position of chain & rear derailleur when in the small gears

[rockyroller]

You have introduced new information (chain suck occasionally in lowest gear).

thank you, I'll look into changing just the small chain ring. I've been dealing with this for some time ( a year or two) & I'm been keeping out of the mud, because of it. I've had to stop & clean the drivetrain on a cpl trips, even go so far as this


View: https://youtu.be/JMdL6hTGATI


I've read about the ziptie thing but haven't tried it yet. I should. thanks for that link, it must be the only article on chain suck I haven't read

 

[rockyroller]

My rule of thumb is to put the chain on the biggest front chainwheel and the biggest rear sprocket and then shorten it to the minimum length which the arrangement allows. The problem with going to the limits at the other end of the range is that when the chain whips around during gear changes it tends to chip and damage the chain stay.

I don't understand "shorten it to the minimum length which the arrangement allows". when I was investigating last night, live w/ fellow CCers, I noticed when in big, big, the rear derailleur was in what looked like a vertical position, and easily moved forward if I tugged on the chain. I doubt you are suggesting shorten the chain until the rear derailleur can no longer accommodate any more tugging

 

[itboffin]

i'd take two full links out

 

[rockyroller]

a chunky ziptie round the right chainstay up where the chainstay joins the BB shell

I've seen photos but not way up front at the BB. also, some photos show ppl leaving some of the ziptie tail & some others just have the nubs. suggestions about cutting the tail off?

 

[Ajax Bay]

I cut the tail off - it would interfere with normal running. This is on a road bike.
When the chain is running normally on the inner ring the ziptie on the chainstay is not in the way, but if the chain sucks it rises up to chainstay level and the ziptie's 'block' (where the ratchet/internal serrated surface is) tips the sucking chain and dislodges it from the teeth, and the tension/force provided by the rear mech spring overwhelms the force holding the chain on the ascending teeth. If it were more visible I'd share a photo, but it isn't.

 

[rockyroller]

I cut the tail off

thank you. how many nubs? 1 or more?

 

[Ajax Bay]

See the tail? That's the bit I cut off. I cannot guess what 'nubs' is a typo for .

 

[rockyroller]

See the tail? That's the bit I cut off. I cannot guess what 'nubs' is a typo for .

lol, the lock, that part you put a pic up of. the black bump that the chain strikes. but how many did you use? I've seen pics of ppl using 1,2,3 & even 4. I suppose if I'm really smart I could use just one, but barring that, I'd think 3 or 4 would be less precise but more likely to work

 

[rockyroller]

well, I got 1 big one on, real tight. when I push the chain up where it would get lodged, it strikes the zip tie lock

 

[Ajax Bay]

Spot on (I used a black one to keep it incognito, mind) and check its position regularly. But best sort out the cause of the chain suck: I commend careful reading of the link I offered.

 

[Once a Wheeler]

I don't understand "shorten it to the minimum length which the arrangement allows". when I was investigating last night, live w/ fellow CCers, I noticed when in big, big, the rear derailleur was in what looked like a vertical position, and easily moved forward if I tugged on the chain. I doubt you are suggesting shorten the chain until the rear derailleur can no longer accommodate any more tugging

Missing from my post is a consideration of the derailleur in question. Your observation is absolutely right for most people's equipment and setup because nowadays the wrap-round rarely gets anywhere near its limits. In this case 'one or two links less' would be the advice as others have noted here. Some gears, though, are very mean with their wrap-round capacity and, for these, taking it to the limit in the big-big combination is the best one can do. Hours of fascinating comment on this and similar subjects on the following site, which you may well be familiar with: http://www.disraeligears.co.uk/Site/Home.html

 

[T4tomo]

I don't understand "shorten it to the minimum length which the arrangement allows". when I was investigating last night, live w/ fellow CCers, I noticed when in big, big, the rear derailleur was in what looked like a vertical position, and easily moved forward if I tugged on the chain. I doubt you are suggesting shorten the chain until the rear derailleur can no longer accommodate any more tugging

I wouldn't go as far as no longer accommodating any movement, but pretty close to that.
Reason being is that an overly slack rear D / slack chain tension can cause imprecise rear shifting, so a shorter chain will give you slicker shifting. (*)

hence in situations where its "should I take out a link or not?" I'd err on taking a link out.

(*) as this is cyclechat someone will no doubt tell me this is wrong , but the cycle mechanic who advised me of this knows his onions.

 

[T4tomo]

apparently I posted that in the future?? WTF?

 

[rockyroller]

I wouldn't go as far as no longer accommodating any movement, but pretty close to that.
Reason being is that an overly slack rear D / slack chain tension can cause imprecise rear shifting, so a shorter chain will give you slicker shifting. (*)
hence in situations where its "should I take out a link or not?" I'd err on taking a link out.
(*) as this is cyclechat someone will no doubt tell me this is wrong , but the cycle mechanic who advised me of this knows his onions.

oh OK, thank you. it shifts fine in front & rear

 

[rockyroller]

last ride out was fine, as usual. no chain suck but it was a dry ride. chain stayed clean. regardless, I had some free time Saturday morning so I took a cpl links out, especially after looking at other bikes online & that we have in the house. also watched several "chain sizing" videos. I could have used a different technique to size it but I opted to just remove 2 links. seems OK & the bike easily shifts into all combinations on the workstand. I did use a tip from 1 video, a short section of coat hanger, w/ bends in the ends to hold the chain in place while I worked on it. also ordered a new chain