Watts Not Translating To Speed

trek_dan

I only say this as I have some experience from a friend of mine who had a similar issue/obsession with his weight/numbers - are you sure your eating and nourished properly?

iPete

What level of racing is this? He does appear to be using Stages, maybe all his power is in his right leg?

buckmulligan

NapoleonD wrote:

The only explanation I can see is any combination of riding out of the slipstream, on a very heavy bike, with bad tyres, brakes rubbing, sat bolt upright, with a Powermeter with a borked calibration slope.

I know this was mostly a tongue-in-cheek comment, but NapD is right on the money here in that there's likely a lot of different factors at play that are cumulatively robbing you of a lot of speed and/or overestimating your power output. You're going to have to address a lot of different things to close that gap but the good news is that a lot of that is "free speed". Here are the things I'd address (in order of approximate easiness):

(1) Power meter accuracy: You seem fairly certain that the PM is fairly accurate, but I'd take a look at some of your data and see if it correlates with the immutable laws of physics! If you have power data for a decent length climb (ideally 5k+ at 5%+) you can stick it into a number of free online calculation programs (e.g. BestBikeSplit or just do the maths yourself) to see if the power values tally. It has to be uphill (and the steeper and more consistent slope the better) to minimise the effect of aerodynamics, which I think we've established is a big uncertainty at the moment; you'll also need an accurate weight estimation for this ride (i.e. you + bike + bidons + toolkit + food + everything else) but it should immediately give you an idea if your PM is reading 50W out.

(2) Drive-train cleanliness: This shouldn't be underestimated, pushing round a dirty drive train is just throwing Watts out the window. If I read correctly, you're using a crank-based system, so it's guaranteed that not all of those Watts are actually getting to your wheel and driving you along the road. A well-serviced drivetrain will lose you ~5-10W between cranks and road, a badly serviced one could be >20W. Dirty chains, noisy derailleurs, wobbly freehubs and poor lube choices are all Watts being thrown out the window. Think about how hard you have to train to be able to put out an extra 20W and think about how much easier it is to give your bike a quick service. And that draggy freehub means that you're pedaling whilst everyone else is coasting; every one of those pedal stokes is wasted Watts.

(3) Bike components and clothing: I'm mostly thinking of tyres here because they make the biggest difference. If you're running some puncture-proof tank-tracks at the moment (like Conti Gatorskins or Specialized Armadillos), you're wasting Watts pushing them around. If you don't have race tyres already, get some, preferably with latex tubes. Flappy clothing and helmets also add significant drag and you have to put out Watts to drag them through the wind; minimise this.

(4) Bike position: As a tall guy you're going to push a lot of wind out of the way whatever happens and you'll probably need more Watts to generate the same speed as someone who is 5' 6". That's inevitable, but that doesn't mean you can't improve on where you are now. Posting up some pictures of your position on the bike would be a start, but getting yourself lower and narrower at the front is essential. Unless you're climbing or freewheeling along in the middle of the bunch you should be using the drops.

(5) Group riding efficiency: This is where it starts to get harder to pin down, but you're on the right tracks by looking at your competitors data and seeing where you can improve. I recall hearing recently that good crit racers should be aiming to not pedal for 1/3rd of a race; obviously that is highly dependent on the parcours and racing environment, but the ethos is good. Whenever you're putting out Watts in race, you should be thinking about how you can put out fewer Watts. Stay in the drops, draft better, do fewer turns on the front. All of these will save energy, but now we're getting in race strategy rather than power-to-speed discrepancies.

I hope that's of some help!

ForumNewbie

BuckMulligan wrote:

NapoleonD wrote:

The only explanation I can see is any combination of riding out of the slipstream, on a very heavy bike, with bad tyres, brakes rubbing, sat bolt upright, with a Powermeter with a borked calibration slope.

