I'm trying to decide. Is it just a preference thing for each person?
Miche Primato crank 165mm or 170mm. ?

I've only ever had 170's and like them just fine. I technically have an old set of Fuji 165's with the bolted-on chainrings, but haven't used them for anything yet.

its actually alot of a bottom bracket height pedal strike thing .. but as far as preference.. i recently switched out some 167.5's for 170s and was kind of amazed how much different that 2.5 makees them feel

one of my favorite things about my new build is a switch from 170 to 165. the spin is faster and for some reason i feel more in control of slowing with back pressure- may be unrelated as everything else is different, too. mostly i just like more rpms, makes it more fun somehow. on the level of personal preference.

5mm of crank length will give you about .5 mph more cornering speed before you strike, which is about the same amount of change as narrowing your tread width by 20mm.

Now, does that matter? I dunno. Many conversions benefit from shorter cranks because they have fairly low bottom brackets. But many track bikes have pretty high bottom brackets, so you have some more freedom in crank choice.

My Maserati conversion was a real pain, I was pedal striking everywhere on 172.5mm cranks. I got 165mm cranks, and made the tread about 10mm narrower, and its helped a LOT. I feel like I can actually pick up some speed now, and my legs seem to like the feel of the shorter cranks. I can spin better, and it feels more natural. However, even with longer cranks, most track bikes will still have a higher turning speed.

So I suppose a lot of it is personal preference, with a few practical matters cropping up when dealing with conversions, or riding on an actual track with not much bank.

peace,
sam

Everyone seems to be suggesting a false dichotomy here, 165mm or 170mm cranks (or a similar comparison). They DO make 175mm cranks (and I have them)! I suppose the feeling of most of the folks here is that 175mm cranks are pure heresy? Seriously, should I begin to question my crank size? Or am I just overestimating the height of the contributors to BikeForums?

i'm quite short. when i'm in the drops i feel like my knees are gonna punch my chest. i use 170's and want to change. that's what i have to say about this subject.

In my experience, switching from 170mm to 165mm cranks leaves me feeling like my legs are doing some sort of weird doggie-paddle for the first five minutes. After that I notice absolutely no difference whatsoever.

The tangible benefits of shorter cranks are fairly negligible, imo. Somewhat objectively speaking, dropping a few milimetres off your crank length will make your gear feel marginally stiffer. According to ye olde Sheldon Browne, 47x17x170mm has a gain ratio of 5.4, while 47x17x165mm has a gain ratio of 5.6. ie, for every metre the pedal travels around the bottom bracket, you'll travel .2 metres (20cm) further with the shorter crank.

If you're using a conversion, the extra few mm of clearance in the corners is handy, but it can just as easily be achieved with narrower pedals. The BB on a track frame is usually around 25mm higher than on a road bike, so obviously that'll have a much greater bearing on clearance than +/- 5mm on your cranks. Similarly, if clearance is the issue, or if you feel like your knees are pounding into your chest when you're in the drops, why not go to 155mm cranks? 165mm is such a slight difference that it really doesn't seem to me to merit a switch so I'm baffled as to why it seems to have become this magical FG crank length. Then again, cranks are expensive and I am cheap...

If there's a problem you are trying to address, switching crank lengths seems like an expensive way of going about it. Knees in chest? Raise your stem. Need more clearance? Get a set of narrow, $25 track pedals. Want a stiffer feeling gear? Get a new cog. All of those things are a lot cheaper than dropping $150 on new cranks. If you really do need new cranks for some reason - or just want to treat yourself to something shiny - by all means switch up the length. Go nuts - it's not going to hurt anything. I just think it's a fairly spurious rationale for convincing yourself that you need to change something. Ultimately, I'm a big proponent of using what you've got. I can't honestly believe that anyone thinks dropping 5mm off of your crank length is going to make any real difference in a non-competitive, commmuting, urban riding setting that couldn't otherwise be achieved in a more cost-effective manner.

It basically boils down to a feel thing, I guess. That being said, it's been my experience that I only notice the difference when getting off of a bike with one length and getting onto a bike with a different length. Even then, I only notice it for a few minutes. It could just be that I'm incredibly un-fussy about these sorts of things. YMMV, blah blah, lol, w00t, rotflmao!

I rock a road conversion...170mm...and MKS sylvans...haven't pedal stricken once..

then again...I rode the same bike as a freewheel with the same cranks, a longer BB spindle, and wider pedals for years.....and I would almost ALwAyS pedal through corners

I think either way, you just get a feel for how much lean you are able to handle, and become comfortable with it...
usually the road surface (gravel, dirt, salt) is more of a deterrent against me leaning too much than my pedals are

as long as they only 'feel like they're gonna' punch, and don't punch your chest, you're ok

I think that's because your bike doesn't fit too well, not because of a crank length issue.

Shorter cranks will spin up easier/faster. [at the expense of leverage]