deacon mark

I don’t have power meter but for almost 58 years old strong cyclist. I run too but slow primarily a runner but better at cycling as i age.

So so today on relatively flat 43 mile course I average 17.8 mph. Wind was ok loops so fair as far as time with wind and into wind. Strava says I averaged 132 watts burned 720 calories. They use same calorie count as garmin connect which I upload to.

I know the calorie thing is off my guess is I am burning about 600 per hour was out 2:25. The watts seem off too and I think I am putting out more watts than that. Is there any way to estimate watts on a curve of some kind. For me this was not a huge effort but steady. I generally ride 17-19.5 mph on rides of 30-70 miles. I just don’t know enough about watts to say a thing. Running is easy to tell it is all speed.

TrojanHorse

If you don't care enough about your power to buy a measurement device, why bother? You can get single sided crank arm power meters for under $400... strava's estimates are horrible - as are the calorie measurements (which is another thing a power meter can help with)

In the meanwhile, you can play with a variety of online tools that can help you out:
Bicycle Speed (Velocity) And Power Calculator

base2 

Strava's guesstimates don't know very much. I think it improves with all the relavent data you can provide about the bike, bike weight, wheel weight, tire weight, your weight, heart rate, etc...but it still doesn't know wind conditions, drafting, inflation pressure of tires, the surface you are riding on, and other stuff like that.

PowerTap chainrings are $350 & come in 53, 52, 50 tooth varoeties all with a 36 inner ring. Could be a really cost effective way to kill 2 birds with one stone if you needed rings or wanted a power meter.

Strava/Garmin work really well with direct measurement. Garmin even can tell you how you pedal, as if that kind of information is useful...but, there you go.

rubiksoval

Can't buy them anymore as of last week (though you can buy them for 700 from various places). SRAM took over. I emailed the guy, pissed I missed the switch over. Said they're only providing warranty; no more new units.

rubiksoval

220 watts usually buys me 19.5-20 mph with ~50 feet of climbing a mile at 165 lbs in not-super-windy conditions with an aero bike and fast tire setup and generally more-aggressive riding position. 250 + watts is more in the 20.5-21 mph range. 200 watts is more in the 18.5-19 mph range.

Lots of qualifiers there, because lots and lots of things affect speed at various power outputs.

deacon mark

So what is power meter to get? In my research I don’t want pedals because they obsolete my Shimano s i like with cleats. I was thinking the 4iiii for left crank only. I think it could be reasonable accurate compared to many other options.

Seattle Forrest

PowerTap hub.

Branko D

Enter all the data right (your weight, height, bike weight, bike type) and Strava estimates are reasonably good on uphill segments, typically agreeing within 10% of powermeter data. That's good enough. Similarly I use cycling calculator (Bike Calculator) to figure out how long will I need to tackle a climb of X at power I intend to produce, and results are pretty much in agreement with reality. Where Strava / etc will really estimate wrong is flats and especially downhills. Position on the bike, aerodynamics and winds play too much of a factor here for estimates to be good.

I've got a Stages left crank meter on one bike and it's really good (do a zero reset now and then and especially if you drop the bike or hit something with the left crank / pedal, because that'll knock the calibration off a bit), while it's left side only it's in good agreement with the power I get on the turbo trainer which measures total power. Going to get a Quarq crank based meter on the other bike (the carbon fiber version is also lighter than my current crank, so.... eh, double win).

Kind of not sold on pedal based power meters, myself.

132 watts sounds realistic for 28,48 km/hr on the flat without wind on a road bike. If there was wind, you have done more. Doing a loop when it's windy even if you are going with the wind 50% and against the wind 50%, your average watts for the same speed will be always higher.

On my touring bike with a hub dynamo and touring tires, which I use for bad weather / bad terrain or zone 1/2 rides (or night rides), I do zone 2 rides on a mostly flat 40km loop, and at 145-150W the average speed tends to be about 25-26 km/hr. I'd expect to go about 3 km/hr faster on the road bike for the same effort.

canklecat

Try the Elevate extension for Strava (Chrome browser only for now). It offers more data than Strava and fitness trends.

rubiksoval

Good enough for what? Might as well just pick the number you want it to be at that point.

LowCel 

Depending on your size that estimate doesn't sound that far off. On a tough rolling course (5,400 feet of elevation gain total) this past weekend I averaged 163 watts while riding an average speed of 17.1 mph for 100 miles. I weigh around 220 pounds so my average watts are higher than most "normal" sized cyclists.

https://www.strava.com/activities/2396579509

Branko D

Within 10% of actual watts is good enough for determining how hard you were trying, really. I don't have a power meter on my latest bike, so when I'm training on it based on perceived effort it tells me if I've paced it near correct or not.

