Strava power output, what type of bike?

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LancsGirl
Posts: 255
Joined: 5 Jun 2021, 9:57pm

Strava power output, what type of bike?

Post by LancsGirl »

Dear all

I notice Strava has this power output thingamajig. I've read the various opinions, which add up to - "it's not much use". But people seem to think that over a longish continuous hill it can be fairly accurate. I've identified one such, and set it up as a Strava segment for power measuring purposes.

My bike weighs about 15kg, and has 32mm Marathon tyres, with mudguards. These days I wear cycling-ish clothing, close fitting but not super-tight. I've entered my bike as type "road" into Strava. Would "gravel" be more appropriate?

Thanks
Nearholmer
Posts: 3930
Joined: 26 Mar 2022, 7:13am

Re: Strava power output, what type of bike?

Post by Nearholmer »

My guess is that it is using some figure based on vague description of bike type to pick a set of rolling and wind resistance figures from a menu, and I think that at low speeds, of the two, tyre rolling resistance will dominate, so you are right on the border of road and gravel tyre sizes, possibly erring on road!

Why not do the run twice, selecting the two options?

The slower you are going, and the longer and steeper the hill, the more accurate, I think, because under those circumstances the really dominant factor is simply lifting mass from one level to the next, in a given time. It will far outweigh resistance components unless you ride with the brakes on or have flat tyres and rusty bearings.

PS: does it ask about junk and luggage hung from the bike? It should, because several kg of stuff will make a significant difference on hills.
LancsGirl
Posts: 255
Joined: 5 Jun 2021, 9:57pm

Re: Strava power output, what type of bike?

Post by LancsGirl »

Nearholmer wrote: 28 Jun 2022, 7:30am My guess is that it is using some figure based on vague description of bike type to pick a set of rolling and wind resistance figures from a menu, and I think that at low speeds, of the two, tyre rolling resistance will dominate, so you are right on the border of road and gravel tyre sizes, possibly erring on road!

Why not do the run twice, selecting the two options?

The slower you are going, and the longer and steeper the hill, the more accurate, I think, because under those circumstances the really dominant factor is simply lifting mass from one level to the next, in a given time. It will far outweigh resistance components unless you ride with the brakes on or have flat tyres and rusty bearings.

PS: does it ask about junk and luggage hung from the bike? It should, because several kg of stuff will make a significant difference on hills.
Thanks. All it asks about is the weight of the bike. I weighed it immediately pre-ride, with water, saddle pack etc. Then weighed me, ready to ride.

I don't suppose there's a dramatic difference between road/gravel. But Strava does seem to remember changes, by which I mean if you change bike weight or rider weight it doesn't change the wattage for past rides, so yes, I could "play" with it. The hill I'm using isn't particularly long or steep. But it is a continuous uphill. I might try and seek out a longer steeper one.
Nearholmer
Posts: 3930
Joined: 26 Mar 2022, 7:13am

Re: Strava power output, what type of bike?

Post by Nearholmer »

I thought about this later: is the gravel/road question actually about the bike, or the surface you are riding on?

To me, it would make more sense as a question about surface, because rolling resistance over unmade surfaces is a great deal higher.

Sometimes, I come off “gravel” (various forms of bumpy stuff, mostly nothing like actual gravel) to go on the road when I get tired, and it is soooo much easier.
LancsGirl
Posts: 255
Joined: 5 Jun 2021, 9:57pm

Re: Strava power output, what type of bike?

Post by LancsGirl »

Nearholmer wrote: 28 Jun 2022, 10:16pm I thought about this later: is the gravel/road question actually about the bike, or the surface you are riding on?

To me, it would make more sense as a question about surface, because rolling resistance over unmade surfaces is a great deal higher.

Sometimes, I come off “gravel” (various forms of bumpy stuff, mostly nothing like actual gravel) to go on the road when I get tired, and it is soooo much easier.
Hi there. It's a question about the bike. Which is a steel framed road bike but with 32mm tyres, guards etc. I suppose it's a "traditional" frame, definitely not "aero". But drop bars.

I ride almost exclusively on tarmac. In fact the short segment I have set up as personal power output test has a very smooth surface, with no chippings ("surface dressing"?).

So I suppose the answer is that it's a road bike. But maybe more at the "gravel" end than the "race" end of the road bike spectrum. Except I don't really know what a gravel bike is, though I keep seeing the term used.
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