Quote:
Originally Posted by Maynard
This is incorrect. Size of contact patch is a function of weight and psi (so lower psi gives bigger patch, among other benefits). Wider tires mostly give more rubber overall, so on a racetrack there is more resistance to heat and wear. Wider rims mean better-supported sidewalls (not always a good thing in the drags), and more weight. Tire width isn't that big a deal - I've seen a car on much narrower dedicated drag tires regularly eat the lunch of more powerful cars on wider street tires. Rotating weight, especially on driven wheels, is a big deal. And, if permitted, tire prep sprays can also be a help (to e/t but your wallet).
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Actually I am correct. My original comment suggested wider wheels & tires to accommodate a better launch, and my comparison for my sake on the m240i was going from DWS06 (all season tires) to MPS4S (summer tires) and I had mentioned using a softer compound tire as well (all season isn't as soft as summer). I had also mentioned that I went from 19" all season tires to 18" summer tires. I didn't mention how the thicker sidewall does help with launch because it allows for more flex in the sidewall, thus increasing grip for launch. I agree, tire pressure and softer tire compound do play a roll in launch capabilities, as well as the vehicle itself and the driver. However, I am correct in saying that increased tire width on a properly sized wheel will indeed increase the contact patch of the tire. What classifies a "properly sized wheel" is the manufacturer.
Lets take a look at the good ol' Tirerack website on this matter:
https://www.tirerack.com/tires/tiret...jsp?techid=199
"Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used."
When looking at tires, lets say the 265/35ZR18 MPS4S that I was running in the back, Michelin states a Measured Rim Width of 9.5" and a section width of 10.7" (referring to the link above, the section width is ONLY met when mounted on the standard rim width for that tire size (in this case, 9.5"). HOWEVER, the tire can be mounted on wheel widths ranging from 9" to 10.5"
Back to another article on Tirerack regarding Rim Width Range:
https://www.tirerack.com/tires/tiret...jsp?techid=198
"The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim."
That link also has a nice little chart to give you an idea (relatively) how wheel width affects section width. But, in essence it is like this: if you have to pull in the sides more, then you have to get the extra length from the section width. This is done by pulling part of the contact patch in to the center of the tire so it can be mounted on the wheel. This causes a "Bulge" look on the tires. Putting a tire on a wider wheel than the measured rim width will cause the sidewalls to start impedding on the section width, which means it is now part of the contact patch.
YES: Lowering the air pressure of a tire that is the same width mounted on the same width wheel will increase the contact patch. Softer compound tires will increase launch capabilities. Larger sidewalls allow for more flex to increase launch capabilities [why dragsters use such large sidewalls (yes at a lower PSI as well)]. Camber and Toe configuration of the suspension will affect contact patch. Weight of a vehicle plays into the width of contact patch.
There are a ton of factors that can play into the launch capabilities of a vehicle. HOWEVER, if all other variables are kept the exact same, increasing tire width by mounting it on the appropriately sized wheel WILL increase grip because it will have an increased section width. If going to purchase new tires, then ensuring it is a softer compound, as well as wider and mounted on the correct width wheel would be a good starting point for lowering your 60ft times (again, keeping all other variables the same meaning driver and launch technique) and your 1/8 and 1/4 times (other variables come into play once in motion).