The 1923 races was the first time the Sidecar TT race was run, over 3 laps of the Mountain Course won by Freddie Dixon and passenger T.W.Denney with a special Douglasbanking-sidecar at an average race speed of 53.15 mph. For the 1926 races the Sidecar TT and Ultra-Lightweight TT were dropped due to lack of entries. The Sidecar TT race was re-introduced in the 1954 event for machines not exceeding 500 cc engine capacity, run on the Clypse Course. A non-championship 750 cc class for sidecars was introduced for the 1968 event. From 1975, the previous 500 cc and 750 classes were replaced by a 1000 cc engine capacity class. For 1976 the event became a race held over two-legs. The new FIM Formula 2 class for Sidecar outfits was introduced for the 1990 races.
1954–1959 Sidecars not exceeding 500 cc engine capacity. Race held on Clypse Course.
**The Sidecar may be placed either side of the motorcycle. Hinged sidecars and steerable sidecar wheels are prohibited.
**The three road wheels may be disposed as to give two or three tracks.
**If three tracks are made then the centres of the tracks of the motorcycle shall not be more than 75mm apart.
**The main chassis frame must consist of, at a minimum - a steering head, a frame to accommodate the engine and a main spar to the sidecar wheel which will be made from good quality steel tube.
**The tubing used for the construction of the frame may be of a circular or non-circular section, and the outside diameter shall not exceed 101.6mm.
**Monocoque construction is prohibited and the use of composite construction is forbidden with the single exception of the sidecar platform.
*Engine Position
**The engine must be positioned behind the steering head and in front of the driver.
**The final drive must be transmitted to the road through the rear wheel of the motorcycle. An engine positioned behind the driver and in front of the rear drive wheel is prohibited.
**The engine must be positioned so that the centre-line of the engine will not exceed 160mm beyond the centre-line of the rear wheel of the motorcycle.
*Dimensions
**Width 1575 mm. Wheelbase 1651 mm. Track 800 mm minimum, 1105mm maximum. Height 800 mm
**Weight 136.5 kg without fuel. The addition of ballast to reach this official minimum weight is prohibited.
*Wheels
**Wheel rim diameter of 254 mm and 64mm in width. The diameter of the tyre must be as least 400mm and the width 100mm; maximum front tyre width 220mm. The use of slick tyres is permitted.
*Steering
**Steering of the front wheel must be by a non-adjustable handlebars securely fixed to the forks or yokes of the motorcycle with no intermediate push or pull rods and all steering elements must be located on the sprung portion of the front suspension unit.
*Brakes
**All three wheels must be braked and use only ferrous brake discs.
Official Qualification Time
115% of the time set by the third fastest qualifier in the class.
Speed and lap records
The lap record for the Sidecar TT is 18 minutes and 59.018 seconds, an average speed of set by Ben Birchall and passenger Tom Birchall during Race 2 in 2018. They also set a new race record of 57 minutes and 25.040 seconds, an average race speed of for 3 laps of the Mountain Course, bettering their own race-record set in 2015.
