DH and I have been riding the Bromptons for a couple of months now and we are very happy. He takes his on the bus every day, so I really scored! I'm happy that it is making his commute so much easier.

I have a 3-speed Raleigh Sports that we both love. My two other bikes are an 8-speed Retrovelo Paula, heavy but geared low enough to get up really long hills and a Nuvinci-hub Raleigh SuperCourse, which is overkill for my riding.

I decided to go with 3-speed Bromptons because 95% of our riding is multi-modal, picnics, and shopping. I planned to consider a retrofit to a BWR hub+derailleur or a Schlumpf Mountain Drive.

Some of the very steep hills are defeating me, and it's time to try to add some granny gears. The gearing is already -18% (44x14) on our bikes. We don't need anything higher. We do need lower.

I spoke to David at Electric & Folding Bikes Northwest yesterday and he told me that Schlumpf no longer manufactures the Brompton specific MD, but no big deal because they can be installed on Bromptons.

Using a calculator that I found at https://xldev.co.uk/bgc.html, I came up with the following:



I think the SMD is the best choice for me. I get a wider range than a BWR+derailleur, and more importantly, it is all LOWER gears.

With a 50 I get:



Any opinions?

15-17" is pretty ridiculously low;my Safari's granny is a touch under 20",and I've only used it a handful of times(and I guarantee I've got hills as bad as you do). 69-79" is also pretty low;I'd constantly spin that out going down my local hills.

You'll want to pay close attention to your gearing before dropping the dosh for an expensive upgrade like a 6spd conversion or Schlumpf. How bad is it getting up your hills? Might be a good idea,in terms of both time and money,to swap a 16t cog on the rear and see if that fixes things before doing major surgery. Also,how much have you been riding(daily,weekly)? When I first started out on my old commute with a hybrid,it killed me. Took me a good week and a half before I could get into work without having to get off the bike and push,and a good three weeks before I could do it coming home. A few years later,I got tagged for weekend duty,and over the course of two days had to make the round trip 5 times on a cross bike(36/28 'granny') and managed ok.

It would suck if you spent all that money on upgrades,only to find out in a year's time you don't really need them,and in fact hate spinning out on the downhills.

Really? Like this one, where my sister lives? https://www.seattlepi.com/local/slide...to-1668018.php

I don't spin out downhill now because I have zero interest in riding that fast.

Spinning out on downhills -- not going to happen. Ever. Even when I rode 140 miles a week and kicked everyone's ass on the uphills, they all beat me going down. And not riding super fast served me well the day an ******* decided to cross a double yellow and hit me head on. But that's another story...

I do know my ability well, and I also have stories of hills absolutely kicking my ass and then becoming effortless. These are much steeper hills and I am older. I need lower gears. Maybe I don't need 15"-17", but I seriously do not need any higher. I have higher on three other bikes. I never, ever use them. I never will. I only ever rode fast because I had to to ride with the group I was riding with. I don't want to do that anymore. I live a continent away from them and I just want to get around town and maybe ride to a campsite on one of the islands.

I don't think a 16 is going to do it, but I'm not sold on the Schlumpf, either. Maybe I do the six speed conversion. It would ALSO suck to spend the money on that and find it not low enough for my needs.

I'm going to ride some of those hills on my big bikes and do some calculating.

Speed Drive, is the other option, with a 34t chainring, the 1.6x over drive gear is like the 54t chainring.

their mounting is a bit different, the BB shell gets chamfered edges.
a compressible aluminum conic washer grips the 2 surfaces,and the BB fixing compresses both ends..

I got a MD from this guy , but several years ago
https://foldabikes.com/PriceListHTML/...ountdrive.html

Im using the 54:15 gearing, though the 13 or 14t could be used . the chainring BCD is 130
so other chainrings are possible like a Surly Stainless steel 50t.
The heel and Bar lever double shift works really well.. and Quick, enough,

your contact may be correct about discontinuation, by the Swiss Company as the CHF stays strong
Euro and dollar need more to buy them as they lose value**. ( harder for CH manufacturing.)
they are said to be shifting making them to Germany for this reason.

**[& the plutocracy moves their money to Swiss numbered accounts]

a further thought , the standard MD uses a coaster-brake like strap
around the chain stay, the Brompton version uses a Button, that sits on top
of the piece where the rear Hinge pivot axle is, behind the BB& seat post,
perhaps the 2 small parts can be ordered and exchanged for the standard type's parts.

Or, If you put a sturdy metal Knob in the bolt hole , for the band strap
in the standard torque arm, that would work..

https://www.schlumpf.ch/hp/schlumpf/schlumpf_engl.htm


used Sheldon's gear calculator:

Brompton . MD 54t, / '21.6t'



hub cog on Aw3 ... x .75,1,1.33
L; N; H


13t
50.1/20.0; 66.8/26.7; 89.0/35.6


14t
46.5 18.6; 62.0/ 24.8; 82.6/33.1


15t
43.4/17.4; 57.9/23.1; 77.1/30.8

FWIW Patterson Metro uses a 28T cog, and the same 1.6X overdrive makes a 45t
It is cable shifted from the handlebar, No experience on how you would adapt that to a fully housed cable
as required by the Brommy.. Your LBS may help Fabricate a technique,

also IDK what the crank chainline is..

Other people like Steve Parry in UK have clamp on FD mounts for Bromptons
to run 2 chainrings..

There is, of course, the simple heel Kick down, finger up-shifting by hand, with out a FD.

Hah! That looks like my friend's driveway. I used to do a hill much worse than that almost daily for 7yrs. Don't have the geo data to pull up(shame I'm not still assigned to NGA),but from the pics DC is either equal or worse. Note,I also live at the second highest point in DC.

15-17" is really super low. Like,you'd have trouble going fast enough to maintain your balance. Lowest gear on a standard MTB setup(22/34) is 16.8";my '05 BBU has those gears,and I could never imagine using it unless I was pulling a 100lbs trailer.

Schlumpfs are crazy expensive,like $600+. So if you're going to go that route,it might be better to spend the money on another folder with a derailleur drivetrain you can easily modify(cassettes and rings are comparatively cheap).

Have a MTB,or know anyone with one you can borrow? Ride one of those up the hills,take note of the gearing,and plug the numbers into a calculator to see what you really need. Then check into your options. Does your Brompton have the new standard 130BCD ring crank? If so you can go alot smaller on your front ring for cheap. And if not,swapping cranks is still going to be cheaper than either a Schlumpf or 6spd conversion.

There is the Bike Friday Tikit , in a BTO . same 349 wheel.