Isle of Man TT Rules… For Dummies.

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Put your hand up if you’ve been to the Isle of Man TT. Now put it down, you look like a tit. If you’ve been, you’ll probably have a decent idea of what it’s all about and a rough idea of the rules governing the different classes that race over there. If you haven’t been, well you might not be particularly au fait with the intricacies of the Isle of Man TT rule book. So, because of that, we thought it would be a good time to clear a few bits up. Knowledge is power, and all that.

Race Against the Clock

A mass-start on the 37.7 mile Isle of Man TT Course would be nothing short of ludicrous so, come the races, all the bikes are set off in ten second intervals. Until recently, the top 20 went off in number order, and the rest of the pack went in the order they qualified; now though, all riders go off in number order, regardless of qualifying time. “What’s the point in qualifying then?” I hear you ask. Well the fact is that there will be a lot more entrants to each of the TT classes than there are spaces on the grid. So to earn your place on the grid, you’ve got to go fast enough in qualifying.

After watching the TT on telly, you could be forgiven for thinking there are only 10 starters in each race; but that’s not the case; from 2022 a 1000cc TT race will have 50 bikes and riders lining up on Glencrutchery Road (up to 60 in the other classes) – although it is only really the top ten that get any TV airtime.

The Superstock and Supersport races are four laps long, whilst the Superbike and Senior races are six laps (that’s 150 miles and 226 miles respectively). All of which require a pitstop every two laps for fuel, and sometimes a rear tyre; the really fast lads will usually do a tyre change every two laps, some will throw a new rear in for the last two laps of the six lap races, but plenty will try and get the full six laps out of a set of tyres. The winner is simply the bloke (or the woman) that finishes the four or six laps the quickest.

Supertwin TT Rules

Originally, the idea behind the Supertwin TT was to have an easier, more affordable class of TT racing. It quickly spiralled out of control though; these days a decent Supertwin will set you back more than a competitive Stocker. The rules have just been opened up to allow “any twin-cylinder, four-stroke, water cooled production machine up to 700cc, approved for road use in the UK from 2009 onwards”. Until 2022 it was mainly Kawasaki ER-6Ns that made up the grid with a smattering of Suzuki SV-650s and the odd Paton S1-R, but we’re hoping to see a few Aprila RS660s and Yamaha MT-07s in the mix, now the new regulations allow it.

Frames must remain standard but you can change the subframe, and you can’t run an aftermarket swingarm, but you can run one from the same manufacturer – so, for example,  you could put a ZX-6R swinger in your ER-6 if you could get it to fit. Suspension and brakes can all be changed and upgraded and you can run lightweight wheels (except carbon). The crank, rods, pistons, camshafts, valves and cylinder head can all be faffed with to make as much power as you dare, but remember the bike has to last a four lap race. 

Supersport TT Rules

Supersport bikes are your tuned-to-the-back-teeth 600cc road-bike-based race bikes. Well, 600cc for the most part; you can actually race a bike with 675cc, as long as it’s only got three cylinders, and plenty do, in the shape of Triumph’s Daytona 675. Kawasaki ZX6-Rs, Suzuki GSX-R600s, Yamaha YZF-R6s and Honda CBR 600s are all common sights on a Supersport grid. So what are you allowed to do to them?

Well you can’t increase the displacement or fit a turbo or anything like that, and it’s got to weigh at least 161kg. You can’t replace the standard fuel injection system, but you can modify the throttle bodies if you want to, and you can’t replace the cylinder head, but you can tune the shit out of it. Inlet and exhaust ports, as well as the combustion chamber can be gas-flowed and polished to within an inch of their life, but you can’t change the pistons, con-rods or crankshaft. You can run a ‘kit’ ECU, or a MoTeC one, any exhaust pipe that you want and any suspension that you want, but you have to run standard wheels and treaded tyres. Race bodywork can be used and the fuel tank volume can be increased to 22 litres. Think of a Supersport bike as a baby Superbike.

Superstock TT Rules

Superstock is all about 1000cc sportsbikes (or 1200cc twin cylinder bikes), just like you’d find in the showroom; well that’s the idea anyway. The reality is slightly different. The engine, frame and swinging arm have all got to remain standard so there is no engine tuning, frame lightening or swing-arm stiffening, and you can’t run fancy quick release rear wheel setups. You can replace the rear shock with a full aftermarket unit and the fork internals can be changed, as long as the outers remain the same.

