| Grand Prix: | Isle of Man |
| Gp Suffix: | TT |
| Flag: | Isle of Man |
| Location: | Snaefell Mountain Course (Senior and Junior) Clypse Course (Ultra Lightweight, Lightweight, Sidecars, Clubmans Senior and Clubmans Junior) |
| Course: | Public roads; Mountain Course ; Clypse Course |
| Race No: | 3 |
| Season No: | 8 |
| Official Name: | Isle of Man Tourist Trophy |
| Date: | 4–10 June |
| Year: | 1955 |
| Fast Rider 500: | Geoff Duke |
| Fast Rider 500 Country: | UK |
| Fast Rider 500 Bike: | Gilera |
| Fast Time 500: | 22:39.0 |
| First Rider 500: | Geoff Duke |
| First Rider 500 Country: | UK |
| First Rider 500 Bike: | Gilera |
| Second Rider 500: | Reg Armstrong |
| Second Rider 500 Country: | Ireland |
| Second Rider 500 Bike: | Gilera |
| Third Rider 500: | Ken Kavanagh |
| Third Rider 500 Country: | Australia |
| Third Rider 500 Bike: | Moto Guzzi |
| Fast Rider 350: | Bill Lomas |
| Fast Rider 350 Country: | UK |
| Fast Rider 350 Bike: | Moto Guzzi |
| Fast Time 350: | 24:03.2 |
| First Rider 350: | Bill Lomas |
| First Rider 350 Country: | UK |
| First Rider 350 Bike: | Moto Guzzi |
| Second Rider 350: | Bob McIntyre |
| Second Rider 350 Country: | UK |
| Second Rider 350 Bike: | Norton |
| Third Rider 350: | Cecil Sandford |
| Third Rider 350 Country: | UK |
| Third Rider 350 Bike: | Moto Guzzi |
| Fast Rider 250: | Bill Lomas |
| Fast Rider 250 Country: | UK |
| Fast Rider 250 Bike: | MV Agusta |
| Fast Time 250: | 8:52.0 |
| First Rider 250: | Bill Lomas |
| First Rider 250 Country: | UK |
| First Rider 250 Bike: | MV Agusta |
| Second Rider 250: | Cecil Sandford |
| Second Rider 250 Country: | UK |
| Second Rider 250 Bike: | Moto Guzzi |
| Third Rider 250: | Hermann Paul Müller |
| Third Rider 250 Country: | West Germany |
| Third Rider 250 Bike: | NSU |
| Fast Rider 125: | Carlo Ubbiali |
| Fast Rider 125 Country: | Italy |
| Fast Rider 125 Bike: | MV Agusta |
| Fast Time 125: | 9:02.2 |
| First Rider 125: | Carlo Ubbiali |
| First Rider 125 Country: | Italy |
| First Rider 125 Bike: | MV Agusta |
| Second Rider 125: | Luigi Taveri |
| Second Rider 125 Country: | Switzerland |
| Second Rider 125 Bike: | MV Agusta |
| Third Rider 125: | Giuseppe Lattanzi |
| Third Rider 125 Country: | Italy |
| Third Rider 125 Bike: | Mondial |
| Fast Rider Sidecar: | Willhelm Noll |
| Fast Rider Sidecar Country: | West Germany |
| Fast Rider Sidecar Bike: | BMW |
| Fast Passenger Sidecar: | Fritz Cron |
| Fast Passenger Sidecar Country: | West Germany |
| Fast Time Sidecar: | 9:00.0 |
| First Rider Sidecar: | Walter Schneider |
| First Rider Sidecar Country: | West Germany |
| First Passenger Sidecar: | Hans Strauss |
| First Passenger Sidecar Country: | West Germany |
| First Rider Sidecar Bike: | BMW |
| Second Rider Sidecar: | Bill Boddice |
| Second Rider Sidecar Country: | UK |
| Second Passenger Sidecar: | William Storr |
| Second Passenger Sidecar Country: | UK |
| Second Rider Sidecar Bike: | Norton |
| Third Rider Sidecar: | Pip Harris |
| Third Rider Sidecar Country: | UK |
| Third Passenger Sidecar: | Ray Campbell |
| Third Passenger Sidecar Country: | UK |
| Third Rider Sidecar Bike: | Matchless |
In the 1955 Isle of Man TT the Lightweight 250cc race moved to the 10.75 miles long Clypse Course, also used for the Lightweight 125cc TT race, and the Sidecar TT, and the course was used for these races until 1959. During this period the rest of the TT program remained on the Mountain Circuit.[1]
In the Junior TT, Norton rider Bob McIntyre led for four of the seven laps, but brake overheating and suspension problems forced him to slow, allowing Bill Lomas on a Moto Guzzi to pass, and go on to victory.
