Jarring clunky shifts into smaller sprockets under power

Flat bar road bike conversion, Ultegra 10 speed throughout but with Tiagra 4600 flat bar shifter.

When Im trying to accelerate as hard as possible after finally getting to point downhill after struggling up it, when working my way down the cassette into successively smaller sprockets under power each shift down is always so jolting and clunky. Almost to the point of unsettling my feet off the pedals. (I dont use clipless pedals on this bike)

a) Do I simply need to learn to shift better and ease off a little when shifting to avoid the jarring clunk as the chain catches on the next smaller cog

b) Is that just how normally clunky the Tiagra flat bar shifter is, it just ‘releases’ the gear that ‘joltingly’? Cam anyone say from experience if the 105 rs700 flat bar shifter is smoother (which would mean going 11spd of course so new RD and cassette)

c) It seems both road and mtb 10 spd cassettes have same sprocket widths and sprocket pitches ie distance chain is shifted is identical. In which case I could just go 10spd XT shifter and XT derailleur. Is XT shifter better quality/performing/smoother than the 105 flat bar shifter?

c) Or Is there something likely faulty with my setup? 6700 derailleur under too much tension or my tiagra flat shifter is broken?

Sorry I know that was long but really appreciate any insight from those with more experience, thanks

Back off a tad as you up shift.

Also are your chain and cassette in good condition?

a)

As above.

When Im trying to accelerate as hard as possible

Is there a gear system in existence that deals with this safely/smoothly?

Would you change gear in the car without using the clutch? You just need to learn to soft pedal briefly as you change gear.

fair comments, it does seem a little daft to go and spend on a new shifter, cassette, derailleur and chain when I can just change my pedalling behaviour and I suppose there is no guarantee that it wiil be as smooth as I imagine it should be even after the upgrades.

A.
It becomes muscle memory after a while to back off the power for a split second in timing with the gear shift.

A. For possible consequences, see many DH start gate incidents, which are followed very quickly by coasting the rest of the course. And we’re not all Gwinners. Especially on road bikes.

Shimano’s 12sp MTB groupsets claim to be able to deal with these though, don’t they?

Could be a worn cassette on relatively untouched sprockets, I have it now on my turbo’s 11/12/13/14 sprockets of my 105 5800 11-32 cassette, planning new drivetrain bits and tyres plus tubes over the next week… If it stops raining before my next annual leave!

Generally changing from big to small sprockets on the back (or big ring to small ring at the front) is something that requires a tiny back-off in effort in order to not make the whole thing go “clonk” when you do it. I think most road cyclists will find that an innate desire to have a quiet bike will lead them to find their own way to do silent gear changes, but I know that personally I hate clunking between gears and will always attempt to shift with the minimum noise possible, with no conscious thought.

For the other direction, modern groupsets have pick-up ramps on both cassettes and chainrings, so that changing from smaller sprockets to bigger sprockets is something that can be done with no reduction in power and should be smooth however you do it, even if standing out of the saddle, motoring up a lakeland climb.

Obviously, I can’t see either your bike or your technique, but my instinct would be that this is option (a) – rider 🙂

Could be a worn cassette on relatively untouched sprockets

? Sprockets are part of the cassette.

Could be a worn cassette on relatively untouched sprockets

? Sprockets are part of the cassette.

some sprockets barely used, compared to favourite gears (and therefore chain) being a bit worn/stretched.

+1 on the technique. similar (if reversed) to the technique of getting a mtb downshift on a climb by backing off pedal pressure and moving your body at the correct moment to unload the chain for the shift.

I’ve never had problems shifting into a smaller rear sprocket under load . Sure if you get into a massive gear and are doing about 1mph up a big hill you can get a bad shift but it doesn’t happen in normal riding. Front shifting is different because the chain is derailed at its highest point which is where the power is being transmitted to the rear wheel . Rear shifting happens on the low part of the chain which is not transmitting the power . I would try backing off the gear cable tension a bit .

I would try backing off the gear cable tension a bit .

That’s something I probably should look into. I know when I’m in the 28 tooth and I try to go back down its quite a forceful push, I get a really hard solid click in the shifter back down to the next sprocket, almost like the tension has the shifter stuck. Is it possible the upper limiter screw on the derailleur could do with giving a fraction more movement so the cable isnt tensioning the derailleur tight against the limiter screw, therebey wedging the mechanism inside the shifter?

And how do we reduce tension? If I release tension in cable by screwing in the barrel, making the cable slacker wont that move the derailleur a little out of alignment? This bike is one of those old school Raleigh carbon frames, thats how old it is! The derailleur hanger has taken such a beating over the years I just have to look at if funny and everything goes out of alignment and I get wonky shifting.

I tinker with stuff on my bikes but honestly I’m a hack bodge man I really don’t know the fine art of it all. Im happy to take apart rockshox or fox forks and suspension but something about derailleurs and shifting I just don’t get on with