# Power and Seat Height



## woodys737

Any of you with a PT, SRM or iBike, have you experimented with seat height and how it changes your power output? My post slipped around 10mm over a day or two and I have to admit I feel like I am able to produce more powerful with the lower position. My original fit from the LBS, IMO, got me close enough to not really question the seat height for the past year. At said height I was KOP, but forget how much bend in the knee occured with a level foot at 6 o'clock. FWIW, I was also canted and the cleats have been adjusted (toed in or out) to help me pedal more efficiently.

I settled on a little more than 5mm lower position than from the original fit with no change to the fore aft rail position. Anyway, without a way to measure power I could easily be bass ackwards and am left wondering just what I felt? I'm not looking for opinions on my fit but rather how much difference in power output 10mm can make.


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## bill

I don't have any data, and I don't know anyone who does, but the conventional wisdom is that, because muscles can generate more power if permitted to extend completely, a higher saddle is going to generate more power. I think that the limiter here is that if the saddle is so high that your cadence suffers, then you are going to generate less power.

Generally, people believe that a lower saddle is conducive to higher cadences.


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## iliveonnitro

bill said:


> I don't have any data, and I don't know anyone who does, but the conventional wisdom is that, because muscles can generate more power if permitted to extend completely, a higher saddle is going to generate more power. I think that the limiter here is that if the saddle is so high that your cadence suffers, then you are going to generate less power.
> 
> Generally, people believe that a lower saddle is conducive to higher cadences.


I'd be more willing to believe that too-high of a saddle causes posterior knee pain, which is usually the upper-boundary of proper saddle height...rather than lower cadence.

The better question is if saddle fore vs aft generates more/more efficient power, and that has been discussed before.


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## Kerry Irons

*Define fully extended*



bill said:


> I don't have any data, and I don't know anyone who does, but the conventional wisdom is that, because muscles can generate more power if permitted to extend completely, a higher saddle is going to generate more power. I think that the limiter here is that if the saddle is so high that your cadence suffers, then you are going to generate less power.
> 
> Generally, people believe that a lower saddle is conducive to higher cadences.


I think that both of your statements need clarification. Complete extension of the leg muscles does NOT mean going all the way to a locked leg position, so obviously there is some point of lower seat position is optimum. High cadence would not work if you were at a "BMX height" so you need to be higher than that. Actual conventional wisdom is that the range of ideal seat heights (from the pedal axle) is 108-110% of cycling inseam. There may be some odd ducks that perform well outside this range, but it seems to work for over 90% of us.


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## Eric_H

*The "range"*



Kerry Irons said:


> I think that both of your statements need clarification. Complete extension of the leg muscles does NOT mean going all the way to a locked leg position, so obviously there is some point of lower seat position is optimum. High cadence would not work if you were at a "BMX height" so you need to be higher than that. Actual conventional wisdom is that the range of ideal seat heights (from the pedal axle) is 108-110% of cycling inseam. There may be some odd ducks that perform well outside this range, but it seems to work for over 90% of us.


I agree with Kerry for the most part. There is a range of leg extension that is optimal, somewhere between 25 and 30 degrees of flexion between the femur and the tibia. This correlates roughly to the numbers above and also to the old Guimard 0.883*cyling inseam formula. My own personal experience and what I have observed in others would be that having the saddle just a little too high is much more problematic in terms of comfort and injury potential.

For the OP, what you have done sounds reasonable. If you felt better at a lower saddle height than your original fit, then leave it there. Making changes should be done in 2-3 mm increments, 5 mm would be the max. And if you make a change, leave it there for at least two weeks to evaluate whether it is working out. A lot of times a small change will feel "great" on the first ride, but not so much on subsequent rides - I believe there is a placebo effect at work. This brings me to my final point, and that is to be careful not to become obsessive with your saddle height and position. I have seen more than a few riders who make adjustments almost every other ride, and in some cases saddle position borders on obsessive-compulsive behaviour.


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## sand-racer

as i understand it, the power enhancements felt with the lower seat position are real. the tendon underneath your kneecap is being stretched like a rubberband and helps you produce power. unfortunately this motion repeated numerously due to the cycling motion will produce problems related with the knee and tendons. Your optimum knee bend for the average rider is 25-35 degrees (this measurement is done with your pedals parallel to your seat tube (your maxuimum extension) not at 6 o'clock) . this will put your knee above the pedal axle while parallel to the ground with small discrepancies due to upper and lower leg length. This position described will be the best for you as a rider.