The standard exhaust can be binned off and swapped for a full system from any manufacturer and you can stick a 24 litre fuel tank on it; if you don’t, you probably won’t manage the two laps you need to do to get to your first pitstop. Treaded tyres have got to be used, on standard wheels, and although you can use lightweight race bodywork, the bike has to be at least 172kg and its silhouette has to remain almost identical to that of the standard machine. You are allowed to stick a big screen on though, which is nice. Electronics-wise, you are allowed to fit a ‘kit’ ECU and wiring harness, but you can’t faff with the rev limit which has to remain as standard.

Superbike TT/Senior TT Rules

This is where you can go all out, if you’re man enough and you’ve got a big enough budget. In reality, fewer than half of the Superbike and Senior TT riders bring a full-blown superbike to the party, instead opting to chuck a set of slicks at their Superstock bike and use that instead. A stocker making circa 200bhp is plenty for most TT racers, so it’s only really the super-fast lads (or the ones with a fat-walleted sponsor) that go nuts.

But occasionally they do go nuts and in recent years we’ve seen Anstey and Rutter both having a rip round on Honda RC213V-Ss (a MotoGP bike, kind of) and Lougher ‘smoking’ the opposition (well, not all of them) on a Suter MMX500 (a 127kg, 196bhp two-stroke). But for the most part, Senior/Superbike machines are your 1000cc sportsbikes with very no-holds-barred rules. Ok, almost all of the engine internals have got to be standard parts (you can change valve springs, con-rods and a few bits like that) but you can tune the engine to your hearts content by removing material from the inlet and exhaust ports. Close ratio gearboxes are allowed and any exhaust system can be fitted.

Chassis-wise, you can really go to town with your superbike. As long as you start with a standard frame, you can beef it up as much as you like, and change the sub-frame completely. Any suspension is allowed, as long as it is the same type as that of the homologated machine (telescopic forks, monoshock, etc), and you can use any wheels that fit as long as they are alloy – i.e. not carbon fibre (unless the manufacturer equipped the production bike with carbon fibre wheels, a la BMW S 1000 RR M Sport). Once you’ve upgraded the entire brake system (lever, master cylinder, lines, calliper, pads, disks), you’ll need a 24 litre fuel tank, some race bodywork and you’ll be about there, ready to start the Senior TT. See you in six laps.

IOM TT Factoids

Bang for your buck

It’s not just the Supertwin, Supersport, Superstock and Senior TT races that go on, on the island, heavens no. For starters, the Sidecars will keep you entertained when the bikes aren’t flying round the Mountain Course. But if you happen to be on the island just before or just after the Isle of Man TT, you can get your fix of bike racing, beer and burgers in Castletown, on the south of the island, where the Pre and Post TT Classic races are held. Nice.

Noise limit? What noise limit.

The Isle of Man’s closest neighbours are 20 or so miles away, so they don’t worry too much about upsetting them. Consequently, the Isle of Man TT organisers don’t bother stipulating how quiet your race bike has to be. As far as they’re concerned, the louder the better.

“Do you know why I’ve stopped you, sir?”

There’s a really sweet little law on the Isle of Man that states that any competitor (as long as they have a road bike license) can legally ride their race bike on the public roads from the period starting two hours before a TT race (or practice session) to two hours after, in order to get back to the paddock after having had to pull off the course for whatever reason. You’ve still got to abide by all the speed limits and stuff, but it’s still quicker than waiting for the lads to come and get you in a van.

Points make prizes

What’s in it for the riders? Well the winner gets a big trophy in the shape of Hermes, the Greek god (I have no idea why – and I did try to find out). If you finish within 105% of the winner’s time, you get a silver replica of the winner’s trophy. If you don’t quite manage that, but you do finish within 110% of the winner’s time, you get a bronze replica. Prize money runs down to 20th place in the Superbike, Supersport and Senior races (15th in Superstock and Supertwin), but for the lads at the front, it’s awarded not just for your finishing position, but for each lap that you are in the lead. If you lead every lap and go on to win a Senior TT Race, the Isle of Man Government will write you a cheque for £18,000.


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