# Pros and cons of switching to 180mm cranks.



## FATTRAXX (Nov 26, 2004)

i have always had 175's but am kicking around the idea of going to 180's.anyone who's done this,let me know if it was a good thing or not.seems the extra leverage would be an advantage on a SS.do the longer cranks slow down your spinning? not to concerned about striking the cranks on rocks,my bottom bracket height seems like i would be okay.
let me know what to expect if i make the switch.


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## quaffimodo (May 25, 2004)

Try a search; this one's been discussed a lot.


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## slocaus (Jul 21, 2005)

*54 replies here*

http://forums.mtbr.com/showthread.php?t=229645&highlight=180mm+cranks


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## Cloxxki (Jan 11, 2004)

Don't see 180 as "long" and 175 as "average". If there's be such categories, they'd be both oin the same "average" at best. Try if you can even tell a dfference, it's not all that easy.


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## Upchuck (Jan 30, 2004)

Cloxxki said:


> Don't see 180 as "long" and 175 as "average". If there's be such categories, they'd be both oin the same "average" at best. Try if you can even tell a dfference, it's not all that easy.


I can feel the difference. In fact, I'm so used to using 180s on my SS (primary ride) that I feel a little cramped in the cockpit when I ride my gearie with 175s. BTJM


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## mtnbykr©™ (Jan 6, 2004)

Cloxxki said:


> Try if you can even tell a dfference, it's not all that easy.


really easy for me. i can tell the difference in spin from the 175s to the 180s. seems easier to cruise w/ the 180s.


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## CB2 (May 7, 2006)

I can't tell the difference between 170's and 175's, except I wack my pedals on more rocks with the 175's.
I'd imagine the switch from 175's to 180's would be similar, for me at least.


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## mtnbykr©™ (Jan 6, 2004)

FATTRAXX said:


> i have always had 175's but am kicking around the idea of going to 180's.anyone who's done this,let me know if it was a good thing or not.seems the extra leverage would be an advantage on a SS.do the longer cranks slow down your spinning? not to concerned about striking the cranks on rocks,my bottom bracket height seems like i would be okay.
> let me know what to expect if i make the switch.


i've noticed i get a better spin [for me...] from 180s. i like the way i ride on 180s. i probably do have more pedal strikes w/ 180s but... i fell like i get better torque also. try em.


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## unit (Nov 24, 2005)

*short answer*

Pros:

More leverage.

Cons:

More movement in the stroke.

What does that mean? You can run a taller gear, but will have more oportunity for pedal strike, and more flexure of your knees and hips. This may make spinning more difficult, and may be bad for you if your body is more suited to shorter cranks.

I choose a shorter gear and shorter arms...it just works best for me. I like to ride my bike everywhere....roads, trails, trials stuff, urban, you name it. Shorter works best for me. You may be different (many are).


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## Cloxxki (Jan 11, 2004)

I do notice, but it's not in-my-face noticeble. I notice it most with short steep (dune) climbs, with 175mm the power can't be transferred as well, and you stall sooner.
More than a 5mm change does take some getting used to, for me. I'm now pretty used to 185mm, have it on the SS offroader and the 5spd monstercross commuter.


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## pvd (Jan 4, 2006)

it really depends on how long your femur is.


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## slocaus (Jul 21, 2005)

pvd said:


> it really depends on how long your femur is.


Uh, care to back this statement up with some information, references, links, etc.?


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## bykegnurd (Jun 8, 2005)

*knee pain...*

I had so much knee pain with 180mm cranks I thought I was going to have to give up my SS. I started riding my geared bike with 175's and the pain went away. I switched the SS to 175 and the knee pain has never come back. I'm 5'9", so this may not affect taller guys.

However, anytime I'm climbing a really steep hill, I miss the 180's, they definately give extra leverage that made clearing tough climbs easier. There are a couple of hills I have to walk the top portion of now that I used to be able to clear when riding 180's.


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## Sarvis (May 2, 2005)

slocaus said:


> Uh, care to back this statement up with some information, references, links, etc.?


Bill Boston and Lennard Zinn both use femur/inseam length calculation to suggest crankarm length.

Personally I follow Andy Pruitt's suggestions "Crank length formulas using femoral length or leg length are fine, but if your style is mashing, use longer cranks, and if you are a spinner, shorten them a bit."

S


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## plume (May 26, 2006)

Someone tried to convince me that I should try 170 cranks instead of 175 because they're easier to spin. My first thought was the leverage loss, no thanks, I'll spin all day if it means I can make most hills...


