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2014-09-03 9:40 AM

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DC
Subject: Why am I faster on my tri bike?
Unlike the previous years, this year, I did most of my biking on my new roadie which was a carbon upgrade from an aluminum roadie. The difference in power transfer was immediately evident to me (e.g., easier to pump up hills etc). The upgrade was huge.

My tri race is Sunday, so I started hopping on my tri bike, which I have accumulated thousands of miles on. Was noticing this morning how much faster I am on it... like 3-5 MPH on courses I am very familiar with. I know, many factors are involved in a single ride, but this just seems really fast given the same/lower HR effort.

So, I understand the benefits of aero, but was wondering, how much of it can be attributed to the bike as far as "quality" is concerned? My tri bike is outright teeth-jarring stiff.


2014-09-03 9:55 AM
in reply to: Porfirio

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Subject: RE: Why am I faster on my tri bike?

more aero/stiff.  i think you just answered your own question.  i'm usually 2-3 mph faster on my TT bike over my road bike for routes i ride often. 

2014-09-03 10:02 AM
in reply to: Porfirio

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Subject: RE: Why am I faster on my tri bike?

It's all aerodynamics.

2014-09-03 10:03 AM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
Originally posted by JohnnyKay

It's all aerodynamics.




+1
2014-09-03 10:29 AM
in reply to: Leegoocrap

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Subject: RE: Why am I faster on my tri bike?

Originally posted by Leegoocrap
Originally posted by JohnnyKay

It's all aerodynamics.

+1
To infinity and beyond!

OP take a look through this article, the amount of power required to ride at the same speed (25mph) on a RB (drops) vs TB is significant.

http://www.bikeradar.com/road/gear/article/how-aero-is-aero-19273/

2014-09-03 2:24 PM
in reply to: Donto

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Subject: RE: Why am I faster on my tri bike?
I believe it's also because of your body position, the way you push off the pedals on the tri bike where you use your glutes (which provides more power) whereas you use your quads more on a road bike.


2014-09-03 2:46 PM
in reply to: goran007

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Subject: RE: Why am I faster on my tri bike?

Originally posted by goran007 I believe it's also because of your body position, the way you push off the pedals on the tri bike where you use your glutes (which provides more power) whereas you use your quads more on a road bike.

Unlikely.  Most people actually find they create somewhat less power in an aggressive TT position.  But they are still faster.  Again, it's all aerodynamics.

2014-09-03 4:47 PM
in reply to: JohnnyKay


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Subject: RE: Why am I faster on my tri bike?
3 mph seems a bit much, but yeah, you'll be faster even if the roadie is a better quality bike. That has been my personal experience as well.
2014-09-03 4:55 PM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
aerodinámica pura
2014-09-04 8:10 AM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
Originally posted by JohnnyKay

Originally posted by goran007 I believe it's also because of your body position, the way you push off the pedals on the tri bike where you use your glutes (which provides more power) whereas you use your quads more on a road bike.

Unlikely.  Most people actually find they create somewhat less power in an aggressive TT position.  But they are still faster.  Again, it's all aerodynamics.




That's interesting.
2014-09-04 8:20 AM
in reply to: Porfirio

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Subject: RE: Why am I faster on my tri bike?
Hmm, I wonder why similar power outputs can create such different average speeds:



2014-09-04 8:20 AM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
Originally posted by JohnnyKay

It's all aerodynamics.




Concur. Although I can't help but think that, given the same body positioning & frame, save less stiff, we wouldn't be as fast.

I have been considering purchasing new wheels & if the above holds true, it seems that aero benefits of the wheels aside, stiffer wheels would help.

2014-09-04 8:24 AM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
Originally posted by JohnnyKay

Originally posted by goran007 I believe it's also because of your body position, the way you push off the pedals on the tri bike where you use your glutes (which provides more power) whereas you use your quads more on a road bike.

Unlikely.  Most people actually find they create somewhat less power in an aggressive TT position.  But they are still faster.  Again, it's all aerodynamics.




From what I've heard most people produce a little less power on a TT bike than on their road bike.