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## Speedy

If you analyze the pro tour, you’ll see a lot pointed toes at the bottom of the pedal stroke. I’ve also heard guys will start the season a little lower, and increase the saddle height as they get fitter. I did that this year and it worked well.


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## woodys737

Knee bend angles were taken again tonight with both seat heights. The original was right around 30 degrees while the lower seat height was approx 33 degrees. FWIW.


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## estone2

Speedy said:


> If you analyze the pro tour, you’ll see a lot pointed toes at the bottom of the pedal stroke. I’ve also heard guys will start the season a little lower, and increase the saddle height as they get fitter. I did that this year and it worked well.


That's just as often as not due to muscle imbalance or habits.

I am a toe down pedaller, pretty much regardless of saddle height. Look at a lot of triathletes, they do it too. Runners are infamous for it. It's not as efficient, and this is really evident in my intervals; when I'm noodling along at 180 watts, my knees flare out at the top of the pedal stroke, my toes point down, and I have a tendency to mash along at 90 (being a junior, that is mashing to me - I've hurt my knee before, and I don't want to do it again... young tendons are weak tendons). When I'm at a 400 watt interval, my pedal stroke is flat, my knees are straight; efficiency is important because I'm calling on all my resources and cant waste any doing unimportant stuff. I don't do this consciously, it's my body reacting to different stimuli.

To the OP: When my saddle is 2cm lower, my LT goes down 10 watts, 2cm higher, down 15 watts. When it's just right, my LT is... er, my LT? :idea: 

-estone2


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## woodys737

estone2 said:


> To the OP: When my saddle is 2cm lower, my LT goes down 10 watts, 2cm higher, down 15 watts. When it's just right, my LT is... er, my LT? :idea:
> 
> -estone2


2cm or 2mm? Just want to be sure. Thanks for the reply!


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## estone2

woodys737 said:


> 2cm or 2mm? Just want to be sure. Thanks for the reply!


CM.
I haven't ever tested mm. However, when I've played around with it, I do work harder to put out wattage. I can't give numbers as to how much it drops, since I haven't tried it out, but I can tell you that after 50 miles 2millimeters lower I feel substantially worse, and am putting less wattage out.


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## The Flash

Just redid my bike fitting and I ended up getting moved back up on both my road and TT bike about 1cm. Feels much better and I got about 10w back on my interval today. I think there is also relationship about recruiting not only the quads, but as much of the glutes and hams as possible. I think moving up helps this a bit and perhaps that is the basis for the increase?

The Flash


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## woodys737

estone2 and The Flash,

1cm feels like a world of difference to me and I'm surprised to hear the change in watts with your different seat heights. To muddy the waters further, with a 1cm lower seat height my setback moved forward 5mm. Did you keep the same setback when you changed seat height?

Given I'm in the 25-35 degree range for knee bend with both seat heights I'm chalking this experience up to placebo effect. Being bourgeoisie it's entirely possible I was better rested or had less alcohol in my system concurrent with the mistaken epiphany.

FWIW, thanks!


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## bill

woodys737 said:


> estone2 and The Flash,
> 
> 1cm feels like a world of difference to me and I'm surprised to hear the change in watts with your different seat heights. To muddy the waters further, with a 1cm lower seat height my setback moved forward 5mm. Did you keep the same setback when you changed seat height?
> 
> Given I'm in the 25-35 degree range for knee bend with both seat heights I'm chalking this experience up to placebo effect. Being bourgeoisie it's entirely possible I was better rested or had less alcohol in my system concurrent with the mistaken epiphany.
> 
> FWIW, thanks!


seat fore-aft position, according to people smarter than I am, shouldn't affect power. See, this article by Keith Bontrager. People feel different when the fore-aft position changes because it affects balance on the bike and because it changes your extension. People will wax rhapsodic about how the ideal fore-aft matters to power, but I believe Bontrager. Fore-aft matters to the bike's handling, it matters to comfort on the bike, but I don't see any reason why it should affect power.

http://www.sheldonbrown.com/kops.html


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## iliveonnitro

Eric_H said:


> I agree with Kerry for the most part. There is a range of leg extension that is optimal, somewhere between 25 and 30 degrees of flexion between the femur and the tibia. This correlates roughly to the numbers above and also to the old Guimard 0.883*cyling inseam formula. My own personal experience and what I have observed in others would be that having the saddle just a little too high is much more problematic in terms of comfort and injury potential.


