They were originally designed for the harsh, frozen wilds of Alaska.
But “fat bikes” – bicycles which can be pedalled through rough terrain and snow – are the latest must-have for two-wheel enthusiasts in a region already mad about cycling.
Built for an Alaskan snow race, the bikes have proven perfect for East Lothian’s sandy coastline and look set to become the latest outdoor craze.
Later this month, North Berwick sees the fourth UK Fat Bike Gathering – a two-day event expected to be attended by some 60 enthusiasts.
Bruce Mathieson, 41, took up fat biking after reading an article in a cycling magazine.
He said: “I had a bit of a lightbulb moment and I thought, ‘Those bikes would be perfect for the beach’.
“I got one of the bikes imported and it’s just kind of snowballed from there.
“There’s something about them which makes them so much fun. They’re perfect for the East Lothian coastline, with the dry sand and rocks.”
Boasting wide rims and extra-large tyres, the bikes – which range between £1400 and £2500 in price – can be ridden on terrain which would cause a standard cycle to grind to a halt.
Designed for a cycle counterpart to the Iditarod Sled race in Alaska – their extra large wheelprint ensures they can run at a very low pressure – between six and eight pounds per square inch – compared with around 45 PSI for a standard bike.
Mr Mathieson, head greenkeeper at the town’s Whitekirk Golf Club, has set up a blog dedicated to fat biking called Coastrider.
He said: “You can take the bikes places you wouldn’t be able to go with a normal bike, it just opens up a whole new world of adventure for you.
“I’ve never heard of anybody buying one and regretting it.”
The popularity of fat bikes is spreading, having proven a hit as far a field as Japan and Australia.
David McHardy, who owns Law’s Cycles in North Berwick, has sold around 40 fat bikes and is already taking orders for the next batch, which are built in the US seasonally.
He said:“They’re becoming more popular now as you can buy them complete whereas up until about two years ago you had to buy them as a kit and put them together.
“It’s a very comfortable bike to ride, you can ride it over a shingle beach or you can ride it down stairs. The bike just smooths everything out – they actually make less impact on the sand than walking.
“You can ride them on sand, dry river beds, and it’s a different sort of cycle.
“If you’re not that confident about your balance, they’re great, and if you’re worried about traffic you can take them anywhere. I’ve never seen anyone try a fat bike who hasn’t who hasn’t loved it.”
The UK Fat Bike Gathering, dubbed the Forth Fat Gathering, will be held on April 27 and 28 and will be attended by representatives from fat bike manufacturer Surly.
FAT bikes were built as snow bikes and are immediately recognisable by their chunky wheels.
The large tyres make the bike more stable when riding off-road. Snow, sand and rocks are also suitable riding surfaces.
Minnesota-based manufacturer Surly began selling the Pugsley, the first mass-produced fat bike, in 2005. It is one of the most popular makes available. The front and rear wheels share a common hub size and can be interchanged, allowing for additional gearing combinations.