Tire width Relation

[C4Bird]

I am planning on running a 315/35/17 on the back of my bird, but have yet to decide on a width and series for the front (17's front). How do I figure out what width to run for good track performance and great everyday driving? I don't need to run #1 at the track, but I would like to be able to keep up and still drive it to work the next week. The car will have a subframe with C4 pieces, coilovers front and rear, and the rear will run a 4 link with panard. With a little work I should be able to fit up to 285's up front and still be able to make it turn, but is this a complementing size to the rear? What combo's do you all run, how do you like it? I have the greatest respect for the people on this forum, so any help is greatly appreciated!
-Nate

[baz67]

What are you giving up for the 285 to fit? Generally the wider the better. However you need to address things like turning radius(looks like you are addressing that), fender clearance, scrub radius and power steering upgrades.

The two key ones that I have mentioned are scrub radius and the power steering. If you increase tire width without increasing bacspacing you will increase scrub radius. The more scrub radius you have the twitchier(if that is a word) the car will feel because increasing scrub radius adds more twisting force to the geometry. I am not sure how much it would increase in your application, but it should be one thing to minimize. Also, by increasing scrub radius you increase the load on the power steering. The tire width change, alone, increases the load on the power steering.

Brian

[C4Bird]

As far as fit, should have more than enough room to stuff any size tire in there. I will be building custom inner fenders out of aluminum and since I will be building the subframe myself, I'll be able to set spacing just right on the suspension to clear the outer fenders with no problems (to a limit of course, have to make room for the engine). I started designing the suspension to fit under the car with a ZR-1 front wheel and stock vette suspension pivot points, but since finding PT.com, have seen the light! I still plan on using the stock ZR-1 backspacing, but the mounting points for the rack and control arms will be different I am somewhat new to the pro-touring scene (been building street rods and stock resto's for the past 10 years) and don't have a lot of knowledge on optimal suspension mounting points right now, but I am learning from the posts here at PT and a couple of books I have picked up. The current subframe build is on hold for a couple of months until I can learn and feel comfortable with how everything works. The rack I was planning on using is from a J55 92 vette with shortened spindle arms and tie rods. With slightly improved suspension mounting, C4 vette UCA/LCA spindle and brakes, and J55 rack stand up to the wider tire? If it were possible to get a 315 up front to clear, would this be too big? I guess my question is, is too wide when front becomes wider than rear, or is there a better balance with a smaller front width?
-Nate

[C4Bird]

bump..

[Salt Racer]

Find a late-model high perf car with front/rear weight bias and hp similar to your car, and see what kind of tire width stagger it came from the factory. Try to mimic the stagger in percentage. That should give you a good baseline.

315s may be a bit unpractical up front for daily driving even with small scrub radius, depending on your taste.