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Real world difference between 175mm & 180mm cranks?

#1 2011-10-05 8:46am

GTLover
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Real world difference between 175mm & 180mm cranks?

Could someone please tell me what difference I will feel between the two as far as racing is concerned? Reason I'm asking is that I usually ride 175 (not really sure why, just "always did"), but I recently acquired a nice set of 180's. I would hate to go to all the trouble to sell/rebuy another set just to get the 175's, so I'm seriously considering running the 180's. So, is there a chart out there that shows rider height, leg inseam, or some other factor as to why you run a certain length vs. another? I'll be using 44/15 gearing btw. Thanks for your help.


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#2 2011-10-05 8:57am

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Re: Real world difference between 175mm & 180mm cranks?

You can definitely feel the difference.  I find a lot more speed out of 180's


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#3 2011-10-05 9:01am

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Re: Real world difference between 175mm & 180mm cranks?

Godzilla wrote:

You can definitely feel the difference.  I find a lot more speed out of 180's

Due to the extra length applying more leverage/torque I suppose? Are they much harder to get started out of the gate?


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#4 2011-10-05 9:10am

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Re: Real world difference between 175mm & 180mm cranks?

i go by feel, but i'm sure someone knows of a chart out there.  i had 180's on my Redline, but with the 18.5" top tube it felt like i was climbing a giant staircase while riding, especially going up hills.  i felt over-extended at the apex of the power stroke, and it made the ride feel a little out of control at times.  i changed down to 175's and it made a huge difference - it was surprising to me the difference those 5mm made.  i put the 180's on my Race Inc (with a 20" top tube) and she rides great, with none of the feel of the 180's on my Redline.

don't know if this helps, but i just did this change-up a few days ago and it was surprising to me.  i've never changed my cranks, so to experience the size difference on both my rides was interesting.  i didn't expect it to be as noticeable as it is.  good luck!


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#5 2011-10-05 9:15am

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Re: Real world difference between 175mm & 180mm cranks?

To add a little to this topic - I found this site that explains a bit about the theory and has a chart

http://www.myra-simon.com/bike/cranks.html

I will be using 180s for the time on a new flatland build I am working on. Why? Because that is what I bought tongue


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#6 2011-10-05 9:16am

scarfish
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Re: Real world difference between 175mm & 180mm cranks?

i've always wondered this myself. i don't race, just cruise the hood. alot of hills around here. i'm assuming the 180's would be easier going up hills. would allow you to throw more body weight into peddling. but would be a hurtful when trying to gain speed on flat ground. your legs would have to move more to gain the same rotation. i could be wrong.

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#7 2011-10-05 9:17am

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Re: Real world difference between 175mm & 180mm cranks?

Oaktown Massive wrote:

i go by feel, but i'm sure someone knows of a chart out there.  i had 180's on my Redline, but with the 18.5" top tube it felt like i was climbing a giant staircase while riding, especially going up hills.  i felt over-extended at the apex of the power stroke, and it made the ride feel a little out of control at times.  i changed down to 175's and it made a huge difference - it was surprising to me the difference those 5mm made.  i put the 180's on my Race Inc (with a 20" top tube) and she rides great, with none of the feel of the 180's on my Redline.

don't know if this helps, but i just did this change-up a few days ago and it was surprising to me.  i've never changed my cranks, so to experience the size difference on both my rides was interesting.  i didn't expect it to be as noticeable as it is.  good luck!

That info helps alot, thanks! I'm in the same boat in that I always had 175 on my smaller TT bikes. The one I'm thinking of putting the 180's on has a 19.5 TT, so it sounds like they will work great.


Looking for an OG yellow Kuwahara laidback post for my Bravo. Any condition. PM me if you have one.
I need some chrome Hoffman Love Handles, PM me if you have some for sale/trade. Hoffman Easy Chair seat too!
Brothers on my jock for the way I ride a piece of steel...
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#8 2011-10-05 9:30am

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Re: Real world difference between 175mm & 180mm cranks?

