Need some advice choosing chainrings and cassette please.

[Ajax Bay]

All good. Be aware that the FD cage is curved to fit your 53t current ring, with capacity to go to 56t (with 40 inner).
With the GRX 46t outer the shifting will be sub-optimal (am not saying 'it won't work') with greater risk of dropping your chain (both ways) so careful tweaking required to mitigate that risk.

 

[SafetyThird]

Right, so after deciding all that, I had a reply from spa cycles to my enquiry comparing the GRX chainset with their sub compact chainset as follows.

"Our super compact chainset would be compatible with your bike with the recommended length bottom bracket. You would probably require a front derailleur dropper: https://spacycles.co.uk/m8b0s106p5161/SPA-CYCLES-Front-Mech-Braze-On-Dropper to accommodate the smaller chainring sizes. The advantage of our super compact over the Shimano GRX is that we can offer custom chainring sizes allowing for much lower gearing and it uses a standard 5 bolt BCD which makes sourcing replacement rings a lot easier. As your rear derailleur is a medium cage it is rated to 11-30 cassette however we have fitted 11-32 with the super compact chainsets and not encountered any issues."

So, my current setup would work as it is, apart from needing to add the dropper, and I'd have the option to go even lower on the gearing in future if required. The only downside I can see to it is I don't know if it's possible to add a power meter to those, I'm guessing probably not. However, it's by far the cheapest way to go subcompact for about £112 and I have the tools to install everything already.

 

[si_c]

Right, so after deciding all that, I had a reply from spa cycles to my enquiry comparing the GRX chainset with their sub compact chainset as follows.

"Our super compact chainset would be compatible with your bike with the recommended length bottom bracket. You would probably require a front derailleur dropper: https://spacycles.co.uk/m8b0s106p5161/SPA-CYCLES-Front-Mech-Braze-On-Dropper to accommodate the smaller chainring sizes. The advantage of our super compact over the Shimano GRX is that we can offer custom chainring sizes allowing for much lower gearing and it uses a standard 5 bolt BCD which makes sourcing replacement rings a lot easier. As your rear derailleur is a medium cage it is rated to 11-30 cassette however we have fitted 11-32 with the super compact chainsets and not encountered any issues."

So, my current setup would work as it is, apart from needing to add the dropper, and I'd have the option to go even lower on the gearing in future if required. The only downside I can see to it is I don't know if it's possible to add a power meter to those, I'm guessing probably not. However, it's by far the cheapest way to go subcompact for about £112 and I have the tools to install everything already.

Sounds like a great option. If you wanted to add a power meter later, then pedals are probably your only option, but prices have come down in recent years and while they are significantly more expensive than a crank arm option, it's not prohibitive. Plus you're saving on not needing to replace too much on the bike, so it will probably even out.

 

[Ajax Bay]

Right, so after deciding all that, I had a reply from spa cycles . . .
So, my current setup would work as it is, apart from needing to add the dropper, and I'd have the option to go even lower on the gearing in future if required. The only downside I can see to it is I don't know if it's possible to add a power meter to those, I'm guessing probably not. However, it's by far the cheapest way to go subcompact for about £112 and I have the tools to install everything already.

Got there! Glad Spa Cycles agree. See my posts above #25 and #34. Note you can choose a shorter crank too. The future-proofing of the inner ring (BCD 74mm) meets one of your aims. If you feel power measurement will add to you enjoyment out on the road (I suspect not, go for the HRM option), then a pedal based one is the way ahead.
Once done, you need to get up Lynmouth Hill: it's only a few 100 metres but it's one where you can clearly read the smallest font on your front hub, iykwim.

 

[SafetyThird]

Ajax, yes it was your post that had me looking at that, it just took a couple of days to get a reply from Spa Cycles. I think that's now the way to go. I already have HRM, been using one for about 20 years, started with my running training and just carried over to cycling so yeah, no rush for power at the moment.

Now, the final piece of the puzzle are cassettes, I plan to get two so that I can put the same one on the trainer and hopefully not have any issues with indexing once it's set up. All the Shimano cassettes that go to 30 seem to start at 11, the 12's only go to 28. Miche do 13 and 14 to 30 which I'm considering. 13 maxes out at 25mph and 14 at 23mph. If I'm going that fast, it'll be downhill and I'm not likely to be pedalling, I can't ever see me holding 23mph on the flat. Wondering if there's any reason not to go for 14?

Edit, I'm currently on 170mm cranks so the only shorter option is 165. Having just had a full bike fit, I think I'll stick with 170's given everything else I'm changing.

 

[roubaixtuesday]

Wondering if there's any reason not to go for 14?

Only so you can have fun powering downhills / accelerating into a dip to keep momentum over the other side.

Personally, I really value an 11T for this over closer ratios, but it's purely personal preference.

 

[T4tomo]

Ajax, yes it was your post that had me looking at that, it just took a couple of days to get a reply from Spa Cycles. I think that's now the way to go. I already have HRM, been using one for about 20 years, started with my running training and just carried over to cycling so yeah, no rush for power at the moment.

Now, the final piece of the puzzle are cassettes, I plan to get two so that I can put the same one on the trainer and hopefully not have any issues with indexing once it's set up. All the Shimano cassettes that go to 30 seem to start at 11, the 12's only go to 28. Miche do 13 and 14 to 30 which I'm considering. 13 maxes out at 25mph and 14 at 23mph. If I'm going that fast, it'll be downhill and I'm not likely to be pedalling, I can't ever see me holding 23mph on the flat. Wondering if there's any reason not to go for 14?

Edit, I'm currently on 170mm cranks so the only shorter option is 165. Having just had a full bike fit, I think I'll stick with 170's given everything else I'm changing.

I've been using Miche cassettes for a while, I really like them. I use a 12-29 as I used to run a shimano 11-28. Worth checking with cycle clinic but I think he is now able to supply individual sprockets again (a while back Miche was making him order with 18 month lead-time on individual sprockets so he stopped doing them) as you only really wear the middle 3 or 4 most used ones out.

I'd err on caution and start at 13 maybe, it only one extra 2 tooth "jump"

 

[SafetyThird]

Ok, everything now ordered including a pair of 13-30 cassettes. Hopefully get some time next week to put it all together and report back here. Thank you all for your help getting me here.

 

[SafetyThird]

Just thought I'd add a little update as I've now fitted the new bottom bracket, chainset, cassette and chain. All is working very well though due to the appalling weather here in Devon of late, it's only been on the turbo so far, planning to actually get out on it soon though. Thanks for all the helpful advice, I'm sure it'll make the summer riding much more enjoyable.