Contact Patch - What matters?
10-18-2016, 05:15 PM
#16
Rennlist Member
And now for something completely different. Tried a bunch of things, but now I run a 235 up front and 315 rear. No exotic suspension tuning or camber - turns really quickly, tracks arrow straight and I rarely get a push condition...and on that rare occasion, can usually tune it out with tire pressures. Having meat in the rear is great though (significantly!!).
It is because the small tire in front has LESS contact patch and the car will turn in quicker and dart to the apex. Like a bicycle tire. And with the smaller tire/wheel the center of contact patch is pretty close to center of spinning axis. If you get this right and camber thrust is centered on the tire you will have loads of turning, really crisply, and if camber thrust is centered you will have loads of mid corner grip
camber is most important for turning, you want as much as possible to make the car turn and dart quickly (flat tire doesnt turn) and so that camber thrust centers on the tire contact patch. This will keep the sidewalls intact and supported.
This is the approach i take to setup.
10-19-2016, 11:23 AM
#17
Registered User
stretched sidewall is stiffer providing more feedback and preventing rolling the tire on its side.
I run wheels that are and inch wider than stock (9 and 11) with stock tire width (225 and 275). Actually rear is 10mm narrower than stock due to availability issue.
Of course the civic guys take this and neg camber to a whole new level-but those don't make it to track.
I run wheels that are and inch wider than stock (9 and 11) with stock tire width (225 and 275). Actually rear is 10mm narrower than stock due to availability issue.
Of course the civic guys take this and neg camber to a whole new level-but those don't make it to track.
It works really well, and the 930 handles great. Seems to improve any tendency to oversteer...
10-19-2016, 01:40 PM
#18
Rennlist Member
that is a stretch....but im sure ok... a 305 fits a 10 perfectly, so i would think that the sidewalls would be angled out a bit. but its not a huge difference. a 275 which is the most common tire on a 10" rim and a 245 dont look that different at first glance, so thats probably fine! it actually can make the 245 a bit larger width-wise, so im sure it works well.
10-19-2016, 03:01 PM
#19
Rennlist Member
This
It is because the small tire in front has LESS contact patch and the car will turn in quicker and dart to the apex. Like a bicycle tire. And with the smaller tire/wheel the center of contact patch is pretty close to center of spinning axis. If you get this right and camber thrust is centered on the tire you will have loads of turning, really crisply, and if camber thrust is centered you will have loads of mid corner grip
camber is most important for turning, you want as much as possible to make the car turn and dart quickly (flat tire doesnt turn) and so that camber thrust centers on the tire contact patch. This will keep the sidewalls intact and supported.
This is the approach i take to setup.
It is because the small tire in front has LESS contact patch and the car will turn in quicker and dart to the apex. Like a bicycle tire. And with the smaller tire/wheel the center of contact patch is pretty close to center of spinning axis. If you get this right and camber thrust is centered on the tire you will have loads of turning, really crisply, and if camber thrust is centered you will have loads of mid corner grip
camber is most important for turning, you want as much as possible to make the car turn and dart quickly (flat tire doesnt turn) and so that camber thrust centers on the tire contact patch. This will keep the sidewalls intact and supported.
This is the approach i take to setup.
You need to also think about sidewall height and stiffness since both play a role in contact patch (hint: think about rear tall sidewalls in 911s, and drag cars for that matter) as well as spring rate.
If you want to learn more about tires rather than just the rather limited notions of width, you should start by reading 'The Racing and High Performance Tire' by Haney.
10-19-2016, 05:12 PM
#20
Rennlist Member
Tim and Matt nailed it IMO. This is why I ran skinny 235's all the way around in my old M3...and many here who have ridden in it at speed can attest to how readily it turned and how much mid corner grip it had 
10-19-2016, 05:24 PM
#21
Rennlist Member
Many would argue that the step up to 245s on the M3 (your model) made them a LOT faster.
10-19-2016, 06:00 PM
#23
Rennlist Member
10-19-2016, 07:11 PM
#24
Race Car
Thread Starter
Originally Posted by mark kibort
Many would argue that the step up to 245s on the M3 (your model) made them a LOT faster.
let sleeping tigers lie. Props to VR for not responding.