This Tyre rule

Ok perhaps I should sit and read up on every rule that is thrown at the riders etc. But please someone explain it, I've missed the first 3 races - through no fault of my own and want of trying. But football took presidance at one house and the firstrace, well, after begging and pleading with the bro for a whole weekend only to have it cancelled because of rain ......... and the 3rd god knows where I was, I need help think I missed something.

Okay so Rossi goes into to change his tyres or rather his bike (please bare in mind at this point I was watching BBC incase there was an explanation on eurosport), jumps on, zooms off. Fine with that I understand he's switched to sliks cause its drying up - sort of. Falls off, buggers the bike up and takes it back in to swap bikes.
Firstly how many times can he swap bikes and is it worth it?
Secondly does he have to go out on the same set of tyres (sliks) because they were saying he had both on (sounded like it anyway).
He gets a drive through penalty coz he was speeding - fine.
Thirdly he then swaps back to the bike he fell off of (number 2 bike) which looks sorted.
And toodles along at the back.
If when he swaped back to his first bike and the tyres were wrong how come he didn't get a penalty for that?
Please someone explain.

Well done Jorge - good timing.
Valentino - hard lines, a good sportsman learns from his mistakes.
The rest who followed Valentino into the pit - bunch of sheep :lol

Ok where do I start??
Firstly thanks for the replies.
I recall BBC Saying Rossi had on his third pit pick up a wet front and dry arse or something like that - so i assumed he had to go out with another combination has he had already done the dry and wet. But my understanding at the start of the race was after he ditched the bike and picked up the third one he had to have the same tyres on - all wets.

Now I think I've understood you guys correct. As many bike changers as long as the tyres are different from the first bike (hense the switch). And if they have to come in again - cause its raining for instance the tyres they used on the first bike are not to be fresh ones but the ones they used on the first few laps. Have I got it right??? Do I get a blue peter badge.

As for Toseland and losing 10 secs on Edwards to me it shows Edwards has been out on both bikes during practice (or even remembered settings from previous races in similar conditions) and this is why he stormed past JT. Perhaps JT should have stuck to his own team, cause as for as I can see in these conditions it's not the bike or the biker that can win or lose a race its the mechanics. JT also said he's had problems with the bike fitting to the tyre or was it the other way round i forget i was still half asleep.

SPOILERS oh now I get what that means now!

I also think this year will be close most of the way throough it. And I don't just mean 1st and 2nd I mean 3rd, 4th and 5th. I would like Jorge to do really really well, toseland to do tons better than last year, Edwards to win a race and Hayden, Melandri to get another podium finish and ultamatley Rossi to win again.

As for been sheep - all those directly behind Rossi seemed to follow suit - thats sheep talk in my language lol. However they coped better with the early tyre change than Rossi did. I honestly thought he would have waited at least another lap. But hey I don't even own a bike so what the hell do i know :lol

Oh and the reason for trying to clarify this question is that when i next see the bro I just know he will have watched one race and this will be the one he sees Rossi last and he will rip shreds and question me :lol
Thanks though Guys