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Beginner Power Question

2K views 26 replies 12 participants last post by  pedalbiker 
#1 ·
I just got a Stages, and I'm using it with a Garmin Edge 500.

A few weeks ago, I did a ride: 24 mi, 1000 ft of climbing, 18 mph avg, 225w Avg Pwr, 248w N.P.

The next day, I did the same ride, 17.5 mph, 277 w, 291w NP.

Today and yesterday, I did the same ride again, 18mph, but now Strava says 177w avg pwr, 185w NP.

There wasn't any significant wind on any of those days, so what could account for the differences in power?
 
#2 ·
Go back in and look at the numbers on your Edge. What do they say? Upload it to Garmin Connect. What does it say?

You should absolutely notice the difference between 270+ versus 170+ WHILE you're riding. Did you? What's it actually showing when you're riding and when you're finishing up your ride?

Make sure Strava is actually reading your power meter and not giving you an estimated power number.

Make sure zeros are being averaged in.

Strava really sucks for data analysis. Get Golden Cheetah or WKO+ for real analysis (in my opinion).
 
#3 ·
During the first ride, I was watching the power readout the whole time, and I was really trying to keep it above 250. That ride did feel harder. During the last rides, I was just riding and trying to keep a good pace. I notice that my power curve is steeper on the first ride. I wonder if I went out and really hammered for the first few miles and just burnt myself out. Or if I was putting in a lot more effort on the hills, and then resting more on the descents.
 
#4 ·
Pushing harder in the tougher sections dramatically affects your avg speed. The reason: You spend more time traveling at slower speeds.

Example: 20-mile out and back time trial, First 10 miles with headwind and Second 10 miles with tailwind

Trial A - Baseline:
- First 10 miles: Speed 12 mph, Time = 50 min
- Second 10 miles, Speed 20 mph, Time = 30 min
- Total: Avg Speed 15 mph, Time 80 min

Trial B - Faster Going Out:
- First 10 miles: Speed 15 mph, Time= 40 min
- Second 10 miles: Speed 20 mph, Time = 30 min
- Total: Avg Speed 17.1 mph, Time = 70 min

Trial C - Faster Coming Back:
- First 10 miles: Speed 12 mph, Time= 50 min
- Second 10 miles: Speed 23 mph, Time = 26 min
- Total: Avg Speed 15.8 mph, Time = 76 min

So if you increase speed 3 mph into the headwind, you shave 10 minutes off your time and increase your avg speed by 2.1 mph. If you go 3 mph faster with the tailwind, you only improve time by 4 minutes and avg speed by 0.8 mph.

So, yes, it matters a lot that you pushed harder on the climbs. Apparently you shaved significant time off your ride which produces a faster overall pace.
 
#5 ·
Differences could be from a number of things although the first 2 rides look pretty close the 3rd sounds odd by comparison unless for some reason you were significantly right leg dominate during that ride. I'd go back and look at the ride for specific segments on strava where there's an incline of say 4%or more for a mile and compare wattage vs speed so perhaps get some explanation of the difference.
 
#9 ·
If you have a power meter, why are you worried about average speed at all? There are too many variables that contribute to speed at any given power number to really be concerned about this at all.

If your numbers were oddly low (and that means looking at the actual numbers, not Strava) then I would calibrate the PM and ride again to see if you have an issue there.

Also, are you monitoring your power output while riding? I can tell the difference if I'm doing a ride that will end up averaging 250w vs 200w. It's a big difference. You should do a proper power test as well, that way you know what you're doing zone-wise and can create rides to fit your needs.
 
#10 ·
I don't get it. The difference between an hour at 177w and 277w is huge. The first should have felt like a brisk ride, and the second should have left you gutted. I've won races at lower power outputs than that. You might be a lot heavier than me but still there's a big difference between those efforts.
 
#21 ·
If you use a power meter Strava uses the actual power data, not the estimated numbers.

@OP - Were you drafting? Did you calibrate the power meter properly? Make sure that the power meter was actually used on the rides and Strava is picking it up. Do any of the rides on strava say "estimated" power?
 
#23 ·
Have you checked the torque of the bolt that mounts the stages? I have a sram GXP stages and I've had some issues when over-torquing it since i share it between 4 bikes and get in a hurry some times.

Temperature shouldn't matter for the stages since it is supposed to have firmware that auto corrects for temperature changes.

If you haven't posed the question to stages, might be worth asking them. They've always been good about getting back to me in the 3 years or whatever it's been since they first became available.
 
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