Brompton 39T chainring

Monday 9th September 2024:
Finally! I have, at last, changed the chainring from the standard 50 tooth one supplied with the bike as standard - to a smaller 39 tooth one.
I bought the chainring online from Brilliant Bikes (great service as always), and also watched their KZbin video showing how to swap the chainrings over (as well as numerous other KZbin videos by other people of the same thing!).
It was fairly easy but you do need the right tools and I explain that on the video.
I managed to cut my middle finger badly during the filming, (you won't see that, it's too grisly), so hope you'll appreciate the video and give it a like! That said, I don't pretend that this is an expert illustration of how to do the job - so I do suggest you check other offerings before embarking on this yourself.
I'll be trying the bike out later this week to see how much difference the smaller ring makes when going up hills!
Cheers,
Jeff

[@anniemac3075]

Morning Jeff, you made that look easy but I guess it's quite fiddly in reality. I'd have knocked all the little bits & bobs into the grass & spent hours scrabbling to find them. Think you may have been near a wasp nest, but the yellow of the Brompton would attract them anyway & they're grumpy this time of year too so lucky they didn't take it out on you. Good luck with the hills, hope you get out & enjoy some of the nicer autumn days more now pedalling should be less strenuous. Oh & while I'm here a message to Aintree - We want Gladys We want Gladys We want Gladys!

[@Gladysthenarrowboat]

Morning Annie! Yes it was a bit fiddly at times - I took a chance doing it outside and it'd have been a disaster if I dropped any bits on the grass. I'd have preferred to do/film the job in a workshop setting on my workstand, but I dont have a workshop! Yes, we've had a wasp nest under the walnut tree nearby almost every year. My partner is a beekeeper, so I'm used to being buzzed / stung occasionally, and I know that generally if you don't flap your arms around, you'll be ok. But this time of year, wasps, as you say, are in a bad mood ☹️ So I'm going out today to try out the bike - but at the time of writing (08.30), I still haven't decided where to go! Looks fine but chilly outside. I hope that Aintree gets your message - thanks!!!!👍👍👍

[@fools_opinions]

Nice work, lucky you had some pleasant weather to do it in, not much of that going about at the moment. One recommendation for the bike, if possible it would be best to find a chain guard for it, not only do they help keep the oil off your trousers they also stop the teeth of the chain ring occasionally snagging the seam on the inside of your trouser leg. And it doesn't take long before you start getting holes in all your trousers.

[@Gladysthenarrowboat]

Thanks very much for commenting! Yes, I was lucky - although you may have noticed the wind was quite troubling now and then - pretty awful day today though! I believe some after-market chainrings do come with an attached chain guard, but the SRAM doesn't and there's no obvious method for attaching one to it. On the original 50 tooth one I removed, the plastic guard is screwed into the metal ring. But you're quite right about the teeth causing havoc with trousers! Also, you can easily brush your bare leg against the chain ring and end up with a lovely oily pattern on the inside of your calf that can be hard to wash off. To be honest, as someone who used to be a club-cyclist, and who raced, the thought of adding any additional weight is something I've always steered away from... but having used the Brompton for over a year, I have come to appreciate the value of a chain guard - and I will miss it!👍

[@dcvariousvids8082]

@@Gladysthenarrowboat- Is there a way you or someone else could fabricate a intermediary plate, to bridge the span between the new sprocket and the mounting arms?

[@Gladysthenarrowboat]

my God, what an imagination DC! Um, possibly a 3D printer could be used to fabricate a circular shaped guard which could be attached to the new chainring somehow.? Maybe glued... otherwise it'd mean drilling the chain ring and fitting to the guard by screws... a helluva job. Other videos Ive seen of people changing the ring seem resigned to losing the luxury of a chain guard.

[@fools_opinions]

Yeah I certainly feel you with the weight reduction, before I switched to a motorbike I rode everywhere and my favourite time of year was when I got to remove the mud guards, losing the weight and drag from them was enormously noticeable. Given the lack of attachment options on the chain ring I'd guess your only option would be to look for a different crank, but I doubt that would be particularly cheap unfortunately.

[@Gladysthenarrowboat]

@@fools_opinions Oh yes... I know what you mean about taking mudguards off! As a club-cyclist, I always felt at a disadvantage when riding in a group with my mudguards on when others had already taken theirs off! Psychologically, mudguards make a big difference - let alone their weight / rattling, and aero-dynamic drag. A different crank might be the answer as you suggest, although at some expense. I'm trying to spend as little as I can! 😁

[@DavidJames-rz9lt]

A job well done there Jeff, is there no end to your talents. Hopefully those hills will no longer be a problem. Quite nippy is the old Brompton, a nice bike. I might consider buying one in the future if I start to cycle on canals far from home as you do.

