Login required to started new threads

Login required to post replies

Prev Next
My testing to try and find best crank length with my Velotron
Quote | Reply
So after another poor bike season, being hit by Frank Day again, being off season, looking for a new bike, looking at bike fit, etc. I have started, again, to try and gather real data as to what crank length is best for me, a very tall person at 6'5. Everyone has their opinions, but as an engineer, I want numbers, and so far have not been able to find anyone who, IMO, has done some real testing.

Frank has always told me I all the test equipment needed with my Velotrons, adjustable cranks, etc.

So, you have seen my one post working on bike fit and have gotten some great inputs. But none of them talk about bike cranks since basically no one spends the time, or money, to do real testing!

So working with Frank, I have started to do some testing riding at 200 watts, changing RPM's from 110, 95, 80 and 65 after 10 minute blocks and recording HR to gather some data.

I have been riding basically the same 2 routines, one is a 120 watt spin 90 minute session, the other is an interval setup where I warm up with a step 160 to 300 watt, 1 minute steps, then a 150 watt 5 minute, 190 watt 5 minute, and then 4 230 watt, 10 minute with a 150 5 minute spin in between. I spin a 50/16 gear for 84 gear inches.
I have years of data on these ride on how far I have gone.

So last night I changed my powercranks, which are adjustable from 140 to 220mm, from my normal 200mm cranks to 175mm. Raised the seat 25mm and moved a tad forward, and rode my interval test. I usually ride around 20 miles in 90 minutes. (I rode like 27 twice which I made a mistake and changed the gear to 50/18).

So I get on to ride this morning, and after a few seconds I say time to stop, this feels weird. But, I mentally said got to do some testing. As I was riding, it started to feel a little better. What was weird is with 200's, my rpm would be around 80. But with the 175, I was doing close to 100. My speed with the 200's was around 20 mph. With the 175, it was like 23 or so. At the end I was pretty shocked to see the results. 26.85 miles. Only one data point, but in the 50/16 gear, I have never been able to spin that fast and hold it, had such a high MPH, or ridden that far.

So, now I am asking, were these results correct? If so, .....

So, will continue to post more test results as I get them. I will probably do 2 day cycles. Will do the interval work that I did today. Then tomorrow, I will ride the same setup and do Franks HR test.

Then I will shorten another 5mm, raise seat 5mm, stay at a 50/16 gear, and test again.

Seems at some point the cranks will get too short such that I would be spinning way too high of an RPM to hold. But, shall be interesting to test and see at what point I get there.

So going to put on my 175 cranks on my race bike, do a refit, and post the video on the other thread. I will then race 2 races in October with them that I have done before, and doing with some friends. So I can compare time to past, and time to my friends.

So, do these test seem fair? Has anyone else done test like these and have test results?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:
Has anyone else done test like these and have test results?

Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh

Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh

I just move around.

What test setup did you use to get these numbers? What were your heart rates? RPM's? Gear inches used? Distance traveled?

Why did you stop at 165? How tall are you? Inseam length?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh

Huge point!
Quote Reply
Re: My testing to try and find best crank length with my Velotron [ggeiger] [ In reply to ]
Quote | Reply
ggeiger wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


Huge point!

why

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
I am 6' tall and have tried between 177.5 and 150 from 175 down in 5mm lengths and settled on 160 as I found 150's too short and hard to maintain power constantly without concentrating on pedalling in circles as any deficiencies in your pedal action start to get highlighted more. Over time my cadence DROPPED about 15 rpm on shorter cranks and I still average around the same power at a lower heart rate for an IM. It takes time and all I can say is each time I dropped 5mm was like wow this feels amazing until I went into the 150's which just start to feel too short. What your trying to do is interesting but I don't think is a true representation of what would be the best crank for you based on how shorter time you are testing them as your body and position needs to adapt. I played around over a three year period giving each length a period of time to trial and racing on each.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


I just move around.

What test setup did you use to get these numbers? What were your heart rates? RPM's? Gear inches used? Distance traveled?

Why did you stop at 165? How tall are you? Inseam length?

