HR vs Power

Alex Simmons said:

I have already built the mathematical model but it's practical implementation would likely be combined with telemetry to the following car and a race radio for instruction. Even though I have done the modelling and it would be very funky to do something like that, I don't think it is really all that sensible an idea.

Wind is not that big a factor in pacing. A few watts here and there for differences between head/tail winds. All it does is change the time taken to ride a course. The main element to consider is gradient.

It seems to me that wind is a big deal in pacing because the time it takes to complete the course is what determines how hard one can or cannot go. Now this difference becomes quite small as the distance and time gets long but I suspect that one could ride a 40 k time-trial with a 20 mph tail wind a lot "harder" than a 40 k time-trial with a 20 mph head wind since there might be a 30 minute difference in the time it might take.

Alex Simmons said:

I have already built the mathematical model but it's practical implementation would likely be combined with telemetry to the following car and a race radio for instruction. Even though I have done the modelling and it would be very funky to do something like that, I don't think it is really all that sensible an idea.

Wind is not that big a factor in pacing. A few watts here and there for differences between head/tail winds. All it does is change the time taken to ride a course. The main element to consider is gradient.

i have no idea about this... but sounds like you have thought about it... if i were to do an out an back course, absolutely flat, headwind out, tailwind back.. pacing wise, i should maintain same power out and back?

doctorSpoc said:

i have no idea about this... but sounds like you have thought about it... if i were to do an out an back course, absolutely flat, headwind out, tailwind back.. pacing wise, i should maintain same power out and back?

Perhaps, perhaps not. depends upon what the speed differences are and what your gearing is as your overall efficiency will change at different cadences or different gearing combinations. So, if you kept your power the same but your efficiency declined (or improved) as you turned around you could be either over your limit and going to fail at the end or under your limit and under perform. So, it depends.

Fday said:

Perhaps, perhaps not. depends upon what the speed differences are and what your gearing is as your overall efficiency will change at different cadences or different gearing combinations. So, if you kept your power the same but your efficiency declined (or improved) as you turned around you could be either over your limit and going to fail at the end or under your limit and under perform. So, it depends.

i was thinking more along the lines of the uphill downhill pacing strategy...

i.e. you end up with a higher average speed by hitting uphills harder than downhills... you gain more by the smaller change in drag going uphill at lower speed from an increase in x power than that increase in power x going downhill at higher speed... basically an incremental increase power will get eaten up faster by drag at higher speed going down hill than at a slower speed going uphill... so it's better to use a somewhat higher power going uphill than down hill.. end up with a faster speed/lower time.

i guess i with just wind.. it's the opposite so it cancels itself out.. the effective wind speed is going to be the same at given power so it doesn't matter? Alex?

Fday said:

It seems to me that wind is a big deal in pacing because the time it takes to complete the course is what determines how hard one can or cannot go. Now this difference becomes quite small as the distance and time gets long but I suspect that one could ride a 40 k time-trial with a 20 mph tail wind a lot "harder" than a 40 k time-trial with a 20 mph head wind since there might be a 30 minute difference in the time it might take.

If talking about a point to point race and a killer wind, then yes the time to complete would be different so if you are talking about a 20-min race becoming a 30-min race, perhaps some change in power but really, a 50-min race becoming a 55-60-min race, not much in it really.

Most TTs however are a loop or out and back of some kind.

doctorSpoc said:

i guess i with just wind.. it's the opposite so it cancels itself out.. the effective wind speed is going to be the same at given power so it doesn't matter? Alex?

The effective wind speed isn't the same in a headwind and tailwind at the same power because the energy to overcome rolling resistance is a factor also and it varies with the speed, not the square of the speed.

doctorSpoc said:

i have no idea about this... but sounds like you have thought about it... if i were to do an out an back course, absolutely flat, headwind out, tailwind back.. pacing wise, i should maintain same power out and back?

Yes, I have thought about it a lot, and have modelled it extensively. You do go a little harder into the wind and a little easier with it. It tends to happen naturally anyway.

Take a 40km out and back with head/tail wind, assume dead flat. Really the time saving with optimal variance in power from an isopower strategy will be quite small. But the risk of blowing up increases.

Think about it - you'll spend more time into the headwind, so if you attempt to ride at too much more than your MMP for the duration, well you could blow.

An example:
40km TT dead flat out and back.
Ignore start and turn accelerations (same in each case anyway).
Head / tail wind @ 2.5m/s (9km/h) at rider level*.
85kg bike + rider. Crr 0.005, CdA 0.27 m^2, Power at rear wheel. FTP 300W.

Iso power: AP/NP 300W:
Out @ 300W: 33:08 (36.2km/h)
Back @ 300W: 25:17 (47.5km/h)
Total: 58:25 (41.1km/h)

Optimised:
Out @ 308W: 32:46 (36.6km/h)
Back @ 289W: 25:36 (46.9km/h)
Total: 58:22 (41.1km/h)
AP: 300W, NP 300W

Time saved over isopower: 3 seconds.

