Yes. 10 speed cassettes are actually slightly narrower than 9 speed (10 speed cassettes use a small spacer between the freehub body and the largest cog to compensate. W/ 9 speed cassette, you won’t need it.
I had a decent quality nine speed gathering dust so I decided to use it rather than needing to swap out the wheel. My other road bikes are 10 speed. When I changed over from the 10 speed cassette to the nine speed, I continued to use the spacer at the bottom of the free hub.
My LBS mechanic dialed in my shifting but I find that it shifts perfectly on the outside of the cassette but begins to miss and rattle somewhat toward the inside. I wonder if I should remove the cassette and take out the spacer?
TL/DR version: Make your life easy and remove the spacer for 9-speed.
It’s hard to say. Theoretically? There’s no need for the spacer w/ a 9 speed cassette - but I’m a little confused.
Are you saying that you have a direct-drive trainer (or a dedicated trainer wheel for wheel-on use?) that you’ve installed a 9-speed cassette on (w/ spacer) to use with a 9-speed bike and:
the shifting was dialed for real-world use with its rear wheel (w/ no spacer?)
now, on the trainer - it’s skipping on the larger cogs?
If all of the above are true, then yes. Remove the spacer… particularly if you plan to use this bike outdoors again any time soon w/ a wheel that doesn’t have one.
OTOH, if this is to be your dedicated trainer bike indefinitely? You can probably set it up to work ok without removing the spacer - but you’ll have to adjust the derailleur’s limit screws slightly.
The spacer has the effect of moving the whole cassette slightly outward and - most likely - your cassette lockring isn’t threaded into the freehub as far as it should be as a result. If your LBS mechanic set up your derailleur w/o a spacer installed, then your ‘Low’ limit screw is probably a little on the loose side (because the derailleur would *normally* sit farther inboard than it does with the spacer on there). So, when you shift to your larger cogs now, the derailleur alignment is off. At best, you’ll have a chain that doesn’t want to stay in gear. At worst? You’ll pitch the chain over the largest cog and into the spokes (or get it stuck between the cassette and trainer in the case of dierct-drive).
a) remove the spacer
b) adjust the limit screws as needed to align the derailleur with your smallest and largest cogs. Also check cable tension while you’re at it.
Thanks for the feed back and comments. I have tack smart trainer with fixed back wheel that you put a cassette on at the moment it has a ten speed the same as my road bike. which is fine as my road bike is ten speed . need to start using my bike on the road now as weather is getting better my other bike is a nine cog setup which I don’t us much so was wondering if I could put this on the ten cog trainer wheel to use for training purposes hope this explains my problem.
Hey John, lots of great information here! Apart from some of the advice I’m seen in other riders’ replies, if you’re still unsure about fiddling with your equipment, you can always reach out to your bike mechanic for best results.
Tacxshould also be able to offer their recommendations regarding the specific trainer you’re looking to use with you’re bike!