megavovan

Hello guys!

I bought 2009 Dahon Boardwalk Folding Bike. Here is the complete spec sheet for it. Most notably, chain and cogs are 1/8 inch wide (not 3/32).

My "perspective" gear inches table (read on...)
From the get-go I don't like it's low gearing: 44x14, at 20" wheels, which gives me just 63 gear inches. I have my road bike set up for 78 GI and it's a tad too tall, so I want around 74 GI on this folder.

First I took apart the rear wheel, and found the cog: Three Cogs: top one with 3 notches is one that was on the bike. What is this cog called and where can i buy 12 or 13T one of that type? (two other cogs are: down left: a 12t from a 7 speed casette and down right is single speed splined 3/32 16T cog. neither fit.)


Now, having no luck replacing cog I want to replace the front chainwheel ( pic 1 pic2 pic3).

How do I replace the chainwheel? What tools would I need? Please show me example of chainwheel I need to buy (I want BIG! 52t and 48t maybe?)


Thank you in advance!

AEO

use 20x1.75", lower end dahons are actually equipped with 20x1.5" or 406x38, but close enough.

for SS/FG, if you like your knees, and with that bike, you only want around 60~70GI.

megavovan

Hi dear mechanics, I finished editing the OP (oops I hit the post button too early before).

I live in the flats, and the bike is single speed with coaster brake. I have been running my Road bike with 78 GI for a couple months.

So how would I change the chainwheel? What chainwheel should I buy? What is the rear cog type called? (If I place 12 or 13T I may keep original chainwheel).

operator

The boardwalk is square taper bull**** crankset. You can buy anything that will take a whatever chainring size you want. If you want a wider range cassette. Consdier changing out your shifter and a different wheel to accept more cogs in the back.

Anyways, i've built and warrantied more dahons than anyhone else on the face of the planet. ****ing.

megavovan

There is no casette, no shifter - it is a single speed and i want to keep it that way, just bigger chainring or smaller cog.

AEO

everything about the drive train is as standard as any other bike. you just need a crank puller to switch out the crankset.

it uses a JIS square taper BB, so get whatever you want to put on it.

I'm not sure about the rear cog.

52T for 130BCD cranks are so easy to find as well.

megavovan

Alright, so I went to bike shop today and bought the crank puller ($20) but then in my other Dahon thread in folding bikes members pointed out that these cogs are 3/5 speed coaster hub cogs and they are in Sturmey Archer catalog - I went there, found sprockets page and looked up model name ( HSL713 or HSL854 for 13T) and found it in UK bike shop.

Later on another member recommended me to search eBay for "KORE BMX COG", which they have 12T and 13T.

I bought the KORE 12 and 13T for $15 shipped for both.


Now as for changing gear upfront, I'll need entire crankset (crank arms, "spider", ring, and bolts for ring), because I don't think they make one-piece cranks bigger than 44T.


edit: I'll wait for 12T and 13T to arrive and see if it's enough for me.

badmother

You do not want one-piece cranks, that means both crank arms plus BB spindle is all made in one piece, and on such bikes the Bb shell is normally bigger than on your bike. I think you want a one chainring crank.

If you buy a new front ring you should first find out if you can keep the crank arms and just buy a new ring to fit on it. Your pix do not show what is behind the plastc. If the ring can be swapped out you ned to buy a ring with the same amount of holes for bolts but also with the same distance between the center of the holes. Thre is standards for this, I think Sheldon explains it on his pages. If this is stock with the bike Dahon should be able to help you.

Remember single chainrings are different from the double and tripple rings. I am curently using a modern (from a MTB triple) front ring (+ crank arms) on a IGH folding bike with similar chain and rear cog to yours. I do this to find the right size for the front ring. It creaks and complains, the chain and front chainring is not happy to be together. On a similar bke I do the same, but here the front ring (+ crank arms) is from an older 10 speed bike. Looks like this works good, no creaking and complaining.

I tend to use cranks and chainrings from old 10 speed bikes on my folders, I then put "hybrid range gearing" on the oldies (hilly area). This way I`ve got cheap cranks/chainrings for the folders. This works when you can try it out first. If you need to buy, and maybe buy online it might be better to go for the right stuff.

Edit: The rear cogs you asked about comes in two (at least) main types. The ones with a dish and the flat ones. Sone hubs only take one of the types. I think the dished ones can be found down to 16 teeth but the non dished ones can be found smaller. Maybe this is why you did not get quick "spot on" answers.

megavovan

I appreciate your expertise, badmother!
I am sorry I did not update this thread. I installed a 12T, non-dished rear cog, kept the stock front 44 (by the way there is no bolts/spider, just ring and the crankarm in the middle). This gives me gear ratio about 69 inches, which is nice. I'm satisfied