However it is my understanding that your body position on the 2 should be very similar just rotated about the crank to put you in a more aerodynamic position. If this is true shouldn't you be producing the same power on either bike, but moving faster on a tri bike because of aerodynamics? If you are not producing as much power on the Tri bike does this then me you are not set up properly?
2014-09-04 8:28 AM
in reply to: DanielG


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Subject: RE: Why am I faster on my tri bike?
Originally posted by DanielG

Hmm, I wonder why similar power outputs can create such different average speeds:




This is a great visual, never seen it before but pretty much breaks it down very simply.
2014-09-04 8:59 AM
in reply to: mike761

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Subject: RE: Why am I faster on my tri bike?
Originally posted by mike761

From what I've heard most people produce a little less power on a TT bike than on their road bike.

However it is my understanding that your body position on the 2 should be very similar just rotated about the crank to put you in a more aerodynamic position. If this is true shouldn't you be producing the same power on either bike, but moving faster on a tri bike because of aerodynamics? If you are not producing as much power on the Tri bike does this then me you are not set up properly?


If you consider this image:



This is for riding at a normal (72ish) STA and you can see that the hip extensors are involved basically from 12 o'clock to about 3:30 while the knee extensors are from about 2:30 to 5:00 and the ankle plantar flexors are from 4:00-6:00. If you ride steep you are going to change when the various recruitments happen and for most, even if perfectly setup, your power will be decreased. It is quite likely that the engagement of the hip extensors will be delayed (say until 12:30) so you delaying the power phase and while you may be able to continue the power phase a little beyond 6:00 due to the rotation, the ankle plantar flexors are much weaker than the hip extensors so the added push at the end (even if you are able to do it) is not likely going to makeup for what is lost at the beginning.

Shane

2014-09-04 9:31 AM
in reply to: gsmacleod

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Subject: RE: Why am I faster on my tri bike?

So this is the premise that Rotor Q-rings/Osymetric rings are suppose to be helpful, or is that another subject all together!

Originally posted by gsmacleod
Originally posted by mike761 From what I've heard most people produce a little less power on a TT bike than on their road bike. However it is my understanding that your body position on the 2 should be very similar just rotated about the crank to put you in a more aerodynamic position. If this is true shouldn't you be producing the same power on either bike, but moving faster on a tri bike because of aerodynamics? If you are not producing as much power on the Tri bike does this then me you are not set up properly?
If you consider this image: This is for riding at a normal (72ish) STA and you can see that the hip extensors are involved basically from 12 o'clock to about 3:30 while the knee extensors are from about 2:30 to 5:00 and the ankle plantar flexors are from 4:00-6:00. If you ride steep you are going to change when the various recruitments happen and for most, even if perfectly setup, your power will be decreased. It is quite likely that the engagement of the hip extensors will be delayed (say until 12:30) so you delaying the power phase and while you may be able to continue the power phase a little beyond 6:00 due to the rotation, the ankle plantar flexors are much weaker than the hip extensors so the added push at the end (even if you are able to do it) is not likely going to makeup for what is lost at the beginning. Shane



2014-09-04 9:40 AM
in reply to: mike761

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Subject: RE: Why am I faster on my tri bike?

Originally posted by mike761
Originally posted by JohnnyKay

Originally posted by goran007 I believe it's also because of your body position, the way you push off the pedals on the tri bike where you use your glutes (which provides more power) whereas you use your quads more on a road bike.

Unlikely.  Most people actually find they create somewhat less power in an aggressive TT position.  But they are still faster.  Again, it's all aerodynamics.

From what I've heard most people produce a little less power on a TT bike than on their road bike. However it is my understanding that your body position on the 2 should be very similar just rotated about the crank to put you in a more aerodynamic position. If this is true shouldn't you be producing the same power on either bike, but moving faster on a tri bike because of aerodynamics? If you are not producing as much power on the Tri bike does this then me you are not set up properly?

I'll go with scientist Shane's explanation. 

My comment was mostly observational.  I do know people who say they can achieve the same power in road and TT position.  But I think the big difference is that as you go more agressive, you close your hip angle further.  I assume that helps account for the different engagement patterns that Shane is taking about.  You certainly don't want to close up this angle so much that you lose a lot of power and negate any aerodynamic savings.  But, becuase aerodynamics are so critical, you can afford to lose some power and still be faster.  Of course, a seperate issue is if you are comfortable enough in riding that way to get off and run well.  That can depend how long you have to saty in the position (eg, a sprint vs. IM).

2014-09-04 9:45 AM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?
This isn't meant to be snarky, but is your computer calibrated for the tires on the TT bike? If you had 25mm tires on your road bike and moved your computer to your TT bike w/ 23mm tires, it would show an increase in speed. Not sure how much, and I'm throwing out a pretty "out there" scenario, but it could happen.
2014-09-04 9:51 AM
in reply to: Porfirio

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Subject: RE: Why am I faster on my tri bike?

