This, I’m sure, has a factual answer. But it is a sport, so if mods feel it is better suited for the games thread, then please move.
Anywho, specifically asking about top fuel categories, but I’m interested in lower categories as well. How many runs are a set of tires good for? And what rules are there regarding such? In the world of F1, they would replace them as often as their budget and regs allow between various practice and qualifying sessions. Which leads me to think tire manufacturers for top fuel would design them to last only 1 run each, if they were allowed to do so. What’s the straight dope?
Unfortunately you have to be an NHRA member to access their rule book, but I’ve been told by one race team that the tires are good for about 5-6 runs. Drag slicks have very, very soft tread compound which is meant to melt a bit when heated and get very sticky (thus the burnout) and the sidewalls wrinkle and flex an incredible amount under torque.
I was not a professional racer, went to the track 5-6 times a year, made 5-6 runs each time. The terminology (which may or may not still be in use) was Sportsman class, high 11 second range. All this said, I kept my slicks for two seasons.
Back to the original question, it’s dependent on so many factors that an answer quickgeneral answer is almost impossible to provide.
I remember a mention that top fuel racers want to use new but broken in tires in competition. They do spin the tires ahead of time to heat them up and soften them. The distortion of the tire from the centrifugal force must make the tires unreliable in a very short time. The tires would be a minor cost in racing those top fuel cars, the cost of the keeping an engine running would be much more.
it’s not that which does them in. those kinds of drag slicks are designed to do that; nitro cars are direct drive (no transmission) so the tire increasing diameter as the speed increases essentially lowers the final drive ratio as the car goes down the track. The tires are not belted nor do they have rigid sidewalls like most regular car tires; the sidewalls of drag slicks is strong but very limp/floppy. What eventually ruins a tire is the shearing forces in the sidewalls at launch.
Example:
those tires are hanging on for dear life trying to put about 10,000 horsepower to the pavement.
It also shows the special beadlocker wheels (all the small black fasteners around the rim) necessary to keep the wheel from simply spinning inside the rubber tire.
IIRC Goodyear actually makes the tires. I don’t have a factual answer for the silver patch. I assume it’s something like an index mark for whoever is mounting the tire on the wheel. Maybe to indicate a seam or heavy spot.
It’s a slippage mark. All the TF teams video each launch at the starting line, and the review of the video will show how much tire slip was encountered during the launch. Watch very carefully from 2:21 to 2:24 in the YouTube video linked earlier.
That tire slippage will influence the crew chief/tuner’s decisions on clutch and fuel tuning “at the hit”.