It's really tough to get info on this festival. It seems to happen sporadically, but the people that go seem to love it!

The Festival kicks off with a welcome and registration party on the evening of February 18th at John Crow’s Tavern (the Festival HQ) located in the heart of Ocho Rios – the vibes capital of Jamaica’s beautiful North Coast.

The bicycling begins on February 19th with a day for Jamaicans to show off their own riding skills. Dubbed “A celebration of Jamaican Bicycling Culture” the Jamaica Bicycle Bash is designed to provide a unique, fun-filled atmosphere centered around all things bicycle. Highlights include a 5 mile race looping through Oracabessa, Skills Course race, the ever-popular Rambolympics and many other games and contests that provide great entertainment!

Bike Magazine went in 2010 and did this nice write up on the event.

FAQ (pdf)

Old write up follows:
The St. Mary Off-Road Bicycling Association (SMORBA) is pleased to announce that the coolest mountain bike event on the planet is back! The 9th Annual Jamaica Fat Tyre Festival is set for February 8-11 in the lush, tropical mountains of St. Mary. This year?s event will feature even more of the ?irie vibes? that led Rob Story from BIKE magazine to proclaim that riding in Jamaica: ??doesn?t remove you from people; it enables you to meet them in strange places under sublime circumstances? (BIKE, June 1997, p. 63)
The Festival is set to kick off with a welcome and registration party on the evening of February 7th at John Crow?s Tavern. This will also be our meeting spot each morning and is located in the heart of Ocho Rios - the vibes capital of Jamaica?s beautiful north coast. The first full day of riding will take participants, including our invited pro riders, deep into rural Jamaica near Robin?s Bay, St. Mary. These amazing, technical singletracks are the same trails that were featured in the June 2006 issue of Mountain Bike Magazine. The day will culminate with a complimentary meal and soiree at Robin?s Bay Beach Hotel.
February 9th will see riders trek to Pimento Hill in St Mary, for a more relaxed day of singletrack, downhills, and waterfalls, ending at Black Sand Beach where a meal of roast breadfruit and other local dishes will be prepared by local SMORBA dude, Natty Grant. In what will almost certainly become a favorite tradition of the JaFTF, local fishermen will shuttle riders from the beach to the pick up point by boat!
On the 10th riders will shuttle up to Murphy Hill, perched high above Ocho Rios. After taking in the view it will be time to let brakes overheat on the blistering descent to world reknown Dunn?s River Falls. After regrouping at John Crow?s, the crew heads out to the friendly communities of Oracabessa, Hamilton Mtn, and Jacks River. Checking out SMORBA?s trails in western St. Mary is sure to prepare riders for the after-ride relaxation at famous James Bond Beach and Stingray City in Oracabessa.
February 11th will be local Jamaican?s day to shine with the staging of the National Rambo (local slang for mountain bikes) Bicycling Championships in Hamilton Mtn. SMORBA is expecting over 50 local riders to compete for the honor of being named National Champion. Of course, overseas guests will be encouraged to pit their skills against those of our local ?intuitive? riders in a spirit of semi-serious, healthy competition!
Spots for this year?s Festival are limited, so if you are interested in attending, or need more information, drop us a line at smorbaja@hotmail.com, smorbaja@yahoo.com, Marshall Paul at madmantours@hotmail.com, or andrewgiles30@hotmail.com, Thanks!
The 2007 Jamaica Fat Tyre Festival is being supported by: Jamaica Tourist Board, Chukka Cove Adventure Tours, IRIE FM, John Crow?s Tavern, the Island Sport Trust and is sanctioned by the Jamaica Cycling Federation.