Chain tension help?

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CRASH

CRASH

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I don't deal with coaster bikes much, so I'm a little stumped. My son's chopper had the slick rubbing the front of the chain stays with the chain pulled tight. There was still room in the drops. So I added 1 link to his chain. The wheel pulls all the way back in the stays, but the chain won't tighten. So it's floppy. My son was just riding and the chain fell off in a turn. The only solution I can think of is get a new chain and hope it's slightly shorter? But "hoping" isn't a solution. Anyone got an idea?


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Since it needs to be way back in the dropouts for the slick to clear, change out the cog to one with one more tooth. It'll be a little easier to pedal too.
 
Good advice there. I think I have some 18 tooth Bendix if that is the hub your running.
 
Not sure, but isn't there a solution called a half link? I've never used one, but I've heard them mentioned.


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Had that happen twice on my Felt wheels with the offset cog. Don't know of a solution.


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What kind of hub is it? It looks like a Shimano sprocket. Is it a Bendix hub? I bet those raised sections on the sprocket won't let the ring seat properly. If all else fails try grinding them off with a dremel tool..
 
If it won't work with the larger cog, change the chain wheel out to the next smaller size, and change out the cog to less teeth also to keep the gear ratio about right. You may have to take out a link in the chain to get the right tension. I did all this trying to get a coaster hub to work in a bike with a vertical dropout, it finally worked after a couple different combinations. Yours is about the same problem because of the big tire, there's only one spot where it will work.
 
I didn't see a 21t cog on Ebay. Was one ever made? I do see 22t, but wouldn't I have to add another link for the addition of 2 teeth and be right back in the same boat? Conversely, wouldn't dropping down to a 19t require me to take a link away and put me right back in the boat of having the tire too far forward?

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The extra tooth may not add the same length as one link, and vice versa. I did all kinds of combinations before I found one that worked. You could make extensions for the dropouts, but that's a lot of effort also, but you would clear that slick and have plenty of room for adjustment.
I looked around and found a 21 tooth cog, but 15 bucks is kinda high priced. It could be that cog with just 1 extra tooth would need a link added, then it's back to square one again. A headache for sure.
As for the retainer spring, make sure it's seated in the groove tightly. If it's a little out of the groove it may be bent or stretched too widely.

21 tooth cog:
http://harriscyclery.net/product/shimano-sprocket-for-internal-gear-coaster-brake-hubs-1362.htm

Dropout extensions:
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I think what I'll do tonight is put the 19t cog on their and try to adjust the chain accordingly. A little harder to pedal, a little harder to wheelie, which he can't do anyway yet, but at least if it works it'll be rolling and out of my hair a while. I need to work on other bikes. :)
 
How many years have I worked on bikes? I've never known about a half link. Have never needed one either until now. Interesting! I'll keep that in mind!

I didn't have time to work in the shop tonight. I'll tackle this soon.
 
Update: Figured out that the spoke protector was the cause of the sprocket retention ring not seating, so ditched the protector as it was there for looks only and the Fun Wheel gives all the visual it needs. So I put a 19t on the hub and dropped the chain back a link. The original problem of tire rubbing is back, and now the hub sounds like absolute crap. It's "chunking" for some reason.
My solution: I was thinking of pulling that Taiwan hub out of there and threading in a Bendix I'm going to rebuild from the parts I have. Then I realized I have a whole rear wheel for sale, so maybe I'll just use it! But it's a 20h rear off a girls bike, but it's got a Bendix in it. I'll just need to true the wheel, adjust the hub, swap the tire and Fun Wheel and I should be golden.

We'll see.
 
The rear wheel I have had some really rusted nipples, so I couldn't true it. So I ended up cutting out those spokes, rebuilding the hub, and relacing with some black leftover spokes I had. So all that mess is now done. But I'm still stuck with the chain problem. So I've ordered a half-link and I'm going to put the 20t cog back on because it'll be easier for him to pedal like that. Hopefully the half-link resolves the last of the issue.
 

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