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How to stop idler chain catch?

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RoyMacdonald View Drop Down
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    Posted: 07 April 2019 at 10:14pm
I've returned the D6 to it's original chain line but I can't get the original idler (I assume) off the bent bolt it is on. It runs much better with the original chain line and it takes far less effort at the shifters to change now (chain does not keep falling off the selected gear either) but the chain still goes at a very slight angle to the biggest gear (lowest) on the cassette from the smaller chain ring through the idler and the 9 speed chain protruding rollers catch the new idler by the holes and keeps lifting the chain slightly. I can change to narrower 10 or 11 speed chain but I still don't like the way the chain will rub the side walls and sit out of square to the idler teeth.

I don't want to change the angle of the idler as when it is in the middle of the cassette the chain run true though the idler. I'm wondering what the usual way to solve the problem is as it must have come up before. Chain tubes? I can't remember how the idler was when I owned the bike before as I don't remember or did not notice it happening. I didn't take photos of the transmission side either (let this be a lesson to always take loads of photos)

Anyone know?

All the best.

Roy


Edited by RoyMacdonald - 07 April 2019 at 10:18pm
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AlanGoodman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlanGoodman Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2019 at 10:19pm
Are you able to allow the idler to "float" a little side to side? That's how it was set up (by Ian Perry) in the Quest I had and it worked very well. 

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RoyMacdonald View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoyMacdonald Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2019 at 10:32pm
Thanks Alan. Not without some modifications. Paul has made the chain run very close to the frame tube anyway and the idler mount tube sits slightly out from the face of the main tube. I could grind some of the projection away and gain maybe 3 mm and find an 8 mm idler mount bolt with a short length of thread and longer to give freedom for some float. I am inclined to think that the chain will rub along the length of the main 50 mm frame tube because it will be so close. I do have some self adhesive Teflon sheet though, that I could stick along the frame tube. 

I'm puzzled it does not happen to the Fujin as that looks very similar to the D6's geometry. That does have a chain tube though. Might have a wider rear hub as well that moves the cassette more to the offside. (right)

All the best.

Roy 


Edited by RoyMacdonald - 07 April 2019 at 10:34pm
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RoyMacdonald View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoyMacdonald Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2019 at 10:44pm
Thinking about the Fujin I think maybe that does not have an idler with a gear in it but is just a plain return idler on the drive side. I'll check in the morning.

Roy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoyMacdonald Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 11:59am
The Fujin has approx 145 mm dropouts and the chain runs through the idler at a slight angle just like the D6 but the idler is small with solid sides so no holes to catch and it has no gear teeth in it but a fat rubber O ring that the chain runs on and it has a chain tube but I think that is to keep grease off the tyre side walls.

I can get Ginkgo idlers with chain tubes or Terracycle ones that float but I can't have a floating idler and chain tubes. Which would be best? I could try and get a Fujin one I guess, but that can be a rather slow process from past experience. Not sure on the timescale at the moment because I still do not have my wheelset yet. I am going to need to keep grease off the sidewalls as from my experience faired bikes spend a lot of time  at extreme angles of lean.

Roy
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RoyMacdonald View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RoyMacdonald Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 10:57pm
When I say best I mean the lowest drag. And I suppose the least wear of the idler teeth if I use a toothed idler. I noticed that riding the bike has noticeably worn the aluminium teeth on the sides already. I had a spare ICE Sprint idler in my box of bits and I tried that and that works fine (even though it is bigger than the toothed idler) as it has no teeth and no holes around the sides that are also sloping slightly. There is a lot of tension from the chain when pushing the pedals though so I can see why the chain wears teeth onto the plain idler surface. 

Maybe I'll have to try all the options and see which works best. I'm guessing just a floating toothed idler would be best but I'm not at all sure I can make it work with the amount of angle to idler teeth and frame clearance I have. I'm thinking if it couldn't be done on the Fujin the same will apply to the D6.

Roy 
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