chainsuck - getting worse

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bluespeeder
Posts: 101
Joined: 9 Nov 2021, 3:40pm

chainsuck - getting worse

Post by bluespeeder »

I have experienced chainsuck where the chain jams between the big ring and small ring since changing components a couple of years back but this is now getting frequent (almost daily - 30miles) and seems to be worsening. The chain remains part on the big ring part on the small ring. I tried filing the burrs on the outer ring (the usual advice) this morning but still had one incident of chain suck.
The set up is as follows:
Giant speeder
big ring 53t fc5600 (shimano 105) - done about 10K, worn but not badly
small ring 40t original biopace (steel so not much wear)
chain is sram pc850 and near end of life (about 0.4% wear)
cassette 23-12 sram 8spd very worn but not skipping

Previously I ran a fc5700 chainring and HG40 chains with no problems but availability of these parts is getting more tricky (I know the FC5700 is nominally 10 spd) and the HG40 chains are made of cheese (the sram chains last at least 50% longer) I did try a stronglight ring a few years back but but this caused chainsuck straight away before I got as far as trying it on the road.

I am wondering if there is a set up issue.
The front mech is set up about 4mm above the big ring - this is where it has been from new but does look a bit high (2mm seems recommended).
The ring spacing is about 8mm teeth to teeth, there is a 1mm spacer on the small ring so removing these would make 7mm.
Are either of these potential causes/solutions?

It could be chain wear but I am not convinced as I have worn chains more than this in the past without problems. I am hoping to get to spring before replacing the chain and cassette.

Any thoughts greatly appreciated
mumbojumbo
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Joined: 1 Aug 2018, 8:18pm

Re: chainsuck - getting worse

Post by mumbojumbo »

Use a newer chain.
wirral_cyclist
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Joined: 17 May 2010, 9:25pm
Location: Wirral Merseyside

Re: chainsuck - getting worse

Post by wirral_cyclist »

I'd have thought going from round to oval and back isn't going to help when wear rates on each ring differ.
Nearholmer
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Joined: 26 Mar 2022, 7:13am

Re: chainsuck - getting worse

Post by Nearholmer »

If the small ring is oval(ish), and the large round, isn’t there a condition under which, as the chain transfers from big to small the distance between the two points of contact increases markedly during the transit, pulling the chain tight and causing it to snag on the teeth of the larger ring?

I think there is another condition under which the distance between points of contact decreases during the transit, risking a sort of “hump up” of the chain and a twang as the chain finally releases from the big ring.

If both are the same shape, and in the case of ovals and other unusual shapes in phase, then the transit distance will be constant throughout the transit.

Try doing it slowly on a workstand, initiating the change at different points on the small ring, to see if I might be right.
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531colin
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Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: chainsuck - getting worse

Post by 531colin »

viewtopic.php?t=116834&hilit=reverse+we ... e&start=30
Picture at the bottom of that page shows chainring wear when I was getting "chainsuck".....
............specifically, changing from the big ring to the middle one, the chain would transfer to the middle ring at the top, but fail to peel off the big ring at the bottom......then the chain ("bridged" between the 2 rings) would carry on round until it jammed up under the F. mech.

Cured for me by filing the "hooks" off the teeth of the big ring.
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Mick F
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Location: Tamar Valley, Cornwall

Re: chainsuck - getting worse

Post by Mick F »

Worn front mech.

Been there, seen it and felt it, and sorted it ............ with a new mech.
Mick F. Cornwall
peetee
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Location: Upon a lumpy, scarred granite massif.

Re: chainsuck - getting worse

Post by peetee »

Mick F wrote: 4 Feb 2023, 6:39pm Worn front mech.

