Chainring Choices | How to change the chainring on a Brompton
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- čas přidán 25. 06. 2024
- The why, what and how of choosing and fitting a chainring for a Brompton bicycle.
Even with a '12% reduction' 44-tooth chainring on my Brompton, I was caught out on the hills on a couple of rides last summer, so for this year's exploits I've fitted a 40-tooth chainring.
CHAPTERS:
00:00 Introduction
00:21 Why change the gearing?
04:33 Chainring options
06:08 Tools for the job
06:39 Removing the old chainring
07:46 Brompton Chainring bolt hole profiles
08:18 Fitting the new chainring
09:11 Torquing the chainring bolts
09:36 Adjusting the chain length
10:47 Releasing the chain masterlink
11:44 Removing links with the chain breaker tool
12:37 Refitting the chain masterlink
13:15 Job done! Test ride
13:50 Outro
I'm living in Korea and there are not many flat roads but mainly surrounded by a lot of mountains where have many extreme uphill climbs unlike England or other Europe. It makes us to do the DIY like this. Well, among many DIYs to my Bromtpon, changing mine to H&H 40T is the best one as far.
Glad you found the video helpful.
You inspired me with so much confidence I went out and bought a 39 chain ring for 2014 6 speed. The local bike cooperative had a box full of rings; I got a second hand hardly used steel ring. I’m surrounded by hills so I’m looking forward to have fun going up and down. Thanks for taking the time to make this vid; it really is very useful to us out here. Cheers from Auckland, NZ.
Thankk you! Glad you found it useful. Enjoy the hills!
I ride my 6-speed Brompton in London. Only a brute with massive thighs would ever be able to use Gear 6 with the standard chainwheel, even in London. I honestly don't know what Brompton were thinking when they chose it.
It takes a bit of effort! Thanks for commenting.
Ah man I'm glad I found your channel, I've just bought exactly the same bike and I put a39 tooth on it ( no chain guard on it ) my mate runs a 38 tooth and it rubs the spider very slightly, I'm down in Cornwall so it's hilly here also, I look forward to your next video :-).
Thanks. The smaller ring does make a difference.
Love it!! Finally took the plunge to change my 3 gear Brompton chainring from a 50T to a 40T - your video influenced me on what size to go with. Looking forward to seeing the difference it will make. Thanks for your thorough video!! 🙂
Thank you! Going from a 50T to a 40T is a big reduction. You'll certainly notice a difference.
I always love your videos and explanations. Thank you again 🫶🏼
Thank you.
Good informative video, applicable to any bike thank you 👍😎
Thank you. Yes, the principle is the same but chainring bolt torque setting for different cranksets may vary.
Thank you for this very informative video, you've really opened my eyes up to the many changes that can be made to the Brompton - they're great bikes
Thank you. Glad you found it useful.
Nice informative video.. .thank you.
Thank you.
Hello,
A very interesting video... thank you.
Take care
Paul,,
Thank you.
SO USEFUL!!! Thanks so much! I didn't know what a chain ring was when this video started, and now I understand huge bits that will help me with my new 6 speed Brompton.
Warmest regards
Jennie
Thank you! Enjoy your new Brompton.
I have a three speed B75 'cheapie' and a 44 T chainring is fitted as standard, but I still find at the age of 77 I'm struggling up the hilly lanes of Sussex. I wish Brompton would build your bike to the specifications that you want, rather than letting the customer make do with a standard setup. If I'd had the choice I would have opted for a 39 T chainring which, although it restricts the maximum speed, wouldn't bother me because I can never get to use top gear unless I'm drifting down a slope.
Thanks for the comment. I think the ratios in the 3-speed hub differ from the wide ratio hub used on the 6-speed but yes, Brompton gearing was never designed for riding hills! Although the 40T chainring does lower the gearing, what I've appreciated most is that it brings all the ratios slightly closer together.
Great analysis. Totally agree the standard Brompton gearing is designed for London commuters. Here in the US we rarely have enough uninterrupted space to achieve a speed that would require those bigger gears. Mine came with 54t and I swapped for 44t. Would go lower if it were easy to do but 44t is usable.
Thanks for commenting.
Brompton manual recommends changing cogs and chain at same time and not re use chain when changing gearing like this. I’ll be adding a 44 this week
Thanks for commenting. Brompton rightly recommends changing the cogs when changing a worn out chain. Chainrings tend to last a lot longer, more so if the chain has been replaced at the right time. A chain checker is a cheap tool that should be in every cyclist's toolkit.
Great video, I live in Aberdeenshire and I have already gone to the 44 and like you it's still too big. I will now look out one of these 40 chain rings, thanks for bringing this to my attention! Cheers, Rob
Thanks. Glad you found it useful.
Great video! For some reason I can't explain I have the feeling you could also fix the drive of the USS Enterprise.
🤣 Aye Captain, beam me up! Thanks for commenting.
I have recently purchased a 6 speed. Finding the gears ok where I live. But good to know smaller chainrings are available. I have used sjs cycles for my Brompton. Good video 👍 very informative
Thank you. Enjoy your new Brommie!
