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Old 09-03-06, 08:04 PM   #1
odyssic
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Brompton Gearing Upgrade Options

Hello,

I just joined. And I just got a 3 speed Brompton and am looking to substantially increase gearing for a tour next spring in a hilly region. Can we go over my options and the pros and cons if anyone has knowledge in this department?

Rohloff Speed Hub
Swiss Mountain/ Speed Drive

I did get the 3 rather than the six speed Brompton to keep the bike light and simple, easy to maintain, so I'd like to keep it that way as well as far as possible. So far it weighs about 24 lbs with all the touring racks and things.

I was thinking the Mountain gear, but folks say the speed gear might make more sense for a small wheeled bike.

Any advice appreciated.

Thanks!

Steven
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Old 09-03-06, 09:40 PM   #2
Wavshrdr
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I don't know why you didn't go with the 6 spd up front as your other options will weigh more and not provide much additional ability. I don't think you can get a Rohloff in a size to fit a Brompton. All the options you mentioned are quite expensive.

If you wanted to keep it light, the 6 spd was a better way to go than the options you listed. You could have customized the rear sprockets with different sizes and had a light efficient gear system. In general the Bromptons are geared too tall for hills from the outset. I'd suggest a retrofit of a rear Brommie derailleur and get the sprockets you need for hills.
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Old 09-03-06, 10:00 PM   #3
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Or change the front chainring/crankset to a lower number of teeth.
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Old 09-03-06, 10:40 PM   #4
odyssic
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Well, the six speed refines the gaps in between the gears but the high is barely higher and the low isn't much lower. I'm thinking of modifications for hilly touring.

Thanks!

Steven
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Old 09-03-06, 10:48 PM   #5
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Hi

This link might give you some sarting threads to answer your question:

http://groups.yahoo.com/group/Brompt.../message/28284

Edd
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Old 09-04-06, 10:42 AM   #6
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Quote:
Originally Posted by odyssic
Well, the six speed refines the gaps in between the gears but the high is barely higher and the low isn't much lower. I'm thinking of modifications for hilly touring.
The three speed has a gearing range of 178% while the six speed has a range of 213%. I opted for the six speed with optional lower gearing, which gives you a 12% lower low gear without sacrificing anything in high gear. This gearing is very satisfactory for hilly rides - at least for me. I haven't ridden the bike loaded down for touring, though, and that may make a difference.
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Old 09-04-06, 02:28 PM   #7
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I guess you are running a 50T/13T combo on the 3 speed? If so, I would go with the Mountain Drive. You will get approx 19", 25" and 34" at the bottom end which should get you up most gradients when fully loaded.

With this set-up the top-end remains unchanged, and therefore not particularly tall (mid 80"s?), but you could bump all the ratios up with a 54t ring.
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Old 09-04-06, 05:54 PM   #8
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Some of you missed my point. There are aftermarket gearing upgrades based on the 6 speed version. You can have a wider gear range with the 6 speed than what Brompton gives you just by going with different rear sprockets. The rear derailleur will apparently handle it. You can have lower AND higher than the stock gearing. Most common special ordered option for Brompton is the lower range gearing option.
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Old 09-05-06, 02:28 AM   #9
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Mrs LWaB has a front changer on her Brompton (48t & 32t) with 14t SA 5-sp hub. Another option with some negatives (everything has some negatives).
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Old 09-05-06, 03:25 AM   #10
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Quote:
Some of you missed my point. There are aftermarket gearing upgrades based on the 6 speed version.
That is correct, but as the OP was fairly adamant that he wanted to stick to a 3 speed hub (which i agree is not the best choice for his needs) outlining various options can only help in the decision making process.

I have mentioned the Highpath wide-ratio sprocket upgrade in past posts. It is a fairly cheap upgrade and if you have reasonaby good mechanical skills, it can be fitted with little probem (maybe a bit of machining will be needed however). The only real drawback is that sprocket life on the 12t is reduced - worth taking into account if you are touring longer distances.

