Tyre selection is critical, usually done by the individual rider based on bike 'feel' during practice, qualifying and the pre-race warm-up laps on the morning of the race, as well as the predicted weather. The typical compromise is between grip and longevity—softer compound tyres have more traction, but wear out more quickly; harder compound tyres have less traction, but are more likely to last the entire race. Conserving rubber throughout a race is a specific skill winning riders acquire. Special 'Q' or qualifying tyres of extreme softness and grip were typically used during grid-qualifying sessions until their use was discontinued at the end of the 2008 season, but they lasted typically no longer than one or two laps, though they could deliver higher qualifying speeds. In wet conditions, special tires ('wets') with full treads are used, but they suffer extreme wear if the track dries out.