The steepest 500 meters in the United Kingdom.

Cycling the indomitable Afon Ddu, Wales

Ride only 600 meters but at a stunning 21.3% average grade.

Simon Warren (100 Greatest Cycling Climbs, UK) ranks this as the hardest climb in Wales and he will get no argument from us on that front! This climb comes with the steepest 500 meters in all of the UK at 25%, and it comes at the beginning of the climb so be prepared to strain at the outset.

The climb is named after the stream that flows near it and originates well up the mountain at Llyn Cowlyd Reservoir.

Climb summary by PJAMM Cycling’s Brad Butterfield:

Afon Du is forever burned into my muscle memory. This is a climb so steep and treacherous that making it to the summit is not guaranteed. Obviously excellent fitness is required, but so is low gearing. I used a 34x42 and never once even considered dropping down into a harder gear. This climb will have your legs in flames and your lungs begging for mercy. For the adventurous and brave, there is no better destination in Wales than Afon Du. Bring your best.

Climb start.

In his Cycling Weekly article about this beast, Simon Warren refers to the Afon Ddu climb  as “Baby Zoncolan.”  This is an informative and entertaining article about Afon Ddu by Simon:

“‘There’s always a bigger fish.’ That’s what the ancient proverb says, and just when I thought I’d ridden the steepest road in Britain, and put the matter of determining the country's toughest cycling climb to bed once and for all, up popped another hideous incline to further move the goalposts and redefine suffering. . .” (Britain's Baby Zoncolan).

This climb is steep beyond belief with a full 100 yards in the middle averaging 25%.  

You know you are in for it when the road surface is cement with traction grooves etched into it.

For your road bike, bring low pressure and at least 28mm tires and a 34/42 and end at the gate.  However, if you have a mountain bike, you can keep going to enjoy the trail, but be on the lookout for sheep. No matter what, you're going to want to make sure those brakes work well and with anything other than hydraulic disc brakes you're going to want to check those pads after.  This is one of those climbs where it is very difficult to maintain braking traction on the descent.

Thank you gate!