GTLover wrote:

Oaktown Massive wrote:

i go by feel, but i'm sure someone knows of a chart out there.  i had 180's on my Redline, but with the 18.5" top tube it felt like i was climbing a giant staircase while riding, especially going up hills.  i felt over-extended at the apex of the power stroke, and it made the ride feel a little out of control at times.  i changed down to 175's and it made a huge difference - it was surprising to me the difference those 5mm made.  i put the 180's on my Race Inc (with a 20" top tube) and she rides great, with none of the feel of the 180's on my Redline.

don't know if this helps, but i just did this change-up a few days ago and it was surprising to me.  i've never changed my cranks, so to experience the size difference on both my rides was interesting.  i didn't expect it to be as noticeable as it is.  good luck!

That info helps alot, thanks! I'm in the same boat in that I always had 175 on my smaller TT bikes. The one I'm thinking of putting the 180's on has a 19.5 TT, so it sounds like they will work great.

180's on a 19.5 TT sounds like it would work for me... it's all about feel.  the 180's on my RI provide more leverage and feel great - the bike overall feels faster, and the extra torque needed at the start was easy to get used to.  on my second ride, it wasn't an issue... but it wasn't in a race situation.  it's been years since i raced, so i cant help you there.


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#9 2011-10-05 9:33am

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Re: Real world difference between 175mm & 180mm cranks?

Axel10 wrote:

To add a little to this topic - I found this site that explains a bit about the theory and has a chart

http://www.myra-simon.com/bike/cranks.html

I will be using 180s for the time on a new flatland build I am working on. Why? Because that is what I bought tongue

Thanks for that link. I just got done shoving a book in my crotch. And now my book smells funny.......hmm


Looking for an OG yellow Kuwahara laidback post for my Bravo. Any condition. PM me if you have one.
I need some chrome Hoffman Love Handles, PM me if you have some for sale/trade. Hoffman Easy Chair seat too!
Brothers on my jock for the way I ride a piece of steel...
So what cha saying?

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#10 2011-10-05 1:21pm

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Re: Real world difference between 175mm & 180mm cranks?

There's a huge difference.  180's  are way faster and torkier if you got the leg length and strength.    Only draw back is your toes may hit the ground more often so you have to remember to keep your bike more level when pedaling out of a turn so you don't scrape.

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#11 2011-10-05 1:28pm

timt
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Re: Real world difference between 175mm & 180mm cranks?

My inseam suggests 175's. That's what I rode all summer. I just switched to 180's and I like them much better.  If they are too long your peddling will seem choppy when trying to ride fast. That's my take at least.

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#12 2011-10-05 1:35pm

jerseybob
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Re: Real world difference between 175mm & 180mm cranks?

you can run a little more gear with the 180's,or run the same ratio and be quicker. same principle as a car,motorcycle or anything else.  more torque,less gear ratio required.

they do push your knees up a little more when riding,and can make a small frame feel worse. usally raise seat too like 10 mm. to compensate

I have everything from 165's to 190's on bikes.  the online chart for me says 177. 175's work pretty good  for me.

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#13 2011-10-05 2:08pm

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Re: Real world difference between 175mm & 180mm cranks?

If you can spin 180s, the advantage of the extra torque out of the gate is significant.  If you can't spin 180s without getting choppy, you'll have to go with masher gearing (higher) and that will cancel out the benefit out of the hole.

General rule of success in BMX racing: run the longest cranks you can spin, but no longer!

I run 180's on the bikes I cruise around on and 175s on my race bikes. On the track 180's get choppy and I get unstable, 175s feel much better.  My inseam in pants is only 29", if your inseam is 31" or more, I would expect 180's to be fine for most people.


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#14 2011-10-05 3:27pm

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Re: Real world difference between 175mm & 180mm cranks?

175s give you a little more clearance if you run pegs. if you are use to  175 and switch to  180 you may clip your heels. on the pegs.that is what happens to me so i switched back to 175.


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#15 2011-10-05 5:20pm

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Re: Real world difference between 175mm & 180mm cranks?

