We carry on the extracts from the technical articles that you find in the latest issue of Vroom International. This extract is taken from ‘Don’t let it freeze’, which is about some precautions to face the lower temperatures of this time of year, and how they influence the performance of your kart.
10/01/13 - Garage
Author: Vroomkart International
To give you an example of set up in antithesis with “golden rules” of the definition of set up, take camper: in normal conditions, with karts (because it works differently with cars), the straighter the wheels are more hold there is: while if we have negative camber, that is, tilted inwards, they tend to skid. The thing is that at times, when it’s cold and temperatures are very low, when the tread rests on the asphalt best, it can't be not stressed much so it doesn’t warm up. But, if we reduce the area where it touches the ground, increasing camber, the tyre is subject to more load, so it manages to warm up and there is more grip. Obviously these are limits and in very low environmental temperatures, but they help us to see haw, at times, you must be a bit elastic with “set up regulations”.
LOOKING FOR WARMTH
And as we are dealing with the characteristic geometry of the wheels, don’t forget that an adjustment that helps both aspects directly (more grip and more heat for tyre) is adjustment concerning toe in. so open the wheels at the front with too much hesitation, even up to 20mm and if necessary (remember we are talking of extreme cases, let’s get there but always gradually), because we’d get contemporarily more directionality and tyres would warm up quicker. Moreover, being the front ones and therefore not subject to torque drive torque, they usually take a bit longer. In fact, in defining these setup, it is up to the driver’s sensitivity (and experience) to feel if less grip depends on adjustment or the fact that tyres haven’t warmed up enough and if we have lack of balance after some laps it could depend, say, on the fact that front tyres reach the right speed after the rear ones. To conclude the topic on steering geometry, usually it is good to increase caster, that is, spindle pin tilt back: this happens because the minimum lateral road hold tends to let the internal rear wheel lift, with a consequent more “nervous” behaviour of kart as it travels round turns, something that is, instead helped by increasing caster angle.
The image shows how front wheels geometry changes when you act on the toe-in – which can be close or open, the latter being more frequently used in karting.