I've done this on a Computrainer as well as Tacx Neo with an SRM as well as Power2max power meter equipped bike. The when you're doing power testing I feel gear inches and cadence for that matter are pretty irrelevant as is distance on a Computrainer as that varies with the press on force. It's watts you can produce for 20+ minutes that we're really interested in!!!! Heart rate is probably worth monitoring for grins and giggles. Mine runs a bit lower at a lower cadence for the same power up until ~ threshold power.

My dear 5'2" wife switched for 170s to 155s with the same result i.e. able to ride with more power in aero but no greater or lessor power when allowed to manage hip angle.

Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
Dave, you need to move your saddle 2.5 cm higher and 2.5 cm further back in my view. don't move the saddle forward.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:
ggeiger wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


Huge point!

why

The tight hip angle caused by the long cranks when riding in aero will greatly magnify how much they hurt your power production compared to shorter cranks. Sitting up as much as you want will open the hip angle allowing you to produce more power with the longer cranks. I can make just as much power riding aero with 165s as I can sitting up but with 177.5s my power is down at least 15 if not more watts while riding aero.

Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [Shambolic] [ In reply to ]
Quote | Reply
Shambolic wrote:
I am 6' tall and have tried between 177.5 and 150 from 175 down in 5mm lengths and settled on 160 as I found 150's too short and hard to maintain power constantly without concentrating on pedalling in circles as any deficiencies in your pedal action start to get highlighted more. Over time my cadence DROPPED about 15 rpm on shorter cranks and I still average around the same power at a lower heart rate for an IM. It takes time and all I can say is each time I dropped 5mm was like wow this feels amazing until I went into the 150's which just start to feel too short. What your trying to do is interesting but I don't think is a true representation of what would be the best crank for you based on how shorter time you are testing them as your body and position needs to adapt. I played around over a three year period giving each length a period of time to trial and racing on each.

In some ways true. I have years of results from these training runs. And by doing this on the velotron, I collect lots of real time data. Yea, riding each setup for a long time might be ideal, but not practical.

So, I will do at least some tests kinda like you have done and collect the data. Once I get enough, and decide to use a certain length based on data, I still will be able to ride this 7 days a week collecting more data comparing to the years of data I have. I then would start be able to compare against race results on races I have done for years. It may not be perfect, but it may be way better than where I was starting these changes.

Any idea why your RPM's dropped back down over time?

At 6'5, stuff below 200mm feel short. But, if I can see the data in my testing, that at shorter lengths my HR is lower, my RPM's stay up, and my distance increases, well, shorter I will go.

Thanks for the inputs.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
h2ofun wrote:
ggeiger wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


Huge point!


why


The tight hip angle caused by the long cranks when riding in aero will greatly magnify how much they hurt your power production compared to shorter cranks. Sitting up as much as you want will open the hip angle allowing you to produce more power with the longer cranks. I can make just as much power riding aero with 165s as I can sitting up but with 177.5s my power is down at least 15 if not more watts while riding aero.

I assume you meant not riding aero.

Yes, I have seen that kind of power increase when I move from sitting up on the hoods, to being on the hoods, to being aero.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [devashish_paul] [ In reply to ]
Quote | Reply
devashish_paul wrote:
Dave, you need to move your saddle 2.5 cm higher and 2.5 cm further back in my view. don't move the saddle forward.

I raised the saddle 25mm higher.

But, I see no logic moving back. The seat moves back when raising, which would seem to decrease the angle. I like riding real steep, like 80 or 81, rather than a slack road bike angle of what like 74.. So if I push the seat back, seems it would make the bike more slack? And if I move the seat back, seems I would then need to move
the aero bar pads back. I also should raise the pads but at the moment, at least on my race bike, I have no way of doing that. Will deal with that later, depending on how my back and other parts work out with the change of cranks and seat height.

Thanks

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:
sciguy wrote:
h2ofun wrote:
ggeiger wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


Huge point!


why


The tight hip angle caused by the long cranks when riding in aero will greatly magnify how much they hurt your power production compared to shorter cranks. Sitting up as much as you want will open the hip angle allowing you to produce more power with the longer cranks. I can make just as much power riding aero with 165s as I can sitting up but with 177.5s my power is down at least 15 if not more watts while riding aero.


I assume you meant not riding aero.

