Jem
Viscount
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Posts: 3,389 
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Post by Jem on Jul 5, 2023 9:44:11 GMT
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Post by wheelson on Jul 5, 2023 14:32:52 GMT
Interesting topic, looking forward to reading this in depth. A quick comment on my personal experience: Over the last 10 years or so I’d experienced various leg and hip pain/discomfort, not on all my bikes though. I finally realized that the culprit bikes had 175mm crank arms. I guess my 74 year old “frame” shrinkage may have contributed to this. For reference, my inseam is 31”.
Case 2 is Mrs.W. I’ve always had trouble fitting her comfortably on any bike, most success being on an extra small Cannondale mtb. Even at that, hip discomfort has always been a problem. A few years back I happened upon an article written by a woman specifically addressing this issue. Using her calculations, I came up with an amazing 155mm length for my better half! I’m embarrassed to say over the years I’d never really considered this factor since most classic era bikes had few options below 170mm, perhaps 165mm. After considerable searching, I found a 155mm crankset for the Cannondale and for the past couple of years, virtually no hip pain while riding.
If I can find that article again, I’ll pass it on. I know I said a “quick comment but a little extra food for thought.
Thanks, Jem, for getting this started.
Best,
John “wheelson”
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Jem
Viscount
?
Posts: 3,389
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Post by Jem on Jul 5, 2023 15:05:35 GMT
It never occurred to me until I found the link. I thought it was a universal truth that there were only 2 crank lengths.
I recall a few years back when I was carrying maybe 2 stone extra, my thighs 'fought' against my belly at the top of every turn and it really detracted from the joy of cycling. I am almost certain that shorter crank arms would have remedied that.
I no longer have that issue with the extra weight , but with a 29 3/4" inside leg, that site advocates a 155mm length. Only 1cm shorter than all of my bikes, so, although I am not about to swap them all, I would be intrigued to try it.
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Post by oldroadietehachapi on Jul 5, 2023 17:53:51 GMT
Is this a new fad? This is another crank length calculator; it seems to favor shorter crank arms than what has been common practice. The only cranksets I have seen in 155 are for BMX bikes; perhaps this is influenced by BMX riders graduating to road bikes? Some modern road cranks are available in 155, but they do not seem to have been available in days past. Vintage road cranksets varied from 165 to 175 (a few 180); if they came in 155 I cannot find a reference in any of my vintage catalogs. Tradition puts short people on a 165 and tall on a 175 with most folks happy with the very common 170.
My inseam measures 32.5 so it calculates a 165 max; I need another 1.5" to calculate to a 175. I have but one 165 and did not like it; it now resides on my wife's bike. I prefer a 170 or 175, both are comfortable. Perhaps what matters most is what you are used to?
Confused as Usual
Jim
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Post by wheelson on Jul 5, 2023 22:36:59 GMT
Jim, this is all pretty new stuff to me, too. Origin 8 makes a very nice 130/74 bcd triple in 155mm. I found a 155mm mtb triple with a built-in chain guard for my wife’s Cannondale. I’ll probably put the Origin 8 on the tiny Lambert for her as that will probably be the only way she’ll ever ride it.
There are some bmx cranks in 155mm, and I have a double in that. Curiosity, it has undrilled pads for a triple.
As far as crank arm lengths, Campagnolo NR and SR, TA, and others were made in 180’s. I remember either a 160 TA triple on eBay but it was too dear for me. I also think there are perhaps some spec’d as juniors, maybe in Canada?
You’re right, though, 170’s we’re the norm during the ‘60s and ‘70s. As far as this being a fad, I don’t know. I had been reading about saddle height and frame size in trying to solve my wife’s hip pain. I followed her while riding one day and saw that there was way too much leg extension and hip rocking. That’s when the “dumb me, why didn’t I think of shorter crank arms?”
bell rang in my head. One of the CR guys shortens crank arms but only certain modern ones. So I think that the increasing availability is indeed a more modern thing. Anyway, it solved the Mrs.W’s problems.
Best,
John “wheelson”
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Post by wheelson on Jul 5, 2023 22:41:16 GMT
The crank arm length write up I referred to earlier can be found at petitebikefit.com
Best,
John “wheelson”
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Post by wheelson on Jul 5, 2023 23:44:25 GMT
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