Well I have had 215/45 and 225/45 tires in the car in the past and my current summer tires are 235/40. The only issue with comparing them is they have all been different tires. I can say my star specs in 235/40 held traction amazingly well. Now I don't see why a 235/40 would have more or less traction than a 235/45. They are the same width.