Very helpful video, thank you. I'm in the market for a Brompton and as a (albeit quite fit) 66-year-old, gearing is probably the number 1 factor. I came across the Brompton gearing chart (exceptionally helpful), but your video has provided me with excellent insight into the "how low can you go?" question. Thanks again!
Thank you. I'm glad you found it helpful. The other advantage of the lower gearing that I've only realised since posting the video is that the gear ratios are slightly closer together which helps maintain momentum when changing gear.
I changed the stock 50T chainring on a 2010 P6R for a 45T Shimano Alfine crankset with holotech bottom bracket when I damaged the original in a little tumble. It works very well
Thanks for commenting!
Well done for airing this subject. You’re right that Bromptons are generally over-geared. My family has had about 25 Bromptons over the years and I do long tours in Europe and N America on them. With the 3 speed models, as well as a smaller chainring it can be a good idea to fit a larger rear sprocket (14Tooth as against the standard issue 13T). A simple, cheap job. But on the 6 speed, if you really want to achieve a lower gear range, experienced Brompton dealer Tim at Cyclecare in Purton, nr Swindon can swap out the standard 13/16T sprockets for 14/18T. He expertly and files away a tiny part of the rear frame to accommodate the larger sprocket, and it works a treat. The end-result is robust and reliable. Highly recommended.
Thanks for commenting! It's always interesting to hear how Brommies can be adapted for particular uses.
Interesting. I've bookmarked that shop's webpage in case I decide to go for that modification on my Brompton. Thanks! BTW where would you purchase replacement 14/18T sprockets??
Tim cannibalises a Shimano or SRAM cassette to get the 18t, and I think he keeps the standard Brompton 13t or 14t. The 13t means you retain the higher top gear, albeit with uneven intervals between gears. That’s what I have, and I am used to it. It’s been completely reliable and bullet-proof over about 2,000 mixed miles so far. Alternatively, using the 14t smaller cog reduces the top end slightly, but helps to even out the gear spacings. A friend of mine recently got Tim to do the 14/18 conversion, and has done about 600 happy miles without incident.@@Muddy283
@@john3892 Thanks for that clarification, John. And thanks for responding so swiftly. I'm planning in the mid-term future to do some serious bikepacking sorties, so I'll definitely bear the possibility of that interesting Cyclecare mod in mind. Thanks again!
I'm getting older now and a smaller chainring is looking like a good idea. Like you I don't use the top gears so much. When the bike needs a service/new chain, I think I will change the size then..
Thanks. Whatever works for you ... just keep pedalling!
44 T is the best transmission!
It is a good all-round choice!
Excellent video 👍 what about changing the rear cogs ⚙️ to something larger? Would that interfere with shifting? I’ve also been told that its possible to have 2 chainrings and make that shift manually with a slight kick with the heel. Of course shifting it up to larger chainring would mean stopping and getting your finger to lift it back. Brompton is such an interesting bike - am still marvelling at its ingenuity.
Thanks for commenting. Bromptons produced in recent years use a Shimano splined hub so you should be able to fit any Shimano splined sprocket. However there needs to be room between the largest sprocket and the top jockey wheel to permit movement of the chain when changing gear. I'm not sure anything larger than 16T would leave enough space. I've seen videos of adaptations to the crankset but for me that's a step too far on a Brommie!
Hello mate! I just LOVE your scottish accent! Good lord, I swear, scottish people get insta +10 carisma due to their accent! The stronger, the better!
Thank you for the video, I had a lot of fun watching and now I know how to do the first upgrade on my future bike (as soon as I get it).
I just wonder if it's needed some blue Loctite or some sort of lube on those five chainring screws?
Anyway, thank you very much!
Thanks for commenting. A wee dab of thread locker doesn't go amiss, and just to confuse matters a tiny smear of copper grease helps to prevent seizing!
Hi. Like the video. I’ve done the same and have the h&h 40t. The only problem is that the front mudguard stay often gets caught between the chainring and chain guard when I fold. Have you had same issue? I’m going to go at the stay to mangle it to keep it away.
Thanks, glad you liked it. My mudguard stay rests against the chain guard when the bike is folded but its a good 5 mm clear of catching behind it. Fettling the stay sound slike a likely fix!
Just bought (in LA, CA, USA) a "C Line Urban" which has only 2 gears... and just as you say, my impression is, this bike is made for commuting in London in bike lanes where you can go fast. Here in the we-love-cars USA I need gearing which is one normal gear, one easy gear for going up hills. I can't ever go fast because you have to always be conscious of drivers of huge SUVs who almost certainly are looking at Tik Tok, not at the road. So that big huge gear is useless. My bike came with a 54T chainring for some reason. I am changing to 44T as soon as I can.
