You should if you find yourself frequently spinning out on your fastest gears. I personally use a 52T on my TT.

What the other guy said. Deserts can be windy. If you catch one of those magical pure tailwinds on a long, straight, road you can be going >30MPH with little effort...and a 50x11 is a 90 cadence around 32MPH.

Some people can go long periods of time at a 90-100 cadence. When putting out lower effort, as in a pure tailwind, I prefer a more chill "tempo effort" cadence.

It's all personal, though.

Then you turn around and it's pure hell, but that's another thread....

Are the road bikes 165mm cranks too? I'm going to offer an alternate view (for balance). Shorter cranks you have less leverage and the smaller inscribed circumference means you should be able to naturally spin at a higher cadence (feet less distance to move per rev).

If you're looking to race 40km or less TTs, sure perhaps think slightly bigger. But for tri as above, at 100rpm you can do 35mph. And in rough terms, even with a 20mph tail wind that's still going to need you to push 200W+. No wind and its 450w to hold that 90 rpm. For reference if on the way back you manage to hold 300W (impressive) then that 20mph headwind means you'd be doing 16MPH. (Note all these figures clearly based on some spurious assumptions on rider size, aero Bike Calculator).

So I'd say to consider both options. It's not a clear cut decision and will depend on your unique pedaling style.

Why are you going to use 165mm cranks?

Why are you going to use a 10 speed cassette?

I have short legs (just kidding.) I want to try 165 based upon some research that I saw that suggests that 165 is the best length for my size and purposes. Less effort over time. I'm starting to think this is one of those topics that will be argued about to infinity.

I like a 10 cassette, as I prefer friction shifting. A 10 is about as large a group that still allows me to shift precisely without too much effort and error. A 10 also give me plenty of gear range. I typically use 2-3 gears while training (on a 1x9.) On my last sprint, I hit one very short hill that required me to use my highest gear, and I actually could have gotten by in a lower gear, as I totally miscalculated the climbing effort.

How tall are you?

5 feet, 8.75 inches. Call it 5'9. I have a 30 inch inseam.

You should probably be using 155mm cranks.

Thank you. I appreciate your input. But why 155s?

Because even if you're 7' tall, whatever value you select, Jim will recommend 10 less.

There is a school of thought by some on this forum that we are extremely sensitive to crank arm length, and we should almost be all using shorter crank arms.

It's an interesting discussion, but I wouldn't necessarily take it very seriously if you've never had an issue with the crank arm length you have.

It's all likely very subjective and "minimal", in terms of gains. But I think I'll try the 165 length. I can always change it out. Thanks!

Are your hips rotated?

I believe they rotate a bit as I pedal. Not too much.

This is a math exercise, and we don't have enough information to give you a reasoned answer.
Figure out the lowest/highest gear ratio you need/use on your current setup. Derive the equivalent gain ratio(s) after changing crank length. Whatever chainring sizes make that work are what you need.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Thank you. I'll do my best.

52-36. With an 11t on the back (10sp) that will give you a spin out of 34mph (127") at a 90rpm cadence.
https://www.gear-calculator.com/...;UN=MPH&DV=teeth

That calculator doesn't include crank length/gain ratio, which makes it not particularly useful in regard to a question like the OPs. This tool is much better.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

It doesn't include crank length, but 165mm is not much shorter than 170mm: an entirely normal crank length (OP is 5'8"). The cadence can be adjusted so if it's thought that 165s would allow the OP to rev up then that variable can be increased. The OP's issue is not the lower gears (which is affected (effectively) by crank length) which Sheldon's calculator helps with.

We don't know what the OPs original crank length is/was, and even "just" going from 170/165 is close to the equivalent of a 2 tooth change in chainring size. It *is* the equivalent of a 2 tooth change if moving from 172.5 to 165.
We do know that the OP is currently using a 50T ring, so your suggestion of switching to a 52 on the 165s is likely at minimum the functional equivalent of putting a 54 or larger on his current bike, somewhere between a significant jump in gain ratio and a huge jump in gain ratio. We can't actually know which. Maybe you can "adjust" to a difference of that magnitude via changes in cadence, but most riders simply can't.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/