Fifty Plus (50+) - I have a short crank!

:D

Conventional wisdom has it that a person my size, 6 ft - 34.5" stand over, should use a 175mm crank.

I quite accidentally found that I am most comfortable with a 170mm crank.

Anyone else bucking convention?

Has this anything to do with bonking?

Has this anything to do with bonking?

I was bonking more when I had the longer crank!

:D

My wife is 4' 10 3/4" 'tall' and has used 170mm crankarms on our tandems for 31+ years (and over 200,000miles) . . .
Whatever you're comfortable with . . . convention be damned!

A lot of potential for fun with this thread.

Conventional wisdom
Who decides what's conventional and what's not? I'm 6' 1 1/2" and find 170mm to be work just fine.

I'm 6'1" and I use a 165mm crank on my track bike, 170 on my fixed gear all-weather bike, 170 on the tandem, and 175 on the CF road racing bike. I can't really tell the difference, even though I've got 35 years of riding experience. Probably because I don't really care. I figure the 175's help me push a bigger gear on climbs (longer lever), and the 165's help me spin faster on the track (smaller pedal circle means that for the same angular velocity (loosely translated as rpm's), my feet don't need to travel as fast in terms of linear velocity than if I were using a longer crank).

One of the top pro 6-day bike racers of the 60's and 70's was a big Dutch dude, Peter Post. He was about 6'4" but he only used 167.5 cranks.

Having said that, though, my best pursuit time over 3000 meters was done using 175mm cranks.

- L.

Short or long, some cranks are considered stiffer than others and therefore more able to transmit your power. A longer crank will give greater depth to your stroke, however, a short crank will seem to move your legs at greater speed. The terrain you are moving over may also dictate the desirability of crank length. Keep in mind that bottom bracket width may also be a factor in gaining leverage.

Older riders may find themselves riding "softer" more relaxed frames which often come with wider bottom brackets. More youthful riders often opt for more performance oriented frames which can be demanding and exhausting to ride-- and often come with more narrow bottom brackets.

Willis,

Mimi, (my '68 U08) has 168.5's. I'm 6' and 200lbs and reasonably powerfully built in the legs from playing soccer for years. Mimi is a 60cm frame.

It's my opinion from riding other bikes this year while Mimi is being refurbished, that I CAN notice a difference in leverage with longer crank arms. I'm not sure what that really means, though.

Sheldon Brown says that the smaller arms lets you stay in the "sweet spot" of your stroke easier and that in the old days, riders wanted that when practical. With 30 speed bikes, I'm not sure it means much. Brown's statement as to the real world effect was that he could tell a difference immediately after a switch in arm lenghts, but after a ride or two, couldn't tell the difference, and if there was a difference, he wasn't even sure which was better.

Who knows?

Tyson

It's not the size of your crank, it's how you use it.....

Oh Great! Now the new guy has something else to worry about...crank lenght. :eek:

The adjstable cranklenght is the key, based on the long-standing rule that men who have bigger feet will naturaly require larger cranks. 'Some cranks are almost fully extended at all time, while other chranks remain at small size until they need to rise to the occasion and demstrate a level of penitrablity which satify the needs that Knees need as they assume the missionery position. Most missionaries actually road their bike to minister to their parish. Hence what was originally a term to describe a missionaries favorite bike riding position, with the hands on the drop bars and away from the brakes.On long day a minister confused his bike with his wife, and a Myth was borne.

For $50 I can tell you how to lengthen your crank

Snap the crank 'll pop!

:D

Conventional wisdom has it that a person my size, 6 ft - 34.5" stand over, should use a 175mm crank.

I quite accidentally found that I am most comfortable with a 170mm crank.

Anyone else bucking convention?

I'm 5' 10 3/4" (was well over 5' 11" when younger, just short of 6') - 34.75 inseam
If having to make a choice between 175 & 170 will always choose 170.
The leverage increase is very little for a 170 to 175 (less than 3%) but to maintain the same cadence the legs have to move signifcantly faster and with greater degree and range of movement. This is easily noticeable for me at cadences over 90, and very noticeable at any cadence over 100. AT lower cadences of around 60, the 175 does feel good. But I almost never ride down that low
For me this is another case of 'less is more', 'smaller is faster'.

A lot of potential for fun with this thread.
I will bite my tongue, I will bite my tongue, I will bite my tongue . . . .

So, if you have a longer crank will you bonk more ???

This page:

http://www.machinehead-software.co.uk/bike/cranks/cyclist_crank_length_calculator.html

Informs me that I should be using a 155mm crank.

If true, then right now my crank is too long.

Smiling Bob should be able to shed some light on this!

On long day a minister confused his bike with his wife, and a Myth was borne.
Oh heck! Now my secret is out!

"Hi! I'm Bob. And I'm smiling!"

I tried out some 155s this past spring. Although they felt smooth and my knees really liked them, I was slower all around and there was this 8% hill that should have been a doddle but I had to walk. After that, I went back to the 170s.

edit: oh, and my cadence ran about 10 rpm higher with the short cranks.

This got me to thinking about the cadence thing. Because I've had a very hard time getting my cadence up to 80. If my crank is 15mm too long (I should ask my wife about this) then that may be a factor.

I'm 5'10", and have had much better success with 170 over 175. Seat height is a bit less critical, and the loss of leverage is marginal.