Last edited by Fear&Trembling; 09-05-06 at 07:56 AM.
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Old 09-07-06, 03:10 AM   #11
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Quote:
I'd suggest a retrofit of a rear Brommie derailleur and get the sprockets you need for hills.
I am not sure that you can retrofit the derailleur system to the 3 spd SA hubs Brompton have reverted to. If you have a Sram hub, it will not be a problem.

@odyssic - why did you choose a 3spd Brompton for touring purposes? What have you decided?

Last edited by Fear&Trembling; 09-07-06 at 08:30 AM.
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Old 09-09-06, 11:29 AM   #12
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I too chose the Brompton with only 3 speed because I wanted to keep things simple. I also have my other present bikes (Dahon Boardwalk and a old Phillips) using the simplier drivetrain too. Before those bikes, all my bikes were 10 or more speeds derailleur bikes. I live in an ever-changing terrain from straight flat one to large hill at it's base runs a street (so I cannot get a running start madly pumping up the flat part before I go up the hill).

This is what I have experienced:

As suggested above, my chainrings all are in the mid-forties (Dahon at 44t, Phillips and Brompton at 46t) and the cogs are (Dahon-14t, and Brompton-13t, I don't know what the Phillips is but I think that it is similar to the Dahon's). The Brompton will eventually be changed to a 16t or even larger cog diameter. I think it will improve the hill climbing a bit for the Brompton.

Check tire pressure to see it is at the maximum suggested on the tire's side. I am still suprised at people buying the best tires around and not checking pressure everytime they go out with the bike.

I keep my bikes light (except for the Dahon). I tend to limit what I carry with me to the basic needs of the particular trip I am doing at the time. My Phillips only has fenders/mudguards, and the Brompton came stripped down already at purchase. The Dahon is fully accessorized but adds a good 4-5 pounds.

I take things alot more slowly now. I don't push myself as much anymore. If I need to, I do walk up a hill now rather than riding even more slowly up it. I don't try to impress others. I want to take care of my body for another 50 or so years (and ride a bike too). I rarely have to exercise this walking up option 99% of the time. I do usually find that I can easily make it up the hill that I am going up on. The other 2 factors listed above pretty much garentees that I am able to tackle any hill. Or I simply hitch a ride on another vehicle going up the steep hill. That is one of the beauties of the little bike. It gives you the most flexiblily way over any bike-even other folders!

Last edited by folder fanatic; 09-18-06 at 12:05 PM.
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Old 09-17-06, 05:16 PM   #13
odyssic
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Thanks for all the info. I'm leaning towards schlumpf. I didn't go with the derailleur because I've always used them and they always seem to go out of whack and I thought I'd just try the sturdy hub gear, which I've never used. Also, was thinking of fitting Mountain Drive anyway if I like the bike. Wouldn't want the mountain drive plus shifters at each hand. Too many gears!

I live where there are some very steep hills and am practicing spinning more so maybe I'll need much lower gears. Many Brompton people have suggested the Schlumpf mountain drive with 54 t chain ring. Sounds fairly simple well engineered and easy to maintain. Just the price. I'm less worried about investing in the folding bike because I should be able to always keep my eye on it, but even so it also seems easy for someone to steal so I didn't want it to be that pricey.

Anyway, I think of it as replacing a car so that is my rational for spending so much I guess, the titanium and the schlumpf perhaps. That will give an evenly spaced ratio of 21 to 93, 6 gears with the 54t. 443%. If I'm calculating correctly.

Steven
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Old 09-17-06, 05:19 PM   #14
odyssic
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Also the seller influenced my decision some. A single speed bike rider. And my mother used to have a trainer that would win bike races on a trail up a mountain on a 3 speed cruiser! Not loaded down, but still. Physical condition over gears.

Steven
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Old 09-20-06, 10:29 AM   #15
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There's a guy in the UK called Steve Parry that does various high-end Brompton customs. He does I think do a Rohloff but it involves re-engineering the whole rear triangle to accept the wider hub and tweaks to make the fold / latching still operable. Kinetics in the UK offers bromptons with the schlumpf retrofitted if you wanted to find out more...

http://www.kinetics-online.co.uk/
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Old 01-07-08, 03:59 PM   #16
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Wide Ratio gears made by Highpath

see also thread Brompton Wide-ratio gears for a light and cheap option.

Jos
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