Made the switch to 155mm cranks

Oct 21, 13 11:56

Post #1 of 60 (13859 views)

I've been riding 165mm cranks without any problems for a couple seasons. 2 months ago, I started upping my running mileage from 50mpw to 70mpw and started hating being in the aerobars (maybe due to the decreased flexibilty I had experienced?) I tried raising my bars by 1cm, but it still wasn't ideal. I decided to switch to 155mm cranks via Origin8 and a 107mm sq taper bottom bracket.

After installing the new crank /bb, I raised my seat 1cm to maintain my saddle height. I left the saddle set back and arm pad stack the same. All I can say is wow, I feel so much better. No change in power ouput, but I can comfortably ride low without the need to come out of the aerobars.

I really love the 155mm cranks. Will I prefer 150mm or 145mm (smallest I can go without losing power as per Jim Martin)?

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 21, 13 12:49

Post #2 of 60 (13783 views)

Nick,

Are you riding with a Powertap power meter or is it just your perception that power is the same?

Thanks for the information.

Hugh

Genetics load the gun, lifestyle pulls the trigger.

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 21, 13 13:00

Post #3 of 60 (13740 views)

Ya i dropped 10mm to 165's and felt a ton better, but i think 155 will be my sweet spot too. Just have been too lazy to switch, or just waiting for nicer cranks to come in that length. I believe there are a few companies where you can order custom sizes now? Glad to hear you found your sweet spot. What a difference a little bit can make in how your entire position can feel.

Clinchers are faster, short cranks are faster, wide is often more aero than skinny, i feel like i'm in some bizarro world. Of course i'm using my early 80's mentality to compare it too. Just glad i'm not too old to accept change from some really entrenched ideas from the cycling world.

Re: Made the switch to 155mm cranks [monty] [ In reply to ]

Oct 21, 13 13:04

Post #4 of 60 (13717 views)

I dunno, I think Mavic's kona yaw angle data may suggest the wider is more aero than narrow (for wheels) is wrong!

At least, if you are willing to run a narrow tire anyway. So we still have that, maybe!

monty wrote:

Ya i dropped 10mm to 165's and felt a ton better, but i think 155 will be my sweet spot too. Just have been too lazy to switch, or just waiting for nicer cranks to come in that length. I believe there are a few companies where you can order custom sizes now? Glad to hear you found your sweet spot. What a difference a little bit can make in how your entire position can feel.

Clinchers are faster, short cranks are faster, wide is often more aero than skinny, i feel like i'm in some bizarro world. Of course i'm using my early 80's mentality to compare it too. Just glad i'm not too old to accept change from some really entrenched ideas from the cycling world.

Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
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Last edited by: jackmott: Oct 21, 13 13:06

Re: Made the switch to 155mm cranks [sciguy] [ In reply to ]

Oct 21, 13 13:44

Post #5 of 60 (13649 views)

sciguy wrote:

Nick,

Are you riding with a Powertap power meter or is it just your perception that power is the same?

Thanks for the information.

Hugh

Similar question: How does power vs torque play into the issue of a shorter crank? I would think that since the lever is shorter, one would either have to apply greater power to turn a crank at the same speed or if the same power is applied less maximum torque could be generated. The question becomes how are torque, power and human anatomy related to speed at the rear wheel. Can a physicist explain this to me?

Re: Made the switch to 155mm cranks [sciguy] [ In reply to ]

Oct 21, 13 13:47

Post #6 of 60 (13631 views)

sciguy wrote:

Nick,

Are you riding with a Powertap power meter or is it just your perception that power is the same?

Thanks for the information.

Hugh

I use a wired Power Tap Comp.

Re: Made the switch to 155mm cranks [monty] [ In reply to ]

Oct 21, 13 13:54

Post #7 of 60 (13608 views)

monty wrote:

Ya i dropped 10mm to 165's and felt a ton better, but i think 155 will be my sweet spot too. Just have been too lazy to switch, or just waiting for nicer cranks to come in that length. I believe there are a few companies where you can order custom sizes now? Glad to hear you found your sweet spot. What a difference a little bit can make in how your entire position can feel.

Clinchers are faster, short cranks are faster, wide is often more aero than skinny, i feel like i'm in some bizarro world. Of course i'm using my early 80's mentality to compare it too. Just glad i'm not too old to accept change from some really entrenched ideas from the cycling world.

John Cobb has some nice cranks available in 145, 155, and 165 in either standard or compact with a good bottom bracket for $300. Rotor 3d + also has a power meter in 155mm.

I may go the John Cobb route once I figure out how short I want to go.

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 21, 13 14:07

Post #8 of 60 (13573 views)

Very tempted to take the plunge and get some 105 165mm crank for $148. Pretty cheap "upgrade" if it allows my to bike stronger while training a high running volume.

I can save my Ultegra cranks that came with the bike for a future 10 speed upgrade of my road bike.

