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Can I convert a 36 to a 34 chainring?

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Can I convert a 36 to a 34 chainring?

Old 07-04-06, 10:27 AM
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NRRider
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Can I convert a 36 to a 34 chainring?

I have an FSA SLK compact crank, 50/36, and wanted to get the 34 tooth small chainring. Do I need to get a whole new crankset or can I replace the chainring? Does the 50 tooth only go with the 36 tooth chainring or will it be compatible with the 34?
Lastly, where is a good place to buy chainrings? I assume I need to go with an FSA(?)
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Old 07-04-06, 10:34 AM
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Well, you can't convert the chainring itself (at least not meaningfully), but a 34t chainring will fit on a crank with a 110mm bolt-center diameter. The bolt-center diameter is what determines whether a chainring will fit on the crank.

The combination of a 50t with a 34t is a 16-tooth differential, and some frotn deraillers may not have enough capacity to handle it. But most will.

Finally, you can buy a 34t chainring from whatever manufacturer, as long as they're in a 110mm bolt pattern. (Well, any manufactuere except Campagnolo. They designed theirs to be different so it's only compatible with itself. *%#holes. Although the economics of it makes sense for now.)

Manufacturers would like to (and often will) tell you that you need chainrings designed for 9- or 10-speed chains, if you're running a 9- or 10-speed drivetrain. But you don't. The indside width of narrower chains is the same as chains designed for 6, 7 and 8-speed systems, and the actual width of the teeth on the chainrings is the same as well.

Lickbike has Sugino chainrings in 110mm bolt pattern for $16.
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Old 07-04-06, 01:19 PM
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Originally Posted by timcupery
Well, you can't convert the chainring itself (at least not meaningfully), but a 34t chainring will fit on a crank with a 110mm bolt-center diameter. The bolt-center diameter is what determines whether a chainring will fit on the crank.

The combination of a 50t with a 34t is a 16-tooth differential, and some frotn deraillers may not have enough capacity to handle it. But most will.

Finally, you can buy a 34t chainring from whatever manufacturer, as long as they're in a 110mm bolt pattern. (Well, any manufactuere except Campagnolo. They designed theirs to be different so it's only compatible with itself. *%#holes. Although the economics of it makes sense for now.)

Manufacturers would like to (and often will) tell you that you need chainrings designed for 9- or 10-speed chains, if you're running a 9- or 10-speed drivetrain. But you don't. The indside width of narrower chains is the same as chains designed for 6, 7 and 8-speed systems, and the actual width of the teeth on the chainrings is the same as well.

Lickbike has Sugino chainrings in 110mm bolt pattern for $16.
Thanks Tim--so sounds like you're saying that Sugino chainring will work with the FSA crank. Just to confirm, there's no special ramping or the like on the FSA?
Also, you mentioned some FDs can't handle the 16-tooth diff. I have a DA 7800 FD--you think that can handle it?
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Old 07-04-06, 01:30 PM
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Ramps and pins are useful to chainrings that are not the smallest - they help to lift the chainring up from a smaller ring onto the larger ring that has ramps and pins. Hence, on a double crankset, it's only worth having ramps and pins on the large (in your case, the 50t) ring. FSA doubles don't come with ramps and pins on their small rings anyway.

I'm not sure about the DA front derailler. Shimano Lists the Dura-Ace double front derailler as having a capacity of 15t difference between large and small rings. I suspect that it will have no trouble with 16t, but am not sure.
I suspect this question has been asked before, but hopefully someone else can chime in here.
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Old 07-04-06, 01:42 PM
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I was looking at listings for FSA SLK cranks and it looks like they normally have 34's already, are you positive it's a 36?
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Old 07-04-06, 02:34 PM
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Originally Posted by mechBgon
I was looking at listings for FSA SLK cranks and it looks like they normally have 34's already, are you positive it's a 36?
Yes, seems they come both ways. This particular one came off of this bike: http://www.cannondale.com/bikes/06/C...el-6RR5KC.html
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