Originally posted by Stealth
What is the tread life on each, or does that not matter?
A little google / tire rack / searching will help you out to find the answers to that. it kind of matters, but there's only a corellation between treadwear and grip, not a proven cause & effect.
Originally posted by agent
i would go with the wider tire. first off is wheel protection. second, the wider tire should give off more smoke( if setup is for competition) because it has more surface area. third is with the lower profile is should have less sidewall flex, giving more solid feedback to the driver.
just my 02.
you are absolutely correct about the more smoke.. more rubber burning means lots more smoke giving off due to the extra surface area. you're also on the right track with that thinking.. think about something else that will happen because of the larger tire. The less sidewall flex may or may not be true. it kind of depends on the tire manufacturer. the 245 will have approximatly 98mm of sidewall whereas the 215 actually has 96.7mm of sidewall. so in actuality, even though the 245 has a lower profile, the sidewall is smaller on the 215/45/17. also more solid feedback is directly dealing with the actual stiffness of the tire, not necessarily the sidewall.
Originally posted by Taylor Durden
go with the stickier of the two. smaller tire will stretch and reduce your sidewall flex and the higher traction compound will provide stability higher speed runs. a wider less traction tire will only simulate a slightly higher traction coefficient will not providing the true grip needed. plus higher traction compunds usually wear a little more predictably than lower traction tires. (you dont see Toyo RA-1's chunking)
I used to go about things this way, but after playing with a couple of different setups i've actually come to a differnet conclusion. Remember that we're not going from an ultra high performance summer tire to a standard touring all season, but in fact an ultra high performance all season tire. the levels of grips are pretty close to one another. yes, the stretch will reduce sidewall flex to a certain degree and give you a little bit more stability but i'm finding more and more it's to allow more extreme fitments of wheel etc. it will increase the instantaneous point of breakaway (my generic term) for some tires however, notably the ones with a softer sidewall from the factory.
you have to remember that an RA-1 does'nt chunk because it is a completely different compound than a street tire. Almost all street tires, even with 160 treadwear like an AVS Sport will eventually chunk if you give them enough of a beating.
These are all good replies, keep them coming! I'm not going to post my answer until a few more people have chimed in.