.197 inches difference. That's about an 1/8 of an inch, and really a lb of tire pressure makes more of a difference than that. With theory you can always pick the fly poop out of the pepper, but what's the use? Run what you got


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#16 2011-10-05 10:32pm

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Re: Real world difference between 175mm & 180mm cranks?

Here is an artical from bike guru Sheldon Brown explaining the answer to your question: http://sheldonbrown.com/cranks.html


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#17 2011-10-05 10:43pm

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Re: Real world difference between 175mm & 180mm cranks?

I think its all about cadence. Longer crank slower cadence shorter faster.

I couldnt run 180s on my flatlander the pedals would hit the pegs. Good luck with the 180s.


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#18 2011-10-06 6:18am

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Re: Real world difference between 175mm & 180mm cranks?

Since the original question was specifically target at racing, then yes, the 5mm can and will make a difference.  After re-reading the original post, GTLover says he's going to run 44/15 gearing.  Unless you are running a serious downhill track, that is masher gearing not spinner gearing.  You'll probably want the 180's to help you get out of the gate with gearing that tall.  If you're a big powerful guy, then you should choose a good strong chain, not a cheap one and replace it on a regular basis.  Racing with long cranks, masher gears and a small freewheel put a lot of load on the chain.


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#19 2011-10-06 9:41am

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Re: Real world difference between 175mm & 180mm cranks?

The difference is about 5mm .big_smile


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#20 2011-10-06 11:47am

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Re: Real world difference between 175mm & 180mm cranks?

cwstnsko wrote:

Since the original question was specifically target at racing, then yes, the 5mm can and will make a difference.  After re-reading the original post, GTLover says he's going to run 44/15 gearing.  Unless you are running a serious downhill track, that is masher gearing not spinner gearing.  You'll probably want the 180's to help you get out of the gate with gearing that tall.  If you're a big powerful guy, then you should choose a good strong chain, not a cheap one and replace it on a regular basis.  Racing with long cranks, masher gears and a small freewheel put a lot of load on the chain.

Yep, I'm talking about racing only. Not worried about FS bikes. What do you mean by "masher" & "spinner"? I haven't heard those terms before. As far as getting out of the gate, would 44/16 be better? How about overall 44/16 with the 180's?


Looking for an OG yellow Kuwahara laidback post for my Bravo. Any condition. PM me if you have one.
I need some chrome Hoffman Love Handles, PM me if you have some for sale/trade. Hoffman Easy Chair seat too!
Brothers on my jock for the way I ride a piece of steel...
So what cha saying?

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#21 2011-10-06 11:49am

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Re: Real world difference between 175mm & 180mm cranks?

K-frame wrote:

Here is an artical from bike guru Sheldon Brown explaining the answer to your question: http://sheldonbrown.com/cranks.html

I'm gonna take a look at that article. I read a bunch yesterday. Problem I have with most of the articles is this. Really great info overall, but the road bikes differ so much from bmx. Most of the time those guys are sitting down getting their full leg crank length. Us bmx'ers are standing the entire race.


Looking for an OG yellow Kuwahara laidback post for my Bravo. Any condition. PM me if you have one.
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#22 2011-10-06 11:54am

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Re: Real world difference between 175mm & 180mm cranks?


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#23 2011-10-06 12:24pm

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Re: Real world difference between 175mm & 180mm cranks?

GTLover wrote:

cwstnsko wrote:

Since the original question was specifically target at racing, then yes, the 5mm can and will make a difference.  After re-reading the original post, GTLover says he's going to run 44/15 gearing.  Unless you are running a serious downhill track, that is masher gearing not spinner gearing.  You'll probably want the 180's to help you get out of the gate with gearing that tall.  If you're a big powerful guy, then you should choose a good strong chain, not a cheap one and replace it on a regular basis.  Racing with long cranks, masher gears and a small freewheel put a lot of load on the chain.