Kerry is advocating 1.08 or 1.10*inseam height, whereas the Guimard is .882*inseam. This is a big difference. For me, the difference between these two formulae is a 72.9cm saddle height and 90.8cm saddle height. Uh, 18cm difference? Either of you care to clarify?

Whoever posted saying that saddle fore-aft doesn't affect power: I completely disagree. Try moving your saddle back .5" (and seat height lower to compensate) and do a 2 minute interval. Now move it back to original and forward .5" (seat higher to compensate) and do a 2 min interval. Which has more power? I guarantee the forward position will.

During hard efforts, do you notice that you (and pros) wind up sliding forward on the seat? This is, to a lesser degree, similar to standing. This can affect many things, but a big one (mentally referencing Bicycling Science, 3rd edition, MIT Press) is that moving forward in the saddle puts your position more directly over the bottom bracket. This translates to more power to the pedals. It also increases the tendency to mash. In the long run, there is back pain, too.

Many bike fitters get saddle fore-aft wrong. When using a plumb line, you should not measure from the top of the knee. If you straighten your leg and pinch the patella on each side of the knee--that should be the reference point. This is another reason why most people slide too far forward on their saddle during normal riding conditions...improper fitting.


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## woodys737

My lack of knowledge and experience with these matters leads to ignorant questions and conclusions. So, understand I am not trying to be pretentious here. 

The CG changes due to a power response as Bontrager implied. I interpreted fore-aft paramount to comfort and handling which is not power exclusive. CG moves forward when sprinting and back during seated climbs. So, just as the rider changes CG for different types of riding a fore or aft seat position on the rails has to change CG (while seated). Therefore, I'm guessing here, if your CG is way aft while trying to sprint you'd be less efficient and produce less power. If that is true then the same can be said about being seated which fore and aft position has a direct effect.


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## Speedy

bill said:


> Fore-aft matters to the bike's handling, it matters to comfort on the bike, but I don't see any reason why it should affect power.


You must not race. 

Trust me, people don't ride on the rivet for comfort. Being over the cranks is more powerful than behind them - period.


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## bill

iliveonnitro said:


> Kerry is advocating 1.08 or 1.10*inseam height, whereas the Guimard is .882*inseam. This is a big difference. For me, the difference between these two formulae is a 72.9cm saddle height and 90.8cm saddle height. Uh, 18cm difference? Either of you care to clarify?
> 
> Whoever posted saying that saddle fore-aft doesn't affect power: I completely disagree. Try moving your saddle back .5" (and seat height lower to compensate) and do a 2 minute interval. Now move it back to original and forward .5" (seat higher to compensate) and do a 2 min interval. Which has more power? I guarantee the forward position will.
> 
> During hard efforts, do you notice that you (and pros) wind up sliding forward on the seat? This is, to a lesser degree, similar to standing. This can affect many things, but a big one (mentally referencing Bicycling Science, 3rd edition, MIT Press) is that moving forward in the saddle puts your position more directly over the bottom bracket. This translates to more power to the pedals. It also increases the tendency to mash. In the long run, there is back pain, too.
> 
> Many bike fitters get saddle fore-aft wrong. When using a plumb line, you should not measure from the top of the knee. If you straighten your leg and pinch the patella on each side of the knee--that should be the reference point. This is another reason why most people slide too far forward on their saddle during normal riding conditions...improper fitting.


um, the difference is that one measurement is to the center of the bottom bracket, and the other is to the pedal spindle.

as for fore-aft, there is this law of conservation of energy, see, and when you stand to get on top of the pedals, yes, you can move your weight so that your weight can be used to push down on top of the pedals, so that your muscles aren't being flexed to do it quite as much through that range of the pedal stroke. But it's the same amount of power, overall, because you have to lift your weight. 

