Presumably something to do with my positioning on the bike, but I’m not sure why, on long road rides I get tight/sore achilles. If it makes a difference I use SPDs cos I’m not a proper roadie.

Should add that other activities like running, shorter rides, hillwalking etc don’t cause any problems.

I have Achilles issues in general. Ironically now due to separate injuries on either side

Of course I have no real idea but one of the things I have learnt is one of the things your Achilles hates is poor ankle alignment. If you carves or ankle joints get tight then your knee can end up taking a route inside of your foot (ideally your patella lines up with the ball of your foot). IF this happens the Achilles can kink and not be loaded across it full width. Some shoes are better at stopping this rolling in than others. Calf stretching helps me. But I often end up riding in walking boots to keep the ankle tracking straight. Which looks really stupid on the road so I tend to ride off road. Well I did until I injured the other ankle…

Hmm I do sometimes have issues keeping my knee straight, sorted but working on the strengthening muscles around it, so that would make sense.

Possibly the saddle too high causing the calf area to in effect “over-reach”. You would probably find some knee soreness/ ITB soreness if this was the case though…

Most likely seems the alignment of your (hip, knee and) ankle as you look at the bike front on could do with a bit of closer inspection. Keeping everything in a line is the general recommendation but it isn’t always as simple as that. If your knee does not track straight it might not be bad and equally strengthening the muscles around the knee might not be any help. Tightness in the hip and back could give issues which transfer down to the ankles as could a multitude of other factors.

What pedals? I have found Crank Brothers Eggbeaters to be particularly poor at giving any support which might irritate old niggles.

Generally speaking a cleat position further towards the heel reduces the contributions made by the calf during pedalling which is an extreme option to tests perhaps.

Basically…. it could be any number of things and I doubt anyone here will be able to solve this. Best bet is to see a physio I would say