Yep, I'm talking about racing only. Not worried about FS bikes. What do you mean by "masher" & "spinner"? I haven't heard those terms before. As far as getting out of the gate, would 44/16 be better? How about overall 44/16 with the 180's?

The term spinner is used to describe riders with fast leg speed that can maintain smooth pedaling/riding with a high RPMs on the crankset.  Spinner gearing is usually lower than 44-16.
(43-16, 42-16, 44-17 etc.)

The term masher is used to describe riders who don't have the leg speed so they gear higher and try to use brute force at a slower RPM to achieve the same speed on the track.  Masher gearing is usually 45-16 and higher (46-16, 44-15 etc.)

All other factors being equal, lower gears and longer cranks will get you out of the gate quicker, but your top speed will be limited by your ability to spin fast enough to reach top speed.

44-16 with 175-180 cranks is classic BMX gearing which has been around for decades.  It's a great place to start, you can make adjustments from there. 

If you feel like you get "spun-out" without reaching full speed, then you might need to gear up or practice more smile

If you feel like your pedaling gets "choppy" like you aren't able to pedal fast in smooth circles, you might want to shorten your cranks. 

It sounds like you might be new to this, in which case, don't worry so much about your gearing or cranks.  Buy some good safety gear and take it easy on the track for a while until you get the feel of things and you start to develop some bike control skills big_smile  Adults starting out are usually able to go way faster than their bike handling skills will support.  The end result is usually a nasty crash and several weeks off the bike. 

A lot of guys come out to the track, assume it's all about pedaling, race a few times, crash hard once and never come back again.


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#24 2011-10-06 6:27pm

Axel10
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Re: Real world difference between 175mm & 180mm cranks?

Good info Chris. Thanks.

cwstnsko wrote:

GTLover wrote:

cwstnsko wrote:

Since the original question was specifically target at racing, then yes, the 5mm can and will make a difference.  After re-reading the original post, GTLover says he's going to run 44/15 gearing.  Unless you are running a serious downhill track, that is masher gearing not spinner gearing.  You'll probably want the 180's to help you get out of the gate with gearing that tall.  If you're a big powerful guy, then you should choose a good strong chain, not a cheap one and replace it on a regular basis.  Racing with long cranks, masher gears and a small freewheel put a lot of load on the chain.

Yep, I'm talking about racing only. Not worried about FS bikes. What do you mean by "masher" & "spinner"? I haven't heard those terms before. As far as getting out of the gate, would 44/16 be better? How about overall 44/16 with the 180's?

The term spinner is used to describe riders with fast leg speed that can maintain smooth pedaling/riding with a high RPMs on the crankset.  Spinner gearing is usually lower than 44-16.
(43-16, 42-16, 44-17 etc.)

The term masher is used to describe riders who don't have the leg speed so they gear higher and try to use brute force at a slower RPM to achieve the same speed on the track.  Masher gearing is usually 45-16 and higher (46-16, 44-15 etc.)

All other factors being equal, lower gears and longer cranks will get you out of the gate quicker, but your top speed will be limited by your ability to spin fast enough to reach top speed.

44-16 with 175-180 cranks is classic BMX gearing which has been around for decades.  It's a great place to start, you can make adjustments from there. 

If you feel like you get "spun-out" without reaching full speed, then you might need to gear up or practice more smile

If you feel like your pedaling gets "choppy" like you aren't able to pedal fast in smooth circles, you might want to shorten your cranks. 

It sounds like you might be new to this, in which case, don't worry so much about your gearing or cranks.  Buy some good safety gear and take it easy on the track for a while until you get the feel of things and you start to develop some bike control skills big_smile  Adults starting out are usually able to go way faster than their bike handling skills will support.  The end result is usually a nasty crash and several weeks off the bike. 

A lot of guys come out to the track, assume it's all about pedaling, race a few times, crash hard once and never come back again.


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#25 2011-10-06 8:10pm

hollywood23
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Re: Real world difference between 175mm & 180mm cranks?

What about 175 drive arm and a 180 or the other way. Running a different sizes on each side.

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