the idea that a few mm or even a cm of fore-aft can discernibly influence the power you develop is really kind of absurd, when you think about it, particularly for the reason you cite. You slide around on the saddle way more than that couple of mm. Yeah, when you are "on the rivet," you are forward. It's a natural thing. But I think it has more to do with leg extension than anything else. as you madly turn the pedals and your form goes to sh*t, you creep forward. I'm not sure exactly why you creep foreward, truly, but you don't, I believe, get more power out of the deal. It's about shortening the reach more than getting more weight on top of the pedals. You already have plenty of weight over the top of the pedals. If your bottom isn't moving up and down with the pedals, the weight is doing no work. That's elementary physics.

as for the measuring from the patella or wherever thing -- come on. what does that anatomical feature have to do with ANYTHING? anything at all?


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## bill

Speedy said:


> You must not race.
> 
> Trust me, people don't ride on the rivet for comfort. Being over the cranks is more powerful than behind them - period.


well, actually, I do race, and while I am a sh*tty finisher, one thing I can do is put out big power for a long time. when I find that I am on the rivet, I relax my upper body, I try to stabilize my pelvis and use my core strength, which invariably means sliding back a bit, and I feel as if I have more power. I don't know whether I do or not, but it's then that I close the gap, and I certainly don't feel as if I have more power sliding forward. As above, I think that it has something to do with shortening the extension as something of a natural reaction to . . . those moments.


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## bill

> Try moving your saddle back .5" (and seat height lower to compensate) and do a 2 minute interval. Now move it back to original and forward .5" (seat higher to compensate) and do a 2 min interval. Which has more power? I guarantee the forward position will.


this is an extraordinary claim. do you have any evidence of this? this would be quite a revelation.


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## bill

> Therefore, I'm guessing here, if your CG is way aft while trying to sprint you'd be less efficient and produce less power. If that is true then the same can be said about being seated which fore and aft position has a direct effect.


why do you think that being aft would negatively affect your ability to produce power? The longer extension makes it harder to maintain a higher cadence, I think, but I don't think that the CG position itself matters to this.

This is one of those sacred cow issues for which there just isn't any evidence, other than "years of experience," "how can 14 million Frenchman be wrong?" etc., etc.


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## woodys737

bill said:


> why do you think that being aft would negatively affect your ability to produce power? The longer extension makes it harder to maintain a higher cadence, I think, but I don't think that the CG position itself matters to this.
> 
> This is one of those sacred cow issues for which there just isn't any evidence, other than "years of experience," "how can 14 million Frenchman be wrong?" etc., etc.


I was thinking in the context of chasing a break down. While seated in your "normal" position what would happen to power output if your seat were able to slide back 10cm? 20cm? Rediculous, but I made a poor attempt to try and convey that at some point fore/aft position will effect CG. Thus, at some point, fore/aft will effect power too.

I'm going to a race, so ya'll have a great week-end!


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## bill

woodys737 said:


> I was thinking in the context of chasing a break down. While seated in your "normal" position what would happen to power output if your seat were able to slide back 10cm? 20cm? Rediculous, but I made a poor attempt to try and convey that at some point fore/aft position will effect CG. Thus, at some point, fore/aft will effect power too.
> 
> I'm going to a race, so ya'll have a great week-end!


but moving back wouldn't affect power because you've moved your center of gravity, it would affect power because at some point you can't reach the pedals.

have a good race.


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## Eric_H

iliveonnitro said:


> Kerry is advocating 1.08 or 1.10*inseam height, whereas the Guimard is .882*inseam. This is a big difference. For me, the difference between these two formulae is a 72.9cm saddle height and 90.8cm saddle height. Uh, 18cm difference? Either of you care to clarify?


bill already addressed this, but the Guimard/Lemond is from the center of the BB to top of the saddle. The 1.08-1.10 number is from the top of the pedal surface to the top of the saddle, with the crank arm down and in line with the seat tube. It should be noted that with the variations in shoe sole thickness and the distance from the outer sole to the center of the pedal spindle, both of these methods are not absolutes, but decent ballpark starting points.



iliveonnitro said:


