- This topic has 25 replies, 14 voices, and was last updated 13 years ago by hels.
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165 crank length?
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dirtbiker100Free MemberPosted 13 years ago
I'm 5ft 8 with 30" leg, currently riding a trance but that may one day change to an ST4, maybe a 5, not sure yet. Current cranks are 170 length
Are 165 crank length going to be too short for me?
Seen some ISIS middleburn arms for £45 and am tempted.dirtyriderFree MemberPosted 13 years agono they will not be too short
165 are recommended for 32" inseams, the whole 175mm as a norm is just a cost exercise
it doesnt REALLY make a difference though
mangatankFree MemberPosted 13 years agoI'm the same height (bit taller) and use 170mm after a knee injury a few years ago. Shorter cranks means it's easier to spin at higher cadences without putting so much strain on the knee joint. Obviously this is more relevant to road cycling, and the theory for longer off-road cranks is that rough terrain benefits from the extra leverage, but ideally you should get the correct length of crank for your size and personal needs. Try not to let money dictate the choice with something like this.
A quick Google will give you all the information you need on the subject.
mboyFree MemberPosted 13 years agoTry em, you might like the shorter length.
For £45 it's not going to be an expensive exercise at least if you don't like em, you can sell em for what you paid probably.
Personally, I use 170's across the board, I've got a 33" inseam. 175's feel a touch long to me, but it's what I'm used to, and I used to have dodgy knees so tried shorter cranks to combat it ages ago and stuck. 165's would probably feel a touch short for me though, may work for you with a shorter leg.
avdave2Full MemberPosted 13 years ago30" or so inside leg here and I use 165mm cranks. I took my old Marin out for the first time in over 4 years recently which has 175mm cranks and did notice a lot more pedal strikes but that was about it. Off road I don't think it makes a huge difference but on the road I have noticed a difference and find the shorter cranks better for my knees. I think the difference between on and off road is that I tend to use a higher cadence for more of the time on road sections and also on the road I spend much longer in one position whereas off road I move more around on the saddle and stand or hover over it a lot more.
If you like to spin rather than grind then go for the shorter cranks.
coffeekingFree MemberPosted 13 years agoI think they'll probably be fine. I have a 34" leg and foudn 165s ridable but a snatch short, so it stands to reason you'll be fine with them.
elaineanneFree MemberPosted 13 years agohmm i was asking about 165 crank lenght last year… im just 5ft small with about a 27 inside leg…. i have 170 cranks on my orange bike… i do find when im out riding with other people i have to crank up abit faster cos whilst they are doing 2 turns of the cranks im doin about 4… no dont tell me to go faster cos i already do ! lol prob cos my bike is only 14 inch frame so abit smaller than your average persons bike ? is this taken into consideration ? but yeah i do have to pedal that bit faster,,,.. gud job ive got enuff muscles then.. 😆
futonrivercrossingFree MemberPosted 13 years agoCripes – using the chart – I need 160mm cranks! I'm assuming you measure your inseam with shoes on?
Where did you find those cranks???
mangatankFree MemberPosted 13 years agoim just 5ft small with about a 27 inside leg
You sound like a candidate for new cranks! I'd say that 170mm were far too long for you. Part of it is spinning, but the other part is long term wear and tear on cartilage and tendon. That can't be repaired easily, if ever.
Have you tried the plumb line test? Sit on the bike (supported by a wall) with your pedals level and drop a plumb line down from your forward knee. The plumb line should drop through the centre of the pedal axis. If it does, then you've got less to worry about. If not, then you're certailny straining things. Saddle and stem position can help of course, but only up to a point.
elaineanneFree MemberPosted 13 years agoyep i have my saddle and stem postion about right (i have a ragley seatpost on my bike and its numbered so i know the exact position that feels right as seatposts go…
i wonder if the bike shop shud have mentioned smaller cranks when i bought the bike ? they new how small i was… i huess its all down to personel preference… so run this by me agin someone…whats the theory with having smaller cranks…does this means harder peddling tho ? (more spins of the crank as opposed to 170mm..mangatankFree MemberPosted 13 years agoPut simply, shorter crank lenghts give less leverage over rough terrain, but you'll gain in your ability to spin the gears more efficiently on climbs. Importantly, the shorter length will also put less strain on your knee joints.
