Sponge

The Sponge is a set of unlockable tires in Mario Kart 7. They offer an acceleration boost, but they also hinder speed and weight. The Sponge offers the second lowest weight boost, losing only to the Roller tires.

The Sponge tires also appear in Mario Kart 8, where they have identical stats to the Cushion and Wood wheels.

Stat boosts
Stat values are out of 6.

Mario Kart 7

 * Speed: -0.25
 * Acceleration: +0.5
 * Weight: -0.75
 * Handling: 0
 * Off-Road: 0

Mario Kart 8

 * Speed: -0.25
 * Acceleration: +0.25
 * Weight: -0.25
 * Handling: -0.25
 * Traction: +0.5