Gearing question

I know roughly what the numbers say but keen to hear you advice.

My TT bike had gearing of 36/52 and 11-28 both on the Zipp wheel (which I still have) and the same cassette on my turbo.

Now I have the Bianchi with Campag but running on the Shimano cassette in the trainer. Bianchi has 50/34 and 11/29 on the HED wheel I run it with on the road.

In my box of spares, I have a new 12/27 Campag cassette and my intention was to put this on the turbo, once I’ve bought the freehub.

Just wondering what the real world difference would in the feel/effort on the trainer between 52/36 - 11/28 and 50/34 - 12/27?

I can get a 11/29 Chorus cassette but they’ve leapt in price to £140 and and are harder to come by.

Have you checked out bike calc website and done the numbers?

Yeah I did and if I did:

34/29 - 1.17

34/27 - 1.26

36/28 - 1.29

I guess my question is, will I feel that in the real world?

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On a turbo it depends on the wheel speeds (which is a proxy for inertia really) you want on the turbo, for me 50x12/13/14 would be too large jumps in the areas I’d need to be for harder efforts, so if you want high inertia and have a capable turbo it may not be enough - but you’ll know if you’re normally riding up in the middle of the cassette currently, then it won’t make much difference, may even improve things as you’ll have a 18/19 or so extra in there.

On the road, 50x11 is false flat downhill tailwind in TT’ing really, so not much of an issue in triathlons (you’re better off taking advantage of a rest/chance to eat) as your numbers suggest your 34x27 36x28 is probably no more than a few extra watts needed, in race terms this really should be a rescue gear anyway, unless you’re fully optimising for a hill climb - that is as in if you’re slightly under par for the day / it’s a headwind, an extra gear will mean you can still spin at target watts rather than being forced to work too hard, so again shouldn’t make much of a difference.

Personally despite the the harder “easiest” gear, I would not spend 140 quid for that difference.

Cheers Jim, makes sense. I’m not much of a climber but have managed to get round the IM Wales course 5 times with with 36/28 on the TT bike.

Now I’m down to a road bike and no real races on the horizon, just club stuff. I do spin out my 50/11 descending but that’s only getting it up to speed as I tend to descend faster than most (or used to, might be a tad rusty next year).

Strangely, I was thinking more the other end of the spectrum as I’ve lost bike power, so the numbers should help me on Zwift for climbing but not for sustained descending on the Alpe.

I think I’ll leave the 11/29 on the road bike wheel (and of course the 11/28 on the Zipp wheel whenever I use those) the 11/29 has plenty of wear left.
I’ll put the 12/27 on the trainer and take it as it comes. I was thinking just now that by the time I’ve used these cassettes up, the groupset on the Bianchi will be so outdated that I’ll either change bikes or change groupsets. (it’s rim braked though)