Power output - Watts ?

[dylanparry]

You are, of course, absolutely at liberty to label your bike whatever you like.

Just be aware that to call a mountain bike a "track bike" is akin to calling an SUV a "go cart". So you will sow confusion whenever you call it a "track bike"

A "track bike" has no brakes, a fixed gear, slick tyres (sometimes tubular, "tubs") and is designed to be ridden in a velodrome.

eg

Yes, sorry - rookie mistake in that labelling by me. I'm consoling myself by stating it is a particularly chunky mountain bike. (well it is as I have a little bit of experience of mountain bikes previously)

 

[dylanparry]

What are you using to set and measure tyre pressure? Again, it is unlikely to be accurate but should be consistent, so it's good you keep on top of it. I'd be surprised at a typical tyre pressure gauge being accurate to 0.5psi though. 65psi is a lot for a "knobbly dirt track tyre", although if you are staying completely on the road then it's probably for the best, but then again if you are staying on the road you would benefit from more road-appropriate tyres.

Yes, I definitely could do with more road tyres. this is the slight dilemma I have at the moment - invest in a new bike of not. 65psi is the absolute maximum recommended for the tyre. They are Kenda tyres. I measure the pressure with a AA digital tyre pressure gauge AA1634.

 

[freiston]

Which is why I said "If you keep things like bike weight and so on constant" (I only named bike weight, but yes, there are quite a few) if you wish to use it for comparison.

Yebbut the "so ons" are much harder to (identify,) control and maintain constantly ergo the algorithm is still a problematic tool for comparison of two instances of the "same" ride. I suppose if you were to use averages over many rides (so that the variables also average out) chronologically, then you might get a decent tool for gauging your (relative) power output.

 

[IanSmithCSE]

Good evening,

These charts suggest 124Watts would give me an average on a mountain bike of 12mph. On the Strava app I am averaging 170-ish Watts and my average speed is around 10.5. I am guessing this means that my weight and weight of my bike and the fact it is not a road bike are responsible for this?

Ah well as long as I keep seeing improvements in my time on segments and routes overall, and am enjoying it as well, I guess that is all that matters. Competing against myself not anyone else right! lol.

These charts are very much a starting point.

As others mentioned it is impossible to get your numbers from simple calculations, if you try, yet will probably get my numbers or something similar. :-)

Power meters are the only way to go if you want to know the truth and if you do get one you will see why a general discussion can only quote general numbers.

There is a site called https://www.bicyclerollingresistance.com/ which is probably where the 30watts per tyre for the Vittoria Randonneur came from.

The numbers assumed a level surface, so your and bike weight don't matter, the differences come from what is necessarily an informed and plucked out of thin air values for wind resistance, people on mountain bikes tend to sit more upright with outspread arms and have wide soft tires with flexible treads.

There is no way that my numbers are correct for you, they are simply a starting point.

There is a web site where users of power meters up load their data and there are a lot of riders in the 200-250 watt range, given how self selecting such a site must be, you might infer that if you genuinely were putting out 170 watts for say an hour then you would be pretty cycling fit.

Bye

Ian

 

[freiston]

. . .There is a site called https://www.bicyclerollingresistance.com/ which is probably where the 30watts per tyre for the Vittoria Randonneur came from. . .

Yup!
https://www.bicyclerollingresistance.com/tour-reviews/vittoria-randonneur-2015
And for clarity, these are the original bog standard Randonneurs - not the Randonneur Pro, MkII, Randonneur Tech etc.

 

[Cerdic]

Hi Dylan.

If I were you, I wouldn’t worry too much about power and watts and stuff. Concentrate on gradually increasing the distance of your rides. More time in the saddle is the simplest way to get fitter and faster.

A proper road bike sounds like it might be a good investment for you. It will make riding on roads much easier, less effort. What it says on the tin! There is no need to spend a fortune. A couple of my mates have £500 to £600 road bikes that do a perfectly good job. They’ve done the London to Brighton for example, no problem.

Just my twopennoth…

 

[cougie uk]

Friend of mine rode his first ironman on a £400 decathlon job and did a decent time. It was a few years ago though so it'd probably be around that 5-600 mark now.