> Whoever posted saying that saddle fore-aft doesn't affect power: I completely disagree. Try moving your saddle back .5" (and seat height lower to compensate) and do a 2 minute interval. Now move it back to original and forward .5" (seat higher to compensate) and do a 2 min interval. Which has more power? I guarantee the forward position will.
> 
> During hard efforts, do you notice that you (and pros) wind up sliding forward on the seat? This is, to a lesser degree, similar to standing. This can affect many things, but a big one (mentally referencing Bicycling Science, 3rd edition, MIT Press) is that moving forward in the saddle puts your position more directly over the bottom bracket. This translates to more power to the pedals. It also increases the tendency to mash. In the long run, there is back pain, too.
> 
> Many bike fitters get saddle fore-aft wrong. When using a plumb line, you should not measure from the top of the knee. If you straighten your leg and pinch the patella on each side of the knee--that should be the reference point. This is another reason why most people slide too far forward on their saddle during normal riding conditions...improper fitting.


Regarding fore-aft, I think your assumption that more power is produced by being more "over the top" of the cranks (this is a sentiment also conveyed further along in this thread) is not exactly correct. You are considering power produced over one type of interval, but road racing happen on variable terrain. Racers (including pros) do move forward in certain situations, but I think you will find that it is usually to facillitate faster pedaling in very fast situations, while deep in the drops. This generally will allow the rider to pedal at a higher cadence and might increase peak power. Conversely, they tend to push rearward during climbing to enhance the ability to push a larger gear. This has the effect of lengthening the saddle-pedal distance and allowing more leg extension. I cannot say for certain because I am not a power meter junkie, but I would guess for extended periods power the rearward position will produce a higher average power.


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## Mark McM

*"Sitting on the rivet"*



iliveonnitro said:


> During hard efforts, do you notice that you (and pros) wind up sliding forward on the seat? This is, to a lesser degree, similar to standing. This can affect many things, but a big one (mentally referencing Bicycling Science, 3rd edition, MIT Press) is that moving forward in the saddle puts your position more directly over the bottom bracket. This translates to more power to the pedals. It also increases the tendency to mash. In the long run, there is back pain, too.


I think if you examine it more closely, the tendency to "sit of the rivet" (i.e. slide forward on the saddle) during hard efforts is due to something else entirely. When a rider is going all out, they tend to use their upper body and arms more, pulling on the handlebars. Normally, riders tend to ride with just a slight bend to the elbows, but actively pulling on the handlebars is more effective with more bend in the elbow. Thus, riders who are riding hard bend their elbows more, pulling themselves closer to the handlebars, and thus sliding forward on the saddles.


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## bill

Mark McM said:


> I think if you examine it more closely, the tendency to "sit of the rivet" (i.e. slide forward on the saddle) during hard efforts is due to something else entirely. When a rider is going all out, they tend to use their upper body and arms more, pulling on the handlebars. Normally, riders tend to ride with just a slight bend to the elbows, but actively pulling on the handlebars is more effective with more bend in the elbow. Thus, riders who are riding hard bend their elbows more, pulling themselves closer to the handlebars, and thus sliding forward on the saddles.


I think that this is exactly right. I was thinking about it today, at lunchtime, as I sat on the rivet trying to chase down some f*ckers who had increased a gap from 20 m to 150 m by beating a light. f*ckers.


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## Mark McM

*Sliding back in the saddle for climbing*



Speedy said:


> You must not race.
> 
> Trust me, people don't ride on the rivet for comfort. Being over the cranks is more powerful than behind them - period.


Maybe you race, but you must not actually watch racers - or else you'd know that in some situations, racers tend to push themselves further back, behind the cranks, not further forward, to generate power.

In particular, many riders tend to sit back in the saddle when climbing. This is for several reasons:

- Moving back in the saddle tends to increase leg extension, increasing leg force. Many riders tend to decrease cadence when climbing, and compensate by increasing pedal force. The rearward position is not as conducive for high cadence spinning, but can produce higher pedal force.

- Many riders climb in the bar tops. This decreases handlebar reach by 100 mm or so. To compensate, riders tend to sit further back in the saddle.

As mentioned in the previous post, sitting on the nose of the saddle is often more a case of accomodating a more compact upper body position (i.e. elbows bent to pull on the handlebars), rather than a desire to get over the pedals.