The problem with estimates is that you don't have one real-time, which makes it of very limited utility. If you could get a 3s or 5s average estimate which is within 10%, you could pretty much train and pace off that, wouldn't be ideal, but still more useful than, say, looking at heart rate. Seeing an estimate after the ride, eh, not terribly useful.

PepeM

400 watts.

wphamilton

The point, that I usually see made about this anyway, is if you're OK with plus or minus 10% on your training zone you can do that with perceived effort or heart rate, without needing to be concerned about a power number. Hence the conventional wisdom is that power measurement is *only* useful for precise, real-time training metrics, and the *only* way to do that is with an actual strain-gauge power meter.

I don't necessarily agree with the conventional wisdom - I think that knowing a little bit more about what you're doing or have done is generally a little bit better than knowing a little less. ie, Strava power estimates can be useful, just not in the same way as they use their power meters.

DrIsotope

I'm not a racer by any stretch, but have power meters on both of my bikes. Primarily to use as "fuel gauges," because I'm an idiot. I absolutely cannot ride by RPE, and the same goes for food/water intake based on time or miles. Watching the rate of work done tells me when to put fuel back in. You'd think after a few years I'd get a handle on it, but you would be mistaken. If anything, I've gotten worse.

LAJ

Estimated watts to help you get on the estimated podium. Nothing says job done like a Strava podium.

deacon mark, I run Quarq with good results, but also started out with a Powertap hub, which is still going strong. There are tons of crank based out there, and DC Rainmaker has reviewed them all.

RShantz

If I wanted to do 300w intervals using the +/- of 10%, that'd give me a range of 270w-330w. I can tell you there's a big difference in feel (to me) of 300w compared to 270w. And obviously much greater difference in feel from 270w to 330w. So +/- 10% doesn't work for all.

base2 

I see you are correct. I have no nice words right now.

Stages has what looks like complete Ultegra cranksets for $999 right now. I might buy one of theirs out of spite. My wifes bike is due out of the frame builder in a week & the plan was a Powertap C1. I think we can limp along on the P1 pedals, for now, but the necessary shoes really suck the utility out of a custom S&S coupled touring/car replacement bike.

Not happy with SRAM right now. To buy up the competition & then discontinue the competing product is the very definition of anti-competetive monopolistic anti-free-market behaviour. A product or company *should* succeed or fail on the basis of it's merits. What SRAM did runs counter to that, & this consumer has been hurt to the tune of about $700 for the next comparable option.

WhyFi

Power2Max has options starting at $490 - these are spider-based and give you total power rather than doubled single-sided power.

Dan333SP

If anyone wants to get into training with power (or accurate Zwifting/whatever), the cheapest way in is still a Powertap rear wheel, preferably with the wireless unit.

https://www.ebay.com/itm/CYCLEOPS-PO...wAAOSwsO5cLUCZ

They seem to be selling for around $220-250 these days. Cheaper than the pedal or crank units, and more reliable from what I understand. Assuming they're property calibrated and serviced.

base2 

Not to highjack the thread, but my wifes bike is an S&S coupled Rolhoff equiped travel/touring bike. Are the Power2Max options suitable for disassembly/reassembly in the usual manner of travel bike breakdown? Sorry if I don't know about removable crank-spider type cranksets...but there is a dizzying array of options.

I looked at the dual-sided Shimano options & in addition to being expensive & needing a special charger, the 2 sides are connected by wires, that seems like a red-flag to me.

WhyFi

They make them in different flavors (FSA, SRAM, etc, mine is a Rotor) but, that I'm aware of, removing any of the Power2Max cranksets is no different than most modern cranksets - take off the NDS arm and slide it out.

Sojodave

I bought Powertap P1 pedals and when you own a power meter, you will find that power is measured differently. There is 3 second power, average power, nominal power, etc. Average power usually isn't a good stat to go by because if you free wheel at all, it is included into that number. I've gone 17.8 and barely doing 130 watts and I've also gone 17.8 doing 260 watts depending upon the wind or if you're drafting.

caloso

One day I decided to do an experiment when there was a 10mph wind that was either a perfect headwind or tailwind depending on the direction I rode on one of my interval roads. I picked the same pace (20mph), same gear (53x16), same cadence (80 rpm), same position (hands on hoods) and compared the power output as measured by my Quarq: 309w headwind v. 158w tailwind.

https://www.bikeforums.net/19545151-post28.html

I also decided to compare my measured wattage against what Strava estimated. Measured power: 306w. Strava estimate 167w. (As you can guess, this was from one of the headwind sections).

https://www.bikeforums.net/19545157-post30.html

So, I would not call that close enough.

deacon mark

Ok if I go with a 4iiii that seems the easiest because I just swap a crank arm, If I like it I can upgrade otherwise I am not out a lot cash at $300. My question which may be stupid but what to I use for the head unit. I have a Garmin 910xt. This is the triathlon watch that you can take off the band and put on bike. Would that work of do I need something else?