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-   -   Downtube 8H chain alignment (http://www.bikeforums.net/folding-bikes/457253-downtube-8h-chain-alignment.html)

BikeKraft 08-22-08 03:25 PM

Downtube 8H chain alignment
 
1 Attachment(s)
I have a Downtube 8H. New with the standard stuff on it. I'm wondering how aligned the chainwheel and the rear sprocket should be. I have another internally geared bike that has everything on the money, all ducks in a row. The Downtube has quite a noticable bend in the chain as it leaves the chainwheel. Looks like the chainwheel needs to move toward the down tube. Is this normal, no big deal or a problem? As I look at the bike all seems well with the frame and wheels. I have attached the best picture I am able to take with my camera. The green line was drawn in by me, it is fairly true to the teeth of the chainwheel. But due to the perspective it may be a little off. However it does show the correct direction of the chain as it leaves the chainwheel. Any downtubers out there that can set me straight?

makeinu 08-22-08 03:51 PM

Mine is like that and I know at least one other forum member's bike is like that too. You could try putting the chainring on the inner side of the crank spider and adding some spacers until it's straight (or another forum member put a one piece double chainring on the inside of the crank spider), but I don't know how much of a difference it will make to the operation.

jur 08-22-08 05:09 PM

The SA hub has quite a inward chainline. A fair few have moved their Mini's chainwheel to the inner position, me too. You could do it on that bike too. It is not sure if you would be able to keep the inner chain guard.

dschwarz 08-23-08 06:53 AM

I'm thinking of buying a Downtube 8H, reading the above comments I am not sure if the bike is okay as-is from the factory, or if this is a flaw that really needs to be corrected. Some perspective, anyone?

BikeKraft 08-23-08 09:06 AM

Quote:

Originally Posted by dschwarz (Post 7327690)
I'm thinking of buying a Downtube 8H, reading the above comments I am not sure if the bike is okay as-is from the factory, or if this is a flaw that really needs to be corrected. Some perspective, anyone?

Don't want to throw water on your purchase, I'm likely to buy a second one for my wife. She love's it too. I'm going to use jur's suggestion and move the chainwheel in. I know it's not what you want to have to do on a new bike and it may not be necessary. But there is just something in my brain that wants certain things to line up. Buy the 8H, it will put a smile on your face!

BikeKraft 08-23-08 11:32 AM

Quote:

Originally Posted by jur (Post 7325456)
The SA hub has quite a inward chainline. A fair few have moved their Mini's chainwheel to the inner position, me too. You could do it on that bike too. It is not sure if you would be able to keep the inner chain guard.

Hey jur,
if you're still tuned in. I looked at the chainwheel and it seems straight forward. HOWEVER! The 5mm hex nut or bolt seems extremely tight and I'm a little concerned with the amount of touque I would have to apply to get it to loosen. Any tips short of take it to the shop. I've removed chainwheels before but this just seems a little more snug.

BikeKraft 08-23-08 03:49 PM

I decided to turn up the mega-watts and remove the bolts. No problem, no doubt normal. I'm just getting more cautious with age. Anyway the process suggested by jur took all of about 20 minutes. All went back together including the inner chain guard. Now it looks much better to my eye though it could be improved still. I doubt I'll do any more with it. Well there are a couple more things I want to modify on the bike but, that's what bikes are for!

kaseyem 08-24-08 07:53 AM

Mine was like that too. I moved the gear inside, added spacers, and changed the bottom bracket, and now it is straight. I also added a used gear with the teeth ground down, to the outside to act as chain guard.


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