rojas28

hi i am 5'9 with a inseam between 78 79 cm i am currently running 172.2 mm cranks that came with my bike i have toe overlap in my bike and am planing to change my cranks to resolve the problem and maybe to get more comfortable in my fit ..also running 50 34 planing on getting 52 36 cranks because in 34 plate i spinn to fast and has to cross chain will i notice any negative effect on this changes... if u can help me please ?? or it will better just to get 165 mm cranks with 50 34 and also if i can use ultegra frc8000 11 speed crank with 10 speed chain and cassette derelerius etc....

JohnDThompson 

What kind of riding do you do?

Toe overlap is only an issue at very low speeds and sharp cornering; most road riders never encounter situations where this would be an issue.

Technical, off-road riding is more likely to have a problem with toe overlap.

rojas28

i think endurance on flats on a bike lane not alot stops but on my way home i do have some stops and i know is not a problem but i just ruin a brand new shoes because i cant get use to not hit front tire sometimes when i stop and accelerate from a dead stop i just steer and pedal and hit the shoes i know cant be avoid but is not funny destroying shoes while u learn not do it i also read shorter cranks should benefit shorter riders and also be most comfortable i dont not if a 7.2 mm difference combine with a 23 c tire on front will give me enough clereance too??

smashndash

Of all the reasons to change your crank length, toe overlap is probably one of the least important.

Your optimal crank length is determined by your performance goals, your pedaling preferences, your leg length, your torso angle, your hip joint flexibility, your tibia length/knee height, your saddle fore-aft position, and probably a few others I’m forgetting. Notice how toe overlap isn’t on here.

That being said - you’re in luck. Based on pure interweb conjecture, I think you’ll like 165mm cranks more than 172.5mm. I say go for it if you have the funds. Just understand that a) you need to move your saddle up and back, b) you need to go into an easier gear and pedal faster.

delbiker1 

What area of your foot are you planting on the pedal., and at what angle? I see quite a few people, especially younger ones, with the instep or the heel on the pedal. That can surely cause toe overlap, and to me, it looks quite uncomfortable.Your reasoning for going to 52/36 isn't making any sense to me. If you are spinning to fast on the 34 tooth, gear up to the 50 tooth ring.

rojas28

i know but that why if i do i plan to just get 52 36 so dosent affect my cadence that much what you think ??

rojas28

am using spd cleat and dosent matter how much i move the cleat foward still get toe overlap and sometimes when u get wind front of you u just lower the front gear because with the 50 is to hard to pedal so with the 34 unless u dosent cross change it u gonna spinn to fast

Drew Eckhardt 

That's normal and you're not going to fix it with shorter cranks.

At low speeds just make sure your outside foot isn't forwards when turning.

BlazingPedals

Dumb thought, but if you're spinning too much in the 34T, shift to the 50T. Anyway, if you're going to use shorter crank arms, it's normal to gear lower, not higher. Shorter arms will make your pedal circles smaller and allow you to increase cadence for a given foot speed; which offsets the lower leverage offered by shorter arms.

smashndash

Cleat position should NOT be adjusted to remedy toe overlap.

Actually, if you are riding more than 2 or 3 miles, literally no fit adjustments should be made based on toe overlap. Get a bike with a longer reach or “front center” measurement and a slacker head angle, then put on a shorter stem if you really want to get rid of toe overlap.

I have a bike with an high amount of toe overlap. Probably more than yours. If you put some effort in, I promise it’s not an issue.

Going to shorter cranks means less leverage. Your gears will become effectively harder. I say stick with 50/34 if you want to get new cranks. It’s ok to cross chain a little. Just don’t use the 34 x 2 hardest cogs or 50 x 2 easiest cogs, if you have 10 or 11 speed.

jgwilliams

As others have pointed out, if you move to shorter cranks you will tend to increase your cadence so I would initially stick with the 50/34 combo until you get used to the new cranks.

Technically it's clearly true that a shorter crank will give you less leverage. However, I saw a report many years back, when I was considering it myself, that suggests that in practice it makes almost no difference. The researcher had experimented with a number of different crank lengths from 120 - 220mm. (I can't find it but it was a 2001 study with prof. Jim Martin). He found the power output varied by only 4%.

The reason, I think, was due to the natural change in cadence. If you think about the design of piston engines, they used to use a much longer stroke. A high performance car from 1930 would typically top out at 4,500 rpm. Nowadays engines use a much shorter stroke but turn at a far higher rate to generate more power. Obviously there are many factors at play there but the stroke length is definitely a factor.

Phil_gretz

I've read all of the remarks to this point. I echo what others have said. You do not need to change your cranks. You need to learn to spin, to comfortably sustain rpms at that rate, and to adjust the gearing to stay in the higher rpm range. Unless you are a very strong man who can grind higher gears for the duration, of course. These people exist, but it's likely that you are not one of these.

