Nicknamed “Hellfire Pass” for having marked generations of riders in the British Milk Race, this Welsh wall ranks among the most feared climbs in the UK despite its short length.
A concentrated wall to 545 metres
From Llanymawddwy, the road climbs just 3.4 km for 387 m of elevation gain, averaging 11.3%, with a section reaching 24.1% in places. The short length packs all the difficulty into a few minutes of intense effort.
A legendary climb in British cycling
Renowned in the 1970s and 80s as the most feared climb of the Milk Race, a now-defunct British amateur stage race, the southern side of Bwlch y Groes remains a benchmark today for riders looking to test their limits.
Getting the ride right
A wide-range cassette, with at least a 34- to 36-tooth sprocket, is essential to avoid grinding to a halt on the long 20% section.
When to go
April to October, as the road stays narrow and exposed to the elements outside this window, like most mid-mountain Welsh passes.
Good to know
Dinas Mawddwy, below on the southern side, is a practical starting point for the climb, while Bala, to the north, opens onto other scenic roads through Snowdonia.
