## Let's play a quick little game. Guess the watts.

Questions about bike hire abroad and everything light bike related. No off-topic chat please

Moderators: robbosmans, Moderator Team

## How many watts to hold 32mph/51.5kph Additional details below.

250W-
2
2%
300W
5
6%
350W
11
13%
400W
18
21%
450W
22
26%
500W
14
16%
550W
12
14%
600W
2
2%
650W
0
700W+
0

Karvalo
Posts: 2957
Joined: Fri Aug 10, 2018 6:40 pm
spartacus wrote:
Tue Jan 10, 2023 5:36 am
I could go out on my fastest bike and try for 32mph but nothing will satisfy anyone here because the conditions can't be known apparently,
So far you've just said you did a segment at X speed without even linking to the segment or the ride - so you haven't begun to attempt to satisfy anyone.

Plus if it's a KOM it's a near certainty that the conditions are partially known - there was a tailwind. And that's not a dig of any kind - it's just axiomatic that any flat segment that gets any kind of traffic will have a KOM set with a tailwind or some other special conditions because the effect is so big.

spartacus
Posts: 914
Joined: Mon Apr 04, 2011 6:53 pm
maxim809 wrote:
Tue Jan 10, 2023 6:35 am
spartacus wrote:
Tue Jan 10, 2023 5:36 am
Interesting information. I was on a touring bike with 32c tires (lol) not a racing or track bike, does have a power meter though, I was surprised how fast I was going. I was just cruising around though at those speeds and staying towards the bottom.
Yes it actually doesn't take "too much" power to hold ~20mph once you look at it on a closed circuit like a velodrome. I think often what happens out in the real world, is there are lots of stops and goes which kill average speed. And also the safety and management with traffic and pedestrians -- all of which can tank average speed for an inflated average power with zero's removed, once you look on Strava.

Those who ride quiet country roads and never have to brake for gravel or potholes will probably have closer experiences to the one you had at the velodrome, compared to say someone trying to get out of downtown Sydney/New York/Sydney/Tokyo proper.
spartacus wrote:
Tue Jan 10, 2023 5:36 am
I could go out on my fastest bike and try for 32mph but nothing will satisfy anyone here because the conditions can't be known apparently, I believe the math I suppose.
You should!

Here's an actual checklist of additional data that should be enough to get rid of a tough crowd:

1. Average Power of run
2. Date & Time the sample was taken
3. Avg Wind speed and direction information sourced from Wunderground for the location of your outdoor run
4. Rough temp & Weather conditions at time of run (can also be sourced from Wunderground)
5. The direction you traveled 32mph into (need to reference against 3)
6. Tire brand/model/size/psi

Those should be the big ones, and the minimum needed to get a rough estimate. There are other things we can look at if the data looks off, but I would start with these 6.

That said, Tobin back-calculated your CdA as 0.30 with the data you already provided. This is a very, very realistic coefficient of drag number for the nominal sized, nominal roadie. This can either be a very small rider sitting up, an average sized rider starting to get low, or a larger rider in an aero position. If you were doing loops in a velodrome, then as long as the wind wasn't blustering crazy, we can squint and hand-wave the conditions out.
spartacus wrote:
Tue Jan 10, 2023 5:36 am
but nothing will satisfy anyone here
Put differently, for a first glance with minimal data I'm pretty satisfied with the analysis! The rabbit hole can of course go as deep as you want.
Thanks for the informative post. When I get a chance I'll give it a try. The touring bike in question had significantly higher and wider bars than my road bike and I was wearing a loose kit, so I know I can do better on my SL7, but looking more at the math I'm starting to doubt I can hold 30+ for more than a few minutes if it's actually flat and wind free. Oh BTW the velodrome was Helsinki and I was a little scared TBH and there was a little wind. My fastest laps were 27+mph at close to 385 (?) w-ish but it's hard to say what I was doing on those laps as far as pacing.

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spartacus
Posts: 914
Joined: Mon Apr 04, 2011 6:53 pm
Karvalo wrote:
Tue Jan 10, 2023 12:28 pm

Plus if it's a KOM it's a near certainty that the conditions are partially known - there was a tailwind. And that's not a dig of any kind - it's just axiomatic that any flat segment that gets any kind of traffic will have a KOM set with a tailwind or some other special conditions because the effect is so big.
That's a good point and I think you're right, there had to have been a slight tail wind. Also after I got the KOM a couple guys got pissed and took it back at 35MPH working together

BTW 4400 people on the segment.