Mountain bike world record attempt in Snowdonia
A team of two disabled and two able-bodied sportsmen is attempting to set a new world record in north Wales.
The Project ENDURO team hope to achieve the greatest number of metres descended in 24 hours, on specially designed four-wheeled mountain bikes.
Gower College in Swansea and the University of Wales Trinity Saint David have been involved in the bike's development.
The event, at Antur Stiniog, Gwynedd, started at 12:00 BST on Wednesday.
Paralympic athlete Nathan Stephens and paraplegic racing driver Brian Roberts are among the four riders.
Team manager Calvin Williams, an engineering lecturer at Gower College, helped to design the bikes.
He said they were designed primarily for disabled people but could be used by able-bodied people too in a bid to create "a downhill sport that is accessible for everyone".
On the record attempt, Mr Williams said: "We would really like to at least do the equivalent of riding from the top of Everest down to sea level which is 8,000 plus metres."
All money raised from the challenge will be donated to Disability Sports Wales.