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-   -   Need help with IGH chain tension.. (https://www.bikeforums.net/bicycle-mechanics/857385-need-help-igh-chain-tension.html)

cycle.stig 11-12-12 05:17 PM

Need help with IGH chain tension..
 
2 Attachment(s)
So I bought a MEC Chance commuter bike with an Alfine 11 internally geared hub.
http://www.mec.ca/AST/ShopMEC/Cyclin...cle-unisex.jsp
When I got it the chain seemed to be tensioned almost perfectly. Since then I've ridden about 500 kilometers and the chain has begun to sag a bit. In the picture below I've used string to show how much sag the chain has. It's about half an inch. It looks easy enough to tension. The rear hub drop outs are on metal slides that ca be adjusted forward or backward to tension the chain.
I'm just wondering if the chain even needs to be tensioned. I've read that chains don't actually stretch and it's so new that I'm confused how it has begun to sag.
Any advice is appreciated.
http://bikeforums.net/attachment.php...hmentid=283346
http://bikeforums.net/attachment.php...hmentid=283347

Andrew R Stewart 11-12-12 05:48 PM

You are basicly correct in that the metal the chain is made of has not stretched. But each link has a bushing/bearing at each end and these do wear. Even a tiny amount of wear in each bushing vwill add up after almost 100 units. Additionally the cog and chain ring will wear a bit allowing the chain to settle into the teeth a little bit more. If you keep your chain clean and lubed then this wear will be initially faster then seem to slow down. This is just one of the reasons that a bike should be returned to the LBS for a tune up after a few hunderd miles. Andy.

FastJake 11-12-12 06:01 PM

+1 The chain doesn't physically stretch, but gets longer as the inner parts wear out. In any system without a derailer (fixed gear, single speed, IGH) there shouldn't be any actual tension in the chain but rather it should spin as smoothly as it would if it were slack. Then take out as much slack as possible without actually making it tight. I'm probably not describing this very well but hopefully that makes sense.


Originally Posted by Andrew R Stewart (Post 14941434)
This is just one of the reasons that a bike should be returned to the LBS for a tune up after a few hunderd miles.

I would change that to: This is just one of the reasons it's nice to know how to work on your own stuff when adjustments and problems arise.

FBinNY 11-12-12 09:14 PM

To built on Fast Jakes post. There shouldn't be any chain tension at all. The standard test for correct (non)tension is to move the center of the lower loop up and down. It should be free to move about 1/4" either way.

fietsbob 11-13-12 02:33 AM

Year around riding, I get a year out of a chain [53:16 turning a 20" wheel]

Larger wheel Circumference may not be same since 1 rotation covers more ground.

DieselDan 11-13-12 05:55 AM

You have sliding dropouts on the frame. Loosen the bolts, ease the dropouts back a bit, then tighten back up. Then you will probably need to adjust the shift cable. I don't know how to do that on an Alfine, but I would start by looking up Shimano's website.

Juha 11-13-12 06:04 AM


Originally Posted by DieselDan (Post 14942580)
Then you will probably need to adjust the shift cable.

Which is why I wouldn't bother to adjust the chain at all. The slack seems small enough.

cycle.stig 11-13-12 06:36 AM

Thanks for the responses guys. Although I have a year of free maintenance included on this bike I have to drive an hour or more to use it. Aside from that though, I like to do my own maintenance wherever possible. To reiterate, I'm pretty sure I can adjust the chain tension with ease, I just wanted to double check if it was even necessary. As for adjusting the IGH shifter cable, that's easy and takes only a few seconds. I think I'll double check my measurements and give the adjustment a go myself.

Dan Burkhart 11-13-12 07:15 AM

That is not excessive chain slack. You have chain guides on both the chainring and the cog, so it's not going to throw the chain. Ride it and be happy. (But make sure the sliding dropout bolts are tight.)

mconlonx 11-13-12 07:33 AM

Since the cable stop at the hub end is part of the hub assembly which moves with the wheel when adjusting chain slack, why will shifting or shift cable tension need to be adjusted as well?

When adjusting chain slack, check while you're doing it by rotating the crank through a couple of revolutions. Neither the chainring nor the drive cog are perfectly round and static adjustment at any one point may mean too loose or too tight at other parts of pedal revolutions.

Reynolds 11-13-12 09:25 AM


Originally Posted by mconlonx (Post 14942762)
Since the cable stop at the hub end is part of the hub assembly which moves with the wheel when adjusting chain slack, why will shifting or shift cable tension need to be adjusted as well?

When adjusting chain slack, check while you're doing it by rotating the crank through a couple of revolutions. Neither the chainring nor the drive cog are perfectly round and static adjustment at any one point may mean too loose or too tight at other parts of pedal revolutions.

+1, no need to adjust shifter cable. And even if it were, it's a 10sec job.


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