It wouldn't be. Just swap the stock rear wheel and shifter with the new parts. Hardest part would be getting the handlebar grip off without tearing it. Just make sure the spokes are tensioned as I'm guessing that's a machine-built wheel.

You can check with the seller to find out the inner rim width,and compare it to this chart,but I'd be really surprised if it was that much narrower than a stock rim.

FYI,the SA 5spd hub was the standard config before the 6spd setup,and the hub's made by the same folks that made the hub you have now.

but back then there were 2 indicator-shift chains out opposite axle ends , an entirely different hub.. 234 were closer together .

& then the 5star was made in England , now the Sturmey brand is owned and made by a new division of Sun Race , in Taiwan.

Oy, the options. This has spawned a paroxysm of obsessive Googling.

The five speed wheel seems like a viable option. However, it has the narrow rim, and a presta valve. My from valve is Schrader.

This seems like a better option:

Brand New 16 x1 3 8" 349 Sturmey Archer Black 5 Speed Wheelset Brompton | eBay

However, they don't offer free shipping, so total real cost is $83 more.

I'm still thinking about a whole new Brompton, and now also this:

Tern Link P24h, The Versatile folding bike

It has a huge gear range, and ticks a lot of nice bells and whistles, rack, fenders, lights, etc. It uses a three speed internal gear hub rather than front derailleur and triple chain ring, which I find rather cleaver. I just might be able to make it fit in my glorified closet. However, it weighs in at ~30 lbs.; weight matters climbing four flights of stairs.

I'm also looking at Bike Fridays, though I'm not sure they fold as small as I'd need them too. I don't think I'm interested in a Tikit, as I already have a compact folder. Does a Tikit ride significantly better than a Brompton?

Decisions, decisions.

SRF5(N) hub not sold anywhere but in Taiwan?

BTW, what exactly is the difference between (N) and (W)?

Axle width and the indicator chain to shift it , and 28 instead of 36 spoke holes in the hub shell..

Net, I think excessive Googling is good if it leads to you taking lots and lots of test rides.

FWIW, I think the Brompton is one of the best utility bikes out there. There is (almost) always space for a Brompton in the stable ... except for mine apparently! If it satisfies 90% of your rides and purposes, I'd stick with it and try to find another bike that best addresses the 10% assuming that you have the space for it. I grew up in NYC so I understand how small apartments can get. Only you can decide whether another bike using some space is acceptable and the best tradeoff.

In general, I'm not a big fan of the SRAM DD. But I find it acceptable and have one on the triplet.

Picasa Web Albums - Geof Gee - Bike Friday T...

Broadly speaking, the more unusual the person, the more Bike Fridays will fit people better. For fun and/or long rides, fit matters a lot. That said, I think that there are some wonderful Dahon, Tern, Downtube, and so on options where you can add a front derailer. IMO, a front derailer and two well selected chainrings will address most people's needs. In my case, both the boss and I found the Brompton's ride "OK" so once we stopped using them regularly we sold them. The tikit's ride is pretty good but not outstanding. I'm still playing with fit and such so that might change in the future. But it's fair to say that I'm particular about a bike's ergonomics.

I forget what that other 10% is for you and whether that 10% includes a super compact fold. But if I had a Brompton, I'd probably go towards a light NWT or Crusoe as the second bike if the fit on a stock bike was too far from optimal. And I'd always consider a used Bike Friday if I wasn't too different from the general population; i.e., if you're 6'6" then finding a used folding bike is an exercise in futility.

I just fitted a front mech and changer to my Brompton when I added a double chainring. I was the cheapest Shimano mech I could find, the cage needed cutting to allow the chain to slip out of it when folding and the mounting bracket needed some work with mole wrenches and a Drehmel to make it fit. I did the same to my partner's Brompton too. This "bodge" has worked fine for over 1100km of touring.

I also fitted 8 speed Nexus hubs into the bikes at the same time (modified hubs and spread rear forks). We built our own wheels which saved some money but the cost of the Nexus hubs, rims, rim tape and spokes was somewhat less than a new Brompton rear wheel and 6 sp BWR.

