle cog it wont work but from smallest cog to middle and big cogs no problem?thank you
Sounds like it could be too much cable tension. It can be pretty tricky to get the indexing right with the stock chain pusher. There is a bit of slop in the middle cog so it can be hard to get it to shift well in both directions. I found the friction shifter helpful for this.
@@eliotandal thank you so much
What spacers are used between the cogs?
The spacer between the largest and middle cogs is one of the spacers from the original 11 speed cassette. The small cog has a lip built into it that acts as a spacer.
@@eliotandal are u able to measure the thickness of the spacer? Thanks.
The spacers from the cassette I used measured 2.18mm thick.
What is shifter brands
I used the Velo Orange thumb shifter mount with an old Shimano downtube shifter (I dont know the model) but I think the Microshift or Sunrace ones would probably be better. Any friction shift thumb shifter should work though.
Would have been a lot better without the incredibly annoying “music”
Just mute it, there’s no talk anyway 😊
This would be a nicer video to watch if the abrupt and repetative noises in the soundtrack were not there. As it is, I can't be bothered to mute them, so I am off to watch something (anything) else.
I might have preferred a more constructive comment but thanks for the feedback
@@eliotandal Sorry, Elliot... but sometimes it is good to call on the opinions of people who don't agree with us... which piece of wisdom applies to me too, of course.
However, I thought I WAS being constructive. My suggestion was for a "nicer video," ... one I could watch all through.
Best wishes to you.