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Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 21, 13 14:09

Post #9 of 60 (13567 views)

Nick_Barkley wrote:

I may go the John Cobb route once I figure out how short I want to go.

In the meantime Stronglight Impact Kid is a cheap way to try short cranks (I have used them for petite riders for many years).
PCD 110 mm
130 / 145 / 150 / 155 mm

Re: Made the switch to 155mm cranks [Asilverm1970] [ In reply to ]

Oct 25, 13 19:36

Post #10 of 60 (13354 views)

Asilverm1970 wrote:

sciguy wrote:

Nick,

Are you riding with a Powertap power meter or is it just your perception that power is the same?

Thanks for the information.

Hugh

Similar question: How does power vs torque play into the issue of a shorter crank? I would think that since the lever is shorter, one would either have to apply greater power to turn a crank at the same speed or if the same power is applied less maximum torque could be generated. The question becomes how are torque, power and human anatomy related to speed at the rear wheel. Can a physicist explain this to me?

Depends on what you're comfortable with, in terms of spinning whatever gear you run.

If you switch to long cranks, from what I've read, people love mashing that with a lower RPM and having positive results. However, if you're a spinner, you can sit in a smaller gear with the shorter cranks and just spin away. You're also using a smaller range of muscles due to pedaling in shorter circles; I don't know how that bit translates to power, though.

Re: Made the switch to 155mm cranks [Asilverm1970] [ In reply to ]

Oct 25, 13 22:23

Post #11 of 60 (13259 views)

Asilverm1970 wrote:

I would think that since the lever is shorter, one would either have to apply greater power to turn a crank at the same speed or if the same power is applied less maximum torque could be generated.

That is true. On the flat, one would need to increase cadence to compensate if using shorter crank. On hills, one would need to shift to the next larger cog.

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 25, 13 22:31

Post #12 of 60 (13253 views)

Come down and ride with Dave and I. We will see how comfortable you are after a hour or so :0)

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Re: Made the switch to 155mm cranks [monty] [ In reply to ]

Oct 26, 13 6:59

Post #13 of 60 (13081 views)

Ya i dropped 10mm to 165's and felt a ton better, but i think 155 will be my sweet spot too. Just have been too lazy to switch, or just waiting for nicer cranks to come in that length.

Been riding 150s the last year on the TT, and 172s on the road. No problem switching back and forth.

And I can testify that I've not lost a bit of power even with 20mm more drop... many data points on the same TT course. I was hoping for an increase, but oh well. And the short cranks *feel* much better in aero. That may be more important for you poor guys who have to run afterwards.

I'm running old Ultegra octalinks that have been shortened by Bikesmith. That is an option if you don't want to use BMX cranks.

http://bikesmithdesign.com/..._Cranks/shorten.html

Last edited by: rruff: Oct 26, 13 7:03

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 26, 13 7:04

Post #14 of 60 (13074 views)

Do you tend to ride at a higher cadence, or lower cadence? Wondering if those experience loss of power when switching cranks may prefer lower cadence, and thus might want a slightly longer lever.

Re: Made the switch to 155mm cranks [rruff] [ In reply to ]

Oct 26, 13 7:29

Post #15 of 60 (13049 views)

rruff wrote:

I'm running old Ultegra octalinks that have been shortened by Bikesmith. That is an option if you don't want to use BMX cranks.

http://bikesmithdesign.com/..._Cranks/shorten.html

One side note with bikesmithdesign, he is currently not doing much work due to an accident last month. See webpage for info:
http://bikesmithdesign.com/Short_Cranks/index.html

I'm really interested in trying 155mm cranks but have a Quarq Riken so that's an issue.

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 26, 13 7:48

Post #16 of 60 (13020 views)

Interesting, I've been looking to drop from my 175s down to 170 or 165 but I'm having trouble finding small cranks with 130 bcd. I don't want to give up my 130 bcd Osymetric rings because I have been riding and running REALLY well with them.

Powertap / Cycleops / Saris

Re: Made the switch to 155mm cranks [Francois] [ In reply to ]

Oct 26, 13 8:10

Post #17 of 60 (12995 views)

Wondering if those experience loss of power when switching cranks may prefer lower cadence, and thus might want a slightly longer lever.

I'm not aware of anyone who has lost power with short cranks.

Re: Made the switch to 155mm cranks [rruff] [ In reply to ]

Oct 26, 13 8:13

Post #18 of 60 (12991 views)

Move to 1cm crank and tell me if you lose power ;-)

What is suggested is that you switch to the shorter cranks that do not affect power. My question is whether those preferring lower cadence will experience the power drop sooner than those with higher cadence, while trying shorter and shorter cranks.

Re: Made the switch to 155mm cranks [RichardL] [ In reply to ]

Oct 26, 13 8:17

Post #19 of 60 (12986 views)

On the flat, one would need to increase cadence to compensate if using shorter crank. On hills, one would need to shift to the next larger cog.

Nope... you can push harder, spin faster, or apply force effectively over a greater % of the circle... or a combination of the 3.

