mine needed the air in the bags but had a 10 inch contact patch.that's alot of rollout and it was very tight,not to mention raising the rear of the car up..the taller tire takes the initial hit so well but the roll out really ended up hurting my combo.our time slips are almost identical and that taller tire slowed my car down with the bigger exhaust housing. if you have a t.63 on that 66p it will work better if your trying the 29.5 inch tire if its a t.82 or pte.85 it wont wake up till much later in the rpm range.28inch=87rollout,29.5=93 hope this helps