Originally posted by Porfirio
Originally posted by JohnnyKay

It's all aerodynamics.

Concur. Although I can't help but think that, given the same body positioning & frame, save less stiff, we wouldn't be as fast. I have been considering purchasing new wheels & if the above holds true, it seems that aero benefits of the wheels aside, stiffer wheels would help.

The difference in stiffness of bike frames has no measurable difference in power transfer to the road.  If your TT bike is too teeth-jarring for you, let a few psi of air out of your tires.

2014-09-04 10:12 AM
in reply to: 0

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Subject: RE: Why am I faster on my tri bike?
not to nit pick, but I'll nit pick - stiffness can affect the amount of power transferred to the pedal from the body, and it can be measured in power output...but you're right if the OP is describing stiffness as 'teeth jarring', that's not so much referring to frame and bottom bracket stiffness as it is the combination of wheel and fork stiffness, which don't directly affect power output (other than the fact that he's uncomfortable with the teeth jarring, which indirectly affects power!). So, yes, let the air out a bit. Make sure you're not using studded tires, stop riding on gravel (just kidding on both), and if you have the means, switch to a carbon wheelset. Wheel stiffness is a totally separate discussion, which fortunately for us was nicely examined on ST, and deserves a read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html

edited - the author of that article was not Dan Empfield, it was Greg Kopecky.

Edited by fisherman76 2014-09-04 10:14 AM
2014-09-04 10:42 AM
in reply to: fisherman76

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Subject: RE: Why am I faster on my tri bike?

Originally posted by fisherman76 not to nit pick, but I'll nit pick - stiffness can affect the amount of power transferred to the pedal from the body, and it can be measured in power output...but you're right if the OP is describing stiffness as 'teeth jarring', that's not so much referring to frame and bottom bracket stiffness as it is the combination of wheel and fork stiffness, which don't directly affect power output (other than the fact that he's uncomfortable with the teeth jarring, which indirectly affects power!). So, yes, let the air out a bit. Make sure you're not using studded tires, stop riding on gravel (just kidding on both), and if you have the means, switch to a carbon wheelset. Wheel stiffness is a totally separate discussion, which fortunately for us was nicely examined on ST, and deserves a read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.htmledited - the author of that article was not Dan Empfield, it was Greg Kopecky.

I'll not nit pick either, except that I will.  

Power that is transfered to the frame (through flex) is mostly returned to the pedals (minus a VERY small amount of heat loss).  The amount of loss is so small that I suspect you would not be able to measure it with most power meters and can safely ignore when trying to figure out what might be making you 3mph (or even 0.1mph) faster.



2014-09-04 1:06 PM
in reply to: gsmacleod

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Subject: RE: Why am I faster on my tri bike?
Originally posted by gsmacleod

Originally posted by mike761

From what I've heard most people produce a little less power on a TT bike than on their road bike.

However it is my understanding that your body position on the 2 should be very similar just rotated about the crank to put you in a more aerodynamic position. If this is true shouldn't you be producing the same power on either bike, but moving faster on a tri bike because of aerodynamics? If you are not producing as much power on the Tri bike does this then me you are not set up properly?


If you consider this image:



This is for riding at a normal (72ish) STA and you can see that the hip extensors are involved basically from 12 o'clock to about 3:30 while the knee extensors are from about 2:30 to 5:00 and the ankle plantar flexors are from 4:00-6:00. If you ride steep you are going to change when the various recruitments happen and for most, even if perfectly setup, your power will be decreased. It is quite likely that the engagement of the hip extensors will be delayed (say until 12:30) so you delaying the power phase and while you may be able to continue the power phase a little beyond 6:00 due to the rotation, the ankle plantar flexors are much weaker than the hip extensors so the added push at the end (even if you are able to do it) is not likely going to makeup for what is lost at the beginning.

