village idiot

I've been reading the debates and kind of getting nowhere.

If I bumped up on tire width (255/35F, 305/30R), am I going to see any performance gains? Slower turn in, I know but it would be really helpful in braking and pure lateral grip. Those keep me close to the factory diameters so stability control and etc don't go crazy.

If not, I'm perfectly content sticking with stock sized tires.


Stock C6 Z51

thanks!

Bill Dearborn

I would go with more in the front. I used to run my C5Z with 315/35/17 on all 4 corners. Car ran great that way. Nowadays a lot of people are running 305s on 18x10.5 C5Z rear wheels on all 4 corners. Your car is very similar to a C5 so if you can have the correct rim for the tires you should get as wide as you can without damaging the body work. The stock front to rear ratio is (rear dia/front dia =) 1.04. From a system standpoint keeping the front to rear ratio is more important than front to rear diameters but if you can stay within the range of 1. to 1.06 you should be fine.

Activation of Active Handling isn't determined by these ratios. It is determined by steering angle, yaw rate and lateral Gs. Once activated it bases how much to activate a single brake based on the stock tire compound and size. It won't go crazy.

Bill

0Anthony @ LGMotorsports

I know a lot of guys that do a 275 front and 305 rear on C6's and that seems to work out very well too.

Now almost every single C5/6/Z0 has a major push, so more front tire is almost always a good thing to have. I don't know if it is going to slow down turn in that much though....

ratt_finkel

Need a lot more info here. What type of racing are you doing? How competitive are you trying to be? What surface? What speeds? What are the alignment settings? What size wheels? Budget?

Without knowing any of that. As a purely general statement. The vast majority of tires will perform better with a properly sized wheel supporting them. That means that the sidewall is not pinched. And yes, you can go too wide as well.

While it's perfectly capable of squeezing big tires on small rims. AND still gaining grip, it would not be an ideal solution.

PS. As far as I'm concerned, no corvette should have anything less than a 295 on the front end. (C5 and up)

RX-Ben

You'll recoil in horror knowing that some of us competed on 275 (and sometimes 245) square setups for years. With a bit of success.

village idiot

sorry, I forgot a key piece of information: On stock wheels. Doh!

Street car I mess around with at the track. And I'd love to run 295's all around, I'm not sure I want that on the street. Can I just run the factory Z51 rear wheels in the front?

0Anthony @ LGMotorsports

If you have stock wheels on the car, then I wouldn't try much wider than a 255 on the front. You start trying to squeeze a wide tire on a narrow wheel and you can get a lot of movement in the tire when turning and dull the steering on the car.

ratt_finkel

You poor poor bastards

I knew someone would come back with this comment. I'm sure you could throw 205's on the front and surprise some ppl too. But that wasn't my point


Sounds like you would be running street tires then. And that means you will be limited to fairly small tires. As the Z51 widths are small.

255-275 front.

295-315 rear.

Keep in mind, the wider you go. The more pinched the sidewalls will be. You may have a bit more ultimate grip. But you will lose transitional response and feel.

village idiot

thanks for the help.

Any thoughts on getting another set of the Z51 wheels and running the 10 inch "rears" all around?

ratt_finkel

You could certainly do that. If you're going to get a second set of wheels. Might as well throw some r-comps or slicks on it. If you are still learning, then you can get a dedicated set of street tires for the track. Hankook, Rivals, etc.

Stepping up to a 10.5" wheel will allow you to run a 285 hankook and it will be happy. No doubt the fronts will stick out a bit from the fender. But who cares

For a track car, I would recommend a bit wider in the rear. Just so you will have a natural tendency towards understeer. Everyone has a preference. And you can certainly make a square set up push. But it will be more likely with larger (IE) more grip in the rear. Note that every drivers perception of understeer and oversteer is different. I don't mind a loose car. Can't stand a pushy car. But there is a happy medium. I can handle big slip angles without thinking twice about it. Other people might need a change of underwear.

B Stead

On the OEM wheels run 245/285 or 255/295 or 255/285.

The top street tires are RS3, Star Spec, AD08 R, Rival, Pilot Sport Cup 2, Ecsta XS, and RE-11A.

The Z51 spring rates are 526/645. Those who are running the same size front and rear tire are increasing the front spring rate and front roll stiffness. Otherwise, the wider front tire is not getting any additional load.