I know this was mostly a tongue-in-cheek comment, but NapD is right on the money here in that there's likely a lot of different factors at play that are cumulatively robbing you of a lot of speed and/or overestimating your power output. You're going to have to address a lot of different things to close that gap but the good news is that a lot of that is "free speed". Here are the things I'd address (in order of approximate easiness):

(1) Power meter accuracy: You seem fairly certain that the PM is fairly accurate, but I'd take a look at some of your data and see if it correlates with the immutable laws of physics! If you have power data for a decent length climb (ideally 5k+ at 5%+) you can stick it into a number of free online calculation programs (e.g. BestBikeSplit or just do the maths yourself) to see if the power values tally. It has to be uphill (and the steeper and more consistent slope the better) to minimise the effect of aerodynamics, which I think we've established is a big uncertainty at the moment; you'll also need an accurate weight estimation for this ride (i.e. you + bike + bidons + toolkit + food + everything else) but it should immediately give you an idea if your PM is reading 50W out.

(2) Drive-train cleanliness: This shouldn't be underestimated, pushing round a dirty drive train is just throwing Watts out the window. If I read correctly, you're using a crank-based system, so it's guaranteed that not all of those Watts are actually getting to your wheel and driving you along the road. A well-serviced drivetrain will lose you ~5-10W between cranks and road, a badly serviced one could be >20W. Dirty chains, noisy derailleurs, wobbly freehubs and poor lube choices are all Watts being thrown out the window. Think about how hard you have to train to be able to put out an extra 20W and think about how much easier it is to give your bike a quick service. And that draggy freehub means that you're pedaling whilst everyone else is coasting; every one of those pedal stokes is wasted Watts.

(3) Bike components and clothing: I'm mostly thinking of tyres here because they make the biggest difference. If you're running some puncture-proof tank-tracks at the moment (like Conti Gatorskins or Specialized Armadillos), you're wasting Watts pushing them around. If you don't have race tyres already, get some, preferably with latex tubes. Flappy clothing and helmets also add significant drag and you have to put out Watts to drag them through the wind; minimise this.

(4) Bike position: As a tall guy you're going to push a lot of wind out of the way whatever happens and you'll probably need more Watts to generate the same speed as someone who is 5' 6". That's inevitable, but that doesn't mean you can't improve on where you are now. Posting up some pictures of your position on the bike would be a start, but getting yourself lower and narrower at the front is essential. Unless you're climbing or freewheeling along in the middle of the bunch you should be using the drops.

(5) Group riding efficiency: This is where it starts to get harder to pin down, but you're on the right tracks by looking at your competitors data and seeing where you can improve. I recall hearing recently that good crit racers should be aiming to not pedal for 1/3rd of a race; obviously that is highly dependent on the parcours and racing environment, but the ethos is good. Whenever you're putting out Watts in race, you should be thinking about how you can put out fewer Watts. Stay in the drops, draft better, do fewer turns on the front. All of these will save energy, but now we're getting in race strategy rather than power-to-speed discrepancies.

I hope that's of some help!

I don't know much about power meters but I've been reading this thread with interest, and some good points made in this post. Note to self - I should give my drive train a thorough clean.

Am I right in thinking that if 1 above is the problem, the OP is not generating as much power as the data shows. However if his power meter is okay but 2, 3, 4 and/or 5 is the problem then he a very strong rider but is wasting a lot of the power he is generating?

slowandsteady1

I'm by no means an expert but your numbers don't seem to tie up.

If you take 10% off your 20 minute effort you should have very close to your hour power. You dont.

I too suspect your PM or calibration of it.

amaferanga

slowandsteady1 wrote:

I'm by no means an expert but your numbers don't seem to tie up.

If you take 10% off your 20 minute effort you should have very close to your hour power. You dont.

I too suspect your PM or calibration of it.

While it may be a PM issue, I'm not sure where you get FTP being 90% of 20min power from....

His 20min and 60min power numbers may be entirely consistent for him.

okgo

It doesn't look correct really. 250w in a bunch on a fairly flat course and you are going less than 22 mph, doesn't stack really..also, yesterday, 350w for ten mins on the pan flat, with very low wind and you're doing 23mph, yet the next interval seems to be 40w less and you go faster..was this a two up?

350w at your size, on flat ground, to go 23mph is either wrong, or you're terribly unaero.

markhewitt1978

okgo wrote:

350w at your size, on flat ground, to go 23mph is either wrong, or you're terribly unaero.

okgo

Ha, max speed on the flat on a boris surely well below 20

spredy

okgo wrote:

It doesn't look correct really. 250w in a bunch on a fairly flat course and you are going less than 22 mph, doesn't stack really..also, yesterday, 350w for ten mins on the pan flat, with very low wind and you're doing 23mph, yet the next interval seems to be 40w less and you go faster..was this a two up?