That's some serious tinkering bud. Bravo!

I just purchased the SRF5(N) from the fellow on Ebay who sells the complete 5 speed wheelsets. I was surprised when I first opened the package to see that the hub was labeled as (W) not (N), but it is the model with the nine spline freewheel. I only purchased the hub, and built the wheel using my stock 3 speed BSR spokes and rim. I had to have the spokes cut to 133mm and 135mm to build the wheel. I have it installed now and it is working well. To adjust the hub you need to line up the mark on the shifter with the 3rd gear of the thumb shifter, (I have the SA thumb shifter that I converted to a bar end.) and then align the pulley chain at the axle to have the green mark 1mm out of the axle. I noticed that the hub shifts perfectly when you stop pedaling to perform the gear shift. It is a bit unreliable if you shift while pedaling (regardless of the pressure applied to the cranks). I was able to shift the BSR while pedaling more consistently, but not always.

I'm currently running 44T x 14T with the 5 speed hub. It is enough to handle the terrain in my area that the BSR gearing couldn't.



I've also mounted the 16T cog that came with the hub. I just needed to remove the dust cap from the hub, install the 16T, then a spacer that came with the kit, the 14T cog, and snap ring. The Ebay seller sent this link, glorbec.com/bike/bro-srf5x2/, with photo's on the process to convert to 5x2 (Although the text did not translate).



Since I have an M3L, my next project is to get the parts to add the shifter mechanism from the 2/6 speed and use a bar end shifter on the left side to achieve 10 speeds. It should be about a $100 in parts to install the pieces on the chain stay. I'm planning to use a SA 3 speed bar end shift or Dura Ace friction shifter on the left side of the bars. If anyone has experience with this set up please let me know if this is adequate for replacing the stock Brompton 2 speed shifter (I sure hope so!). I think the 10 speed gearing covers a pretty good range and brings the steps together a bit closer than the 5 speed wide range. I also have the options of a 13T too (I don't know if 11T or 12T are an option, as well as anything bigger than a 16T?).

I've checked into a Schlumpf Mountain Drive also, but I'm not sure if I need the gearing that low. Although, it is a cool bit of kit!

The Speed Drive is cool too.. 2nd gear is Overdrive. so 34 acts like a 54t


110t BCD 34+t chainring...

A cheaper option would be to fit a 5 speed Sturmey Archer hub...or an 8 speed Sturmey Archer hub.....buy the kit from Tiller Cycles...or why not fit a front derailleur..They can be fitted...

In my experience a 14t cog runs a lot more smoothly on a Brompton than a 13t does, under the pressure exerted by the tensioner. So a 14 and 16t combination ought to make for a very smooth drivetrain. I'm running the old standard range 5 speed hub but would consider the wide range with dual shifter. Good range and spacing.

The nice thing about the 5 speed is that there isn't a weight penalty you have with the 8 speed. Also, I have tried changing the crankset once already and had trouble with the fold. So I'm a bit wary of going with a FD and double chainring

Greasy finger shifting the double chainring removes one complication..

Steve Parry in England is one of the fabricators modifying Bromptons , he makes a clamp on mount to adapt a Braze on FD to work..

I have a Similar one made for the Fold A Bike Shop in California, not going to use it, sell for C$. (with thumbshifter and BZ on FD. + ship)

for a frame builder shop the bracket is not a big challenge to make..

it just has to compensate for the seat post being a Pass by, Behind The BB, since the standard frame the Seat Tube is aligned into the BB..






......

I was thinking of doing the same thing you did with the 5 speed. However, I would use a 17T cog and this would allow me to ride in 4th gear at 54 inches! It would leave me with one high gear which is fine for me. However, it would make for a very low 1st gear at 28 inches!! I could live with that easily!

Had a Mk2 Brompton , 15t was the max before the cog hits the frame tube end, and wont turn .. so that is what I used for my Mk4 M3L.. 15t.

so you will need to look at the chainring end of the drivetrain to increase or decrease that external Drive ratio..



An 11? No , but for the 2 speed , a 9 spline 12t cog is made to put on that Brompton version.

