Using speed instead of power?

chrisw12

amaferanga wrote:

Gav888 wrote:

amaferanga wrote:

Gav888 wrote:

Thanks for the advise guys, ive done quite a bit of zone 2 and zone 3 sessions so far on the turbo this year and end of last year so ive got a good idea of what speed I can do for those zones, and using the percentages from Joe Friels power zones I can work out the speeds for each zone, and for zone 2, 3 and 4 they work out fairly accurately with what I can do. At the end of the day its giving me an idea of what I can do without having a powermeter and also when heart rate cannot be used.

Conditions are generally the same, the only thing that wouldnt be is a few degrees temperate difference between winter and summer, I use the same bike, check the tire pressures every other session, fan is set to the same speed each time, and the turbo is a Elite Crono Fluid so resistance is via the gears on the bike. Say that, ive just remembered there is a small plug on the side of the resistance hub that you can plug something in, do these turbo's have an optional power meter?

I will keep an eye out for a 2nd hand power meter, didnt think of that, but I feel I will need one sooner or later as I do like looking at data

You've got the same turbo as me, only mine is the digital version with a head unit that displays speed, distance and something they call power. I'll have a powertap soon so I'll know for sure, but I think the resistance varies quite a bit with temperature (mine is in the garage).

Interesting... once you have the powertab it would be interesting to compare the data from the turbo to see how accurate it is....

I still don't have the powertap, but here's one example of why I'm sceptical about the repeatability on my Elite fluid trainer:

Friday: 20min near-maximum effort, average 'power' = 330W (this is almost certainly an overestimate ), average speed from Garmin = 31.7km/h, average heart rate = 161bpm (93% of MHR, range 90-98% MHR)

Sunday: 60min fairly comfortable, average 'power' = 323W, average speed from Garmin 31.5km/h, average heart rate = 141 bpm (81% of MHR, range 78-85% MHR)

Tyre pressure was the same, warm-up was the same. So based on these sessions, my avHR to maintain 31.7km/h for 20 minutes is about 161bpm, but I can maintain 31.5km/h for 3 times as long at an avHR of only 141bpm :?

For both sessions my cadence/speed drift upwards throughout (as the unit gets warmer and the resistance falls away) with no increase in RPE.

So what this actually tells me (something I've known for a while) is that if I do intervals then unless I progressively increase the speed that I do them at they're actually getting easier. The speed may be useful for comparing the same session, but as an accurate proxy for power its pretty useless.

Good work. It's very nice to see someone use some numbers to back up what they are saying.

You've given a good exmple of the problems with using speed as a proxy for power on a turbo.

Alex_Simmons/RST

Jeff Jones wrote:

That is one of the best places to attack on that circuit, because it's just before people want to wind up for the sprint. I've won a few races myself doing that. It hurts though, as it's 1min flat out.

Good luck on Tuesday!

(Sorry to take things OT but it's good to see you win)

Thanks. Yeah - I've used that spot to attack and win before (and not win as well).

Just back from the Aussie Day race. Frank the Bank insisted I was to be in B grade for the B/C/D group handicap. So I went out there and smashed it up for 15 laps, hung tough and finished with the B boys (including a few guns like Computer).

A grade were a separate race with Kersten, Lang, Milostic, Cater et al.

44.5 min with an NP of 319W. That was 'ard!!

amaferanga

Gav888 wrote:

amaferanga wrote:

Gav888 wrote:

Thanks for the advise guys, ive done quite a bit of zone 2 and zone 3 sessions so far on the turbo this year and end of last year so ive got a good idea of what speed I can do for those zones, and using the percentages from Joe Friels power zones I can work out the speeds for each zone, and for zone 2, 3 and 4 they work out fairly accurately with what I can do. At the end of the day its giving me an idea of what I can do without having a powermeter and also when heart rate cannot be used.

Conditions are generally the same, the only thing that wouldnt be is a few degrees temperate difference between winter and summer, I use the same bike, check the tire pressures every other session, fan is set to the same speed each time, and the turbo is a Elite Crono Fluid so resistance is via the gears on the bike. Say that, ive just remembered there is a small plug on the side of the resistance hub that you can plug something in, do these turbo's have an optional power meter?

I will keep an eye out for a 2nd hand power meter, didnt think of that, but I feel I will need one sooner or later as I do like looking at data

You've got the same turbo as me, only mine is the digital version with a head unit that displays speed, distance and something they call power. I'll have a powertap soon so I'll know for sure, but I think the resistance varies quite a bit with temperature (mine is in the garage).

Interesting... once you have the powertab it would be interesting to compare the data from the turbo to see how accurate it is....

Well I did a comparison last night between PowerTap power and the Turbo (Elite Elastogel Fluid) power.

Results didn't surprise me. It took a good hour before the resistance stabilised (45 minutes of that at 250W on the PowerTap). I did a 10 minute warm-up, then averaged 248W for the next hour. After about 5 minutes of the hour my PT power was 248W and the TT power was about 25W higher. After 30 minutes the PT power was the same, but the TT was getting on for 300W. After about 45 minutes the TT power stabilised reading 85W higher than the PT.

Unfortunately the TT drift is due to changing resistance so my speed (from the PT) increased from about 28km/h at the start of the hour to 32km/h at the end.

Here's the session in Garmin Connect (first 5 minutes is missing cos I forgot to press start on my Garmin :oops:):

Garmin Connect

Not many people spend more than an hour on their TT so taking almost an hour to stabilise is not really much good.

Conclusion - the Elite Elastogel Fluid Digital Chrono Wireless turbo is a useless piece of kit unless you have an independent means of measuring power

Alex_Simmons/RST

Here is a ride I did last week on a Computrainer Lab model - comparing with my (calibrated) SRM power meter. This was after a 10-min warmup and roll down calibration of the CT.

amaferanga

I guess the Computrainer (and even the Tacx Flow) is in a different league to my Elite turbo.