Going to a lapping day this week and noticed my spare tires I bought were the wrong make. Rears are Pilot Sport N2 and Fronts are Pirelli Pzero.. The tire sizes are good... Is this a bad idea?

 

yes, not a great idea for the street if you drive aggressively...you won't like it if you get anywhere near the limit...if your first lapping day then maybe not so much...you might not pass tech with mixed tires (depends on the event provider)...at least they are matched in the front and in the rear

 

I've done about 50 lapping days over 10 years.. They both have the same treadwear...

Is it a big enough deal I should go buy new tires? These are just for the lapping day, I have another set of wheels/tires (properly matched LOL) for daily driving.

The track is a high speed track..

 

You'll be fine. Just don't go crazy until you figure out the grip levels as with switching any part of your car. It is just tires and as long as they don't fall off, you will be fine.

 

I figure I can play with tire pressures to compensate if there is a big difference?

 

I would advise against it. On the street you may be fine but at the track you will be pushing the car and th adhesion differences between the tires will be very noticeable. I did it once on an M3 to save money by using up a pair of tires I had and literally ruined my weekend since it was very hard to push the car.

 

As long as the tires are in good condition, no problem. There is no alchemy or danger
that will make the front tires act differently or worse than they should, just because
the back ones are made somewhere else... There is so much else that can alter how
your front or rear will stick, such as tire pressure, alignment, shock settings, sway bar
settings, etc that *if* the tires behave significantly differently, the car will act, and
can be re-adjusted, just as if one or more of any of those other factors had changed.
So, in summary, it is possible, depending on how different the tires are from what
you are used to, that the car will behave that much differently at the end you have
the strange tires on, but it's not an explosion waiting to happen, and you can/should
drive conservatively enough at the start to detect any difference safely. It is entirely
possible that your car may even handle *better* than before! I have more than once
seen racers use different tire brands front and back to tune car dynamics.