Saris h3 trainer rear derailleur rubbing against trainer in lowest crank and largest cassette

Hi and Merry Christmas.

My wife and I just purchased our first smart trainer and are setting up our Opus road bikes.

The Saris H3 didn’t come with a cassette so we purchased a separate Shimano 105 11 speed cassette. Pretty much matches our bike cassettes.

Tried both the medium and large through axel hub but are running into the same issue with both. On the small crank and largest cassette (lowest gear) , the rear derailleur rubs against the body of the trainer causing a chatter.

Any suggestions?

Thanks in advance.

A few solutions:

Don’t use the lowest gear that moves the derailleur closest to the trainer body?

Check the derailleur hanger alignment.

Use some kind of spacer to push the cassette out father. I’ve seen this done on a Tacx.

It’s probably just a design flaw and the combo of your bike and long cage rear derailleur aren’t matching up perfectly. Solution #1 is probably the most likely fix.

Mine does the same thing. Doesn’t really affect the performance on that gear, you COULD just sand down the plastic cover there to create some space if it bothers you. I’ve used the H1, H2, and H3 and all share this “flaw” but it’s yet to impact my bikes shifting inside or outside. I had the same issue with my 6800 and 8000 derailleurs

If you use it in ERG mode any gear will do so aim for the best chain line being around the middle of the cassette. Can’t see much need to be up in those gears…

I have that. I don’t have rub. That seems to not jibe with others, for whatever reason, but my shifting is perfect and no rubbing. Or do you mean the lower pulley is rubbing against the leg? My cage doesn’t rub against the body, that would mean the cage is more inboard than the cassette cog. I haven’t had the cage rub against the legs neither, FWIW. :man_shrugging:

Check the derailleur hanger alignment (there’s a tool for doing this), just to be sure. You’d need to use a real wheel with the bike and take the bike off the trainer in order to check the alignment angles.

Same issue on H1 but has never bothered me since only use lowest gear occasionally on a Sim ride.
Depending on your derailleur make/model and gearing the outer cage may hit that plate in lowest gear. It’s not actually rubbing that causes wear but you hear a sound when the derailleur cage is pressed up against the plate. Mine is more of a whir. Chattering could indicate chain/cog wear.
A spacer might remedy the situation but if too thick you’ll need to adjust your gears.
Ideally you want to switch from indoor to outdoor bike without any adjustments needed.

Thank you for the response. Great insight. I was able to remedy the problem by switching to my bike cassette. Guess the 11/32 was too big when my 11/25 came with the bike. In the spring I may get a longer rear derailleur and chain so I can use the 11/32 cassette. Need any advantage at 51 when climbing. Lol