Is my chain too short?
yeachan153
Posts: 401
I measured the chain by wrapping the chain around the lowest gear cassette and larger chain ring, finding where the chains meet then adding two plus the missing link.
When I put the chain around the derailleur and I shift to the low chain ring and lowest gear, it works, but occasionally there is movement in the gear. I feel as if it is shifting down, but it doesn't and instead it remains in gear. But that jumping is a bit annoying and makes me wonder if my chain is too short and could do with a link, or whether it can be sorted with a b tension adjustment. Reason I ask is because the chain tool just broke!
Large chain ring, highest gear = two jockey wheels are aligned properly; the part of the derailleur that extends to hold the second jockey wheel remains perpendicular to the ground, so that probably means chain is the correct link. However, chain length does make it impossible to go on big chain ring and lowest gear at back; I know I shouldn't do this anyway but I 've never had a case where this is impossible.
Do you think its just a matter of putting on another link of chain and going from there?
Using a 53/39 & 11-28
When I put the chain around the derailleur and I shift to the low chain ring and lowest gear, it works, but occasionally there is movement in the gear. I feel as if it is shifting down, but it doesn't and instead it remains in gear. But that jumping is a bit annoying and makes me wonder if my chain is too short and could do with a link, or whether it can be sorted with a b tension adjustment. Reason I ask is because the chain tool just broke!
Large chain ring, highest gear = two jockey wheels are aligned properly; the part of the derailleur that extends to hold the second jockey wheel remains perpendicular to the ground, so that probably means chain is the correct link. However, chain length does make it impossible to go on big chain ring and lowest gear at back; I know I shouldn't do this anyway but I 've never had a case where this is impossible.
Do you think its just a matter of putting on another link of chain and going from there?
Using a 53/39 & 11-28
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Comments
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I think chain length is a red herring here. What you basically appear to be saying is that you have lazy shifting so if it is lazy in just the one direction then try twisting the barrel adjust in the appropriate direction (just half turn at a time). A turbo is great for this kind of tweaking, if you have one, or just go out for a ride and adjust mid ride to see the effect.
Turning clockwise will lower the cable tension so that will assist upward shifts (as in going to a tougher gear) and vice versa.
If shifting is lazy in both directions (and assuming your cassette and chain are in good nick) then you might need to re-index.
BTW, a 53x11 combo is a bit crazy IMO unless you are a racing superman (a 120 cadence at that ratio would see you breaking all kinds of records) so why not opt for a closer range of gears next time? Personally I find a 53x13 top gear to be fine (I am happy to spin out at a cadence of 110) but even dropping to a top of 53x12 would get you an extra gear in the mid range which you may find much more useful.0 -
Yeah, it was a new chain I installed so thought that may have been the problem.
I will try the barrel adjuster, but I did give it a good look by going into the inner ring then lowest gear on cassette, and the derailleur lined up with the cassette; also there are no ghost shifting at any other gears, in fact the other gears shift perfectly, which led me to think it was a b tension measurement job.
I'm not sure which way the lazy shifting is happening, because it only happens every 30 seconds or so when ridden. The issue doesn't show up when the bike is upside down and I spin the cranks, and not having a turbo or a stand means its quite hard to look which way it is lazy shifting.
Reason I did get the 11-28 is because I wanted a cheap way of getting an extra bail gear at the top from the 12-25; and the gear ratio's seem fine for me and I am going away to do some big climbs this summer0 -
yeachan153 wrote:Reason I did get the 11-28 is because I wanted a cheap way of getting an extra bail gear at the top from the 12-25; and the gear ratio's seem fine for me and I am going away to do some big climbs this summer
Good stuff. Assuming your setup is 10 spd Shimano then it might be worth considering a 5700 12-27 next time around. You won't feel the difference between the 28 and 27 so either would be a good bailout option when mixed with a 39, IME (I normally ride with a 13-28 on my 9 spd Campag standard doubles, btw)0 -
Just rereading your posts to see if I understand the problem. Are you saying that you only get a problem when trying to get to the lowest gear combo and that problem is that the gearing grumbles, feels like it is shifting but doesn't? If so then you will need to look at the low stop setting.
The same solution would be for another problem which is when you can actually drop into the bottom gear (or top gear for that matter) but the chain then grumbles when in that gear. That usually indicates a limit stop issue in that the chain is not able to seat itself properly on one or two teeth on the cog (they are pitched at differing angles to aid shifting) and so the appropriate limit stop needs adjusting.0 -
yep, lowest gear combo and the chain feels like its shifting then settles on the same gear again. The derailleur is aligned and the cassette rings pierce the chain right through the middle without making any rubbing sounds. But it still makes the sound.
Still think it could be a limit stop issue? (assume that's the b tension?)0 -
Aha! Bear in mind that limit stop and B tension are two different things (apols if you know this). The B screw moves the top jockey wheel relative to the cogs and the general idea is to set it so that gap when on the biggest cog is about 5mm.
I think your issue is the limit stop. If you flip the bike over, then change into the lowest combo and then rotate the chain slowly and trace its path over the whole of the biggest cog you may find that on one or two of the teeth the chain is catching one of the outer plates (which is causing the grumbles as the chain lifts off and drops back on). Adjust the lower limit stop by small increments until this stops. I am always quite cautious about the low limit stop in case I lose the chain over the side, so to speak, when shifting so it might be worth doing a quick ride around the block shifting into and out of the lowest gear and then checking again visually before setting off on a decent ride. The alternative is to fit a dork disk but, heh, who wants to be a dork
Here's a good overview:
http://www.parktool.com/blog/repair-hel ... derailleur
This link is quite good for checking the chain length without fussing with the chain:
http://www.machinehead-software.co.uk/b ... hcalc.html0 -
Thanks for the help Bobbings, I'll give it a go!0