[@Gladysthenarrowboat]

Thanks Dave! I'm lucky that I have had the chance to have a go at many things in my life - but there are plenty of people far more talented than me in all of the things that I do.. You'd love taking your bike on trains I'm sure Dave - two pleasures for the price of one! 😁

[@dcvariousvids8082]

Wasps, well it is the time of year, looking for their last meal and there’s a great big ‘Bumblebee’ yellow bike. Is there a reason why the near-side crank+pedal, is noticeably heavier than the off-side? Is it the side with the folding pedal? Point of minor interest to other, maybe non cyclist viewers. A tool I referred to in a previous vid as a ‘pin-pusher’, is actually a rivet extractor. Also known as and here presented, as a chain-splitter. The same tool is also used to push the ‘pin’ rivet back into the chain when reassembling.

[@Gladysthenarrowboat]

Haha - yes they were troublesome DC, and maybe the colour attracted them! I think the left (folding) pedal is heavier than the right hand one - not much heavier, but enough to tip the balance - well spotted! 👍 I had to rush production of this video as I am working today (☹️☹️☹️☹️☹️☹️), but hope to get out tomorrow to make my regular Saturday one - no idea where yet though!

[@dcvariousvids8082]

@@Gladysthenarrowboat- We’ll be waiting. Good to know your time with MI6 was not wasted and old habits die hard. Some of the more technical work, expertly hidden from onlookers.

[@Gladysthenarrowboat]

Yes, standing in front of the camera was entirely deliberate - after all, I must keep some things secret 😉

[@MadisonTen]

Well done, Jeff. You’ll be flying up those hills quick time! 😊 I’m not sure what type of grease you used with the bolts, and I’m no cycle expert, but if your intention is to stop corrosion on the bolts then may be use a light weight thread lock (loctite 248 or may be lighter again) as grease can potentially allow you to tighten further than the indicated torque I believe. Threadlock should give you some corrosion protection while ensuring the bolts stay in place. Just an idea 😊 now, go find those hills.

[@Gladysthenarrowboat]

Hi Madison - well, there was a time I regularly flew up hills - but I do like the sound of your enthusiasm! I'm sure the 39t will make a big difference and hopefully I won't have to get off and walk quite so often. No, my use of grease is just out of old habits - the bolts were in very nice condition so I wasn't worried about corrosion. I actually used only a tiny bit on the outer casing of the part you thread the Allen bolts into. You make a good point though - grease could mean tightening more than I intended. Disappointingly, I was a little taken aback at seeing some rusty patches on the chain - not much, but I think I may fit a new one before long. As for keeping bolts in place, I've always favoured using PTFE (plumbers) tape. I recall using it to stop a headset from unscrewing on one of my Vitus 979 frames years ago... now, THAT was a bike to fly up the hills! I so wish I'd kept it.😒 I have been working today (remotely, online), and have square eyes now, so am looking forward to getting out tomorrow to try out the new chainring - not sure where yet, but yes, I will go find some hills! Hoping to see your latest adventure soon too 👍

[@MadisonTen]

@@Gladysthenarrowboat Yes, I totally agree, that bigger sprocket should help you no end and more important than top speed, especially on a Brompton. Hopefully it'll be just right. I expect you'll be ok with the torque, 10nm is hardly anything as it is and I suspect there is a +/- tolerance anyway. Ah yes, regrets getting rid of certain things! You and me both. I work full-time in front of a screen and then it's evenings to do the video. Hopefully this weekend if I can get enough done. Enjoy your next trip out.

[@Gladysthenarrowboat]

you're right - speed isn't an issue with Bromptons! I'm still wondering where to go to film tomorrow. 🤔 I only work now and then these days, but when I do, I spend hours staring at this thing - I don't envy you! I have the luxury of more spare time than you - but don't worry, you'll be my age one day!😁

[@snowy2875]

Thank God I found you! Sir, may I ask after install this 39t onto your bicycle, would it be like extremely slow to ride? I been thinking to choose between 39t or 44t. Can sir please advice.

