Does anyone know how much difference a properly set up coilover alone will make in terms of lap times with street tires?

 

Better Tires would drop your times more.

 

It would depend on the track of course, different types of corners would produce different gains, but recently we saw some #s with an STi, where Stock vs one with correct spring rates, ALIGNED and cornerweighted went a little more than a second faster around Roebling Road Raceway in Savannah, GA. with OEM Tires.

this was a gain of 2% on a course with very long corners at high speeds. (80mph +)

But like was mentioned Tires would help more, and any part you put on it isn't going to help as much as it can if not properly used. (slap those coilovers on, dont mess with alignment/corner weights and you might very well go slower. )

Jon K
www.seat-time.com