Been there, seen it and felt it, and sorted it ............ with a new mech.
This. And could be an easy solution if your front mech has a press-in nylon shift ramp on the cage plate as spares are available.
So, what is the front mech and how well used is it?
The older I get the more I’m inclined to act my shoe size, not my age.
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: chainsuck - getting worse

Post by rjb »

I experieced chainsuck on a new triple chainset but only when changing up from middle to big. (39 to 50) After several random episodes I realized the crank was always in the same orientation. Careful examination didn't revealed any burrs but dressing the teeth on the middle ring in the area where it was occuring with a file and using only a couple of strokes removing minimal material cured it completely. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
bluespeeder
Posts: 101
Joined: 9 Nov 2021, 3:40pm

Re: chainsuck - getting worse

Post by bluespeeder »

Nearholmer wrote: 4 Feb 2023, 5:57pm If the small ring is oval(ish), and the large round, isn’t there a condition under which, as the chain transfers from big to small the distance between the two points of contact increases markedly during the transit, pulling the chain tight and causing it to snag on the teeth of the larger ring?

I think there is another condition under which the distance between points of contact decreases during the transit, risking a sort of “hump up” of the chain and a twang as the chain finally releases from the big ring.

If both are the same shape, and in the case of ovals and other unusual shapes in phase, then the transit distance will be constant throughout the transit.

Try doing it slowly on a workstand, initiating the change at different points on the small ring, to see if I might be right.
The oval ring could be a factor although I have run it with a standard big ring for many years without problems.
I do not see how the points of contact can increase in distance while both part of the same crankset. Having said that, on the downshift when the chain drops to the small ring it will land on the teeth differently depending where the shift is made. It may mesh perfectly or it may land with the rollers sitting on the tops of the teeth. This has me thinking if standard chainring combinations are effected by this also.
Big ring teeth 360/53 degrees apart, small ring teeth 360/40 degrees apart so only 1 pair will line up. But if the chain lands say 5 teeth back will this distance always be the same?
I feel there is some compatibility issue with the current components - maybe teeth shape or width and maybe chainplate shape. Added to this wear is probably a factor also.
I have also just realised the front mech position would have been set originally for an oval ring hence the larger than usual gap.
This only happens roughly 1 shift in 100 so hard to reproduce, I will start replacing parts to see if I can eliminate the problem.
bluespeeder
Posts: 101
Joined: 9 Nov 2021, 3:40pm

Re: chainsuck - getting worse

Post by bluespeeder »

peetee wrote: 4 Feb 2023, 6:53pm
Mick F wrote: 4 Feb 2023, 6:39pm Worn front mech.

Been there, seen it and felt it, and sorted it ............ with a new mech.
This. And could be an easy solution if your front mech has a press-in nylon shift ramp on the cage plate as spares are available.
So, what is the front mech and how well used is it?
Time for fleabay shopping, the mech has seen a lot of wear the last few weeks with muddy roads.
bluespeeder
Posts: 101
Joined: 9 Nov 2021, 3:40pm

Re: chainsuck - getting worse

Post by bluespeeder »

mumbojumbo wrote: 4 Feb 2023, 5:26pm Use a newer chain.
I have just measured the chain wear. 1/40th inch in 10 inches which is .25% which is about half way to .5% when I usually swap. The rollers do look worn though.
mumbojumbo
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Joined: 1 Aug 2018, 8:18pm

Re: chainsuck - getting worse

Post by mumbojumbo »

Mixing oval with round rings is not advisable ,plus a worn chain and tired mech means every factor is compromised..
Jupestar
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Joined: 29 Feb 2020, 3:03pm

Re: chainsuck - getting worse

Post by Jupestar »

I would suggest there is not one single cause for this, but the oval to round is probably reducing the tolerances...
bluespeeder
Posts: 101
Joined: 9 Nov 2021, 3:40pm

Re: chainsuck - getting worse

Post by bluespeeder »

Jupestar wrote: 5 Feb 2023, 2:17pm I would suggest there is not one single cause for this, but the oval to round is probably reducing the tolerances...
I agree that it is probably a compatability problem (possibly between chainring/chain/oval small ring) combined with wear/burrs.
I dont want to ditch the biopace small ring as I think it reduces knee problems for me. I know this system can work because it has done for about 20 years without problem until recently. The recent changes have been chainring and chain make so I suspect tolerances between these are not helping.
I inspected the chainringl again this morning in strong sunlight and found another burr which I removed. I had no chainsuck while out today so I have my fingers crossed. Meanwhile the front mech will be replaced when the "new" one arrives - this is worn to the point where a pin hole has appeared in the side plate. Failing this I will go back to the old chainring to see what happens.
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