Hot enough to measure and keep a data log.I'm going to restate what I've said previously. Tire Temps are important, measuring the temp isn't. Reading the tire tells all. If the tire tells you it got too hot, adjust accordingly. Actively reading tire Temps will give you information, but you can get that same info from reading the tire(and saves you $500 on the mychron kit).
Just curious though, how warm can tires get on dirt? On asphalt?