[jman]

So I had a 150 Diablo Rosso II on the track yesterday.
I have to say I think I like the way the 140 feels better. I wasn't able to use all of the tire. Had another ride(way more experienced and faster than me) ride it and even he couldn't get all of the contact patch

Wouldn't that be safer then as you still have more tire to go before it loses traction? Just curious and I'm thinking about upgrading tires also and trying to decide between a 140/70/17 or 150/60/17 rear.

 

[jman]

You're likely not using all of the side of the tread due to the decreased radius of the cross-section of the tire. Follow me here. You're putting a wider tire on the same width rim which originally had a narrower tire. In essence, you're scrunching the wider tire outward, away from the rim, to cause a overall larger diameter tire. Which is why you have to go with a smaller "aspect ratio" (shorter side wall). Now, in scrunching the wider tire outward (to make it fit a narrower rim), think of what you're causing the tread of the tire to do. Is this making sense?

Let's say you take the same corner at 80 mph with 140 and 150 tires. For the 140 tire it'll be scrubbing on the edges to make the corner. While on the 150 tires, there's still over an inch on the outside of the tire. Does this make the 150 tire more safer as it's not maxed out? Just trying to figure out which would be best. Thanks.

 

[jman]

You're running 160/60/17 rear, what about fronts? For the S21 I see 120/60 or 120/70. Which one fits better?