rando_couche

IME, the danger of pedal strike is overrated. In 50 years of "serious" cycling, I've experienced pedal strike on the road exactly twice, both in my racing years and cornering very aggressively. I didn't fall either time. Neither of these happened when I was riding my bike with a 10" bb height (SUPER low) and 180mm cranks. On the mtb, it's a different story. I've broken at least two pedals by slamming them into rocks. And FWIW, I HATE high bb's. I loved that bike with the 10" bb.

Of course, YMMV. I'm probably an outlier.

repechage

When the Campagnolo pedal form factor reigned supreme, for criterium wins a high bottom bracket was a distinct advantage, with 167.5 cranks and an 11” high bottom bracket I would lead out the final corner, I could pedal through and those who rode a bike with less cornering clearance would pedal strike and while they did not crash it made winning easier. I had a road geometry bike for road courses.

clubman 

I think so. Mtn bikes made 175's more popular because of their higher BB higher clearance and the style of riding required to climb steep terrain. Early 20th century roadsters also used long cottered cranks but large frames and wheel diameter accommodated them.

I should have thought this through. Low speed tight turns on a fixed gear are the issue. I used to commute on a fixed wheel and was literally thrown through time and space on two occasions because I used 170's on a typical steel road bike with low BB.

Kontact

Well, they are not. 175s are common on large sizes and were actively sought out in the early 2000s for their supposed advantage. None of those people were riding bikes with different BB heights.

Velo Mule

This is good. The thing with crank length is that it depends on the individule. When I was racing, I kept going slower. I was diagnosed with chrondomalcia patellae, similar to you. I ended up quiting racing and even cycling. Then decades later took it up again, but if I went too long the knee pain (and effects) came back. I went to 165 cranks to reduce knee flexion and I can ride longer without problems. If you don't have problems. Keep doing what your doing.

As some of these references above and Neill Tanbury, bike fitter, point out, it depends.

The good thing for both of us, and it should be a lesson for anyone that is dealing with issues related to pedaling is, try different length cranks and cadances. You may find something that works for you and enjoy riding again.

By the way, Matt Appleman, referenced above, is a taller guy, however because of an injury, rides shorter than 170mm cranks.

Steel Charlie

So here's a summary of the entire discussion and everything else that I have read in the past:

It depends.

HTH
Cheers
Charlie

P.S. The really excellent news is that exactly the same rule applies to everything associated with individual bicycle fitting.

clubman 

There's very little room for discussion or opinions here, is there. Who mentioned a 2K timeframe? What about the 70's? I know the marketplace had always had long cranks for tall people but to insist that they were as abundant or available before the 80's ATB development is dubious imo.

cyccommute 

And where do you shop for these mythic short cranks? I’ve been trying to find them for 40+ years and so far have come up with nothin’. I even had to go so far as to make them myself.

oldbobcat

We just learn to not pedal through corners. Of course, with the current trend toward shorter cranks, 175 mm is becoming odder and rarer.

Pros who used 175s seem to have their own reasons. Jacques Anquetil was a time trial specialist. Eddy Merckx has long legs. Greg LeMond was coached by Cyril Guimarde.

If you go back in time, the old CONI book was pretty dogmatic about 26.5 mm as the correct BB height for road bikes. That would be with 21 mm tubular tires, I'm sure.

My 61 cm Gios had the most BB drop of any bike that I owned. I'd scraped my pedals a few times but never catastrophically. My current road bikes, an older Madone and an '80 Masi Gran Criterium, put the BB at a more modest drop. To this day, for stability and easier dismounts, I prefer lower.

Chuckk

Seems to me that longer cranks climb a little better on the road, but 170's spin quicker on the flat.
Same with handlebars - 42 climb better than 40's but at the cost of more wind resistance on the road.

clubman 

Here's a couple. Stronglights are cheap but decent with square tapers. The Cobbs are top shelf SRAM style. I have both
https://www.xxcycle.com/10030-cranks...mpact-kid.html
https://speedandcomfort.com/collections/short-cranksets

Clyde1820

A couple of makers that I know of: Middleburn (with their RS7 and RS8 line); and Spécialités TA (with their Carmina line).

https://www.mountainbikecomponents.c...x-type-cranks/
https://specialites-ta.com/recherche...arch&s=carmina
https://www.peterwhitecycles.com/carmina.php

velomateo

Cobb Cycling sells (modern) cranks in lengths down to 145mm at speedandcomfort.com.
There several sets, including bottom brackets, available on shopgoodwill.com.

