The cage of the derailleur moves across, but it ‘sticks’ on the small ring. Could it be something to do with changing when there is force on the pedals?
Yeah, I suspect it has to do with “when and how” you are attempting to shift. Typically, there are two basic sections where shifting from the small to big ring is designed to happen on modern setups. There are numerous pins and ramps at two stages in the crank. If you shift AFTER that start point on one side, the ring will make noise and float a bit until it hits that second set of pins & ramps.
One thing to make sure is that you HOLD the force against the shift lever until the shift is completed. Sometimes (most of the time?) we can just shift and release, and it will still shift. But that little extra bit of tension and motion we get at the cage can help when you miss that timing or have a stalled shift for any reason.
As ever, shifting under a hard load should generally be avoided. That is where the “Hard-Soft” effort I teach my friends comes in. You gas it a bit hard just prior to shifting to get the bike momentum going, then drop your effort “soft” ever so slightly when you throw the shift lever. This reduces the load on the chain, allowing the shift to happen with less issues from overloading the pins and rams, which can result in them slipping on occasion.
As mentioned above, there is a definite timing element to shifting. With some attention and practice, you can actually learn the best time to shift (relative to your foot position in the pedal circle) to better time your actual shift throw relative to current foot position and make it even better. This takes some attention, but being stuck on rollers is a fine time to pay attention and learn it.
So my main tips:
- Make sure you are holding the shift lever long enough (don’t just dump & release).
- Do the “hard-soft” effort to de-load the system and allow the shift to happen easier.
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To clarify - the chain sticks on the small ring.
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Yup, that is what I understood, and covered above.
Thankyou so much for your reply. Your advice should be really helpful. There is no practical reason so it must be a question of technique. I’m looking forward to putting this into practice. Thanks again.
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The more I think about it, considering that many rollers lack a notable flywheel, it is more likely that there could be an issue with loading since it may be more difficult to get that hard-soft action I mention. It is possible that people already employ this outside with no thought. When they come inside, the difference in “inertia” at the wheels is likely different on rollers, and leads to a different result despite applying the “same technique and timing” as done outside.
That is my guess at least. So it may take a bit of a different approach from that aspect.
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A bit of anxiety about easing off on rollers sounds plausible, maybe leading to rushed shifting.
I think a well-adjusted derailleur should still shift though, even if the rider doesn’t ease off, so maybe it’s not set up 100% right.
I sometimes have to shift “decicively”, that is push the lever across quickly and firmly to initiate a shift. Then hold it a bit, or work with the tension, a bit like you used to do on friction shifters (nobody will know what I mean 
). I actually think it’s to do with cable tension, but I find it hard to get the tension right on my front mech.
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I have a little bit of trouble shifting small ring to big when riding on rollers (using a steel frame Colnago w/ 10 sp Campy Record). I’ve found that shifting up to a 21 or 23 cog first, picking up the cadence and then (as recommended above), throwing the lever hard and decisively remedies the issue
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Au contraire!!
I tried a few times to explain this in context of non-index friction shifting but gave up as didnt seem clear enough to help the OP. Back when I started riding rollers it was a 5 speed block with 52/42 rings and down tube shifters. When learning to ride 'em, boy howdy reaching for that DT shift lever to go small ring to big ring was pretty scary.
Anyway, my being a dinosaur aside, you are spot on.
The way I think of this problem:
The issue on rollers is inertia. Or lack of inertia. A new roller rider is tentative because they have heard stories of people falling over. When they want to shift they get a bit scared and tentative.
Shifting from little to big ring with mechanical takes some force. Losing momentum on the spin, a hesitant or weak push on the lever, continued loss of momentum and gyroscope all lead to the rider to feel like they are going to fall over. That makes things worse quickly as they will stop pedaling and then everything stops fast and the rider is panicked reaching for something to grab onto and stay up.
