9 speed cassette on a previous 8 speed bike

Put my old 9 speed wheel on my wifes 8 speed bike and it worked fine.
John.

Two things to consider are the shifting mechanism and the width of the chain. If your rear shifting mechanism is indexed...if there is a click for each gear, you will have to eitehr switch it over to friction shifting, or get a shifter that has 9 'clicks' instead of 8. The other thing is the chain itself. You may need to buy a 9 speed specific chain.

If you throw it on and it doesn't work, removing one of the rear rings still won't make it work, as the issues are with the amount of space between each cog in the back, not just the total number of cogs.

You may be able to just throw it on and have it work. If it doesn't, it's not a disaster, just stop by a bike shop and get some advice from them.

CJ,

You cannot run a 9-speed cassette without swapping the chain, chainrings and shifting mechanism.  Derraileurs are more than likely needed as well, but not always.  Sometimes you can fudge it and it will work.

But you can run even up to a 10 speed cassette of your existing hub/wheel without any issues.

It would be relatively cheap to upgrade your bike to 105 if you EBay stuff.  You could probably get the complete drivetrain and shifters for well under $300 - even new.  Then just swing on over and I'll install them.

Edited by Daremo 2010-02-13 11:19 AM

Rick,

I know that you've worked as a mechanic and so have much more experience here than I do, but I've had success mixing and matching 7 to 10 speed components.  My tribike was seven speed rear derailleur, chainrings and barcons (set to friction to run 9 speed) and 9 speed everything else.

Maybe it was dumb luck but I had no problems with this setup.  However, I am definitely with you on the chain and shifters (swap if STI or friction if barcon).

Shane

As I said, sometimes you need to replace the derraileur.  The main reason to do this is that a 9-speed chain is narrower and the cages/guides on the 7 or 8 speed stuff are wider which can run the risk of the chain coming off in shifts or at the worst getting stuck.

You can definitely do it on the cheap if you are willing to ake the chance.  But CJ has Sora STI on his bike and cannot run friction without switching to bar end or down tube shifters.  He definitely cannot run a 9 speed rear with his current shifter mechanism.

I was just checking as to whether it was pure dumb luck or not  

Shane

Depends on the vintage of the chainrings.  Because 8/9/10/11 all use the same ID chain, modern chainrings work for all of them.  Older chainrings might have something funky going on, but then you'd also get the advantage of unworn chainrings and probably a stronger crank/BB .

It's the OD thats different between a 8, 9, 10, and 11 chain.  A 8 speed chain would, if used on an 11 speed cassette hit the +1 and -1 gear while trying to seat in a gear.  It would be bad...