Shane




As I look at this, if you then rotate your fit around the crank for the tri bike your power phases from different muscle groups should shift the same amount of degrees and power should be the same. That tells me that we theoretically try to rotate around the crank but in general do not rotate as much therefore losing some power. This would than come down to bike dimensions and athlete proportions to how close we get in that rotation. But in the end we go for a better Aero position rather than maintaining that perfect rotation around the crank as the aero will gain you more speed. Am I correct in the way I thinking about that?
2014-09-04 1:23 PM
in reply to: JohnnyKay

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DC
Subject: RE: Why am I faster on my tri bike?
Originally posted by JohnnyKay

Originally posted by fisherman76 not to nit pick, but I'll nit pick - stiffness can affect the amount of power transferred to the pedal from the body, and it can be measured in power output...but you're right if the OP is describing stiffness as 'teeth jarring', that's not so much referring to frame and bottom bracket stiffness as it is the combination of wheel and fork stiffness, which don't directly affect power output (other than the fact that he's uncomfortable with the teeth jarring, which indirectly affects power!). So, yes, let the air out a bit. Make sure you're not using studded tires, stop riding on gravel (just kidding on both), and if you have the means, switch to a carbon wheelset. Wheel stiffness is a totally separate discussion, which fortunately for us was nicely examined on ST, and deserves a read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.htmledited - the author of that article was not Dan Empfield, it was Greg Kopecky.

I'll not nit pick either, except that I will.  

Power that is transfered to the frame (through flex) is mostly returned to the pedals (minus a VERY small amount of heat loss).  The amount of loss is so small that I suspect you would not be able to measure it with most power meters and can safely ignore when trying to figure out what might be making you 3mph (or even 0.1mph) faster.




Simply... fascinating!
2014-09-04 1:26 PM
in reply to: JohnnyKay

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Subject: RE: Why am I faster on my tri bike?

Originally posted by JohnnyKay

Originally posted by fisherman76 not to nit pick, but I'll nit pick - stiffness can affect the amount of power transferred to the pedal from the body, and it can be measured in power output...but you're right if the OP is describing stiffness as 'teeth jarring', that's not so much referring to frame and bottom bracket stiffness as it is the combination of wheel and fork stiffness, which don't directly affect power output (other than the fact that he's uncomfortable with the teeth jarring, which indirectly affects power!). So, yes, let the air out a bit. Make sure you're not using studded tires, stop riding on gravel (just kidding on both), and if you have the means, switch to a carbon wheelset. Wheel stiffness is a totally separate discussion, which fortunately for us was nicely examined on ST, and deserves a read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.htmledited - the author of that article was not Dan Empfield, it was Greg Kopecky.

I'll not nit pick either, except that I will.  

Power that is transfered to the frame (through flex) is mostly returned to the pedals (minus a VERY small amount of heat loss).  The amount of loss is so small that I suspect you would not be able to measure it with most power meters and can safely ignore when trying to figure out what might be making you 3mph (or even 0.1mph) faster.

Agree.  IMO, the only people that need to worry about stiffness are road race sprinters and track riders.  The stiffness only matters for a few seconds while putting out max effort...and even at that, may only save them 0.2 seconds.  But to them, that's an eternity. 

If during a triathlon, you're putting down so much power that you're actually giving away speed due to stiffness...you probably need to be more concerned about your run to follow.

2014-09-04 1:34 PM
in reply to: Porfirio

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Subject: RE: Why am I faster on my tri bike?

Originally posted by Porfirio
Originally posted by JohnnyKay

Originally posted by fisherman76 not to nit pick, but I'll nit pick - stiffness can affect the amount of power transferred to the pedal from the body, and it can be measured in power output...but you're right if the OP is describing stiffness as 'teeth jarring', that's not so much referring to frame and bottom bracket stiffness as it is the combination of wheel and fork stiffness, which don't directly affect power output (other than the fact that he's uncomfortable with the teeth jarring, which indirectly affects power!). So, yes, let the air out a bit. Make sure you're not using studded tires, stop riding on gravel (just kidding on both), and if you have the means, switch to a carbon wheelset. Wheel stiffness is a totally separate discussion, which fortunately for us was nicely examined on ST, and deserves a read: http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.htmledited - the author of that article was not Dan Empfield, it was Greg Kopecky.

I'll not nit pick either, except that I will.  

Power that is transfered to the frame (through flex) is mostly returned to the pedals (minus a VERY small amount of heat loss).  The amount of loss is so small that I suspect you would not be able to measure it with most power meters and can safely ignore when trying to figure out what might be making you 3mph (or even 0.1mph) faster.

Simply... fascinating!

I was able to dig this up through the wayback machine.  Towards the bottom, there is an experiment you can do for yourself.

http://web.archive.org/web/20090323002006/http://bikethink.com/Frameflex.htm

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