Riding in wind

Velvind uses the same lines everywhere in the app. The minutes are what the app works out the wind costs straight into it, over 10 km at 25 km/h.

With 8 m/s straight at you at 25 km/h you lose 4.6 minutes per 10 km, and the same wind behind you gives back only 3.6. Time is distance over speed, air resistance grows with the square of the air's speed over you, and nobody banks the whole tailwind. Try your own numbers in the headwind calculator.

This is where a lot of riders get it wrong. In a steady wind, a closed loop has exactly as much headwind as tailwind, whichever way you ride it. Average the headwind over the whole loop and it comes to zero both ways. Turning the loop round changes when you meet the wind, not how much of it you get.

The old advice to ride out into the wind is still good, for a different reason: you take the hard part on fresh legs, and a headwind at the end is the one riders remember. So when Velvind compares directions, it counts the last kilometre twice as heavily as the first.

Direction really matters when the wind turns or builds while you're out, or a shower can be dodged. Then Velvind says if the loop is kinder the other way round. Wind forecast for your bike route shows a day the wind turns after lunch.

A crosswind doesn't slow you in the app's clock: only the part along the road changes your speed. It does make the bike twitchy. Keep a firm, relaxed grip, let the bike move a little under you, and give yourself room from the edge where gusts come through gaps in trees and buildings. Deep rims catch more wind than shallow ones.

• Hold your effort steady, not your speed. Pushing to keep your usual average costs more than the minutes it saves.
• Make yourself smaller: lower on the bars, elbows in.
• An easier gear and a quicker cadence save your legs.
• In a group, take turns at the front and sit close behind the rider ahead.
• Plan the route around the wind: forest roads and valleys give shelter; open fields and coast roads don't.

A forecast's wind is the wind 10 metres above open ground. On a bike you sit low, sheltered by trees and buildings, and often behind other riders. Velvind calibrated its clock against real rides and counts a quarter of the forecast wind when it works out when you'll be home. The colours and words about the wind use the full forecast, so you see how strong it is.

• Headwind calculator Your own numbers: wind, direction and speed in, minutes out.
• Wind forecast for your bike route Head, cross and tailwind for each stretch of your ride.