A GUIDE TO MACHINE PREPARATION FOR THE MANX GRAND PRIX AND CLASSIC TT
- For examples of good practice in wiring exhaust springs please see the photographs HERE -
I would like to take this opportunity to help all riders and mechanics to get through with the minimum of problems by letting everyone know what we expect in terms of machine preparation at the Manx Grand Prix/Classic TT.
Some of the requirements may appear to be idiosyncratic but every regulation has a reason based on many years experience of checking racing machines used on the Mountain Course. I know that many of our requirements are not necessary on short circuits but anyone who races on the Mountain Course regularly will tell you that the long, high speed sections can give rise to problems that will not show up in a full season of short circuit racing.
1) It is an FIM and ACU requirement to have the split in the front brake lines at or above the lower fork clamp. However, we still occasionally get a machine with one brake line looping over the mudguard. This is not acceptable.
2) Brake callipers that have a brake pad pin held in by R-clips (eg Brembo) should have lockwire on the open end of the clip to stop it coming out. It has happened and the brake pads fell out! It is recommended that calliper bolts are lockwired. They have been known to come loose.
3) Tyres must be correctly fitted according to the rotation arrows.
4) Short valve stems are a must. The long rubber stems that are used on car wheels will deflect quite appreciably and must be changed. Long metal stems are acceptable.
5) Metal valve caps, or the latest moulded plastic racing caps which include a pressure seal, must be fitted. The valve core can lift off its seat on long, fast stretches and the rubber seal in the cap provides additional sealing against pressure loss. Do not use the extractor type with the slot in the top as, should this come off, it could go through the tyre of the rider behind you.
6) Wheel spindle nuts and wheel spindles must be pinned or lockwired. There was a case at a previous TT where a front spindle nut worked loose. Where the spindle is flush with the fork legs, lockwiring both pinch bolts on both fork legs is acceptable. Where spindles are retained by bolted or pivoting caps eg 350 Honda classic or RC30 the retaining nut must be wired or the stud end drilled for wire/split pin. Rear wheel spindles that are captive at one end do not require lockwire but the nut does. Spindles using a castellated nut and an R-clip must have lockwire or a cable tie on the open end of the R-clip to secure it.
7) ALL exhaust springs must be wired in such a way so that if the spring breaks, it is retained on the machine and does not go on to the road where it could be a problem for following riders - For examples of good practice please see the photographs HERE
8) Oil containment is required on ALL four stroke machines so please keep a very close eye on the belly pan which should be solid WITHOUT any drain holes or bungs. Any holes must be repaired with fibreglass before the machine is allowed into the holding area. Duct tape or silicone is not an acceptable repair. Unfaired machines must be fitted with a reservoir beneath the engine and the front lip must extend upwards to within 50 mm of the base of the cylinder barrel to guide any oil down into the reservoir in the event of engine failure.
9) The lower rear chainguard (or shark fin) must cover the point at which the chain runs on to rear sprocket. Moving the rear wheel back as far as possible to lengthen the wheelbase and the smaller sprocket used for TT course gearing means that a guard that was OK on short circuits could be a long way from a position where it is effective.
10) Numbers and backgrounds are not supplied by the organisers. The font used for the numbers should be as plain as possible so the marshals, spotters and timekeepers can readily identify the machines as they pass at high speed. Painted backgrounds are acceptable providing that a matt finish is used. Putting the background inside the screen and the numbers on the outside is not acceptable. Shiny backgrounds and a low sun make a bike coming down Glencrutchery Road look like it has a headlamp on! If it is not possible to put the number in the centre of the fairing then it should be on the right hand side when sitting on the machine. Side numbers must be visible from the side. These can be on the fairing or belly pan if the seat unit is too small. Any numbers or backgrounds that are not acceptable will have to be replaced. Please read the regulations and ensure you present your machine with the correct colour plates and numbers fitted.
11) Random checks will be carried out to ensure that identity discs are being worn and the correct helmet sticker is in place.
12) Red rear lights are compulsory for all machines. Please ensure that yours meet the requirements as per ACU Handbook. This will be checked at Technical Inspection. Many of the lights fitted in previous years have not been robust. Please ensure that not only is the light correct, but fitted such that it will survive the rigours of the Mountain Course!
These are the most common problems that we have encountered over the years and if you are fortunate enough to have someone else wielding the spanners, please make them aware of the requirements.
Random breath tests will be carried out throughout practice and race weeks. The permitted level of alcohol is 0.1g/L.
If you have any comments or questions, I can be contacted through the Race Office.
Chief Technical Official
Manx Grand Prix / Classic TT