There are four compounds; Hard, Medium, Soft and Super-soft. Each race, Bridgestone will bring two compounds. Each team must use both compounds during the race, so at some point the each car will be on a less-than-perfect compound. This could make tactics more interesting, with two long stints and one short one. The tyres will be visibly marked so everyone will know which compound is being used at the time.
Tyres generally will be harder, and so slower. There’ll be less grip, so more driver skill required.
CBits Tech Support 
Hey Colin,You’ve been busy on the blog recently! I’m still intending to send you a contribution regarding our karting victory, but I haven’t found time…Thanks for all the 2007 F1 info, nicely summarised. Have you seen the times from Friday practice? Super Aguri is ahead of Honda Racing! Both Davidson and Sato are ahead of both Button and Barrichello! I can’t wait for qualifying; I shall be watching it live tonight, for sure.The tyre rule is interesting, although I personally don’t like it. I feel teams should be able to choose which tyre to use, at a moment’s notice. This is F1 after all, and they should be allowed to optimise their car, especially for something as basic as tyres.I don’t quite understand the ‘pit lane closure during safety car period’ rule. What if I was planning to pit at the end of the lap I was on, when the SC comes out? Will I find the pit lane entrance closed? I’ll have to see this rule actually implemented before I can grasp it…The wait is almost over!Hope you’re well Colin, and regards to Blanche too.Kaz
Hi Kaz. We’re very well thanks.Super Aguri ahead of Honda! That’s embarrassing. I’ve been working, so haven’t had time to look.I think the tyre rule could make it more interesting, as each driver will have to drive on a sub-optimal tyre for a time.I don’t understand the need for the pit lane closure rule either. Potentially, you could have cars running out of fuel.If it’s on ITV live, I’ll watch it, but the cable guide won’t go past 1am at the moment.Thanks for the comment.