It's worth looking into pedalling/crank length theory if only to learn how to protect your body in the long term.
edit:
I should mention cadence, by which I mean the number of turns the pedal makes in a minute. It's a grey area for off-road riding but I try to maintain a steady 70 rpms (revolutions per minute). I say 'try', because it's rarelly possible! The act of trying to maintain that target RPM means that I make good use of the gears while lessen the strain on my legs and maintaining a comparativly high speed. The one thing you don't want to do is heave on the pedals as low speed. People out there will proudly tell you that they never use the 'granny' ring, as if it's some sign of weakness to use the bike efficiently. Try to ignore these people! During every ride I'll use the entire range of gears, and the rare occassion that I'm overtake on a climb, the other person is always using the same technique. Above all, it's good for your knees.
elaineanneFree MemberPosted 13 years ago…but im always on rough terrain…. ! shud i be looking at 165 or 160mm cranks then ?
grtdkadFull MemberPosted 13 years agoI'm 5'10"ish and recently changed from 175mm to 170mm. I ride our local hills (a lot) and have noticed a benefit on the climbs (and my dodgy knee is less of a problem). I have noticed however that I tend to spin out on one of the fast tarmac downhill blasts on the way home…so can't have it all I guess.
mangatankFree MemberPosted 13 years agoIt's hard to source 160mm mtb cranks, but getting as close to your size is worthwhile. XT and XTR come in 165mm. Sadly SLX only comes in 170mm upwards.
http://www.merlincycles.co.uk/mountain-bike-chainsets/shimano-xt-770-chainset.html
Here's yet another link to more bike sizing. Geared slightly towards MTBing this time.
MountainMonkeyFree MemberPosted 13 years ago+1 for what mangatank says Elaine.
I'm 5'4" and have 165s on my mountain bikes and am in the process of changing my road cranks to them too. I have dodgy knees and find 165s make a difference to me – I find less strain on my knees and the bonus is it's easier to spin efficiently too – so it's easier to maintain power while pedaling over obstacles. I'd recommend getting some 165mm XTs if you can afford to – I think you'll appreciate the difference at your height. It certainly made a difference to me.
Oh and dirtbiker – you should be fine, the accepted wisdom seems to be shorter cranks won't do any damage (though could feel odd I guess), whereas long ones can put extra strain on your knees.
Check out the legend that is Sheldon Brown for the full arguments! That's what convinced me to try them and I'm sooo glad I did!
FuzzyWuzzyFull MemberPosted 13 years agoMost people on MTBs sit way too far back anyway (relative to the plumb line optimal position anyway), regardless of crank length. Although I'd agree you want to be careful with crank lengths on a road bike I wouldn't be overly concerned about switching from 170's to 165's (if you can even find 165's).
DrDomRobFree MemberPosted 13 years agoI've just, literally about ten minutes ago, bought the 175mm XT's from Merlin…. I should probably have read this first though, I'm 5' 11" with a 32" in seem, I have no idea what my current crank length is.
Oh well, I am sure it will all be fine!
MountainMonkeyFree MemberPosted 13 years agoDrDomRob – I wouldn't worry too much, I don't think it matters too much unless you're at the far ends of the scales or have dodgy knees (so I tick both boxes), at 5'11" you'll probably be fine on 170s or 175s. As I say, unless you have dodgy knees it shouldn't do any harm. Just enjoy the new cranks!
mangatankFree MemberPosted 13 years agoCheck out the legend that is Sheldon Brown for the full arguments
Ah Sheldon. I owe him a lot too!
Dr DomRob: You're borderline I think. If you're in doubt, go for the shorter ones and pick up the phone to Merlin. They're friendly people.
MountainMonkeyFree MemberPosted 13 years ago😀 Yeah, he was a great man!
Again I agree with Mangatank, Merlin customer service is ace in my experience. I'm sure they'd change them for you, if you wanted.
london_ladyFree MemberPosted 13 years agoTA Vega cranks go down to 155mm
http://www.specialites-ta.com/produits/crank/crankdetails1_gb.htmelaineanneFree MemberPosted 13 years agoyeah ive searched all afternoon for smaller cranks but they are hard to come by…. race face has sum but they are sooo expensive
elaineanneFree MemberPosted 13 years agoaccording to the chart i need 165mm cranks… as opposed to the 170mm i have now..tho we are talking mm… wud i notice any difference at all ? maybe better on climbs ? …
helsFree MemberPosted 13 years agoI have run 165mm cranks on all my bikes for years now, (5ft nothing) it was a revelation. Never really noticed the whole rpm thing, it was more about getting the position right. With 175s my knees were coming up too high, and feet too far apart stadning on pedals. Seems daft that 10mm could make such a difference !!
Clearance way better too, somehow, can't explain that one.
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