I’m not sure if this is the best place to post this, and I’m fairly new to cycling, but here goes…
I have a Triban RC120 bike which came with a Microshift CS-H081 11-34 cassette.
I installed a SHIMANO CS-HG51 8 SPEED 11-28D cassette using the 2 spacers provided with the trainer (as I’ve read works with 8 speed cassettes).
When I shift to the small chain ring, I get way too much slack in the chain, to the point where it’s not useable.
On the large chain ring, the gears on the largest cogs don’t sound great, in the middle cogs it sounds and feels ok and then on the smallest cog, I can’t get it to shift there at all.
I can provide a video if helpful (just not sure how to Share the link).
I’m 99% sure I only use a single spacer with my 8 speed shimano cassette. I have a tacx neo, see this page for some info on that, but I would expect to need the same number of spacers on all direct drive trainers. https://joyfultriathlete.com/changing-tacx-neo-and-tacx-flux-cassettes/
Do you take the bike off the trainer for use on the road or is it just a bike for the trainer? If it’s just for the trainer then you could look at adjusting the rear derailleur, but if you use it on the road and it shifts ok on the road it’s a pain to adjust the derailleur every time you take it on and off the trainer.
I’m sure others with a lot more knowledge will be along soon to help out.
A quick and possibly daft question in relation to your slack chain issue and large chain ring to smallest cog change problem - does you bike ride and perform well out on the road in respect of both these trainer related problems?
The slack chain issue may be due to the chain being too long. You could shorten it, or use the 11-34 cassette on the trainer and see if it’s better. If you plan to ride the bike off the trainer, you might want to size the chain so it’s not too short for the 11-34 cassette.
The shifting problems may be worsened by the slack chain, but it’s likely that the cassette is not in the same position in relation to the derailleur when on the trainer vs the rear wheel. You can adjust the derailleur to address this, but you’ll have to adjust it again for riding with the rear wheel installed. The other option is to try to reposition the cassette on the trainer (using small spacers) so they’re the same, or much closer. That would minimize the amount of readjustment you need to do when switching between indoor and outdoor riding.
If this all seems too complicated, take the bike and trainer to a bike shop and tell them the outcome you’re looking for.
Ok so I swapped the cassette and now I’m using the one from my bike (11-34). It seems the slack chain is no longer an issue (why would that be? I’m learning!) and I’m able to get the bike into all gears on the bike now.
On the large chain ring, all gears appear to be working smoothly (except perhaps it’s not always shifting nicely into the large cog but it eventually gets there).
On the small chain ring however once I get to the middle cogs, the chain starts rubbing against the front derailleur (I think that’s what it’s called) which is causing some noise obviously.
Any clue what’s next?
P.s. I’m still using the 2 x 1.85mm spacers supplied with the elite suito.
Being in a larger cog will use more of the chain, so the rear derailleur doesn’t have to wrap up as much chain with the spring mechanism. The difference between a 28 and 34 tooth cog can be enough that the derailleur is unable to wrap up as much of the extra chain length.
If the chain rubs on the front derailleur on the trainer in a gear where it does not rub with the rear wheel installed, it usually means the angle of the chain going from the front chainring to the rear cog has changed. Different spacers can help resolve that.
These are issues that can usually be resolved if you take the bike and trainer to a bike shop and tell them you want it to work the same whether it’s on the trainer or with the rear wheel installed. It may require using a cassette on the trainer that is closer in size to what you had on the wheel. It’s also possible the chain was a little too long to begin with and there might be a happy medium that would support either cassette without being slack. They might also tell you the rear derailleur spring is worn out and replacing it might allow it to wrap up more chain.
you usually have to index the gears each time you change bike between outdoors/indoors, even if using the exact same cassette.
the front derailer may have 2 positions for each gear, try pushing the changer again to see if it moves it a bit. if not - that may need indexing/adjusting too so it’s not rubbing (get a shop to do it if you don’t know wat ur doing, as messing that up can be a pain in the ***), they shouldn’t charge too much for a quick adjustment as it’s a fairly common job (some will even do it for free if you are a regular )
I had the same issue with a Shimano Sora 9 speed. On my regular wheel the shiftimg was fine but on the Elite Suito I had to adjust both derailleurs. It sucks because it doesn’t allow me to switch easily between zwift and outdoor racing. They advertise it as a quick install but it’s not. Both at Elite and the seller (online webshop) they cant really help you.
I learned my lesson to buy this kind of stuf in a bike store, so they can install it for you or advice you. Its worth the extra price.
TBH adjusting a derailleur is a pretty basic skill for a bike rider. It’s not particularly related to the use of a trainer either. I have extra wheels for a couple of my bikes and they’ll need a quick adjustment whenever I change them as they’re not using the same model of hub.
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