Yes, I have seen that kind of power increase when I move from sitting up on the hoods, to being on the hoods, to being aero.

Are you doing the testing while sitting up or riding aero? Please answer this first. I seem to remember you do all your Velotron sitting up rather than aero but might be mistaken.

Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
h2ofun wrote:
sciguy wrote:
h2ofun wrote:
ggeiger wrote:
sciguy wrote:
h2ofun wrote:
Has anyone else done test like these and have test results?


Not as big a change as you but when I swap from 177.5s to 165mm cranks I output exactly the same power for 5, 10, 20 or more minutes. I am able to ride a vastly more aero position with the 165s or put another way can output more power in a decent aero position with the 165s compared to the 177.5s. Are you doing your testing aero or sitting up?

YMMV,

Hugh


Huge point!


why


The tight hip angle caused by the long cranks when riding in aero will greatly magnify how much they hurt your power production compared to shorter cranks. Sitting up as much as you want will open the hip angle allowing you to produce more power with the longer cranks. I can make just as much power riding aero with 165s as I can sitting up but with 177.5s my power is down at least 15 if not more watts while riding aero.


I assume you meant not riding aero.

Yes, I have seen that kind of power increase when I move from sitting up on the hoods, to being on the hoods, to being aero.


Are you doing the testing while sitting up or riding aero? Please answer this first. I seem to remember you do all your Velotron sitting up rather than aero but might be mistaken.

I move back and forth between sitting up holding the aero bar pads, to leaning over on the bike horns, to in the aero bars. I just do not have the mental to sit in the aero bars all the time on the trainer. This is what I have always done, so at least my testing process is the same. Since I am not measuring power during these tests, and yes I see power going up or down depending on which position I am in. Since I am doing erg testing, the power always stays fixed.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
Dude. Testing? I know you've seen this already:

http://bikeblather.blogspot.com/...erwithin-reason.html

...and if you haven't, then you've been willfully not paying attention!



http://bikeblather.blogspot.com/
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:
I move back and forth between sitting up holding the aero bar pads, to leaning over on the bike horns, to in the aero bars. I just do not have the mental to sit in the aero bars all the time on the trainer. This is what I have always done, so at least my testing process is the same. Since I am not measuring power during these tests, and yes I see power going up or down depending on which position I am in. Since I am doing erg testing, the power always stays fixed.

If you're really riding in erg mode then gear inches and distance traveled are not the least bit relevant and are just confusing the issue at hand. It's the wattage you can produce and hold that are of interest with heart rate at a specific wattage of some slight secondary interest as well.

If you're doing testing setting up like in the photo below it's not going to be very helpful either as one would hope you're not usually in this position for much of a race. You should be searching for a position to race in with solid power output not one to just train in.


Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
h2ofun wrote:

But, I see no logic moving back.

That's because you don't understand geometry, apparently...



http://bikeblather.blogspot.com/
Quote Reply
Re: My testing to try and find best crank length with my Velotron [h2ofun] [ In reply to ]
Quote | Reply
Regarding the distance thing:

Sheldon Brown is rolling over in his grave right now. May he RIP.

We don't need data to prove a higher cadence on shorter cranks will make you go faster -and further (assuming same gearing). It's a scientific fact called gear ratios. Works just like your car engine. Higher rpm's in 5th gear vs lower rpm's in 5th gear..... which one is faster?

Please use this tool to see it for yourself and compare crank lengths and cadences.

http://www.sheldonbrown.com/gear-calc.html

get comfortable being uncomfortable
Quote Reply
Re: My testing to try and find best crank length with my Velotron [Tom A.] [ In reply to ]
Quote | Reply
Tom A. wrote:
Dude. Testing? I know you've seen this already:

http://bikeblather.blogspot.com/...erwithin-reason.html

...and if you haven't, then you've been willfully not paying attention!

Interesting article, and I have, and continue to struggle with this over the years as I have moved around with crank length.

But there is the comment about what helps with a better bike fit. With the 200's, they were way up. Clearly with 175's, they are not.

Clearly there is no one answer. I still was pretty shocked to see the difference in distance on a training session I have done many many times.