30" inseam and by most reckoning I should be using 170MM cranks or less. Have always had bikes with 170 fitted from new. Except for the Tandem and that is 175MM. A couple of years ago I decided to fit the Tandem cranks top the Other bikes and did not notice any difference. Borrowed a set of 165MM from a friend and they were different. The saddle had to go up a bit. Pedalling felt no different but the Spin rate increased slightly.

All my bikes seem to have 175MM on as the replacements, bought on Sell out, only seem to come in that size. Can't say I have noticed that I am wrong, but Slow cadence at low gears might prove me wrong. Luckily- I seem to have just enough gears for the hills so hopefully that will not occur.

Edit- Thinking about it- I did have one set of lightweight cranks that used to bend. That did affect me but perhaps it is not the length of cranks that is the probem. Perhaps it is the strength of the legs that denotes what crank length you can push.

Double Edit-- That is wrong because in theory, a stronger leg would be able to push a shorter crank with its lower leverage. A weaker leg would require a longer crank to get higher leverage- and I know that my legs are pretty strong.

The accepted theory is that if you have shorter cranks you can spin higher and longer cranks require power.

All this talk of cranks and my head has gone- I'm going for a ride to settle the brain. So I can see if my 175mm cranks are better than my other 175mm cranks.

For some reason, everything on bikes, including their frame sizes, are available in all sizes and pretty well every component on bikes are infinitely adjustable - with the partial exception of cranks! I wonder why???? They all seem to come with 175 - 170mm cranks?!? A bike for a 4' 9" or 6' 6" individual all come pretty much with the same crank size?? Doesn't make a lot of sense!

I went to shorter cranks, but for an altogether different reason which is probably not applicable to most people. My LWB bent came with the usualy 175's and I went down to 155's. ?could even be shorter?152's?? Can't remember but they were custom built by a fellow named Mark Stonich in Minneapolis.
I have had several back surgeries and a stroke which leaves my left leg weaker in the knee than my right leg. I ride a LWB bent, the only thing I can ride comfortably more than 5 - 10 miles and still walk the next day. I've learned through trial and error that the best way I can ride, particlarly uphill, is with a faster cadence than other riders. Uphill or downhill, fast or slow, I'm usually about +- 110, often faster! It's just the way my knee seems to work best, and presumably for the same reasons, I sit a bit crooked in the seat, slightly rotated to the left and I think I partially make up for the left knee weakness by using my abdominal muscles on the left pedal stroke. Everyone who follows me comments on it! It works great for me, after trying a variety of other things.
But by going to a shorter crank you should gear down the front chain rings to make up for it, or you will lose leverage and as someone pointed out, you might have to walk up hills. Shorter cranks and overall gearing down a bit MIGHT slow your top speed down a little, but I still easily hit 45+ on downhills before spinning out. Plenty fast enough for this old geezer!
There are many bent riders out there that really do benefit from shorter cranks. The geometry of bents seem to make them more efficient with shorter cranks, as long as you gear down the front chain rings to make up for the loss of leverage. Most bent drivers, (but not all) report significant improvement and increased comfort and climbing ability with shorter cranks and a higher cadfence. Most bent riders (and also a lot of DF riders) report much less knee pain using a shorter crank as well, assuming your knees give you pain with the longer 170 - 175's. A lot of people with mild osteoarthrits or old knee injuries can and do benefit from longer crank arms even though their cadence will increase.
A lot of this may or may not apply to DF riders, though there has been some interesting research on measuring power output from riders with different crank lengths. The results have been mixed, so at this point it boils down to a trial and error situation. I suspect it won't be long before you can order any length of crank you want either as a new or aftermarket component, just as you can currently custom order pretty well everything else on bikes. If it feels good, do it!

Good discussion and links for shortened cranks, especially pertaining to recumbents
bikesmithdesign.com/

What you need is some good Crank Polish: http://www.bikeforums.net/showthread.php?t=248789

I love it , two threads in one !

I'm only 5' 8" and was using a 172.5 then switched to a 170.0 and noticed little if any difference. Back to a 172.5 now. My leg strength is probably a notch above my cardio, and I've read if that's the case you might want longer cranks to allow you to utilize leg power. We're only talking 2.5 mm here, which can easily be accounted for in the type of pedals you use, the cleat on your show, the thickness of the sole of your shoe, etc. Not enough to worry about. I'd say you'd have to jump 5 mm before you'll really notice a big difference.

Even 5mm is only about 1/4 inch more radius of the peddling circle your feet travel, although that translates into a circle 1/2 inch more in diameter. still not a great deal of difference.
I went down from 175's to about 152's which is about 2 inches LESS diameter of the circle my feet must travel. (someone else do the math of the circumference - I'm terrible at math!) As I pointed out, for me in my unique circumstance it has worked out extremely well. For others, shortening up or even lengthening may or may not be beneficial!?!
Still, it makes no sense for the commercial bike companies to make long legs, short legs, and everything in between go around the same circumference......little knees, big knees, arthritic knees, normal knees, knocked knees, etc...... Too bad someone wouldn't come out with some kind of a "trial and error' telescopic adjustable crank arm for bike shops to lend or rent to people to try to see if changing crank arm length might help their power, or their knees, or make things more comfortable for them in other ways.

I find it odd that a company would put a 170 or 175mm crank on a new bike with a 14"-16" frame.

If a 15" frame fits you, then you don't have long legs.