SEATS

The seat is not just a plastic bucket in which to place your bottom.
It is an integral part of the go kart. Aside from holding your ass and preventing it from being scraped against the ground at 60km/h, it is one of the main turning components on the main chasis.

The go kart has no suspension. It is a rigid metal frame with some ability to flex. This flexing is crutial to controlling your kart, or else the only direction you can go is straight ahead. The chasis must flex for the kart to turn into corners; this flexing also impacts the seat and it flexes too.

I.e. if the seat is too still, it restricts the chasis from flexing properly. This will cause the chasis to "bind up" and slow you down.

Some seats allow more flex, and it all goes down into what it is made of. One of the more advanced seats i have seen is a brand called Ribtect, which optimises the flex of the seat with a special layering of materials. The layering of materials used to construct the seat allows it to flex along two diagonal axies, like a letter X. 6 uni directional carbon fiber strips are used to connect the seat from all corners and then the seat is layered with a composite fiberglass, to enhance the cross-flex ability.

What one would ideally want a seat to do is to flex with the kart when the vehicle turns and the inside rear tyre must lift off. This will allow a better feel into the corner and a better launch out of the corner, and thus imporving lap times.