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## serious (Jan 25, 2005)

Use the crank length that is appropriate for your size and use gear ratios to manage torque at the wheels. I am 5'6" and use 175mm for mtb (both geared and SS) and 172.5 for road.


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## Daner (Apr 30, 2004)

I am 5'10" with relatively long legs but low flexibility and power. For several months last season I ran gearies with 170 and 175 cranks and a SS with 180 cranks. Maybe I didn't give it enough time, but I found the difficulty with smoothing out my spin on the 180's distracting enough to more than offset the 2.857% torque advantage from the longer lever arm. In my experience, there is just about always that much more toothpaste in the tube...


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## kapusta (Jan 17, 2004)

slocaus said:


> Uh, care to back this statement up with some information, references, links, etc.?


Being someone with two different length femurs I can attest to the truth of this.


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## hangdog98 (May 3, 2004)

Too many people have failed to factor in the other four levers in the crank length equation. The upper and lower legs are every bit as important in calculating crank length as all the other factors combined. A 6' 6" rider with long legs may need a 200mm crank _or longer_ to optimize his pedal action. A short legged rider of 5' 1" tall may need 155mm cranks to get the best overall performance. The 'normal' sizes are made for one purpose only, to keep production costs down. There are at least a dozen formulae to calculate crank length and only two that factor in the mechanics of femur and tibia length. One advocates longer cranks, the other is closer to conventional lengths. Personally, I like longer. Lance spins like crazy and was reported to use 180mm cranks even though he isn't tall by _any_ measure. Don't be fooled by the people who just want to sell you the cranks they have in stock. If you want the best result you'll probably need longer cranks and you'll need to get used to them, AND you'll need to make sure the rest of your cycling position is in order too. zinncycles is a good resource. Also check out Steve Hogg's work on position at cycling news


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## Daner (Apr 30, 2004)

Factors to consider:
Femoral length
Tibia length
Rider's physical flexibility
Type of bicycle
Geometry of bicycle
Upper cockpit configuration
Type of terrain
Intensity of effort
Duration of effort

and not to be ignored:
Past experience

All of them interact and must be taken into account if the goal is to find the best possible compromise for a specific application. Luckily enough for us, humans have proven to be fairly adaptable, so there is plenty of fun and function to be had with less-than-optimal crank lengths. Many (who inhabit the middle of the bell curve stature-wise) are satisfied enough that they never even think about it.


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## pacman (Jan 16, 2004)

FATTRAXX said:


> i have always had 175's but am kicking around the idea of going to 180's.anyone who's done this,let me know if it was a good thing or not.seems the extra leverage would be an advantage on a SS.do the longer cranks slow down your spinning? not to concerned about striking the cranks on rocks,my bottom bracket height seems like i would be okay.
> let me know what to expect if i make the switch.


I took the 3% extra leverage and changed my chainring from 32 to 33. With an equal pedal force - 3% faster. The longer stroke means you tranfer 3% more energy per revolution. then there's the small matter of your body but ...


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## kapusta (Jan 17, 2004)

pacman said:


> I took the 3% extra leverage and changed my chainring from 32 to 33. With an equal pedal force - 3% faster. The longer stroke means you tranfer 3% more energy per revolution. then there's the small matter of your body but ...


Actually, if you increase the crank and the chainring the same percentage (in this case roughly 3%.) you are not gaining any mechanical advantage. The same force at the pedals will give the same acceleration as before. The difference is that for each pedal stroke you exert that force over a greater distance and for a longer time. So yeah, you are getting more energy transferred to the wheels each stroke, but you are putting in more as well.

I'm not saying the longer cranks don't work better for you as personal experience is the best measure, so if you think they work better for you, then I'm sure they do.


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## eischman (Apr 5, 2005)

kapusta said:


> Actually, if you increase the crank and the chainring the same percentage (in this case roughly 3%.) you are not gaining any mechanical advantage. The same force at the pedals will give the same acceleration as before. The difference is that for each pedal stroke you exert that force over a greater distance and for a longer time. So yeah, you are getting more energy transferred to the wheels each stroke, but you are putting in more as well.
> 
> I'm not saying the longer cranks don't work better for you as personal experience is the best measure, so if you think they work better for you, then I'm sure they do.


I agree....went to 180s and went back to 175s. The 180 were nice when pushing down but the 175s were better when pulling up and spinning. I have actually thought about trying 170s but all my bikes are 175 so I decided to stay put


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