Some things are just hard-wired into a mountain biker's brain, and one of them is the sinking feeling when they see soft sand ahead.
That's because the sinking quickly goes from being figurative to being literal, often followed by a short and bumpy flight over the handlebars if the rider was going too fast beforehand.
So there's a combination of nervousness and incredulity when I hop on a mountain bike and head straight for the sand dunes on the outskirts of Dubai.
And when I leave the tarmac, cross a bit of hardpack then go onto the edge of the dune... there's no change. It's like the surface hasn't altered from hard to soft, and as I head up and over the dune, there's an element of disbelief at what I'm experiencing that's a little bit like the cognitive dissonance of watching a masterful magician at work.
This is a look Ian Ganderton, riding beside me, knows all too well. He experienced it himself and repeats it vicariously every time he takes someone on a test ride.
This is, of course, no ordinary mountain bike. It's called a Surly Moonlander, and the name isn't nearly as weird as how this Frankenstein bike looks, with cartoonishly oversized tyres that are twice as wide as on a normal off-road bike.
It originated in Alaska and was created to be ridden on snow by a mountain biker stymied by the long winters. But then a pioneering Dubai mountain biker, Andy Whitaker, saw one and thought it might also work on sand.
So he bought one on eBay in Britain and had it sent over. When it arrived in May, he invited Ganderton, one of his mountain biking buddies, to help him test it in the dunes near Arabian Ranches.
"Andy went out first and I thought he'd be back in about a minute. He came back 15 minutes later," he recalled. "Then I rode it. When I hit the sand, I expected the work rate to go up but it didn't. I realised right away it was something I had to have. I ran - ran - home and ordered one for myself.
"After riding out here [at Arabian Ranches] and then Big Red, Hill 59, I took it to Liwa. That was the ultimate test, really."
The test was in more ways than one. By now the summer heat had descended on the Emirates. But they went out anyway.
"It was June and there was nobody there. I was staggered by the complexity of the dunes," he adds.
"You can go down the slip face, where they do the racing [on Tal Moreeb], but the best bit isn't that, it's going along the line of the dunes, which twist around. It's beautiful."
From riding the first fat-tyre bike in the UAE in May, Ganderton made contact with Surly to arrange for the outdoor gear company he works for, Global Climbing, to import them into the Emirates. Now there are nearly a dozen here, with more on their way, available from most bike shops in the UAE with a list price of Dh11,000.
So far, the sales have mostly been word of mouth, primarily from mountain bikers being taken on test rides with Ganderton and experiencing the same epiphany; biking on dunes was not just feasible but actually even enjoyable.
The key is really low tyre pressure so that the floppier tyre creates a much bigger footprint to share the weight. It's exactly the same principle used for dunebashing in four-wheel drives except that where four-wheel drives generally deflate to 18psi, the Surly's tyres are at 4psi.
Or at least Ganderton thinks they're at 4psi. The reality is his pump doesn't read any lower than 4psi so it's difficult to know exactly how low it really is.
The proof, of course, is in the riding, and nothing quite captures just how lightly the Surly rolls across the dunes than looking at the tyre tracks. Instead of seeing a channel where the tyre of a conventional mountain bike has ploughed through the sand, there's a wide track but each individual ripple of the dune remains visible.
The result for the mountain bikers of the Emirates is as if the terrain they have available has suddenly increased by many orders of magnitude. And instead of the nearest good mountain biking - on a single track created by keen bikers from enhanced goat trails in the mountains near Showka - being a substantial drive from Dubai, it's now close enough to tackle on an afternoon after work.
For Ganderton, who lives in a community just off the Outer Bypass Road, it means fun mountain biking is now less than a minute from his door.
"Showka has outstanding mountain biking. It's full of single track. But it's an hour away, even farther if you're in Abu Dhabi," he added.
"But with this, you can go out in the desert here on the outside of Arabian Ranches, cross the 611 and cycle all the way to Bab Al Shams, entirely off road. It's a long 30km. We were shattered when we got there because we were going against the grain of the dunes. It took about three hours."
Another of the early adopters was a man who uses it for walking his dog. Previously, with the dog running in the dunes and his owner walking, the latter would be worn out long before the former had had its fill.
"The dog is still faster," Ganderton recounts, "but now he's getting a 10km workout. He loves it when the bike comes out because he knows he's getting a good walk."
The presence of fat-tyre bikes in the dunes of the UAE would have been unimaginable to the man credited with creating the genre, Alaskan biker Mark Gronewald.
Ironically for the fat-tyre bikers of the UAE, Gronewald's snow bike fulfilled the potential originally conceived in the 1980s by a Texan who built a fat-tyre bike to tackle soft sand.
Among the adaptations of the early prototypes were having two conventional mountain bike rims welded together and fitted with two normal tyres stitched together to create a nascent fat tyre.
In 2005, Surly created the first production version, the Pugsley, named after the undeniably odd-looking Addams Family character. The Moonlander is its successor, with tyres one quarter wider again.Now several companies are in the market.
One area of discordance for those using fat-tyre bikes on sand is that the Surly is designed to be used wearing thick mitts in sub-zero temperatures. Ganderton has adapted his with conventional shifting gears since it's possible to go out on the dunes of Dubai wearing just a pair of shorts. The result is another sensory experience: being in the dunes and experiencing all its facets.
"Motorcyclists always say that people in cars are in cages," he adds.
"In a four-wheel drive, you've got your windows up and your air con on and the stereo going - you don't feel anything and you're not connected to the environment.
"But on one of these, you know what the temperature is. You know where the breeze is coming from. You're completely attuned."