Bike 24 (Germany) had Ultegra in 170s, but sold out of 165s while I was busy pondering and researching. Depends on where you are based.
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Ah, just check profile, maybe Bike24 not an option to Las Vegas
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haha, yeah. But still having the same problem. I have an older Ultegra 6700 crankset and having a hard time finding them in any size. I may have to upgrade to 8000’s. But that’s more than I feel like doing at the moment. Maybe in 6 months inventories will improve?
I bought my crankset new on eBay, shipped from Japan the following day.
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Ordered cheap 11speed Shimano RS 510 to try out from Bike24. If it works, it goes later onto my training bike and I buy a nice one for my race bike, if it doesn’t I’ve only lost 90 euros and put it down to experience
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Shorter cranks rock. I’m now on 165s for my diminutive 5’ 8 1/2’’ (170cm in the morning) height with short legs.
I can spin higher cadences easier BUT I can grind low cadences better because I can pedal in circles instead of squares. There is not dead spot at the top of the pedal stroke forcing the leg over. 7.5mm difference from what came with the bike has been monumental.
I thought it would feel like being on a clown’s bike, but it just feels so natural. I’m surer I’m producing more power with the shorter cranks. (although can’t quantify this as I have switched to a new trainer too).
Anyone who is thinking about it, do it.
Last bit of advice, make sure your saddle fits your butt. My new bike had a 140mm wide saddle that came with it and now I have put my old Arione (130mm wide) on the bike, it too, is a revelation.
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Aww man, now I have to revisit THIS idea again! 
Did another round of cadence builds again last night, and again “only” managed to top out at 189rpm. My primary theory is my wheel-on trainer (Kickr Snap) is slipping at high revs, so maybe that’s the best I’m going to get, but I FEEL like I can spin faster than that.
Tricky though, we’re the same height, but I’d imagine it’s more more about leg length than height. I have a fairly normal inseam, and a short troll torso. Think I’m on 172’s?
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It’s worth visiting, but best done with a bike fitter if possible, especially if they have multiple cranks you can test.
I like the idea of shorter cranks, but honestly, for me (and that’s important) crank length makes relatively little difference.
I have two bikes on 170mm cranks, one on 172.5, one I occasionally use on 165s and I have been known to ride my son’s bike on 140s.
The 140s feel like you’re spinning tiny circles, it’s ridiculous, but the others I can switch between without a thought. I’ve always worked on a smooth stroke, comfortable cadence and I have reasonable hip flexibility, but I could step between a 165 and a 172.5 without so much as moments thought.
Of course there are differences, but they’re not the type of differences that affect me, which is the point.
My point being, it will be a big change for some people, not so much for others, so be careful before putting money into it if you’re unsure.
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189 and not bouncing is good spinning. I’m thr opposite of you. Long body and short legs. Bit of a guerrilla. I researched all I could and looked at all the calculators for crank length and for my little legs it was always 160/165. If you have long legs, they may be suitable and add into that foot length. So I think it is a factor of both.
Funnily enough, my 13 year old son is 167cm (just over an inch shorter than me), but much longer legs and has size 45 shoes (mine are 42). He has 172.5s and fine with his long legs and paddles for feet.
On a personal level it works so well for me. I used to top out spinning at 140/150 on 170s but got up to 170+ on 165s. I like the feel of pedalling in circles and no dead spots. But if you are getting it round at 189rpm, your spinning just fine.
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I was bouncing like crazy at 203 rpm. Just wanted to see if I could do it. I hit 140 standing. Not likely to try repeating either of those, as I don’t want to upset my downstairs neighbors.
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Truth in advertising, whenever I do cadence builds I’m usually seated to 125-130 (which is an improvement), then stand to go for whatever max I can.
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Found this thread intriguing at the time but had nothing to add so just absorbed. Recently though I was listening to the latest Service Course (“Drop it like it’s hot”) on The Cycling PodCast and there’s a lot in it about Bikefit and Crank length that some here may find interesting:
The 2 takeaways for me were:
- Our window of adjustability/adaptability for different bike geometries/ setups narrows as we get older so … consider more bike fits.
- Neglect crank length at your peril!
Above particularly relevant for me as when I bought my new gravel bike at the end of last year I had a very basic bike fit - a few days after the first significant ride my right knee (previous ACL reconstruction) blew up! THEN I had a bike fit with the guru that set me up on my new road bike a few years ago and someone I’ve sent multiple others to - I was way out on saddle height and fore/aft. (sounds crazy but with different cleats/ different shoes/ very different bike geometry it’s easier to be more way off than you think!). Almost 4 months later, having to take it really easy for the first 2, my knee is gradually coming good and hopefully will return to pre-injury status.
Part 2 of my situation is that a total knee reconstruction is almost certainly on the cards down the line (in the words of my orthopaedic surgeon) - I reckon a shorter crank length, taking significant strain off the knee by a less acute flexion angle, will hold me off that much longer. Food for thought anyway …
Finally, for those who don’t know - R.I.P. Richard Moore.
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Awww. 
Man, 49 years old, too. RIP brother.
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Pinkbike always bring the science for us MTBers, figured some may like to geek out on this info. The seat thread got me wondering about my sit bones and now I have a pedal length phobia. Is there a therapy module coming out anytime soon? 
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Que interesante, actualmente me encuentro en ese dilema, de seguir en 165 o regresar a 170, leí en un artículo, que era trascendental la diferencia a nivel competitivo, mido 1.68 entrepierna 76. Para algunas formular como el tamaño de fémur encajo bien en la biela 170, pero para el resto no, seguramente soy desproporcionado jajajaajajajajajaj nose si se ese .5 hace una gran diferencia? Dilema total, saludos
There are a few potential benefits to shorter cranks but if your position isn’t dialled in that could still be part of the issue? I’m 6’3 and use 170mm (short for my height) but have set up my position based on several morphological factors such as a short femur for my leg length resulting in a very high but far forward saddle. I did find the shorter cranks helped me with hip flexor strain and also the stretch feeling you can get in your hamstrings and glutes.
Are you feeling that at the top of the pedal stroke you are to flexed in the knee and at the bottom of the stroke too extended?
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I was either too flexed or too extended, depending on saddle height. There was no comfortable middle ground. I opted to replace my crankset with 160mm Shimano 105. Much better now.
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I’m pretty sure some of my knee and hip/back problems would be alleviated by shorter cranks. I’m just under 5’11” and have 175mm cranks. I’d like to move to 165mm. But I don’t want to downgrade from my Ultegras. Plus supply and price isn’t great right now. And I don’t want to do it without a proper bike fit since my frame may also be too big for me which may be a compounding problem that I also don’t have the money to fix, either…