[@Gladysthenarrowboat]

No problem - that's an intelligent question! Truth is, I suppose... yes, a little slower (not very much) . 1st of the 6 gears is now much easier on level ground than it was with the 50T. And I now use the larger of the two external sprockets on the back wheel a lot more than I used to. You can still go pretty fast wen you want to in top gear. I imagine the 44 would be a compromise... but you'd lose out on hill-climbing ability compared to the 39. Hope that helps 👍

[@snowy2875]

@@Gladysthenarrowboat Oh OK! Meaning 44t would be better, but not as easy as a 39t in term of climbing, am I right Sir Jeff? I been thinking for months. To change to 39t or to 44t. Because I cannot afford to keep changing. Some said 44t is best, while many changed to 39t like you, sir. Nah I am not at all brilliant. Currently I am using 50t and I must say is very tiring and I did not use any higher gear, most of thw time I only use the most at gear 3 or so.

[@Gladysthenarrowboat]

"Meaning 44t would be better, but not as easy as a 39t in term of climbing, am I right Sir Jeff?" Yes, thats right. You'd certainly see a difference with the 44, but not as easy as a 39 for climbing. Even with a 39, some hills will still be too steep for me. I think the 50T is fine if you only ever ride around town, on flat roads. If you change to a 39 or 44, you'll probably use more of your gears - and that's a good thing! Good luck.

[@snowy2875]

@@Gladysthenarrowboat Oh I see! Trillion thanks Sir Jeff!!!!

[@Gladysthenarrowboat]

Happy to help 😁

[@GGg-ic9ku]

Good info thanks for posting. Question: your chain is very, very clean and cassette also. I’m just wondering what oil you use to lubricate and what your cleaning strategy is to keep it so sparkling.

[@Gladysthenarrowboat]

Thanks! Well, the best way to keep the chain and sprockets clean is... leave the bike at home! I find that works best! Hmm... well the truth is that until I had a rear wheel puncture a few weeks ago, my chain and sprockets didn't look clean at all! But fixing the puncture meant removing the wheel, and then I saw how dirty it had become, so I spent time cleaning them. For the sprockets, I spray them with WD40 or similar (with wheel off) and then use a thin rag between the sprockets, moving along them until Ive gone all way around. For the chain, I usually clean it while its on the bike - spraying it with degreaser or WD40 and then turning the pedals round with a clean rag in my hands, which the chain passes through. Its a messy job though and you soon need more rags! For this latest job, I spent a while just rubbing the chain with a dry rag , wiping off the old lubricant and dirt, until it was totally dry to touch. Afterwards, I made sure I gave it a really good application of dry-lube, which goes on wet but dries off. You can use a wet type of course - and light oil is probably the best thing, but that attracts the dirt very quickly. I dont know if any of that makes sense - but probably lots of videos on KZbin show a better way!

[@GGg-ic9ku]

Perfect, that’s exactly what I was asking for. Good to know for future bike tours I hope to take with it. I'm surprised you don't use wet lube in Wales, but it's good to know a dry lube works well there. I'm trying a wax-based lube from Squirt on my other bike and will use it exclusively on my new E-Brompton arriving tomorrow. It keeps the chain cleaner on my e-bike. They recommend lubing before a rainstorm or right after drying the chain when you get home. I might eventually try the melting waxing method with an extra chain for easy swaps. I love how clean the waxing method keeps the chain!

[@GGg-ic9ku]

It does require a thorough degreasing before one uses the squirt lube. By the way, I plan to degrease the Brompton a couple times before I apply the squirt lube before my first ride. Though I may not be able to contain my enthusiasm for trying to bike out and may give it a few rise before I put on the squirt lube and grease thoroughly before application!

[@Gladysthenarrowboat]

Very good - glad it helps! I actually live just over the border from Wales - although I am Welsh and lived there most of my life. Yes its true - it rains a lot in Wales... but don't be fooled, as it rains just as much in England! I find the dry lube remains tacky for quite a while and to be honest, I'm more of a fair weather cyclist these days, so I wouldn't usually go out if I knew it was going to rain. It sounds to me that you've got the chain lube thing all sorted anyway... melting wax / extra chains... wow, that's pretty organised, I'm impressed! 👍👍👍

[@Gladysthenarrowboat]

I think you'll need a lot of self control to resist going out on it first! I can understand your excitement 😁

[@julieannwhitehouse8148]

hello by reducing it to a 39t chainring, what was the lowest gear as in gear inches

[@Gladysthenarrowboat]

Hi Julie Ann! I'm sorry, I really don't know the answer to that. All I can tell you is I removed 4 links from the standard chain that came with the bike - the bike is a C Line 6 speed Explore that had a 50t chainring fitted as standard. Someone more knowledgeable about gearing than me might know the answer, I expect. Sorry - but thanks for asking anyway! 👍