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## levels1069

ehhh i'm gonna have to go ahead and disagree with the general thought here...

look at lots of TT riders or triathletes, even for being as aero as possible...the main point is to still try to stay as much centered over the BB as possible. They creep forward on the saddle to stay over the bottom bracket, which stresses your quads more and alows more explosive power. lots of great riders also center themselves over the BB when climbing, moving forward on the saddle. Specifically Jens Voight, Jan Ulrich, Levi Leipheimer...all very powerful guys


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## bill

levels1069 said:


> ehhh i'm gonna have to go ahead and disagree with the general thought here...
> 
> look at lots of TT riders or triathletes, even for being as aero as possible...the main point is to still try to stay as much centered over the BB as possible. They creep forward on the saddle to stay over the bottom bracket, which stresses your quads more and alows more explosive power. lots of great riders also center themselves over the BB when climbing, moving forward on the saddle. Specifically Jens Voight, Jan Ulrich, Levi Leipheimer...all very powerful guys


I don't believe that the forward position has anything to do with engaging the quads or explosive power or whatever. If you have any evidence for your contention, bring it here, because I've heard of this for years and it makes no sense and no one has any support. I understand that people still believe it, but, for example, people have believed and believe to this day that lactic acid causes muscle failure and it just isn't true and it has been known not to be true for a really long time.

The forward position of TT bikes mostly has to do with one issue -- by moving the pelvis forward in relation to the BB, the rider can get flatter and lower on the bike and still maintain the same hip/femur orientation through the pedal stroke. The other adjustments to TT frame geometry have to do with trying to keep as much of the rider's weight back from the front as possible, to add some stability and handling, which is why road frames don't convert very well to TT frames.


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## footballcat

go get fit, i was fit and they measured the angle of ankle to the knee to hip, and 140 degrees to 145 is what he was looking for i belive. I couldnt be happier, solved some of my knee issues, and im comfy on the bike, i do have 13cm of drop though.


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## estone2

bill said:


> this is an extraordinary claim. do you have any evidence of this? this would be quite a revelation.


Look at Dave Z during a time trial.
The position provides more TT-effort type power, as it activates the quads more (or something?). It's very good for on the flats, if you're going solo, butchering yourself.

However, the position SUCKS for climbing. As such, it's not a good position to set your bike up with - no point in getting to the climb really fast and then getting slaughtered.

-estone2


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## bill

the position is aerodynamic. it doesn't "activate the quads" (or it would likely be good for climbing, no?)


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## Speedy

I use to ride on the front only for flat hammering, but after I seeing a number of pros sitting more on the front while climbing, I’ve been doing it too. It depends on the length of the climb, but for a 30min or less - get to the top as fast as you can climb, I seem to get more power there than my usual slid back, sustained climbing position.


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## bill

Speedy said:


> I use to ride on the front only for flat hammering, but after I seeing a number of pros sitting more on the front while climbing, I’ve been doing it too. It depends on the length of the climb, but for a 30min or less - get to the top as fast as you can climb, I seem to get more power there than my usual slid back, sustained climbing position.


Okay, against all evidence, you all are going to insist on this, so I guess I'll give up.
If it works for you, you go ahead.
But here's food for thought -- I sincerely question whether you can detect someone, anyone, shifting their weight forward from watching them. standing? that's different; I'm talking about shifting forward that cm or two or three that we all know as on the rivet.
and maybe you're climbing better because you just got stronger?


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## Speedy

bill said:


> ...and maybe you're climbing better because you just got stronger?


True that.

When I watch others riders, I’m looking at how much saddle is sticking out the back - compared to their other positions, and how upright their torso is. Moving forward brings you more upright when climbing.


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## bill

Speedy said:


> True that.
> 
> When I watch others riders, I’m looking at how much saddle is sticking out the back - compared to their other positions, and how upright their torso is. Moving forward brings you more upright when climbing.


although moving forward is also a function of pulling back on the bars, which tends to happen when the climber is, as they say, under pressure. 

I still don't think it has anything to do with increasing your power per se. you do shorten the extension a little, which makes it easier to spin, but shortening the extension is generally considered to lessen the force you can apply, not increase it, although I suppose if you maintain the same force but increase the cadence, thereby applying that force more times in a given period of time, you're going to go up faster. But it's not going to help you if you are maintaining the same cadence.


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