V8 Supercar. 635 HP, 1410kg. 2.22kg per horsepower.
Leopard Light kart. 27 HP, 160kg. 6kg per horsepower.
In last week's blog, I spoke about that most common of karting problems - trouble accelerating off the corner. If we accept the old racing adage "He who has the most grip wins", the idea that a kart could have too much grip seems a bit silly. Ask this scribe, and he'll tell you that the phrase "too much grip" is a misnomer. Take any kart with slippery tyres, like Dunlop SL-1's, and put it on grippier tyres, like MG Yellows, and even before you've updated the setup to suit the lap times will tumble. More grip makes karts faster. That's a fact.
However, when you first make the switch, the kart will certainly feel sluggish off the corner. With a setup designed for slippery tyres, the kart is unlikely to have the inside rear tyre unloaded at corner exit. As the team adjusts the setup to suit the new tyres, the kart will further increase midcorner speeds, further unload the rear tyre on exit, reduce teeth (taller gearing), and lap times will further improve.
So what's the lesson here? The lesson is that you don't have too much grip. You can never have too much grip. A set of super sticky tyres at their optimum temperature will always outperform a harder set of tyres, assuming the setup is right.
V8 Supercars and karts share the lack of a differential in the rear axle (V8's have a locked rear end). However, a V8 has almost three times as much power per kilogram than even one of the more powerful categories. Senior National Pro has 12.5kg per horsepower - a V8 has six times as much grunt per kilogram! Thus, you'll rarely hear a V8 driver complain of 'gripping up'. Conversely, they're usually looking for as much corner exit traction as they can find.
As a karter, you're looking to reduce corner exit traction, but you won't achieve that by removing grip from the kart mid corner. You need mid corner grip to maintain maximum cornering speed. The best way to improve corner-exit acceleration is to set up the kart to keep the inside rear tyre unloaded as far through the corner as you can.