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Old 05-25-12, 08:03 AM   #1
pengyou
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Dahon Speed needs a new chainring

I just shipped my Dahon Speed (7speed) from Shanghai to Taiwan and the chainring was bent in the process. Is this part something that I can get in any fairly good bicycle shop or is it a part that I have to go back to Dahon for? Also, there are some very small chips in the paint on the underside of the tubes of the bike. I was in a toy store and noticed that they sell a paint for models that is identical to the baby blue of my Speed. Can I lightly sand the chips, paint them with this paint and then put some kind of acrylic (marine grade) over it? Also, my first gear is so low that I never use it. Can I replace the front gear with a gear that has 3 or 4 more teeth?

Last edited by pengyou; 05-25-12 at 08:12 AM.
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Old 05-25-12, 10:32 AM   #2
ttakata73
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I just looked at the Dahon website and it seems your chainring is not a standard 5 bolt type.
We would need to see how that chainring attaches to the crank arm and spindle.

You can get new crank arms with the 130mm BCD standard pretty cheap, maybe its time to upgrade?
With a 130BCD crank arm you can bolt on hundreds of ring and ring guard options, it's probably the most popular chain ring standard.

Sure, you can clean and paint the chips over.
I suggest researching it on the web.
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Old 05-25-12, 05:56 PM   #3
pengyou
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So you are saying that it might be better/cheaper/necessary to replace the whole assembly? Chain ring and cranks?
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Old 05-25-12, 08:04 PM   #4
violini
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The price varies considerably, for example:
http://goods.ruten.com.tw/item/show?21009157904569
http://goods.ruten.com.tw/item/show?11091014855736
http://goods.ruten.com.tw/item/show?21205074779813
http://goods.ruten.com.tw/item/show?21007124594049

You can also replace the gear only, if the crank frame is not damaged.
http://goods.ruten.com.tw/item/show?21106107824282

In March, I traveled from Taipei to Beijing (China International Airlines) and Beijing to Toronto (Air Canada). I disassembled my bike and protected the parts with card board and put them in a soft luggage together with my clothes, nothing happened to the bike.

Last edited by violini; 05-25-12 at 10:39 PM.
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Old 05-25-12, 11:13 PM   #5
BruceMetras
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Originally Posted by pengyou View Post
So you are saying that it might be better/cheaper/necessary to replace the whole assembly? Chain ring and cranks?
I'd remove the plastic pant guard from the chainring and then try to lever it back straight again.. that costs nothing .. and if it doesn't work, you're not out anything.
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Old 05-28-12, 10:45 AM   #6
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^^^ Yes.

If it's a Dahon Speed D7, it's square taper. Use a crank extractor to pull off the crank, put chainwheel in a vice and gently persuade back into shape with a rubber mallet. If it's so bent it snaps, you've lost nothing. Once straightened, its weaker than it was.

Paint chips? It depends on how pristine you want the bike. My local street market sells nail polish in every colour, it's good for touching up minor spots. Car paint touch-up sticks work, too. The toy store paint willl be fine, it doesn't need a top coat, but you can add clear coat over it. (Car store - just mention paint chipped.

If you want to replace the chainwheel, the French Stronglight ones are available in a bunch of square taper sizes. (They are used on Bromptons). Brompton cranksets may also be suitable and come in two teethings. You may need a longer chain. Otherwise, your local Dahon dealer is your friend.

Regarding the low first gear, if you change the chain wheel for larger one, you move all the gearing up and need a new chain. The real question is; is the 'hardest' gear not long enough?
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Old 05-28-12, 12:56 PM   #7
JGaerlan
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If your chainring is welded to the crankarms, might be cheaper just go get an off the shelf crankset. Sometimes, buying individual rings and arms becomes expensive.

If you want to stay with stock 53T, buy a double 39/53 and pop the small ring off. You may have to buy a single ring bolt. Position the ring correctly too so chain angle is not skewed. If you want to shift all gears down, maybe get a triple 30/42/52 and use the 42 or maybe a 26/36/46 and use the 46. Try googling the concept of gear inches and try to find out how low of a gear you need for climbing and what the corresponding high would be. By changing the front ring size, you can shift the RANGE either up or down. It will not give you a WIDER range.

I personally ride a 38T with the stock 11/32t on a P8 and I use it in San Francisco where it is very hilly. I like to borrow the wife's folder with a 30T. With this low of a gear, I can climb the steepest hill in the city sitting down. On the downhill, I just have to coast.
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Old 05-30-12, 06:49 AM   #8
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"If you want to shift all gears down, maybe get a triple 30/42/52 and use the 42 or maybe a 26/36/46"

This could of course mean changing the bottom bracket spindle, too, the cups of which, on the Dahon Speeds, needs teams of oxen to shift.
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Old 05-30-12, 11:03 AM   #9
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Meanwhile, back at the ranch...

You haven't mentioned model/year of your bike, but in any case, unless Dahon has gone even lower spec on their crank sets you only need the chainring, which would be either 110 or 130 BCD and probably 46 or 48 tooth.

My guess is it's a D7 and has an off the shelf alloy taper crank set. At least that was the case with the Speed P8 I had. Cannot recollect the BCD. Dahon also used to give you a small bottle of touchup paint with a new bike. Maybe check with them to see if they can still provide you with one.
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Old 05-31-12, 05:46 AM   #10
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Quote:
Originally Posted by snafu21 View Post
"If you want to shift all gears down, maybe get a triple 30/42/52 and use the 42 or maybe a 26/36/46"

This could of course mean changing the bottom bracket spindle, too, the cups of which, on the Dahon Speeds, needs teams of oxen to shift.
Has anyone actually done triple chainring on a folder with a cassette? I've had double and when on inside ring the chain was pretty close to the tire.
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