nazarus

Hi all,

I am newbie to this site and have all the mechanical biking expertise/knowledge of a cheeseburger.....so please forgive me if this question has been answered already. I probrably just didn't understand!

I have a Brompton M3L since around 2005/6 which I absolutley love - light, fast, bulletproof and all the rest of it. However, I have moved from nice flat London to rather hilly Brighton and the 3 speed cant hack it anymore. I would like to have some lower gears and ideally 1 higher one as well.

There seem to be various methods of getting retrofits, gear hubs to get either 6 or 8 gears. I really like the hub becuase its so simple requiring little maintainence or know-how.

what is the best way for a person who can barely change a tire to get more gears? A new bike ? a retro fit? There seem to be fiddly ways with de-railleur on the front and hub on back, something called a steve parry retrofit, old and new sturmey archer hubs, of 6 and 8 gears, a BWR wide range hub (which on this forums seems to come under some fire for really be a 3 speed - which i dont get!) and many others

I guess i just want it simple like i have - am totally flummoxed by the whole thing with a lot to learn.

Any help or advice or explaination would be really apprecciated

cheers
Naz

invisiblehand

Depends on how much money you have to spend.

My experience with the Brompton would be to avoid a front derailer. The last thing the bike needs is another cable.

But I think that you already have a gist of your options.

(1) retro-fit a six speed ... at one point I thought that this was straight forward. but recently it seems that the six speeds have SRAM hubs while the three speeds have Sturmey Archer hubs. someone more abreast of recent Brompton updates can probably be of more service here

(2) have someone install an eight-speed hub in the rear. probably the most elegant solution in my opinion. Somnatash had this done with the SA 8 hub ... do a search to find the relevant thread. I have seen pictures of Steve Parry jobs where the rear triangle is replace and a more high performance hub is installed.

(3) install a Schlumpf bottom bracket drive.

More generally, I think that you can get better details of Brompton upgrades at BromptonTalk.

EvilV

With all due respect to Invisiblehand's opinion about front mechs, this has worked very well for me in a hilly city. Sadly, the smaller front chain ring simply reduces my gears so that I get approx the following gears:

52 tooth front (80", 60", 45")

39 tooth front ( 60", 45", 34")

I know I only get one different gear, but the point is that the new one can get me up just about any damned hill I meet. It makes the world of difference and for that I am at times pretty grateful. It also works faultlessly, changing up and down with one hundred percent effectiveness and not the least fuss. It was easy to fit and and the new cable went alongside the others like a dream. The clamp is expensive, but the front mech, friction bar shifter and cable were as cheap as you could wish for. Being as my bike is a Merc (Brommy knock off) I was able to take advantage of ultra cheap alloy front chain ring for less than a fiver from the importer, but you will get yours for about six times the price from B. I have done 3000 miles with this configuration without ANY attention to the modification. It just works and flawlessly. It cost me about £50, but I used a second hand friction shifter and cable and a cheapo front mech. The whole thing bolted on in about twenty five minutes and I didn't even need to break the chain - the mech cage unbolted at the back to let the chain in and then fastened right up again. It was dead easy once I got the stuff and the Merc rear chain tensioner managed the difference between the two chain rings easily, so I suppose the Brompton one will too. There is a tiny issue of chain line but it is minuscule and I find no problem even though it is slightly out of perfect line on the big chain ring.


The clamp came from Steve Parry but by an indirect route via a Bromptoneer who had intended to fit the mod, and changed his mind for some reason I don't know or care about. Good Luck with yours.

A suitable front mech is the Mirage 9 speed. Costs a tenner.

https://cgi.ebay.co.uk/06-Campagnolo-...ayphotohosting










EDIT:

If you don't want to go the whole hog, just stick on a 39 tooth chain ring on the inside of the spider and change it by hand, but you will get dirty hands in doing it. My chain rings are mounted outside and inside the crank spider - better just check that will work on the Brompton crank. I think it will since I know Bromptoneers do this mod.

nazarus

Firstly - thanks to both

Invisiblehand -

1)I think the problem with the 6 speed is that it doesnt seem to give me much higher or much lower gears but rather more gears in between - which is not what I'm after really. I just want lower and higher than I already have.

2) 8 speed - expensive but could be the answer but I just need to find out if it will actually help me or just give me even more gears within the range I already have ?

