Tiagra STI's 9 speed

Farnham Gooner

Noddy question,
My wife has an Sora groupset on her bike with an 8 speed cassette, the Sora shifters aren't great. If I upgraded with Tiagra shifters would 9 speed shifters work on a 8 speed cassette or would I have to replace front and rear mechs and cassette?

Cheers

FG

elcani

9 speed won't work, unless you change the cassette and chain to 9 speed as well. No need to change the mechs.

Cheers.

Farnham Gooner

Thanks, I suspected that but good to know I don't have to cahnge the mech's.

andy_wrx

This is changing 9sp to 10sp, but same answer
viewtopic.php?f=40020&t=12862225&p=17698549&hilit=click#p17698549

drlodge

ElCani wrote:

9 speed won't work, unless you change the cassette and chain to 9 speed as well. No need to change the mechs.

Cheers.

No need to change the chain, 8 speed chain should work on 9 speed cassette, but its the cog-cog distance that matters, and 8 and 9 speed are different so you will need a 9 speed cassette with 9 speed brifters. 7 and 8 speed is a different matter tho, the cog-cog spacing on 7 and 8 speed are near identical (0.2mm difference)

Have a look at this http://sheldonbrown.com/cribsheet-spacing.html

elcani

drlodge wrote:

ElCani wrote:

9 speed won't work, unless you change the cassette and chain to 9 speed as well. No need to change the mechs.

Cheers.

No need to change the chain, 8 speed chain should work on 9 speed cassette, but its the cog-cog distance that matters, and 8 and 9 speed are different so you will need a 9 speed cassette with 9 speed brifters. 7 and 8 speed is a different matter tho, the cog-cog spacing on 7 and 8 speed are near identical (0.2mm difference)

Have a look at this http://sheldonbrown.com/cribsheet-spacing.html

Pretty sure that's not right. An 8 speed chain is wider than a 9 speed and will not run smoothly.

drlodge

One speed difference should be fine per http://sheldonbrown.com/speeds.html If the chain is old I'd replace it anyway, just saying its probably not necessary

elcani

drlodge wrote:

One speed difference should be fine per http://sheldonbrown.com/speeds.html If the chain is old I'd replace it anyway, just saying its probably not necessary

Using a one speed narrower chain (as mentioned by Sheldon) would be ok, but not a one speed wider. E.g. 9 speed chain with an 8 speed cassette would be ok, but not an 8 speed chain on 9 speed cassette.

drlodge

One speed wider chain might cause problems on the cassette I agree, but I'd still wager it'll work OK, But for the small cost of a chain, get a new one :-) So as the right honourable man said in the first place...