It will work but you need to have it adjusted by LBS. You will loose 2 maybe 3 gears but will work if adjusted properly there may be some chain wear so watch that.

What you're dealing with is probably a one piece 7 sp freewheel and and 9 sp cassette (individual cogs). They're not interchangeable on the same wheel. Another problem is the rear spacing for a 7 sp wheel is 126mm but 130mm for a 9 sp cassette wheel.

Most nine speed chains will not work with 8spd cassettes/freewheels let alone a 7spd.

if you want to change and really do this you can add spacers to the 7spd rear wheel to come up to the 130mm spacing and then change chain and it could work.


IMHO, not worth the work or cost to save the little tread wear on the tire.

Just my thoughts,
Bob

I'm not so worried about tire wear, but find tires which have more than 100mi on the trainer (5 hrs or so) seem to be more flat-prone on the road.

I've been swapping from a dedicated "trainer tire" to a road tire, but that's a pain in the butt.

Any suggestions?

Check ebay...More than plenty of rear wheels, many times sets of wheels, well under $100 for Mavic rims and Ultegra hubs...Cheaper than $25-50 tires all the time...And saves much aggrevation.

If you have a Shimano cassette hub, you'll be able to make this work with very little fuss. The spline pattern on the freehub body for 7 speed Hyperglide is the same as 9 spd. Uniglide freehubs are different, but with a course file, you can make the cogs fit that too.

Buy a cheap Tiagra cassette ($40) and install the first 8 cogs on the freehub. The 9th cog (the 23,25, or 26t depending on the cassette size you bought) will not fit.

Also some, but not all Ultegra 11-23t cassettes have a pressed in spacer behind the alloy sprocket carrier. If you remove this spacer with a pair of needle nose pliars, the whole 9 speed cassette will fit onto the 7 speed freehub body. The space between the large cog and the spokes gets very close, but this should function well enough on the trainer.

Most of what was said above is true. This is the nightmare of compatibility and why bike shop mechanics can be priceless, or justified in telling their consumers to just buy new, often repairing the old, mismatched, or "great deals" can be quite daunting.

Do it yourself, it is educational. Good Luck!

-SD

---

https://www.kickstarter.com/...bike-for-the-new-era