UCI Downhill – Lenzerheide, Switzerland and Static versus Sliding Friction

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Lenzerheide in Switzerland hosted the fifth round of the 2016 UCI Downhill World Cup. The event saw Danny Hart frustrate Aaron Gwin’s title hopes when he beat him by just 0.096 of a second and Rachel Atherton extend her unbeaten run as she continues to re-write the record books and progresses towards a perfect season.

For the overall womens results click here

For the overall mens results click here

To see the race again click here 

Static versus Sliding Friction

warnercalouriA take away learning point from this race was offered up when commentator Rob Warner said to Claudio Calouri ‘This one’ll be won in the corners’ – he wasn’t wrong.  It looked pretty dusty watching the races as the dry conditions led to the course surface beginning to break up. Rob Warner’s learning point was that what Danny Hart and Rachel Atherton were about to demonstrate better than the rest was their mastery of sliding friction.

It’s pretty obvious but for the vast majority of the time when you’re on your bike, the only contact between you and the earth is through your tyres. The thing that stops your wheels spinning or sliding sideways when you’re pedalling or cornering is friction between your tyres and the track.  It can be a bit of a weird one to get your head around at first but, although your bike tyres are moving, at the exact moment when your tyre is in contact with the surface it is gripping the surface and propelling you forward – this is called static friction.

If you try and drag a heavy box across the floor, at first it’s difficult to move but once it ‘slips’ it gets easier to move as a weaker kind of friction called sliding friction comes into play.  When we slip on a muddy surface or your bike skids on a wet road we lose the force of static friction and sliding friction takes over.  When this happens it is still possible to control the slide or skid and stay balanced and moving in the direction you want but it takes a bit more skill – this is what Danny and Rachel showed during the race.

For a lot of riders there’ll be two options when cornering – controlled cornering utilising static friction and uncontrolled skidding. Elite riders have another layer sandwiched between these two – controlled cornering utilising sliding friction (also called drifting). The key to adding this layer to your own riding is practicing ‘feeling’ through the corners. All too often when you’re trying to improve your cornering the advice is technique based ie keep your elbows up or drop your outside foot. To master sliding friction you’ll need to do something different and learn to feel how the bike is ‘biting’ the ground as you corner so you can adjust your bike’s bank angle and your body position to make the most of the grip that’s available.

If you’re going to take the time to practice, practice like the elite

Adi

 

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