160mm cranks for TT?

Discuss light weight issues concerning road bikes & parts.
jockster
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by jockster

So I am going to switch to a dedicated Rotor 3D crank with a Power2Max on the time trial bike and thought about downsizing from my current 172.5's to 165s or even 160mms to open up the hip angle for better power. With no real experience in the issue i am however worried that 160s could be on the short side as I am 180cm tall.

What do you reckon?

Article on the subject - http://www.cervelo.com/en/engineering/a ... ength.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

preludervtec
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by preludervtec

I switched from 170mm to 155mm cranks about 1.5 years ago and have had really good results so far. It has helped increase my cadence and also helped my run after the bike. As you can tell, I am a triathlete so I am not totally sure how beneficial they are for just road biking.

jockster
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by jockster

preludervtec wrote:I switched from 170mm to 155mm cranks about 1.5 years ago and have had really good results so far. It has helped increase my cadence and also helped my run after the bike. As you can tell, I am a triathlete so I am not totally sure how beneficial they are for just road biking.


Thanks for your input. How tall are you?

preludervtec
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by preludervtec

I'm 5'5"

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Juanmoretime
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by Juanmoretime

At 183cm tall I do run shorter cranks on my tt bike. Road I kind of run short but they feel best at 172.5 and I run 170mm on my tt bike. I doubt if I would go shorter and I do have a 87.9 cm inseam.

You may get better response or better yet do a search at Slowtwitch since there are many threads there on the same subject.
RESIDENT GRUMPY OLD MAN.

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Devon
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by Devon

I always thought longer cranks were better, mechanical advantage, torque etc.
Campagnolo; because it's a bicycle, not a fishing rod.

munk93
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by munk93

I believe it's a question about cadence. If you're a big powerrider, running big gears I believe that the 177,5 or 180 is a great choice. I'm also a bit tall (187cm), but prefer riding lower gears with a higher cadence. My best tt's was on 170 arms, but I don't think that I should go shorter than that. Been riding 175 this year, but I think it's hard to compare, since I haven't been in the same shape, as I was a couple of years ago

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WMW
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by WMW

jockster wrote:What do you reckon?


I'm a little taller than you and ride 150s. It's definitely more comfortable, but so far power is about the same. I have 2cm more drop as well, and aero is a tad better.

172s on the road... no trouble switching back and forth.
formerly rruff...

jockster
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Joined: Fri Apr 13, 2012 7:25 pm

by jockster

Ok, so the summary is that going between crank lengths isn't an issue, neither is power production with a shorter crank and finally, people taller than myself feel happy with shorter cranks than I have intended to get.

But qith facts clearly showing that hip angle can be opened with shorter cranks, resulting in a far more aero position, how come we don't see the pro peloton riders using shorter cranks on their TT rigs?
I know Sastre used 165s in TTs but haven't heard of anyone more recent doing it, or have I just been blind?

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WMW
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by WMW

If any pro is using short cranks (like <160mm) I'm not aware of it.

One thing you need to remember is that pro racers tend to have a large upper/lower leg length ratio which makes it easier for them to run long cranks with less quad-hip pinching. On the other hand some of them are really short... those guys look like they could really benefit from it.

You also might be surprised how much influence myth and tradition have in cycling vs science and logic. I've known many riders who were simply not open to changing their notions about what is fast.
formerly rruff...

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by User Name

I figure the main benefit of shorter cranks is getting more aero, mostly for people with issues with their thighs 'encountering' their guts; and they may also help guys with poor flexibility. Pros rarely seem to have these issues when time-trialing, even with "normal"-length cranks.

A while ago, I was reading about some tri guys who not only go for shorter cranks, but will also drop their saddle, even if they lose power, obviously because the net aero gain outweighs the loss of output.

My opinion on the power thing is that it's pretty much a wash: longer cranks may provide more leverage, but the increased hip and knee flexion makes them harder to push when seated, and vice versa for shorter cranks (easier to pound, but may provide a little less leverage). Riding off the saddle is different: the possible extra leverage of longer cranks can be utilized, because the restrictions of hip and knee flexion go out the door.

I've experimented with every length from 165 to 180s (most of which I still have, but I got rid of the 180s. I'm 6ft with long legs), and after all these years, I still can't tell if I'm faster/stronger on any particular length. However, I do like longer cranks for mashing off the saddle on short hills or bridging gaps, but i prefer shorter cranks when my knees are sore.

When i first read about shorter cranks helping with aerodynamics, I rode 165s for a few months, and was no slower than i was on any other length. Uncanny! :p

I heavily persisted with 180s for over a year, but I ended up just hating the position they put me in.
My regular length these days is 170 or 172.5, mostly because they were more ubiquitous on Ebay every time I wanted a new pair of 7800s. :D

justkeepedaling
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by justkeepedaling

I believe that there is the potential for more aero using shorter cranks, but I believe it was John Cobb who showed that it isn't always necessarily the case.

Burgunder
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by Burgunder

I'm 176 cm with an inseam of 80 cm, and I think I will try 165 mm cranks for my next build for ROAD use.

I have 172,5 cranks atm. but I can't help thinking that it doesn't feel smooth enough no matter what saddle hight I'm using and I'm having trouble with high cadences. It might be relatited to my pedalling technique but I think it's worth a try especially when you add to this that I have some problems with my knees.

mfrassica
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Joined: Thu Sep 26, 2013 7:01 pm

by mfrassica

jockster wrote:So I am going to switch to a dedicated Rotor 3D crank with a Power2Max on the time trial bike and thought about downsizing from my current 172.5's to 165s or even 160mms to open up the hip angle for better power. With no real experience in the issue i am however worried that 160s could be on the short side as I am 180cm tall.

What do you reckon?

Article on the subject - http://www.cervelo.com/en/engineering/a ... ength.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;


I am 173 cm (5' 8") and used 160's a few years ago. I gave them a season to adjust. However, when I went back to 170mm cranks, it just felt right to me and was faster (for me). One way to try out for not much money invested, go with square taper BB, and use BMX cranks (origin8 double ring cranks). The only thing with that is the BCD is 110 not 130, so you may have to invest in some new rings.

But would do that before I dropped serious money into a setup.

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by User Name

Burgunder wrote:I'm 176 cm with an inseam of 80 cm, and I think I will try 165 mm cranks for my next build for ROAD use.

I have 172,5 cranks atm. but I can't help thinking that it doesn't feel smooth enough no matter what saddle hight I'm using and I'm having trouble with high cadences. It might be relatited to my pedalling technique but I think it's worth a try especially when you add to this that I have some problems with my knees.
It's definitely worth a try, in my opinion. 172.5 to 165 obviously gives you a 15mm smaller pedal circle.

You should be able to get some used 165s on Ebay for not much.

A short friend mine of has (I think) an 81cm inseam, and he's always complain that he doesn't like the position he gets in with 170s. I've urged him several times to at least try some of my 165s, but he stubbornly refuses

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