Oh well, at least I have the parts so it really costs me other to play with this stuff. If truely folks going to shorter cranks were "bad", why are so many doing and not saying their bike or run times have been worse?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [stevej] [ In reply to ]
Quote | Reply
stevej wrote:
Regarding the distance thing:

Sheldon Brown is rolling over in his grave right now. May he RIP.

We don't need data to prove a higher cadence on shorter cranks will make you go faster -and further (assuming same gearing). It's a scientific fact called gear ratios. Works just like your car engine. Higher rpm's in 5th gear vs lower rpm's in 5th gear..... which one is faster?

Please use this tool to see it for yourself and compare crank lengths and cadences.

http://www.sheldonbrown.com/gear-calc.html

If Dave is actually testing in erg mode the whole distance or speed variation is irrelevant.

Genetics load the gun, lifestyle pulls the trigger.
Quote Reply
Re: My testing to try and find best crank length with my Velotron [Tom A.] [ In reply to ]
Quote | Reply
+1,000,000,000,000,000,000,000,000,000,000
Quote Reply
Re: My testing to try and find best crank length with my Velotron [stevej] [ In reply to ]
Quote | Reply
stevej wrote:
Regarding the distance thing:

Sheldon Brown is rolling over in his grave right now. May he RIP.

We don't need data to prove a higher cadence on shorter cranks will make you go faster -and further (assuming same gearing). It's a scientific fact called gear ratios. Works just like your car engine. Higher rpm's in 5th gear vs lower rpm's in 5th gear..... which one is faster?

Please use this tool to see it for yourself and compare crank lengths and cadences.

http://www.sheldonbrown.com/gear-calc.html

So, what do you suggest? Or Tom? Just stay with 200's? Am I wasting my time trying to find a better fit with shorter cranks?
How would you do a test to see if the shorter cranks "help"?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
stevej wrote:
Regarding the distance thing:

Sheldon Brown is rolling over in his grave right now. May he RIP.

We don't need data to prove a higher cadence on shorter cranks will make you go faster -and further (assuming same gearing). It's a scientific fact called gear ratios. Works just like your car engine. Higher rpm's in 5th gear vs lower rpm's in 5th gear..... which one is faster?

Please use this tool to see it for yourself and compare crank lengths and cadences.

http://www.sheldonbrown.com/gear-calc.html


If Dave is actually testing in erg mode the whole distance or speed variation is irrelevant.

So, how would you test? Should I just stay with 200's? One second I get inputs that my cranks are too long, the next second is I get inputs
that crank length means nothing.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [sciguy] [ In reply to ]
Quote | Reply
sciguy wrote:
h2ofun wrote:

I move back and forth between sitting up holding the aero bar pads, to leaning over on the bike horns, to in the aero bars. I just do not have the mental to sit in the aero bars all the time on the trainer. This is what I have always done, so at least my testing process is the same. Since I am not measuring power during these tests, and yes I see power going up or down depending on which position I am in. Since I am doing erg testing, the power always stays fixed.


If you're really riding in erg mode then gear inches and distance traveled are not the least bit relevant and are just confusing the issue at hand. It's the wattage you can produce and hold that are of interest with heart rate at a specific wattage of some slight secondary interest as well.

If you're doing testing setting up like in the photo below it's not going to be very helpful either as one would hope you're not usually in this position for much of a race. You should be searching for a position to race in with solid power output not one to just train in.

True, oh well, sorry for not being an expert, but have no issue admitting this.

Of course I am. I guess when I work with folks, my goal is to help them, never to talk them down.

And nope, I do not ride that way all the time, but yep there are times I need to, and that was in a race. Road conditions. Having to stretch my back leg out. Tired.
But at the end of the day, if I were just so so bad, I would be last in all my races and never show up again. Folks can bet me up all they want for my bike. I just smile
and say great race when I run by them and ask why they cannot run, and put in the total best time for the race, not just the bike. :)

So again, what is your expert process to deal with crank lengths and testing?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply
Re: My testing to try and find best crank length with my Velotron [Tom A.] [ In reply to ]
Quote | Reply
Tom A. wrote:
h2ofun wrote:


But, I see no logic moving back.


That's because you don't understand geometry, apparently...

So, teach me, or is that just too low for you?

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
Quote Reply

Prev Next