Same scenario but with a more brutal 5m/s (18km/h) wind at rider level*:

Iso power: AP/NP 300W:
Out @ 300W: 38:24 (31.2km/h)
Back @ 300W: 22:23(53.6km/h)
Total: 1:00:47 (39.5km/h)

Optimised:
Out @ 313W: 37:40 (31.9km/h)
Back @ 275W: 22:57 (52.3km/h)
Total: 1:00:37(39.6km/h)
AP: 299W, NP 300W

Time saved over iso-power: 10 seconds

I would suggest going a little harder into wind but the risks of going too hard far outweigh the relatively small potential time savings.

* note that reported wind speeds are usually far higher than what happens at rider level.

doctorSpoc said:

i was thinking more along the lines of the uphill downhill pacing strategy...

Gradient has a different effect and the variable power pacing strategy is typically more pronounced and effective when you have a variable terrain course.

Alex Simmons said:

Yes, I have thought about it a lot, and have modelled it extensively. You do go a little harder into the wind and a little easier with it. It tends to happen naturally anyway.

Take a 40km out and back with head/tail wind, assume dead flat. Really the time saving with optimal variance in power from an isopower strategy will be quite small. But the risk of blowing up increases.

Think about it - you'll spend more time into the headwind, so if you attempt to ride at too much more than your MMP for the duration, well you could blow.

An example:
40km TT dead flat out and back.
Ignore start and turn accelerations (same in each case anyway).
Head / tail wind @ 2.5m/s (9km/h) at rider level*.
85kg bike + rider. Crr 0.005, CdA 0.27 m^2, Power at rear wheel. FTP 300W.

Iso power: AP/NP 300W:
Out @ 300W: 33:08 (36.2km/h)
Back @ 300W: 25:17 (47.5km/h)
Total: 58:25 (41.1km/h)

Optimised:
Out @ 308W: 32:46 (36.6km/h)
Back @ 289W: 25:36 (46.9km/h)
Total: 58:22 (41.1km/h)
AP: 300W, NP 300W

Time saved over isopower: 3 seconds.

Same scenario but with a more brutal 5m/s (18km/h) wind at rider level*:

Iso power: AP/NP 300W:
Out @ 300W: 38:24 (31.2km/h)
Back @ 300W: 22:23(53.6km/h)
Total: 1:00:47 (39.5km/h)

Optimised:
Out @ 313W: 37:40 (31.9km/h)
Back @ 275W: 22:57 (52.3km/h)
Total: 1:00:37(39.6km/h)
AP: 299W, NP 300W

Time saved over iso-power: 10 seconds

I would suggest going a little harder into wind but the risks of going too hard far outweigh the relatively small potential time savings.

* note that reported wind speeds are usually far higher than what happens at rider level.

I think the data is quite clear. There is some benefit to be gained from "going a little harder" is when everyone is going slow. Into the wind or uphill would be the most obvious examples.

Fday said:

I think the data is quite clear. There is some benefit to be gained from "going a little harder" is when everyone is going slow. Into the wind or uphill would be the most obvious examples.

A little harder in power terms is right. But I think the tendency for many is to go too hard into the wind. Same thing with hills.

While optimal power (from a fastest time POV) is higher going up than down, from a rider/leg sensations POV, riders should take it easier going up and push hard down the other side. That's because the general tendency for many riders to start with is to go too hard (power wise) on the way up and not go hard enough (power wise) on the way down.

Again, with wind, the time gains for a variable power strategy are fairly small (but not insiginificant). However the risk of such a strategy is high and there's no guarantee that the wind will remain constant while riding a course. Go out hard into head wind and then the return tail wind drops off? Oops. Race blown and time lost.

Gradients on the other hand don't change, and so having a strategy for them is far safer.

Alex Simmons said:

I have already built the mathematical model but it's practical implementation would likely be combined with telemetry to the following car and a race radio for instruction. Even though I have done the modelling and it would be very funky to do something like that, I don't think it is really all that sensible an idea.

Wind is not that big a factor in pacing. A few watts here and there for differences between head/tail winds. All it does is change the time taken to ride a course. The main element to consider is gradient.

Amen for that.

It always amazed me that people, especially on the hillier time trials never really accounted for those long downhill sections. If you're using 53x14 and 13 on the flat then what makes you think that 53x12 is going to be a useful gear whilst trying to stay on the tri-bars at 45mph whilst trying to stay low, aero and in control, let alone pedal efficiently. You spend all that money on aero equipment only to have to resort to holding onto 'the drops' and becoming less aero.

Unless there's a good technical descent of more than a few minutes, where it's not possible to maintain your desired race effort, then it's still just a case of change gears as needed and maintain the same effort that you would do on the flat but with the caveat that you need a gears suitable in order to maintain that effort at all points in the course. If that means riding a 56/44 and 11/19 out back then so be it...

