This is the criterion in single player to turn your standard Reinflate Tires into Pro mod for each car. Therefore, while it's not something you must do, it's something you will do for every car you want to max out in the single player. It is offline, easy, and not missable.
First of all you must unlock the reinflate tyres for a car; score bronze (or better) in any 5 of that car's events. For each car there are 5 in the base game, 1 free for everyone in the patches (for Ram Chassis), and 2 in DLC.
You'll need to have them equipped to add to your counter for the pro mods. Since each car has a different selection of events, but the pro requirements are the same for all (but need to be unlocked individually on each), here's the trick that will work for all cars-
Choose Most Wanted Race number 7 (you'll need only 315,000 SP) and don't worry about the race, you can hunt spike strips here and you really will find plenty. There's one spike strip roadblock near the start (drive on the right side of the road), two after the tunnel, and one on the highway. These ones are set and appear every time you do the event, but it's not just these- the police Corvettes (low black cars that tend to overtake you) love to drive in front of you and drop spike strips. Drive straight behind them to give them the chance and you should be able to get plenty in this one race. Slow down even and they'll match your speed and drop spikes when ready.
That's the easy way, you can do it quickly and with every car. The other way is by starting a pursuit, say by attacking a police car, and ramping it up to about level 5, where the police will have Spike road blocks and send high speed Corvettes after you to do the same as above. It's dangerous though- if the pursuit escalates to level 6 you'll get the beastly SWAT van coming after you, and they make extremely tough SWAT roadblocks instead of the spike strips you need. You basically need to abandon the spike strips if that happens (I think the SWAT van will still chase you even if you cool down to 5) and good luck escaping (actually you get lots of speed points escaping a level 6, not that you'll need them).
Things you might need to know: You can run over another spike strip even before your tires have reinflated and it will still count.
You should finish the event rather than restart or quit, even if you've lost.
Popping your own tires with donuts or burnouts [spinning wheels on the spot] won't work for this (but will work for the Online multiplayer Reinflate Pro, FYI).
Any questions please feel free to ask in the comments :)