| Pos | Rider | Manufacturer | Laps | Time | Points | |
|---|---|---|---|---|---|---|
| 1 |  Geoff Duke | Gilera | 7 | 2:41:49.8 | 8 | |
| 2 |  Reg Armstrong | Gilera | 7 | +1:59.2 | 6 | |
| 3 |  Ken Kavanagh | Moto Guzzi | 7 | +4:43.0 | 4 | |
| 4 | Jack Brett | Norton | 7 | +5:49.8 | 3 | |
| 5 | Bob McIntyre | Norton | 7 | +7:03.4 | 2 | |
| 6 | Derek Ennett | Matchless | 7 | +9:24.6 | 1 | |
| 7 | Bill Lomas | Moto Guzzi | 7 | +12:05.0 | ||
| 8 | Eric Jones | Norton | 7 | +12:55.4 | ||
| 9 | Derek Powell | Matchless | 7 | +13:35.4 | ||
| 10 | Peter Davey | Norton | 7 | +14:25.2 | ||
| 47 finishers | ||||||
| [2] | ||||||
| Pos | Rider | Manufacturer | Laps | Time | Points | |
|---|---|---|---|---|---|---|
| 1 | Bill Lomas | Moto Guzzi | 7 | 2:51:38.2 | 8 | |
| 2 | Bob McIntyre | Norton | 7 | +1:00.0 | 6 | |
| 3 | Cecil Sandford | Moto Guzzi | 7 | +1:24.0 | 4 | |
| 4 | John Surtees | Norton | 7 | +3:14.0 | 3 | |
| 5 | Maurice Quincey | Norton | 7 | +4:03.8 | 2 | |
| 6 | John Hartle | Norton | 7 | +5:16.8 | 1 | |
| 7 | Derek Ennett | AJS | 7 | +7:00.2 | ||
| 8 |  Duilio Agostini | Moto Guzzi | 7 | +8:46.6 | ||
| 9 |  Peter Murphy | AJS | 7 | +8:59.8 | ||
| 10 | Jack Ahearn | Norton | 7 | +10:23.0 | ||
| 52 finishers | ||||||
| Pos | Rider | Manufacturer | Laps | Time | Points | |
|---|---|---|---|---|---|---|
| 1 | Bill Lomas | MV Agusta | 9 | 1:21:38.2 | 8 | |
| 2 | Cecil Sandford | Moto Guzzi | 9 | +51.2 | 6 | |
| 3 | Hermann Paul Müller | NSU | 9 | +4:43.4 | 4 | |
| 4 | Arthur Wheeler | Moto Guzzi | 9 | +8:06.2 | 3 | |
| 5 | Dave Chadwick | R.D. Special | 9 | +9:07.4 | 2 | |
| 6 | Bill Webster | Velocette | 9 | +13:27.2 | 1 | |
| 7 | Phil Carter | Norton | 9 | +15:27.6 | ||
| 8 | Bill Maddrick | Moto Guzzi | 9 | +16:16.8 | ||
| 8 finishers | ||||||
| Pos | Rider | Manufacturer | Laps | Time | Points | |
|---|---|---|---|---|---|---|
| 1 | Carlo Ubbiali | MV Agusta | 9 | 1:23:38.2 | 8 | |
| 2 |  Luigi Taveri | MV Agusta | 9 | +2.0 | 6 | |
| 3 | Giuseppe Lattanze | Mondial | 9 | +2:14.8 | 4 | |
| 4 | Bill Lomas | MV Agusta | 9 | +2:59.6 | 3 | |
| 5 | Bill Webster | MV Agusta | 9 | +20:35.8 | 2 | |
| 6 | Ross Porter | MV Agusta | 9 | +22:26.8 | 1 | |
| 7 | Frank Burman | EMC-Puch | 9 | +22:33.8 | ||
| 8 | Len Harfield | LCH | 9 | +27:11.8 | ||
| 8 finishers | ||||||
| Pos | Rider | Passenger | Manufacturer | Laps | Time | Points | |
|---|---|---|---|---|---|---|---|
| 1 | Walter Schneider | Hans Strauss | BMW | 9 | 1:23:14.0 | 8 | |
| 2 | Bill Boddice | William Storr | Norton | 9 | +3:44.6 | 6 | |
| 3 | Pip Harris | Ray Campbell | Matchless | 9 | +5:08.0 | 4 | |
| 4 | Jackie Beeton | Charles Billingham | Norton | 9 | +5:40.0 | 3 | |
| 5 | Frank Taylor | Ron Taylor | Norton | 9 | +8:38.8 | 2 | |
| 6 | Ernie Walker | Dun Roberts | Norton | 9 | +8:42.4 | 1 | |
| 7 | Fred Hanks | E. Donnan | Matchless | 9 | +10:22.4 | ||
| 8 | Derek Yorke | R. Eden | Norton | 9 | +14:48.0 | ||
| 9 | A. H. Skein | F. Westaway | Norton | 9 | +18:27.0 | ||
| 10 | Fritz Mühlemann | K. Tuscher | BSA | 9 | +26:54.0 | ||
| 10 finishers | |||||||
| Pos | Rider | Manufacturer | Laps | Time | |
|---|---|---|---|---|---|
| 1 | Eddie Dow | BSA | 9 | 1:22:23 | |
| 2 | I. M. Atkinson | Triumph | 9 | +1:08 | |
| 3 | R. Kelly | Triumph | 9 | +2:01 | |
| 4 | P. Ferbrache | BSA | 9 | +2:39 | |
| 5 | D. Andrews | BSA | 9 | +2:58 | |
| 6 | A. H. Mustard | BSA | 9 | +3:01 | |
| 7 | F. Wallis | BSA | 9 | ||
| 8 | G. W. Shekell | Triumph | 9 | ||
| 9 | M. W. Gillingham | Triumph | 9 | ||
| 10 | D. J. Hunt | BSA | 9 | ||
| 12 finishers | |||||
| [3] | |||||
| Pos | Rider | Manufacturer | Laps | Time | |
|---|---|---|---|---|---|
| 1 | Jimmy Buchan | BSA | 9 | 1:25:24.0 | |
| 2 | D. Joubert | BSA | 9 | +15.6 | |
| 3 | P. Ferbrache | BSA | 9 | +2:30.8 | |
| 4 | R. Thompson | BSA | 9 | +4:49.0 | |
| 5 | C. McLean | BSA | 9 | +4:50.4 | |
| 6 | W. H. Hocking | BSA | 9 | +4:57.8 | |
| 7 | K. W. James | BSA | 9 | ||
| 8 | D. Jervis | BSA | 9 | ||
| 9 | T. E. Hutchinson | BSA | 9 | ||
| 10 | R. M. Harding | BSA | 9 | ||
| 12 finishers | |||||