 

[Sharky]

If you got a road bike and all the gear you'd just end up being faster for the same effort. It never gets easier you just get faster.

Or in my case, 50 years on from my avatar photo - "It never gets harder, you just go slower"!

 

[presta]

These charts are very much a starting point.

You've assumed that efficiency is a constant 25%, but efficiency varies as a function of intensity, and 25% is well up at the optimistic end of the scale. You're appealing for real world data on your website, are you aware that the American College of Sports Medicine publish a Compendium of Physical Activities with measured energy consumption data for just about every pastime there is? Info, Database.

This is a plot of efficiency vs output power for a 70kg cyclist from their data:

This is a plot of my own efficiency using the data from my Bruce Tests:

"My Data" was an estimate I calculated using my own data, and the stairs at home as a treadmill.

This is a plot of the ACSM data for the input power of a 69kg cyclist compared to my own measured data, and your data for both a touring bike on hoods (as is my own data), and an average of all the bike types and positions listed in your table:

Your optimistic efficiency assumption is showing up as a much lower estimate for calorie consumption.

 

[dylanparry]

Thanks for all the info guys it is appreciated.

I did a 10 mile ride yesterday on my mountain bike (dirt track back with knobbly tyres - lol), and did it in 53:04 averaging my best speed so far of 11.4 mi/h. That is good for me on that bike (both the bike and myself weigh a bit over the average rider and bike ). So I would say I am happy with that. The power output on Strava read 174W so that was the highest I have recorded so for comparison just with Strava along several rides there is an improvement. So I can at least use it for that.

There is a straight and flat back road on the ride (approx 0.7 miles) which was great for powering away at the pedals but when I got around the corner into another straight and flat section (of about 1.75 miles) I was riding straight into the wind and all I could think of all the way was "this is the type of thing that will affect my time and my power output reading, the guys on the forum were right - many variables" - LOL.

The only saving grace was that I was then turning around and heading right back with the wind behind me - I got up to some speed!

Happy cycling guys and girls!

 

[Pokitren]

Thanks for all the info guys it is appreciated.

I did a 10 mile ride yesterday on my mountain bike (dirt track back with knobbly tyres - lol), and did it in 53:04 averaging my best speed so far of 11.4 mi/h. That is good for me on that bike (both the bike and myself weigh a bit over the average rider and bike ). So I would say I am happy with that. The power output on Strava read 174W so that was the highest I have recorded so for comparison just with Strava along several rides there is an improvement. So I can at least use it for that.

There is a straight and flat back road on the ride (approx 0.7 miles) which was great for powering away at the pedals but when I got around the corner into another straight and flat section (of about 1.75 miles) I was riding straight into the wind and all I could think of all the way was "this is the type of thing that will affect my time and my power output reading, the guys on the forum were right - many variables" - LOL.

The only saving grace was that I was then turning around and heading right back with the wind behind me - I got up to some speed!

Happy cycling guys and girls!

The wind ruined a lot of records If your goal was to set your personal record or see some improvement, it's hard to do outside. And even when you turned around, the wind started blowing at your back - you still played a little on the side of luck

 

[CXRAndy]

I have recently started to ride my bike again but taken a keener interest this time. I only have a mountain bike (almost more of a track bike as it has knobbly tyres), and I am using it for road use.

I am using Strava and have inputed my weight, bike weight etc and it is quite interesting seeing times for my rides and segments on Strava improve in the last 3 weeks.

My Power Output in Watts has been lately just under 170 and with a short time trial I gave myself the other day I achieved 177, keeping in mind there is one extreme hill on that ride which is quite challenging. My average speed is around 10.5 to 11mph - again it is a track bike and heavy and there are many hilly sections in my area so I am fairly pleased to keep my pace at 11mph-ish.

Can someone tell me though if I had a road bike, would my Watts power output be greatly affected? I assume my speed would improve but what about my Watts power output?


Thanks.

Power required by using a road bike would reduce for same speed.

177W is OK for starting out on a ride. Similar to power I had after a years layoff from cycling. Now my FTP is 278W with 7 months of Zwift racing