3) Schlumf - expensive but again - I dont understand wether this gives me greater range or simply more gears in the same range. Sorry if I'm making hard work of this but just dont quite get it !

EvilV - thanks that certainly does seem the cheapest and least invasive option by some margin......even if i only get one more gear, it's the low one i NEED and the higher that I merely want

tudorowen1

Best thing you can do is sell the Brompton and get a proper bike like a Bike Friday Tikit..simple..

EvilV

LOL

K6-III

The new Sturmey 8 W will give you 325% gear range, compared to the 177% you have now.

With the 19t sprocket and properly small front chainring, it should be workable.

feijai

Now, now...

EvilV

Is it narrow enough to fit into the Brompton rear triangle, and is there enough clearance to fit the larger sprocket?

Then there is the question of how the chain tensioning system will work with that sized sprocket. The existing chain tensioner is essential to deal with the way the rear end on a B tucks under the BB when the bike is folded. This makes the chain go very slack and it will drop off or dangle unless a tensioner takes up the slack. I mention the rear sprocket size since the tensioner has very small clearance between the fixed jockey wheel and the rear sprocket which is about 13 or 14 teeth and has next to no clearance with the 14 tooth one. Maybe you know this and have solved these problems already, but if not, they will need to be dealt with in fitting the hub you recommend.

Cheers.

invisiblehand

If you change the cogs in the rear, you can get a wider range than the present setup which I think is a 13/15 combination. Perhaps you can swap it for a 12/16 or 12/17.

As someone else already wrote, an SA 8 would increase your range quite a bit.

If you want to get a better idea of gear inches, your present gear range, and the effect of the alternatives, here is a good place to start.

Sheldon Brown's website will be helpful too.

The front derailer setup is more useful than the "one more gear" implies. Essentially you have two modes ... flatland and climbing. Within reason, you should be able to change the chainrings/cog to match your needs. Not too bad an option in my opinion. But as I wrote earlier, all of the cables become a mess IMO.

LWaB

I understand (haven't tried it myself) that the undished 19t cog won't fit on the latest SA8 hub, due to a lack of chain clearance. It also is slightly wider than the previous SA8, requiring more widening of the rear triangle. All in all, not a trivial project to fit a SA8 to an existing Brompton.

EvilV

You can get a lot of advice at the Yahoo Brompton Talk email list.
https://www.foldabikes.com/Talk/BromptonTalk.html

SesameCrunch

Hah! I double dare you to go onto the Brompton Yahoo Groups site and make the same statement!

SesameCrunch

I did the same as EvilV, but even cheaper. I didn't install the front derailleur. Just added a 39t front ring. I use my feet to kick the chain down to the smaller ring when I really need a lower gear (which doesn't come often). When I have to shift up, I do it by hand. It's not elegant, but as you say, it's only when you really need a low gear occasionally.

Jerrys88

I added a 28t front ring to my M6 and just like you, Sesamecrunch, I shift down with the heal of my foot. To shift up I simply bring a short stick along or look for one on the ground along my route. It takes all of 10 seconds to hop off my bike and move the chain back to the larger ring using the stick. It was a good, reasonably priced modification, but then I only need to use it twice along my commute. Best part is that I get to tell people my bike is a STICK SHIFT! If I was biking regularly in a hilly area I'd definitely look into a front derailleur though.

ilovebicycling

The ultimate Brompton upgrade for me would be a Rohloff Speedhub. Quite expensive and one would have to have it done by someone who knows his way with wrenching on bikes.

If I were to tour long distances with a Brompton and have the money, I would go that route.

I know Kinetics does it, but they don't list the price on their website:

https://www.kinetics.org.uk/

I have also heard that you can order a rear triangle with widened spacing to fit an 8 speed hub in the back from Taiwan or Japan.

Oneday, someone will outfit his Brompton with the Swiss Mountain Drive in the front and a Rohloff Speedhub in the back. The Universe will surely implode from that cosmic event.

K6-III

The 116mm OLN 28h model is still available for the new XRF8-W, so it should be possible to fit. As for the 19t cog not fitting, this is the first I've heard of it.

invisiblehand

On the Brompton Talk forum, I recall that they discussed the problem -- intermittently of course -- for well over a year. We sold our bikes and I stopped paying attention to the issue. Then I heard that Kinetics was offering an SA 8 version of the Brompton. Somnatash has such a Brompton now.