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Tech Tuesday: Wet Chassis Set-Up

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Leaning to the outside while negotiating a bend helps increase the grip of the outside tyres

Some drivers love racing in the wet, others hate it. But it is also true that liking or disliking the wet depends a lot on what performance one has in these track conditions. Kart set-up is extremely important in wet weather and driving itself changes completely. Wet conditions set-up The main critical aspect of wet conditions is the extremely low grip of all four tyres. This leads to understeer entering bends and oversteer exiting them, with really low traction. Also braking becomes extremely difficult with frequent locking of the rear wheels. To help reduce all these effects, which persist even when rain tyres are fitted, we must really work on kart chassis set-up. First of all we must balance the chassis to give maximum front grip and maximum rear grip! A narrow rear end increases rear grip as does a wide front end for front grip. The front end can be be made really wide by fitting long front hubs. Now work on the front angles. Caster should be increased to the maximum so it gives incidence to the front tyres when entering a bend and reduces understeer. Camber should be set to zero with the driver sat in the kart. Finally, some toe-out gives some advantage. Sometimes, especially with not very tall drivers, it is important to lift the seat to raise the centre of gravity.

Edgar's Hyundri Super One MSA Series, MSA, KF2, PFI, RSF, Ben Barnicoat, ART.

Love it or Loathe it, At some point it’s going to rain, the right set up makes the world of difference.

This creates a greater momentum when running along a bend which helps increase grip on the outside tyres. Of course if you have to add weight to reach the minimum weight limit then add it as high as possible on the kart seat. Seat stays should be loosened to give more flexibility to the chassis and a stiff rear axle fitted. This last solution though, in my opinion, gives little advantage, since the speed and grip of the chassis are so low in wet track conditions that the forces acting on the chassis are also reduced. This means that the chassis flexes very little and the rear axle may not flex at all. As in dry track conditions, tyres are very important. Pressures should be much higher than for slicks on a dry track since in the latter conditions the tyres heat up much more. Be careful though that, when using rain tyres, all the tyre print is touching the ground and not just the centre section. You can check that after your first run. If you only run on the centre then the tyres won’t last as long and grip will of course be reduced. How to drive in wet track conditions As we have already started to see, in wet track conditions one important thing is to put a lot of load on the outside tyres, front and rear. This can be done by even eliminating some load from the inside tyres. So when driving in wet conditions the position of the driver’s body is extremely important. To give as much grip as possible always lean towards the side where you want to increase the grip. So when running along a bend lean to the outside.

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Go on slicks they said…

An even more sophisticated movement of the body is to lean to the outside and towards the front when entering the bend and then lean backwards towards the outer rear tyre when exiting the bend. This will help reduce understeer entering the bend and also reduce the oversteer exiting it. Another important factor to consider is that in wet conditions it is much better to brake earlier and concentrate on the exit of the bend. Locking the wheels when braking can make you lose control, time and spin. Also, in general, never accelerate with the front wheels turned. Accelerate only when the front tyres are straight and parallel to rear tyres, or almost so. The most important thing though is to drive the kart on completely different lines from those used when track is dry. When the rubber laid down on on the track becomes wet it becomes extremely slippery so it is much better to find grip on wet but clean tarmac. The best line to follow is to run the bend all the way round the outside where rubber has not been deposited. In some bends another possibility is to go out wide when entering the bend and then to cut in to the inside. Finally, to help comfort and concentration, it is a good idea to buy a wet suit to keep your body dry and warm. All these points are just a start, you must gain experience of driving in these conditions and fine tune your kart’s set-up to optimise performance.

 

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