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Discussion Starter · #1 ·
Does anyone know if the chain rings for 7 and 8 speed changed in thickness?
What I'm getting at is I'm building up a 7 speed and have come across 8 speed cranks. Could I use the 8 speed cranks?
 

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In practice shouldn't be a problem. I use 8 speed chains on all my 6 through 8 speed bikes. For funsies I just measured my 7 speed Athena big chain ring and 8 speed Chrous. The were both in the neighborhood of 2.4 mm at the base of the tooth.
 

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I run a 9-speed chain on my 7-8 speed mashup and it's a wonderful shifting system

I'm probably repeating myself, but I don't believe cog thickness, chain thickness, or chainring spacing or thickness changed between 7 and 8 speeds in the campy world.

Cassette cog spacing was the same. The cassette got wider and OLD went from 126 to 130 mm.
 

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Same here. I think you'll find that the SRAM 8sp chains, like the PC870 will work well with both an 8sp Campy cassette as well as a 7sp FW.
 

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Discussion Starter · #6 ·
I run a 9-speed chain on my 7-8 speed mashup and it's a wonderful shifting system

I'm probably repeating myself, but I don't believe cog thickness, chain thickness, or chainring spacing or thickness changed between 7 and 8 speeds in the campy world.

Cassette cog spacing was the same. The cassette got wider and OLD went from 126 to 130 mm.
Speaking of OLD. It seems maybe my rear wheel spacing is a little larger than 126 maybe closer to 130. When I install the rear wheel on the bike it doesn't just slip in, it's tight and I have to spread the drop outs some. The spacer on the drive side is around 13 mm measured looking at Campy parts it's probably more like 12.5 mm. I'm thinking about replacing that spacer with a smaller one.
 

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Speaking of OLD. It seems maybe my rear wheel spacing is a little larger than 126 maybe closer to 130. When I install the rear wheel on the bike it doesn't just slip in, it's tight and I have to spread the drop outs some. The spacer on the drive side is around 13 mm measured looking at Campy parts it's probably more like 12.5 mm. I'm thinking about replacing that spacer with a smaller one.
I wouldn't worry about it unless it really annoys you to do that. There was a transitory period in the late 80's when some frames and I assume wheels as well, were spaced at 128 mm. Even so these bikes weren't made to rocket ship tolerances and there will frequently be a mm or so of "wiggle".

My Merckx Century is 126 mm spaced and I have an 8 speed setup on it; I just spread the stays when I put the wheel in. Works fine though some have said the spread of stays can throw off indexed shifting. Hasn't been my experience. Might be worthwhile to check your dropout alignment.
 
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