chainring spacing
01-25-09, 01:37 PM
#1
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chainring spacing
Hey all, just need your opinions on something!
Upon finishing my thesis i'm planning on treating myself to a bianchi matta titanium frame and building it up to replace my entry level road bike i got in 2006.
I've actually got a shimano 105/600 groupset mix from 1993 and was planning on putting that on instead of forking out for new components. However, I would like to replace the old square taper crankset with a modern one with outboard bearings, so I was wondering if this would still be compatible with the rest of the 8-speed groupset? I'm sure the chainrings themselves would ok with an 8-speed chain, but i was wondering whether the spacing between the chainrings themselves would still be ok? ie. would an old 8-speed front derailleur be compatible with a modern 10-speed crankset.
Cheers!
Upon finishing my thesis i'm planning on treating myself to a bianchi matta titanium frame and building it up to replace my entry level road bike i got in 2006.
I've actually got a shimano 105/600 groupset mix from 1993 and was planning on putting that on instead of forking out for new components. However, I would like to replace the old square taper crankset with a modern one with outboard bearings, so I was wondering if this would still be compatible with the rest of the 8-speed groupset? I'm sure the chainrings themselves would ok with an 8-speed chain, but i was wondering whether the spacing between the chainrings themselves would still be ok? ie. would an old 8-speed front derailleur be compatible with a modern 10-speed crankset.
Cheers!
01-25-09, 02:05 PM
#2
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It may come as a surprise to some but the spacing between chainrings going from 6-7-8-9-10 speeds (no experience with 11 speed yet) is the same. The difference is in the shape of the ramps on the chainrings. Basically, the chainrings designed for thinner chains use wider ramps to help the chain move from one ring to the next and to prevent the chain from getting stuck between two rings. Because of these wider rings, if you attempt to use a wider chain you will run into issues when you try to deviate far from a perfect chainline. The chain will start interfering with the adjacent ring when using gear combinations that normally wouldn't be an issue.
The workaround for this is to use a narrower chain (and typically the matching front derailler too) when using a newer crankset. The front derailler isn't necessary if you are using friction shifting on the front as you can control how far the derailler moves to complete the shift but for index shifting, the wider cage on the older derailler might cause problems as it won't be moving the chain as far as it should due to excessive clearance. Your rear derailler and cassette don't care what chain you are using so nothing will need to be swapped in the back.
The workaround for this is to use a narrower chain (and typically the matching front derailler too) when using a newer crankset. The front derailler isn't necessary if you are using friction shifting on the front as you can control how far the derailler moves to complete the shift but for index shifting, the wider cage on the older derailler might cause problems as it won't be moving the chain as far as it should due to excessive clearance. Your rear derailler and cassette don't care what chain you are using so nothing will need to be swapped in the back.
01-25-09, 02:42 PM
#3
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It may come as a surprise to some but the spacing between chainrings going from 6-7-8-9-10 speeds (no experience with 11 speed yet) is the same. The difference is in the shape of the ramps on the chainrings. Basically, the chainrings designed for thinner chains use wider ramps to help the chain move from one ring to the next and to prevent the chain from getting stuck between two rings. Because of these wider rings, if you attempt to use a wider chain you will run into issues when you try to deviate far from a perfect chainline. The chain will start interfering with the adjacent ring when using gear combinations that normally wouldn't be an issue.
The workaround for this is to use a narrower chain (and typically the matching front derailler too) when using a newer crankset. The front derailler isn't necessary if you are using friction shifting on the front as you can control how far the derailler moves to complete the shift but for index shifting, the wider cage on the older derailler might cause problems as it won't be moving the chain as far as it should due to excessive clearance. Your rear derailler and cassette don't care what chain you are using so nothing will need to be swapped in the back.
The workaround for this is to use a narrower chain (and typically the matching front derailler too) when using a newer crankset. The front derailler isn't necessary if you are using friction shifting on the front as you can control how far the derailler moves to complete the shift but for index shifting, the wider cage on the older derailler might cause problems as it won't be moving the chain as far as it should due to excessive clearance. Your rear derailler and cassette don't care what chain you are using so nothing will need to be swapped in the back.
01-25-09, 02:47 PM
#4
Senior Member
Yeah that's what i'd suspected. As for the rings and front derailleur being tailored specifically for 10-speed chains, I guess I could replace the chainrings with 8-speed compatible rings for a little extra cost. Still, I may eventually just try the bike out with an old square taper bottom bracket and see how it feels. If I really hate it then i may consider swapping the crankset for good
I guess the question that needs to be asked is why do you want to upgrade the crankset/chainrings? Is it simply because you don't like the square taper bottom bracket, do you want improved shifting or different gearing? You can get an 8 speed compatible crankset with something other than a square taper bottom bracket and you can also get a modern square taper 8 speed crankset that should shift better than your older one.