In my case my cadence went up ~3% when I switched to cranks that were 13% shorter. I suspect that most of the difference is made up from applying force over a greater % of the circle since more of that circle is now in the range where I *can* apply force effectively.

Re: Made the switch to 155mm cranks [Nick_Barkley] [ In reply to ]

Oct 26, 13 8:36

Post #20 of 60 (12973 views)

I run 165s now and because I have shitty hip flexibility am stuck at my current front end height. I am curious about going even shorter. Out of curiosity how tall are you and what is your inseam?

Re: Made the switch to 155mm cranks [sciguy] [ In reply to ]

Oct 26, 13 11:15

Post #21 of 60 (12898 views)

I rode 155s all year (coming down from 170s). My mean maximal power curve is right on top of the curves from the previous two seasons--no drop in power whatsoever, that I can see.

Re: Made the switch to 155mm cranks [rruff] [ In reply to ]

Oct 26, 13 11:29

Post #22 of 60 (12875 views)

rruff wrote:

In my case my cadence went up ~3% when I switched to cranks that were 13% shorter. I suspect that most of the difference is made up from applying force over a greater % of the circle since more of that circle is now in the range where I *can* apply force effectively.

My understanding is that the increased cadence is because your foot is traveling at the same velocity but has less distance to travel for 1 revolution. Just like if two people raced on a track at the exact same speed, but one ran in lane 1 and the other was in lane 8; obviously the guy in lane 1 would win. That's why they say the higher cadence associated with shorter cranks doesn't affect your power or endurance or anything, your body is putting out the exact same energy for that higher cadence because foot speed is constant.

Powertap / Cycleops / Saris

Re: Made the switch to 155mm cranks [CSU_Prof] [ In reply to ]

Oct 26, 13 11:46

Post #23 of 60 (12852 views)

CSU_Prof wrote:

I rode 155s all year (coming down from 170s). My mean maximal power curve is right on top of the curves from the previous two seasons--no drop in power whatsoever, that I can see.

Were you uncomfortable on the 170's? Have you been able to get into a more aero position because of the shorter cranks? I ask because I see a lot of "No drop in power" answers. It is my understanding that you should actually see an increase in power since your hip angle is less acute or you can get into a faster position without a drop in power. This is not a criticism just curious as the real actual benefits of going to a shorter crank. I know it has been discussed ad-nauseum here, but I haven't seen any real concrete data, just anecdotal.

The downside as I see it is that you have to raise your saddle which can have a pretty profound cost with regards to aerodynamics.

Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

Re: Made the switch to 155mm cranks [Ex-cyclist] [ In reply to ]

Oct 26, 13 11:54

Post #24 of 60 (12839 views)

Ex-cyclist wrote:

CSU_Prof wrote:

I rode 155s all year (coming down from 170s). My mean maximal power curve is right on top of the curves from the previous two seasons--no drop in power whatsoever, that I can see.

Were you uncomfortable on the 170's? Have you been able to get into a more aero position because of the shorter cranks? I ask because I see a lot of "No drop in power" answers. It is my understanding that you should actually see an increase in power since your hip angle is less acute or you can get into a faster position without a drop in power. This is not a criticism just curious as the real actual benefits of going to a shorter crank. I know it has been discussed ad-nauseum here, but I haven't seen any real concrete data, just anecdotal.

The downside as I see it is that you have to raise your saddle which can have a pretty profound cost with regards to aerodynamics.

There was a paper in a peer-reviewed journal a few years back on crank length and ave./max. power, I can't seem to find it, but I know I've discussed it with a friend before who actually moved up on crank length. Basically it found that crank length has almost zero impact on power production but does impact fit and the range of possible positions. Corroborates all the anecdotal evidence on ST.

____________________________________________

Re: Made the switch to 155mm cranks [Ex-cyclist] [ In reply to ]

Oct 26, 13 12:05

Post #25 of 60 (12828 views)

I have poor flexibility, especially in my hips, so I did it to get into a more aero position and be more comfortable in the aero position. I was definitely able to do that and now get a little bit more speed out of the power i generate. In other words, my power numbers stayed the same in going from the 170s to 155s, but with the various changes I made to my position, partly as a result of getting the shorter cranks, I did get a bit faster.

Ex-cyclist wrote:

CSU_Prof wrote:

I rode 155s all year (coming down from 170s). My mean maximal power curve is right on top of the curves from the previous two seasons--no drop in power whatsoever, that I can see.

Were you uncomfortable on the 170's? Have you been able to get into a more aero position because of the shorter cranks? I ask because I see a lot of "No drop in power" answers. It is my understanding that you should actually see an increase in power since your hip angle is less acute or you can get into a faster position without a drop in power. This is not a criticism just curious as the real actual benefits of going to a shorter crank. I know it has been discussed ad-nauseum here, but I haven't seen any real concrete data, just anecdotal.

The downside as I see it is that you have to raise your saddle which can have a pretty profound cost with regards to aerodynamics.

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