First, welcome, ced_ampo. I've been busy lately and I'm not behaving like a good host, so this is your first post (for me).
So, get this: allow me to differ. Graining happens when you overwork your tyres before heating them.
I repeat: it's lack of patience what gives you graining, not a bad setup. Tell me that is my fault as mechanic when is yours as a driver and I get angry.
If, as ced_ampo says, a driver claims that graining happens just because a tyre is wearing too much, he is implying that he has a failure of the setup. Actually, graining is normally the driver's fault. Do not blame others so quickly before you're enlightened or you might get into trouble with your mechanics... and believe me, you do NOT want to get into trouble with them. Fight the manager, that's what he's there for.
Here you have some pictures, to make it short (thanks, master DaveKillens for the source of the pictures: The Racing & High-Performance Tire, Sports Car, March 2004
). This is also archeology, modbaraban, I got them from a previous thread.
Abrassion (top row) vs. graining (lower row). Pictures to the right are magnified. Slight difference, eh? However, it's crucial.
Front tyre, normal wear ("Good run, kiddo! I think we got the basic setup" )
Front tyre, grained ("What are you doing, kiddo? You toasted your tyres, for the love of Pete!" )
Rear tyre, slight graining on the inside (bottom of the picture: get close to the monitor or you won't see it ). Slippage during acceleration? ("Hey, kid, is this your first time with this kind of power? Easy on the throttle, pleeze!" Also, it could be excessive camber... think twice before talking to your driver)
Finally, blistered tyre.
Vulcanization reversed because of heat, but, normally, it's not the driver's fault: I'd bet on an onverinflated tyre. It generates heat at the level of the ply and the heat "works" the tyre from below
Why graining happens:
During sliding, deflection waves in the rubber turn into peaks which are bent over, exposing the upstream side to abrasion. The peaks wear thinner into teeth and the tips are eventually torn off.
graining is sometimes hard to see, but is always easy to feel (it's exactly like love! Latinos here will get my point.) A good mechanic always "caresses" the surface of the tyres to know what's going on. Check the initial picture: it's easier to "feel" the tyre than to get a microscope. You can feel the little "nipples" easily.
Gosh, I'm going OOT again
Is that clear?