Estimate time for 100 km


(Eltjo de Waard) #1

Just a little calculation question. Can you predict the time it will take to ride 100 km in Watopia (flat course) when riding a constant Wattage. For instance 180 W.


(Bertram Redmeijer (B)) #2

Around 3h20 minutes, depending on your weight, and if you decide to push it a bit on the slopes (even on the flat course you will have to do the esses).


(Eltjo de Waard) #3

Thank you for the answer, but I guess you say that on basis of experience, and not with a calculation?


(Paul Allen) #4

Just giving your estimated wattage is not enough to make a very good educated guess on how long it would take you. It could take you 2hr 30min to 3hr 30min depending on your weight.


(Eltjo de Waard) #5

That’s correct, I thought it would be possible to use the data from previous rides. For instance, if I had a ride of 30 km in exactly 1:00:00 hour with a power of 180 W. With this data you could calculate the time needed for 100 km @ 180 W would be 3:20:00.

But when I used this approach with three different rides it gave three different answers. (200 W, 1:05:21, 35,4 km gives a other number than 171 W, 1:00:43, 30,3 km)


(Paul Allen) #6

Based on that, the only way to fine out how long it would take is to actually ride 100km.  


(Eltjo de Waard) #7

Yes, but how will you convert that value with other Watt’s? If I ride 100 km @ 180 W in 03:20:00, how fast will it be riding 200 W? I don’t believe it will be linear.

 

And for the record, just making a nice conversation. So please don’t take it to heavy.


(Paul Allen) #8

Again that is not enough information to even make a guess. You could use this is to punch in a bunch of number to see what happens: http://www.machinehead-software.co.uk/bike/speed_distance_time_calc.html

 


(Eltjo de Waard) #9

Thank you for the link, but I was searching for the Watt’s. 

And why shouldn’t it be possible? There are calculations that will calculate the time it takes you to climb a mountain with your bike. That’s basically the same thing. The only thing you NEED to know is the total Watt’s needed to ride the distance. And that total needs to take into account the road resistance etc. And that is what Zwift is doing since you see the speed when you’re riding in Zwift.

Small links with examples: 

http://www.u.arizona.edu/~sandiway/bike/climb.html 

http://www.northeastcycling.com/neclimbs_hillcalc.htm 


(Paul Allen) #10

You also need weight and type of bike used within Zwift. This info can change the time drastically. If you are 50kg and doing 180 watts you are moving MUCH faster than someone who is 100kg doing 180 watts. The bikes aero properties come into play also. If you are using a TT bike you can go faster at a given watts than with a standard bike.


(Bertram Redmeijer (B)) #11

The speed you ride depends on roll resistance, air resistance (drag), and the energy you have to use to raise the weight of you and your bike over the hills.

Roll resistance is slightly weight dependend.

Drag is a constant factor times your frontal area times your velocity squared. Your frontal area depends on your length and how wide you are (read: weight).

The height you need to climb is based on your weight times the meters you have to climb.

As you see just putting in the watts isn’t going to make it… it only works for steep climbs where you can ignore the air drag (because you go relative slow, and the energy needed to go up is much higher). Knowing the watts won’t give you a speed on the flat, and that isn’t even taken drafting into consideration.

Or stated differently: there isn’t *a* number of Watts that is needed to ride the distance. The faster you go the more Watts you need.  And the bigger you are, the more Watts you need.

 


(Eltjo de Waard) #12

Hi Bertram,

 

Thank you for your explenation.  You have said it very Nice.

Will be doing the 100 km soon!


(Paul Gray) #13

https://www.bestbikesplit.com Has the tools to do this however it is typically for real world analysis which is of course much harder (variable wind and temp, etc.)  

Using the Strava segment for the Watopia flat course (already exists) you can enter some information and make and estimate. 


(Juan Ferres [BRT]) #14

Constant wattage is not very realistic for a 100km ride. You will get bored easily. 

It’s better change wattage or cadence from time to time. 

I did Zwift Watopia 100km in 2h 52 minutes (35km/h, 207w average). The first 40km i was very soft (2,5kg/w) and the last 60km 2,5kg/w to 3kg/w. 

https://www.strava.com/activities/488411306

 


(Eltjo de Waard) #15

Did the 100 km last saturday: https://www.strava.com/activities/487464334 kudo’s welcome :slight_smile:

Started with 180 W but couldn’t keep up so reduced to 160 W. Average was 166 W @ 3:03:20 @ 2,1 W/kg. (Little drop because I did warming up and cooling down)