As for toe overlap, it happens. It happens in low speed maneuvering where the front wheel swings over a larger arc. Like another poster said, you must be conscious of that and keep your lead foot to the inside of the arc. On my commuter bike, I get toe overlap strikes on occasion. I've learned to avoid them mostly and to ignore the ones that happen infrequently.

Bottom Line: Don't change your cranks.

weight4it

Hi I found an article regarding crank length, interested to hear your thoughts on this:

p.s. I can't post URLs but if you can search it's called "determinants_of_maximal_cycling_power_Crank_length_pedaling_rate_and_pedal_speed"

AnthonyG

Ditto. Toe overlap is the least important reason to change crank length however, based on your quoted inseam measurement I think you would be happier with 165mm cranks.

dubes

I'd like to ask about this, because while I avoid things the "big-big" and "small-small" gear combinations on my triple cranks, I have considered all gear combinations fair game with doubles? (Though to be honest I haven't done small-small because at that point, as has been suggested to the OP above, I'll have shifted to the larger front chainring before then). For me, that's be one of the big advantages of double cranks.

Mike

smashndash

Meh. I regularly use all my combos on accident. Small-small causes rub in my FD so I don’t stay in it very long and big-big is incredibly loud, partly due to the increased RD chain tension. Your chain isn’t going to explode if you use an extreme gear. If I end up in one of those gears, I try to get out whenever is convenient.

Some people like to climb long hills in their Big-big. That sounds like a recipe for accelerated chain wear for sure. It’s not even fast??

I mainly said that as a “best practice” rather than a set rule. A straighter chainline is a better one and an extreme cross chain has a straighter equivalent. The difference between double rings is only like 2 or 3 shifts.

smashndash

The reason power remains consistent is flexible gearing. If you put a 120mm crank and a 220mm crank on a fixed gear track bike, you would see a massive difference in power.

smashndash

“The optimal crank length was 20% of leg length or 41% of tibia length.”

I don’t know how they arrived at this number when they only had 120, 145, 170, 195, and 220 mm cranks. The jumps between each crank length are somewhere around 15-20% each. That’s not enough precision to make that claim. What if 155mm or 165mm was optimal for some people? I’ll need to download the full paper probably.

I have done a lot of reading about crank lengths. The science has spoken. Assuming that you have the gearing you need to maintain an optimal cadence, you should go with a short crank that allows you to pedal smoothly in a low and aerodynamic position while maintaining full breathing capabilities. Ideally with a straight-ish back. This is because we know that getting low makes you faster, breathing helps you go maintain that position for longer/indefinitely and a shorter crank (within reason) will not affect your power output.

If you have a big belly, this goes out the window. Don’t get a 140mm crank just so you can slam your stem. Also, don’t set your saddle back over your rear axle and then say you need a 140mm crank. A low, aero position demands high power to be sustainable, which demands a high and forward saddle position. Get your fit right and work from there.

Miele Man

You're thinking about changing 172.2mm cranks to 165mm cranks to gain an extra 7.2mm of space. How much does you foot presently overlap the front wheel? If it's greater than that 7.2mm then changing the cranks isn't going to get rid of toe overlap.

Cheers

TheDudeIsHere

Toe overlap is fairly common and once you know it is there, not a problem. I have a bit on one of my roadies and haven't hit it in years after knowing it's there

So unless you make slow turns with your pedals at 6 and 3..........

Homebrew01

Yup. Only an issue making tight U-Turns.

I have massive toe overlap on one bike due to tight geometry, and slightly bent back fork, but only think about it in the driveway.

Drew Eckhardt 

Your power at 100 RPM using the 120mm cranks and 55 RPM using the 220 RPM would be about the same as long as you weren't sprinting.

Sustainable power is limited by how fast your muscle cells can produce adenosine triphosphate.

(Sprinting you need 120 RPM to recruit the maximum number of fast twitch fibers)

jgwilliams

Well, clearly. You couldn't use a different cadence if the gearing was the same.

AnthonyG

While it is true that its easier to maintain a higher cadence with shorter cranks this isn't the whole story.
The nature of the interface between human legs and mechanical cranks and the angles that our muscles travel through, through the entire crank rotation means that there are widely differing torque outputs at different points in the cycle.
Longer cranks may increase the torque advantage at one point in the cycle yet also make the torque lower at a different point in the cycle.
Shorter cranks may lower the absolute torque at the max point in the cycle yet they also improve the torque available at the off point in the cycle.
Shorter cranks smooth out the torque delivery through the entire cycle and since power is torque x rpm you don't really lose power with short cranks within reason.
Moving the seat back with shorter cranks in order to maintain your previous KOPS position also seems to open up the angles that your muscles have to travel though which helps to maintain torque through the low point in the cycle.

BlazingPedals

My power drops off precipitously at over 100 rpm, while some people can't even hit that cadence; so I think your number there is highly individualized.