Alex Simmons said:

Yes, I have thought about it a lot, and have modelled it extensively. You do go a little harder into the wind and a little easier with it. It tends to happen naturally anyway.

Take a 40km out and back with head/tail wind, assume dead flat. Really the time saving with optimal variance in power from an isopower strategy will be quite small. But the risk of blowing up increases.

Think about it - you'll spend more time into the headwind, so if you attempt to ride at too much more than your MMP for the duration, well you could blow.

An example:
40km TT dead flat out and back.
Ignore start and turn accelerations (same in each case anyway).
Head / tail wind @ 2.5m/s (9km/h) at rider level*.
85kg bike + rider. Crr 0.005, CdA 0.27 m^2, Power at rear wheel. FTP 300W.

Iso power: AP/NP 300W:
Out @ 300W: 33:08 (36.2km/h)
Back @ 300W: 25:17 (47.5km/h)
Total: 58:25 (41.1km/h)

Optimised:
Out @ 308W: 32:46 (36.6km/h)
Back @ 289W: 25:36 (46.9km/h)
Total: 58:22 (41.1km/h)
AP: 300W, NP 300W

Time saved over isopower: 3 seconds.

Same scenario but with a more brutal 5m/s (18km/h) wind at rider level*:

Iso power: AP/NP 300W:
Out @ 300W: 38:24 (31.2km/h)
Back @ 300W: 22:23(53.6km/h)
Total: 1:00:47 (39.5km/h)

Optimised:
Out @ 313W: 37:40 (31.9km/h)
Back @ 275W: 22:57 (52.3km/h)
Total: 1:00:37(39.6km/h)
AP: 299W, NP 300W

Time saved over iso-power: 10 seconds

I would suggest going a little harder into wind but the risks of going too hard far outweigh the relatively small potential time savings.

* note that reported wind speeds are usually far higher than what happens at rider level.

interesting... thanks!

swampy1970 said:

Amen for that.

It always amazed me that people, especially on the hillier time trials never really accounted for those long downhill sections. If you're using 53x14 and 13 on the flat then what makes you think that 53x12 is going to be a useful gear whilst trying to stay on the tri-bars at 45mph whilst trying to stay low, aero and in control, let alone pedal efficiently. You spend all that money on aero equipment only to have to resort to holding onto 'the drops' and becoming less aero.

Unless there's a good technical descent of more than a few minutes, where it's not possible to maintain your desired race effort, then it's still just a case of change gears as needed and maintain the same effort that you would do on the flat but with the caveat that you need a gears suitable in order to maintain that effort at all points in the course. If that means riding a 56/44 and 11/19 out back then so be it...

Going from a 52 to a 56 is less than a 10% change. This is less than the difference between the 11 and 12 in the back, a miniscule difference when going 45 mph. If that change is adequate that is great but to make a real change one needs to be in the 60 to 65 tooth range. Changing from a 52 to 65 is only a 20% change, sounds huge but it is essentially the same as changing from a 12 to a 10 on the back.

Fday said:

Going from a 52 to a 56 is less than a 10% change. This is less than the difference between the 11 and 12 in the back, a miniscule difference when going 45 mph. If that change is adequate that is great but to make a real change one needs to be in the 60 to 65 tooth range. Changing from a 52 to 65 is only a 20% change, sounds huge but it is essentially the same as changing from a 12 to a 10 on the back.

Ever try changing gear from a 44 to a 56 with a standard front mech? It's not the smoothest process... and I'm not entirely sure that you'd be able to make the jump to a 65.

Besides, 100rpm on 56x11 is somewhere in the high 40mph range - 46 to 48mph if I remember correctly and gives a good 5 to 6 mph over a 53x11, tailwind and gradient permitting....

... or you could use a really big back wheel like Moser did in '85. That "tiny" front wheel is 26"

swampy1970 said:

Ever try changing gear from a 44 to a 56 with a standard front mech? It's not the smoothest process... and I'm not entirely sure that you'd be able to make the jump to a 65.

Besides, 100rpm on 56x11 is somewhere in the high 40mph range - 46 to 48mph if I remember correctly and gives a good 5 to 6 mph over a 53x11, tailwind and gradient permitting....

... or you could use a really big back wheel like Moser did in '85. That "tiny" front wheel is 26"

Yes, I have and 44 to 56 jump is easy. I am currently riding a 39/73 set-up using a Shimano 105 FD without much problem. One has to be careful in this shift but it is done easily and reliably. I have concluded the 73 is a little big for me and that a 65 would probably be better. However, if I were a pro and putting out 100 more watts than I do I don't think this would be the case.

@ Fday

73??????

pinkpanther said:

@ Fday

73??????

73, I will try to get a picture and post it.

that's something i would like to see

pinkpanther said:

that's something i would like to see

Two views showing the chain actually goes onto both rings.

That says 13063 - a 63 tooth ring with 130bcd?

Dude, three words of advice.

Wash your bike.

Ain't looking too good if the inventor of PowerCranks makes it look like his product spews oil all over a $1,000's worth of kit...