Need some advice choosing chainrings and cassette please.

[fossyant]

You can still get the 105 10 speed rear mechs (5701) ( GS - long cage flavour) - the max they will take is a 32T cassette - think you'll be pushing 30 with the current mech. I have this mech on my CX bike.

 

[Cycleops]

If you're going for a sub compact @SafetyThird don't forget to shorten your chain.
Rule of thumb, big front to big rear plus 2 links (Inc the quick link)

 

[bobzmyunkle]

If you're changing the rear mech check out the Shimano compatibility guide. There's a suggestion above you could use a tiagra mech but 10s tiagra is a different pull ratio to most(all?) other Shimano 10s.
Not sure about the shifters you have, but I've run 105 5700 shifters with deore and xt 9s mechs which allows for 34 max cassette.

 

[SafetyThird]

OK, so thinking now is that I go with a 12/28 on the back with the current derailleur and either a compact or subcompact chainset on the front. That way, I know the rear setup will work and I can try out the front. If I think I still need more range, I can always change out the rear derailleur to get a 32T to work.
So now, just the decision between compact and subcompact, which will need investigating to see whether I'd need a new front mech for that. slowly figuring it out.

 

[Spiderweb]

This compact is great value;
https://www.ribblecycles.co.uk/shimano-fc-r7000-105-black-172-5mm-50-34t/

 

[Ming the Merciless]

deore and xt 9s mechs which allows for 34 max cassette.

The 9 speed shadow XT allows for a max 36t cassette

 

[ColinJ]

The 9 speed shadow XT allows for a max 36t cassette

Indeed...

You can do even better than a 34 if you change your rear derailleur too! I had the same problem on my 10 speed cyclocross bike so I changed the little ring to a 34 (it had been a 36) and put a 12-36 10-speed cassette on. To get that to work I put a 9-speed XT mountain bike mech on. NOTE - 9-speed! The cable pull of a 10-speed shifter happens to match the 9-speed MTB mech and those can cope with much larger cogs.

It IS true that the gaps between gears are significantly bigger than before but it was a price that I needed to pay when using a double chainset. Most of my other bikes have tighter cassettes but triple chainsets to get my grovelling gears.

Here it is after the changes ...

View attachment 413820

 

[Ming the Merciless]

Indeed...

Which reminds me, I need new jockey wheels…

 

[Dogtrousers]

I don't really have any advice that hasn't already been given, but best of luck with your cycling plans @SafetyThird

 

[Ajax Bay]

it seems technology has moved on apace. I'll take a look at the hollow tech 2 setup just to see if I would like to potentially future proof my options otherwise it'll be a compact ST chainset on the way.

Technology has not 'moved on'. Square taper BBs offer far more flexibility and 'future-proofness.

I'm going to upgrade to the Hollowtech 2 system. I've had this road bike for almost 20 years and it's the last one I'll ever need for pure road riding (variable geometry, beam suspension) and I've just had a full bike fit so it's very comfortable and setup for me. It's all black so the modern black chainsets will look natural on it. The silver 105 came from my previous bike when I built this one up and never looked quite right. Makes sense to continue the gradual upgrades with a modern bottom bracket while I'm changing the chainset.

H2 is not an 'upgrade', the chainsets will be significantly more expensive.
I recommend a decent Spa Cycles sourced square taper super compact chainset which (with a 12-27 tho' 11-27 easier to source) will allow you to climb out of Lynmouth once your fitness is back up to 2006 levels (ha ha).
They even have black ones: https://www.spacycles.co.uk/m8b0s10...-RD2-Super-Compact-Chainset-with-Zicral-Rings
Worth considering (even if you are 6ft +) shorter cranks to help the knees ease into the sixties.
As you (and we all) get older and weaker, if you want a chainring less than 34t the only route out is this one or a triple (you need a BCD less than 110mm for the inner ring). Trying to run increasingly large rear sprockets means the steps between gears gets larger and larger.

 

[bobzmyunkle]

Spa chainset is essentially a triple - chain guard replaces outside ring. Q factor 159 - 105 is 146. Only important if you're sensitive to such things.

 

[presta]

Your 105 RD will probably manage a 30t

Shimano says not:

 

[All uphill]

I often ride in West Somerset and the east of Devon. So not far from you @SafetyThird . I'm a tourer who typically has a bike weighing 14 to 15 kg loaded, and I'm not interested in speed.

I'm 69 years and am a strong rider with good stamina but I am slow. I'm definitely losing some fitness and gaining some aches and pains.

I get around fine with a 46/30 and a 11/40 9 speed cassette , giving me a range of 113" to 20.3"

I'm planning to change soon to 42/26 rings and a 11/36 cassette giving me 103" to 19.5" with smaller gaps. This will be an experiment to see how smaller gaps work for me.

I hope this gives you an idea of how another rider manages to enjoy the wonderful, but hilly area we live in.

Edit: I use a Sora Rd with extender. This functional, but clunky. I'm hoping for better changes with smaller gaps, and maybe to do without the extender.

 

[Cycleops]

I think we all know Shimano always tend to err on the cautious side @presta . Like I said 'Suck it and see'. You'll soon find out.

 

[bobzmyunkle]

I get around fine with a 46/30 and a 11/40 9 speed cassette , giving me a range of 113" to 20.3"

I have this set up for touring - although with 10s
I find it ok for touring but the gaps a bit big for riding unladen. (Ask Mrs z about her experience trying to draft me on a lightly packed overnighter - she backed off quite a bit after one or two gear changes).
I take out the extender and use an 11 - 34 for everyday riding.