SIDECAR driver Bill Currie and his passenger Kevin Morgan were killed during the TT practice session last night (Tuesday).
The session was red flagged following the incident at Ballacrye.
Both were experienced competitors but this was the first year Bill, 67, from Ellesmere Port in Cheshire, and Kevin, 59, from Shrewsbury, had competed together.
A statement by ACU Events Ltd said: "Bill was an experienced racer who first competed at the TT Races in 1969, when he recorded a third place finish.
"He finished eighth in last year's TT sidecar race in his fastest ever race time of 107.944.
"Kevin made his TT debut in 1984.
"Bill was divorced with two children and Kevin was single. The ACU wishes to pass on their deepest sympathy to the family and friends of both competitors."
ACU Events managing director Jim Parker said: "I have known both Bill and Kevin for many years and am deeply saddened by their untimely death.
"They were a huge part of the sidecar paddock and will be sorely missed by everyone involved in the event."
The coroner of inquests has been informed and an investigation into the circumstances of the accident is underway.
Tributes have been paid to the racers on the iomtt.com forum.
One, by forum user FitzJnr, said: "Was a pleasure to have known you and raced against you. It is going to be one hell of a dust up when we all meet again on the racetrack in the sky.
"RIP Lads, you will be sorely missed by everyone."