Update, bought a compatible bike computer and after a few teething problems with Bluetoothing to Garmin Connect, everything is now hunky dory. It’s a Garmin edge 520 plus. Thankyou for the pointers. Still getting used to what the power numbers mean. Did a sprint today and was surprised to see my power much less than I expected, only 230W average, although this was good enough for 1st vet and 5th overall. One interesting thing, I found it easy to push 300-400w on the hills but hard to hold 200w on the flat. Planning to play with new toy over next few weeks & see.
Raw power figures on their own are fairly meaningless. Powe to weight or even power to CdA are more important figures, especially for comparing
Getting used to the power meter now. Bit of a reality check, im much worse than I thought at cycling. Previously I went by the power estimate on tacx flow. Today did a 20 min effort, tacx said 261W but Garmin said actually 225W normalised power.
I had that many moons ago.
I think my tacx was about 60-80 watts over reading.
My plans of being quick on the bike were quickly brought back down to earth!
It takes a while longer to accept these are just values, you can’t really compare one persons values with another’s because of the variation between power meters, types of power meters, training equipment, and environmental conditions…it’s back to your race results for how good you are 
Hi,
if you are into Strava and you have a Garmin (dont know about your watch) to see your 3 Second Average Watts than a power meter is a lot of fun when trying to beat your climbing segments, but of course you need to take into account if you have lost weight as it is watts/kg that is the important metric. I love looking at my Edge as a welcome distraction on a long triathlon to ensure I are pushing at the optimal Watts and Cadence.
I am just waiting to receive a Stryd and going to see how Power can work to improve my running.
Have Fun
I’ve just purchased a Inride 3 sensor for my Kinetic Road Smart. How you getting on with it?
When it works it’s great, but today it’s failing to transmit to my phone or Garmin. I’ve been on my hols for a fortnight so I’ll replace the battery & have another play with it tomo.
I don’t have “real” power so I’m not sure how accurate it is - DC Rainmaker seems pleased with it - but as long as results are repeatable it gives me another measurement to work with.
On the negative side I bought Training & Racing With Power & it’s taking a lot of reading 
.
the reviews seem to be very positive. its supposed to be quite accurate, but yeah, most of all is repeatable. I currently have the Inride 2 which is Bluetooth only, and its spot on, but wont connect to Garmin, hence the upgrade.
Rather than start a new thread, I will add to this subject:
I have a 10km stretch of fast flat straight road, that is used by many as a Time Trial practice
Last week I did a PB at 48.8kph in 12m18s @ 298W
Today I did it at 48.8kph in 12m18s @ 310W
The temperature was different, 18 degrees last week 13 degrees today
The other difference was clothing, last week I had a aero tri suit, today I had regular cycle top, and a small waterproof rolled up in my pocket
I am really surprised that clothing and small temperature change would result in 12W difference in power
What about the wind, that makes a big difference?
I’ve got a similar stretch (although shorter) that I use but after every run I make a note of the wind from a weather site that gives it at specific times. I didn’t used to but was getting some pretty screwy results so went back and checked, this sit lets you look up the historic weather.
https://www.timeanddate.com/weather/uk/birmingham/historic
Both day completely windless
Could be variation in Power Meter, but would be surpised if it was that big. I put my TT bike back together after Lausanne, and raised TT bars 1 cm in preparation for Nice
The only thing I can think of is barometric pressure. I know in hour record attempts it’s a big consideration, enough to change the gearing of the bike or even abandon an attempt.
Wind last week E 2kph, today E 1kph
Pressure last week 30.19hg today 30.08hg
Looks pretty close weather and pressure wise
How baggy is the cycle top?
There is a big difference between the new fangled aero ones and a more general ‘cycle top’.
And don’t power meters have ±1% error rate (at best) - so that could be 2%.
I could see 10W coming out of those easily. Don’'t forget at such high speeds a few watts doesn’t make much speed difference (wind resistance cubed and all that…)
Yes I was going to mention ed the variance in PM accuracy. Although that could also make it worse either way. The temp could have made a fairly big difference, warmer air is less dense.
What about tyre pressures, the same? What about your weight? Traffic passing etc.
There are so any factors that could impact it and its not a massive difference in watts, although clearly there is a difference.
And humidity and pacing and all sorts, nowhere near enough data for a conclusion.
I hate baggy tops, it was a pretty tight fitting castelli top, however, carrying a waterproof in pocket meant that there was a bulge at the back which would make some difference
I was foggy, so certainly more humid, and colder so air was denser
Traffic was light both times, it is not a busy road, but there certainly are some critical sections where even a small tow from passing car can make a big difference at that speed… and I didnt get any decent tow today
I agree that PM accuracy is probably also a factor
We chase watts, and look at expensive kit to save watts where we can, at the same time, with very little obvious factors, we can see a 12w difference, which in itself is pretty interesting
It OK folks, i’ve got to the bottom of it… Just looked at the track on Strava, and my bike computer seems to have stopped for 8 seconds, so my actual speed was 49.3kph