I finally got the bar end shifter together for the 5 x 2 project. I had to grind a normal derailleur cable end in order for it to replace the shorter cable that comes with the Brompton rear shifter assembly. Unfortunately, there was not enough cable pull (possibly) to get the chain to shift from the 14T to the 16T cog. I may try using an 8 speed bar end shifter to get more cable pull. Any suggestion would be welcome.

I know this is an old thread but it is not "too old" and I like the idea of keeping the info in a few threads and not spread out too much.

What I am working on at the moment:

I wanted more gears and more low gears on my Brompton. Since it started its life as a 5 speed (two wire) I started off buying a newer 5 speed hub for a single sprocket thinking I`ll never do 5x2 at the back.

Then I realised I wanted to do that after all, fixed the rear frame problem and bought this piece to convert the hub to take two (or more) 9 spline cogs: "Sturmey Archer BWR Driver Assembly- ZHSA800" is written on the plastic bag it came in.

That thingy is now installed. I forgot to buy the cogs so I butchered a 8 speed casette I had (actually from my NWT who is also getting an upgrade) and so far I have installed a 12t and a 16t cog. Bike is not yet ridable but playing around with a gear calculator and looking at the front chain rings I have available (and also thinking about cog and chain wear) I started to think about cog sises at the back.

What I wanted to ask: Has anybody successfully used bigger cogs at the back with the stock Brompton der/tensioner? What combinations can it take? Searching for answers I found this old thread but I am not sure if there is a different chain tensioner involved in the 13-16-19 setup.

Anybody out there has experience with this?

I found on my Mk2,.. your 2 cable 5 speed is from that era,.. that 16t hits the end of the tubes that the dropout is brazed into.

So I went with a 15t.. my Low gear was by fitting a Swiss Mountain drive geared crank.. so my 54t is effectively a 21.6t [50/20]

New is the Efneo geared 3 speed gear box crank, sprocket is a 28t, overdrive gears 1.43 , & 1.79, act like 40 & 50t chainrings,

its cable shifted from the handlebars Efneo shop





.....

I am not sure about 19T is doable, but I saw someone installed a 18T cog. Here are the pics he shared for what he did on his Brompton modified from 12T/16T to 13T/18T. Looks like tensioner is not a problem but the rear frame is. (Pic sources: Harvey Hung/ H&H chief designer)

And I saw this Korean guy selling the 4-speed conversion kit. (11T~20T) For $250 you can get a complete kit, I think that's not a bad deal at all.

https://www.facebook.com/brombacher....3oxSgY&fref=nf

Unless you absolutely need that compact fold, I'd look at a Bike Friday Tikit. I much prefer the Tikit as it has more gears, front end more planted and cost much less (used). It is overall a much more pleasant thing to ride. My opinion of course. My Brompton generally lives in the cupboard.

Thank you for answering and for posting pictures. Yes, I found out from this thread: 3 pignons sur une roue libre [Brompton 9 vitesses] •

that they have to grind down the frame to fit the bigger cogs. Not sure I want to do that, at least not with the rear frame that is on the bike now. We now have one spare rear frame so maybe after I modify the spare frame (braze on the missing nut for the chain mower) I could do it on that one. On page three in that thread they posted a picture where one extra spring was added to make it work. Not sure if that is something everybody would have problems with or maybe they used the wrong shifter.

On the three and four cogs at the back: I have decided for now that I`ll only use two. I am also digging around in my spare parts to find a crank set that have or can take two chain rings of the size I want. I`ll use this setup as a start and then decide if I want/need more. The B is not my dayly ride so perfection is not important but I want what I do with it now to work perfect.

Maybe a 17t at the rear is in my future to be able to go up from 12 on the smallest as I am using now (what I could find locally) but I`ll ride my present configuration for some time and then decide.

Do you have a link to where you found the pictures?
Thank yu.

I was stupid to let a used Tikit go that was available locally at £ 350 a few years back. They are as rare as hens teeth around here and prices are slowly rising as peopel get more sivilized (learn about folders).