350w at your size, on flat ground, to go 23mph is either wrong, or you're terribly unaero.

The first interval was meant to be longer a whole lap of the circuit, but I fried myself going into the headwind section and then just coasted in. Does 350 watts at 23.6MPH into a headwind seem like a poor return on my power? While the wind wasn't high, where we were riding was exposed, so whatever there was, we were bearing the brunt of it.

Yeah, the second was a two up. For the second interval my friend Tom average 302 watts, and I did 311. He's a couple of inches shorter than me, and he said he was fading towards the end, so that may also explain the slight difference in power. I guess turns are never perfectly equal.

spredy

slowandsteady1 wrote:

I'm by no means an expert but your numbers don't seem to tie up.

If you take 10% off your 20 minute effort you should have very close to your hour power. You dont.

I too suspect your PM or calibration of it.

The 20 minute power best and the one hour best were both part of the same effort. I averaged 302ish for the first 30 minutes, and then wanted to see what I could push it up to if I emptied the tank, so neither the 20 or the hour are properly paced efforts, but still the best to date.

spredy

What speeds do you guys see for similar watts on your rides, so I can get an idea for how off things are?

JamesFree

Looking at the race file and some of your other files I would say your powermeter is over reading unless you are incredibly un-aero. I found an old race file of mine when I was 68kg & 182cm and managed to get around a 2/3 road race with very similar elevation (maybe slightly lumpier) with an AP 186w and NP 254w at 24mph average.

markhewitt1978

spredy wrote:

What speeds do you guys see for similar watts on your rides, so I can get an idea for how off things are?

I can average 300 watts for about 2 minutes tops so I'm out

jrich

Can you not borrow a mates powermeter (maybe a powertap wheel?) and Garmin and run them both simultaneously on your bike?

Or maybe you could swap bikes with a mate for a ride and then both compare power data afterwards?

The 'how fast for given watts' question is completely pointless. For a 20 minute interval 300 Watts could get you anything from 10 to 30mph depending on a massive number of variables.

buckmulligan

spredy wrote:

What speeds do you guys see for similar watts on your rides, so I can get an idea for how off things are?

See point 1 of my post.

Comparing yourself to other people's data is kind of pointless. Even if you're comparing yourself to someone you're riding along side-by-side with, your CdA's could easily be +/- 10%+ of each other (especially given the fact that your at the taller end of the spectrum), let alone variations in weight, rolling resistance, power reading source, drivetrain efficiency etc etc etc etc etc. If you start looking at different people, on different courses in different conditions, you may as well just take a look at the lottery numbers and compare your numbers to those. If you visit any time-trialling forum, you'll soon see that some people go very fast on the Watts that they produce and some people much slower; there are a lot of reasons for that (and I'd bet that very few of them have dodgy PMs).

You need to start looking at your data and figure out why it looks odd.

As I said, get some of your courses on BestBikeSplit and compare the predictions to your recorded data, it can be scarily accurate once your input parameters are correct. It doesn't take long to pick up the basics of cycling with power and it's something that will make you a faster cyclist. Perhaps start with reading this, it's a very accessible primer on the physics of a moving bike:

http://www.slowtwitch.com/Tech/The_Phys ... e_163.html

okgo

On roadbikes the variation of positions and lower speeds vs TT's mean its easier to see dud data, and that is what we have here IMO.

But the easiest way would be to run two side by side

craigr

The other guy that you are comparing with could have been hiding in the bunch for most of the race too...

Alex_Simmons/RST

okgo wrote:

On roadbikes the variation of positions and lower speeds vs TT's mean its easier to see dud data, and that is what we have here IMO.

But the easiest way would be to run two side by side

There are aerodynamic interference effects when riding side by side. Riding next to someone typically adds to your power demand. How much of course is variable but for one experiment I conducted, it added ~10W (5%) to the power demand compared with riding at the same speed (40km/h) solo.

http://alex-cycle.blogspot.com.au/2015/ ... -drag.html