Bike Forums - Replace single 52T chainring with compact 56/34?

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Replace single 52T chainring with compact 56/34?

Hello

Out of curiosity, is it possible to upgrade a Dahon Mu D8 from a single 52T chainring to a compact 56/34 and get a development of 1.6 - 7.5m?

I happened on this page that sells even bigger chainrings:
SE Chain Ring, 34 - 60T, Bolt Center Diameter: 110mm

What are the limiting factors when attempting that type of upgrade?

Rear derailleur + cassette?
Chain line
Other factors?

Since it's for touring, it'd be great to have a bike that can offer eg. 1.5 - 8.0m development without the weight of an IGH.

Thank you.

Schlumpf Speed drive with a 34t chainring acts like a 54t when you kick it into overdrive , and it shifts instantly.
at any time even bogged down on a hill (I run a mountain drive - Brompton, bigger reduction gear 2.5:1_54t /'21.6't)

your BB shell edge has to be Chamfered as the grip is there to transfer the Torque.

but once done its a low maintenance setup.

their High speed drive is a 2.5x overdrive, the speed drive is 1.65x..

it is certainly possible to put a 110 bcd double crank on It .. needs you to be able to get all the chain tension slack
to make that very big up shift.. so down hills is where I get out if granny gears..

without a FD you use your fingers and stop the bike .. I got a custom FD bracket , to put a double crank on my brompton

the MD works better .. will sell the Brompton clamp on FD bracket .

Read (here) that There is a similar add on for DaHons. then you get a braze on FD, & a thumb shifter..

I'm not sure that a front derailer that can shift a 22-tooth jump. (I know Sheldon Brown did something like that) I imagine if you got it to work the shifting would be awkward.

If it's a square tape crank, then you'll have some flexibility with the chainline. I would not worry about that at the moment.

If the rear derailer is a short cage model -- Dahon NEOS is super short -- chances are you'll have issues with it's capacity with a 22-tooth jump in the front.

From The Art Of Dérailleur Selection ...

Quote:

In selecting a rear dérailleur, the first consideration is how wide of a gear range it will be required to shift. Most 10-speeds have the same high gear (52 teeth on the front with 14 on the rear). The major difference between types of gearing is in how low the lowest gear is and what kind of spacing is used in between.

Dérailleurs usually are rated in terms of "tooth-difference capacity," a number that represents the dérailleur's capacity to take up slack in the chain. To find the minimum tooth-difference capacity needed for the gearing you have selected, subtract the number of teeth on your smallest rear sprocket from the number of teeth on the largest. Do the same for the front sprockets, and add the two numbers. For example, if your rear sprockets run from 14 to 26 teeth, the rear difference is 12. If your chainwheels are 36-52, the front difference is 16. Adding the figures for front and rear, we get a total difference of 28 teeth. If you get a dérailleur with a 28-tooth capacity or more, it should handle the range. If you use a dérailleur with insufficient tooth difference capacity, the chain will be too slack in some gears or too tight in others and you probably will not be able to get it to shift properly.

My guess is that you'll have to use a medium cage rear derailer to get decent performance.

Does your Dahon have a derailer mount? Or will you need to pick up some mount?

FWIW, while I appreciate low gears for touring, I would use a 56 39 combination. With a 32 bottom you still have a low 20s GI bail-out gear but you'll have considerably better shifting in the front.

Thanks for the info.

The derailleur is already pretty close to the ground :-/

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