Robvolz 

Sounds like I should get rid of my 175 campy Strada, from before date stamps. (1968-1973)

genejockey 

All my bikes purchased before 2021 have 175s. It's what I've been using since I started riding again at 38 years old, 28 years ago. But then I got a hankering for a bike from the early 80s, when 170s were all the rage. I got one, rebuilt it all, set the saddle height to the same as my other bikes and boy, did that feel WEIRD! Like I was pedaling flatfooted! But I got used to it within a mile or so. Mostly.

Then one day, I set off on a ride on my old bike with the 170s, and something was wrong with it (Flat?) in the first block so I turned around and went home. Grabbed one of my bikes with the 175s. Now THAT felt weird, like I had to reach with my feet at the bottom of the stroke. Felt that way for about a block, then if felt normal. Turns out that the general recommendation is to raise the saddle slightly with shorter cranks so you have pretty much the same extension at the bottom of the stroke, which should have been obvious.

Once I did that, the one difference I find with shorter cranks is that I spin about 5 rpm faster on average. That's it.

smd4

I just split the baby with the bathwater between 170 and 175, and went with 172.5.

Kontact

Where did I claim that? I said they were now common.

clubman 

Faggedabowdit. Not important.

squirtdad

not scientific..... I ride 175 (5" 11" 32 inch inseam)

I really notice it if I am riding 165.....feels like I am spinning like a rabid squirrel. I replaced 165 wit 170 on my around town bike (what I could find in Arabesque....so will have 165 up for sale soon) and it is way better, need to ride this set up some more

my 84 miyata has 177.5 and I don't really notice that compared to 175

this is all of interest as I am considering getting a Rene Herse crank set and options are 171 and 177

merziac

Much of this shows how important full extension can be and is.

This also fully lines up with range of motion full extension exercises after knee surgery that are critical to optimal recovery.

cyccommute 

Thanks for the links. There are, however, some problems. The Middleburn, and TA cranks are still too long. 155 is close but no cigar. The Cobbs are pricey but are closer to the 140 to 145mm I need. However the lack of a triple is a deal killer. Even as a compact double, it’s a silly combination for someone who is small and needs shorter cranks. A 50/34 crank has way too tall of gears for someone with short legs and less muscle mass.

da Vinci Tandems here in Denver sells a crank that takes a spider of many different BCDs.

noglider 

I found it hard to believe that people could feel small differences in crank length. Then I got a new (used) bike and I couldn't find the right saddle height. I realized it was because the cranks were 175, a length I had never used.

It's not an exact science because there are so many variables. Consensus (or fashion trend) changes, and popular lengths got longer, and I'm glad they're getting shorter again. I mostly ride 170 because it's good enough for me. I have one bike, my street fixie, with 155 mm cranks. It feels only a little weird, and I don't mind at all. I got them as an experiment, and I like them more than I expected to.

sd5782 

Interesting reading comments here. I spent many decades on my old Super Sport and it slipped my mind what length the Ashtabula cranks were. I measured and they were 6.75”. Hmmm, that comes out to 171 mm. Several of the early Sugino cranks also came in 171 too I think. We’re they just going with what we Americans used a lot of?

As an aside, I got a woman’s parts bike that came with some 165mm cranks that I may try sometime. I’m about 5’10” with a shorter inseam, so might be fun.

Kabuki12

I ride tall bikes because I have long legs(35” inseam) . I’m not that tall , only 6’ but ride 62-64cm bikes. Most of my bikes have the 170 crank arm length and that is fine. I have one bike that came with 175 length and I really like riding that bike especially when riding the canyon with some climbs.

smd4

140?? What are you, a penguin?