But also, the 79mm C6 rear wheel is not going to run correctly on the front of the C6 as the lateral center of the wheel would sink-in. (It's a rear wheel off a C5Z that can run correctly on the front of a C6. Then a rear wheel off a C5Z can't run on the back of a C6 unless it is okay to stick-out.)

An easy setup is a 265 or 275 on a 9.5" wide front wheel with a 305 on an 11" wide rear wheel. Then the front wheel offset should be 56mm to 52mm and the rear wheel offset should be 79mm to 73mm. And that doesn't stick-out or sink-in
.

village idiot

Great info, thanks.

I'll probably just get another set of the Pole S04 and some C5 fronts/C6 rear for the track

I know exactly where this is going though: I'm going to need bigger brakes because of the extra heat. Then coilovers and suspension = . Then I'll a new daily driver. Then I'll need a second mortgage and then a really wealthy wife...

B Stead

That's a C5 Z06 rear wheel for the C6 front
.

redtopz

A couple points to think about.

1. Tire width doesn't affect contact patch size only shape. Only tire pressure and weight on the tire affect the patch size.

2. Larger tires are larger heat sinks and can take more abuse on the track for a longer time before overheating and losing grip.

Looking at these 2 points, you can see how a narrower tire would be fine for time trials especially if you get points back to reduce weight and make the car faster. However, going with larger tires such as when racing with Hoosier A6's is the key to making them last 30-45 minutes in a race and not falling off. You have to keep them in a happy temperature range.

ratt_finkel

Not necessarily. Good pads, proper fluid and finally ducting will get you most of the way there. Stock corvette brakes don't suck. Also remember, the more grip you have, the less you have to use the brakes anyway

savage

tire width does not affect contact patch? i dont see a 245/?/? with say -2.5 neg. camber turning as well as a 295/?/? with same camber. i with you on the heat sink, also i never seen a skinny drag tire get the grip( contact patch) a wide tire does. i wish the factory wheels 8.5 and 10 inch wide with tires that fit on them got the times autocrossing that the 10 inch front and 11 inch rears get with much wider tires.

village idiot

I forgot about the heat sink part. That alone is reason for me to go wider. I just kill the fronts at my track (Eagle's Canyon) on the brakes.

My fronts get really hot. Front goes from 27 PSI to 33psi while rears go from 28 to 30... maybe lol

C5 Hardtop

Re: Wider tires vs. Contact patch

As you may now know, the contact patch is where the rubber is touching the road as the tire rolls along.

The contact patch and the slip angle are talked briefly about in Ross Bentleys Speed Secrets book. In a nutshell he diagrams and explains what these things are. His point is we want the tires to slip a little during a corner. When we are not at the ideal "slip angle", we are leaving speed on the table. No slip at all in a corner means we are slow I think a perfect drag launch applies the slip angle principal.

B Stead

Tire slip angle is not slip or slide. Tire slip angle is drift.

The tire has drift as the tire contact patch deflects out of line.

The tire generates cornering force up to the point where it can no longer deflect the contact patch and that's where the slide begins.

The steering wheel is not a directional pointing device but a lever for generating tire force. The direction of the car is the net effect of the drift of the front and rear tires. (When hard in a curve, the front wheels are turned extreme by the steering wheel but only point moderately out of line from the rear wheels. That easily proves a drift of the rear tires.)


Tire contact patch is said to be larger with narrower tires but we know that wider tires have more traction. Why do wider tires have more traction ? It might be the weight distribution in the tire contact patch and then the lateral center of the contact patch is most important ? But look at the points above and it's the strength of the contact patch that is important and that in addition to size of the contract patch. The combination of the strength of the contact patch with the size of the contract patch favors a wide tire.

The tire contact patch has to have the strength to stand up to the forces that are deflecting it out of line.


Here's a tire manual that includes general tuning principals:

https://www.tirerack.com/images/tire...ce_R1_care.pdf

http://social.bfgoodrichtires.com/14...28FINAL%29.pdf
.

redtopz

That's not what I said. I said tire width does not affect contact patch size. It's simple physics. Area of contact patch x tire pressure = weight on the tire. Tire width does affect the shape of the contact patch and sidewall height and strength also plays a part in lateral grip among many other factors.