Only 15" on the rear. We were told these drag radials would knock a lot off the 1/4 mile time. Don't think 650bhp & 15" tyres go & they were simply ripped apart . The 11.5 @ 138mph recorded during those 0-150 runs was on road tyres with 210mph gearing. Also 0-60 4.1, 0-100 in 7.1.