8 speed chainrings with 9 speed chain

ultrazenith

Senior Retro Guru
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I need to replace a chainset on bike with a 3x9 speed Deore drivetrain, and I'm tempted to save money by getting an 8 speed Shimano chainset. Some say the rings on an 8 speed chainset will be too wide for a 9 speed chain, resulting in horrendous chainsuck. Others claim Shimano 8 speed and 9 speed have been using the same width rings for more than a decade now.

Anyone know the truth of all this?
 
Re:

Does not pose a problem. I'm speaking from experience, in a very very short time it will bed in fine; even beefy old school Blackspire DH single rings work fine with 9 speed. Initially a good dose of oil on the chain isn'nt a bad thing to do.

Technically, the rear sprocket width between 8 and 9 speed is as near as damnit the same; only 0.02mm if I recall correctly. Front chain rings vary between manufactures much more than that, and Shimano are always (too) thin in my mind to have any chance of longevity.
 
That's correct, the cassette sprockets of 9 speed are 1.78 mm wide and those of 8 speed are 1.80 mm wide. 8 speed chains are 7 mm measured across the rivet, but 9 speed chains are 6.5 to 7 mm. My LBS swears it's really a bad idea to run 8 speed chainrings with a 9 speed cassette and chain, but I remain unconvinced.
 
Re:

I would go as far as marginally sub-optimum with a barely perceptible if not unnoticeable difference. :)

I mean, front shifting is done brutally - turning sausages over in a frying pan with tongues requires more technique and subtlety.

There is no way it requires the tolerance level that Shimano would like you to believe.
 
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