Solution when shifting small ring to big ring is to be purposeful. Keep your cadence up, relax pressure ever so slightly on the pedals as you shift and give a good firm push on the lever. Chain will move, but the sensation will be that you are slowing down. It’s OK, just push on over with your legs to complete the shift and then get your cadence back up. This all happens fluidly after a while and without thought. Which is why its so hard to explain “how to” in text form.
Austin also has a good tip - to avoid the slowing down and the about to fall over sensation, select a bigger rear cog. A smaller gear will allow you to push over the top into the big ring to complete the shift and get your cadence and gyroscope inertia back up quickly.
Do this experiment: Shift small ring to big ring in a 21 or 23 rear cog. Then try the same with a 16 or 17 and then an 11 or 12. The first test will be an easy shift. The second will be harder and you’ll probably feel a slight stalling of momentum. The third, you might come to a stop and fall over.
TL;DR - It’s physics 
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Thanks for all your input. I had a pretty frustrating time last night trying to sort the problem out. No joy, despite what seems to be excellent advice
It might be technique. I’ve come back to cycling after a (very) long break. In fact I started using my old MTB from years back before moving on to a more up to date, but hardly high end, road bike. This MTB is a dinosaur - like me, but it worked fine after a little TLC. The MTB has index shifting on the rear derailleur on the back and non-index friction shifting on the front. Thumbshifters, Deore XT from the last century ?! Perhaps I haven’t really got the hang of the indexed derailleur on the front, or the lever, on the ‘new’ bike. You get more of a feel for the change with the non-indexed gear. With the indexed gear the derailleur just moves across with a click and there doesn’t seem to be any room for adjustment or feel while making the change. On the road I will usually be shifting with the bike moving downhill in preparation for some higher power on the flat. I am relatively new to rollers but am shifting decisively on them. It’s the chain that seems indecisive! Even spinning the pedals off the bike it can take 2 0r 3 turns of the crank before the chain engages. Ithardly changes smoothly on the road either.
So is it set up badly, or is the lever faulty? The bike is a 2019 Allez with Claris lever and RS2000 chainset. Read the reviews - no complaints about shifting when it came out. The chain? I’ve put a connex link on the KMC chain and also use a Connex chain. No difference in shifting between the two. Could it be the quick link?
I suppose the next step is to use the dinosaur on the roller. It will mean faffing about with the length between the rollers and losing time I could be doing a workout but still…Three rings up front and non-friction shifting on the rollers. It might narrow down the cause of the problem.
Yes, this is bad, full stop. A proper bike setup should never take 2-3 crank revs to get a front shift. At most a full crank will get a shift done properly.
I think your front derailleur is not adjusted properly. A quick link would only ever be an issue at one point in the chain, so I doubt that is the issue.
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Time for me to refresh and update my maintenance skills perhaps. Definitely so if there is no problem changing gear on the MTB on the rollers.
Sounds like your front mech isn’t aligned properly, or needs a new cable.
Considering the guy in the bike shop didn’t know what a waxed chain was, I wouldn’t much trust his judgement regarding the derailleur adjustment either. Take it somewhere else for a service, or do it yourself - there are usually plenty of videos on youtube for advice, but it can be a bit fiddly.
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I agree that fixing your front chain ring shifting will be the key to this problem. I have always used rollers on Trainerroad. Even though I have 3 different resistance settings on the rollers, I still use almost every gear, almost every ride.
You will eventually get to know the resistance levels on your rollers and know what to set it to in advance of each ride. For me, resistance 0 is used only for recover rides, resistance 1 for most rides, and resistance 2 only for high power sprinting. Each change in resistance changes the overall range of power you can use, but unfortunately also increases how much change in effort occurs with each gear shift. Sometimes it’s really hard to find a comfortable cadence for the power the workout demands…but as others said, that’s also an opportunity for improvement. Learn how to spin both faster and slower than you are used to.
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Learning to stand up on rollers would be helpful if you can translate it to outdoors. It’s pretty common for people to throw the bike backwards a few inches when they stand. Rollers don’t let you do that.
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