Thanks for commenting. I think the 2-speed is supplied as standard with a 54T chainring and 16/12T sprockets, unlike the standard 6-speed which has a 50T ring and 16/13T sprockets. Somewhere around 5:15 into the video I have a gearing table. Check out the source link at the top of the table to calculate the difference reducing your chainring to 44T will make. Enjoy your new Brommie!
@@lostinlivi Thanks! I did not know the rear cogs were different on the 6 speed. All the more reason to try 44T on mine, as I see it
Hi. How is it now tackling the steeper hills you struggled with earlier. Are the climbs noticeably easier?
Thanks for commenting. I've not yet tackled any particularly steep hills but I expect to be able to maintain a comfortable cadence for a bit longer when I do. You're never going to get into what I'd consider a proper touring gearing range on a Brompton. The reduction in top gear range hasn't been a problem for me. I'm finding that I can pedal comfortably up to about 32-34 kph before feeling like I'm spinning out, which is fine for me.
I am considering a similar change, there are some sizeable gaps in the 6 speeds available and top gear is pretty high, but 5th gear too low !, have you found that the gaps have evened out more ?
The smaller chainring brings the ratios a bit closer together but they remain quite a stretch compared to say a conventional 3x9 derailleur setup.
Hi, Just want to know where did you buy your front bag (3:05) I want that kind of small bag. Thank you
It's a Carradice 'Barley' that I think I bought direct from Carradice (carradice.co.uk). It's mounted on a frame I bought online, Etsy Ithink but I don't remember the seller.
As a Dane, with a 2019 "SuperlightM6LXBrompton" I have changed much to lighter parts from Titanium and Carbon, for now 9,35 kilo (with mudguards) and I expect to come even below 9 kilo soon, from a little extra changes, and still with mudguards (I'm a "Rainy Dane")?
On the Danish, rocky Island of Bornholm we have serpentine roads so steep, that even my low gears aren't enough and I have to walk going up!
But before that I mostly felt that my low gears are (much) too low, so I would expect an even lower gearing to be - ridiculous!
As named, you are able to buy a double chain ring for the crank, if in need of an extra low gearing, to be changed with a shoe, or a special changer in front? I hardly think it will affect the fold as it is mostly on the inside from the pedal arm.😄 Finn. Denmark
Thanks for commenting. For me, there's a limit to how much you can adapt a Brompton before having to admit you bought the wrong bike for what you actually want to do with it! 😉
Did you noticed a significant difference between the 44T and the 40T chainring?
Time will tell! I don't expect it to make a big difference but to go smaller would mean changing the entire crankset. For my own use it should be satisfactory.
@@lostinlivi Thanks I think i will do the same change. I'm also considering an ATS mountain drive, but price and weight goes up quite a lot
H&h also do a 33/54t dual chainring :)
Maybe so but for me it's adapting the Brommie too much. You have to add a front derailleur and shifter, deal with chain tensioning and possible limits on the way the bike folds.
@@lostinlivi that's conservatism at its finest 😉
If it works it works..
4:44 H&H makes a two in one chain ring 33/50 or 33/54 and it still got a chainguard.
I'm aware of it but to install it would involve also fitting a front derailleur and shifter and dealing with the differences to chain length and tension. I reckon if you need to do that much you've got the wrong bike!
@lostinlivi
What you do is change the ring from 54 to 54/33 (for exemplar) and put the spacer on the bottom bracket - done.
There is nothing to do on the shifters. there is no need for work/ change on chain tensioner. It's just the ring.
The chain only if you going from 44 to 50 or 50 to 54 but you would do it with every range change.
I don't know where you get the info for all this work on the bike, but it's wrong. Also, it's nice to have a big ring for the city (speed) and a smaller touring/ camping (less stressful with all the additional weight)
@@seductive_Octopus If you want to fit a double chainring, go ahead. If you do you'll need a means of moving the chain from one ring to the other - that's where a derailleur mechanism and some means of activating the derailleur (ie a shifter) comes in. On a 54/33 chainring will the standard Brompton chain tensioner be sufficient to account for the difference in chain length that these ring sizes would individually require (approx 8 to 10 links)? I doubt it. And once you've fitted your 54/33 rings the gearing you'll achieve on a standard BWR hub with 13/16 sprockets will only range from 21.9 to 108.1 gear inches - you'll get a wider range on a bog-standard 3x9 setup on a regular commuter hybrid without all the hassle.
I dont use the brompton spider, because i prefer 165 cranks. You can get a sugino spider from Spa Cycles for about £30. If you want to go below 38t chainrings, just get the 110 bcd version.
Thanks for commenting.
So you are keeping the crank arm and bottom bracket and changing out one chainring? The price of the chain ring is far to expensive. I went from 170 mm crank arms to 153 mm arms have a 42 tooth ring on the front and rarely require the top gear.
Good for you! I've shown what works just fine for me.
@@lostinlivi Yes it works just fine for you , I am pointing out an alternative to your standard length crank arms and rings for an existing crank. Shorter crank arms with all the power and a faster cadence using the same gearing is wonderful for the knees.
Most bikes are overgeared, and too many cyclusts won't admit it.
yes