I have a C6 and am in the market for new tires. I am getting 305 width in the back and looking to possibly do the 275 in front like the Z06. My concern is that if I go wider in the front will this cause dangerous oversteer like the Z06 has with the 275 in the front?

"The Z06 is 2.1 seconds faster per lap than the Z51 but is hairy at the limit. We’ve said it before, but the combination of light-switch oversteer, instant breakaway from the Goodyear tires, and a slight numbness in the steering makes for a ride that’s like one of those giant roller coasters: alternately so scary and exhilarating that you’re not sure whether you enjoyed the experience. "

"The loser among these three is the Z06. the Z51 and the ZR1 highlight its major fault, namely that it’s really difficult to drive hard on a track" - Car and driver Z51 VS Z06 VS ZR1

 

First, the Z06 doesn't have dangerous over steer. Not sure where you got that idea but it doesn't have it. It understeers just like every Vette that is delivered from the factory. If you get on the throttle too hard under the right situations the backend will come around just like it will on any stock Vette, but that doesn't have anything to do with the front tires and a lot to do with the lack of driver experience.

What you will get under extreme driving conditions is the front end sticking in a hard turn where with a smaller tire it might not have stuck. If you don't upgrade the rear tire sufficiently to balance the increased traction in the front you will not have enough traction in the rear to complete the turn as fast as the front tire would allow. Putt Putting on the street (95+% of Vette drivers are in this category) you wouldn't notice this at all. Remember there is more to it than tire size. Just because a tire is bigger doesn't mean it has more traction than a smaller tire. The thing that may bite you in the butt is activation of Traction Control. Increasing the front tire diameter (which increases with width) will make traction control more sensitive and it could activate just driving down the road. The best thing you can do is keep the front to rear tire diameter ratio the same so you don't get into TC or Engine Drag Control issues. To be safe you always want the tire with the most traction and best handling capabilities mounted on the rear of the vehicle. This makes it much easier to steer in extreme situations.

As for C&D if they actually drove the car correctly they wouldn't have had those issues. I haven't had them and since C6Zs are very popular at track days because they outrun the other makes I don't know anybody who has had those issues. I ran run flat tires for the first 10 track days I had my car and after I learned how to use the throttle in both on and off throttle situations had no issues. The tires stuck and they stuck better than the NT05s I replaced them with. The Z06 issue isn't with tires it is with knowing how to drive a high torque big inch motor.

Bill

 

I have Z06 rubber on my Z51 car. No issues at all in 3 years. Handles better with the larger contact patch with no real oversteer at all, unless I induce it with the throttle.
The width of the tires will have basically nothing to do with oversteer. The ZR1 has 10mm wider tires than the Z06.
The best bet, IMO, is to get away from the GY's. I went with Bridgestone Pole Positions and like em alot beter.

 

I run 265s to match my 305s and find it a good combination.

I ran 245/305s at my last track event and will be running another ~50 laps in a couple weeks to see how it improves handling.

 

265 up front and 305 in the rear or do 255 front and 295 rear or 275 front 325 rear

the 275/305 combo will get you problems with the traction control at higher speeds due to the front/rear diameter ratio being thrown off so much.


The 275/305 wouldnt be expected to oversteer any more than stock unless you pushed the tire set to the limit of its grip. Even then, the car is set to understeer so much (with stock suspension) that it wouldnt be much if any issue.

Again I dont recommend 275s and 305s together unless you just got a deal on tires and are using them to get around town.

 

Listen to Bill.
Me too, no issues at all.

 

Some good information for balancing your vehicle.....

http://www.timskelton.com/lightning/...orrections.htm

 

I forgot to mention I have the Z51 suspension and I am planning to run lower sidewall profile to make up for the width. The rear sidewall will be 30 and the front 35 same as the Z06 just the rear tire will be 305 instead of 325. Would that still interfere with the AH/TC? How about 30 sidewall in the front?

 

The problem is in diameter. The diameters of the stock tires are 25.7 and 26.9.

The diameters of a 275/35 r18 and a 305/30 r19 are 25.6 and 26.3. The front and rear will be spinning at disproportionate rates to each other compared to the originals. There is supposedly a 3% tolerance in front to rear ratio, that the system will work within, but from what Ive seen I would keep it closer than that.

There arent any 275/30 r18 tires that I know of



a 265/35 r18 will be 25.2" to 25.4" and a 305/30 r19 should run 26.3" to 26.5" (this will depend on the brand and model of tire).

a 255/35 r18 should be 25" and a 295/30 r19 should be 26"

a 255/40 r18 would be 26" and a 295/35 r19 should be 27" - very close to original but only 2 types of tires available: Hoosier R6 and BF Goodrich GForce TA

a 275/35 r18 should be 25.6" and a 325/30 r19 should be 26.7" - this is the sizing the Z06 uses and some people here have shoehorned under their base model cars

 

Bill has a lot of time under his belt with his Z06 on track and I think he is seeing the same things we always have.

Corvette's have a very bad issue with front bite no matter what. They need a bigger front tire, and more aero grip at the front before they need anything at the rear...at least speaking with an AutoX/RR'er in mind.

What I have seen with the Z06 is more of a shock/spring combo at the rear when it wants to come around...that isn't a tire issue at that point. It isn't a dangerous, but can catch a driver off guard if he hasn't been there before with the car.

So the long and the short...a 275 isn't going to be an issue with more front bite on the car.

 

A lot more succinct than I stated it.

Bill

 

Thanks for all the technical info!
Looks like 265/35 r18 and a 305/30 r19 Would make the best combo considering the AH and TC. I usually turn TC off and keep AH on in the dry and keep both on in the wet. The Corvette AH system rocks!! Best thing since ABS Only thing I would change is the time it takes to shut them off if I want to do a quick powerslide. It takes 8 seconds to turn off. By the time its off I have already driven past the spot I wanted to powerslide. =)

 

whew Im glad to see this. I just ordered a set of rims and tires and the Vendor said 265s were on national back order and recomended 275s instead I was a bit nervous of an issue. But I primarily will be driving on the street and maybe a little drag strip

 

Biggest thing to watch is overall height, and rolling diameter if you are going to keep Traction Control and Active Handling active on the cars. Tire heights will screw that up more than anything else so when buying new tires do keep that in mind if you are changing wheel and/or tire size.

If you track the car, and turn all of it off it doesn't care either way.

 

I plan on running 275/35/18's up front and 305/35/18's (that's eighteens) in the rear. The most I drive the car on the street is on the way to the autocrosses, about 30 miles one way, so 60 miles total. Plus the 6-8 runs of around 60 seconds each (times 2 driver's), so I am not too worried. And I turn off all the nannies when I race.

 

Have you had a chance to track this setup at all? I'm in AZ and track my stock C6z51. I have 245/40-18 and 275/35-19 Perelli Euphori@ tires that I've put through 6 NASA track days. Time to move on because they are starting to crumble. I'm thinking of going 18x10.5 all the way around and then doing 265/35 and 295/35 NTO5's. Money isn't spent yet...just planning, reading, and learning at this point.

 

Thoughts on 265/35/19 up front and 305/35/19 rear? I believe the difference should be within that 3% tolerance

 

That would work, but you'll have to buy new rims. I'm running 255/40r18's on stock rims with 305/35r19's on the rear. You probably could run 265/40r18 fronts with the 305's in the rear. I haven't run that combo. Maybe someone will chime in that has. I have a lot of miles on the 255-305 combo though.

 

Thank you! Yeah I jumped the gun a bit since I already have new wheels and before I bought tires I thought I’d come on here. Glad I did!

 

265 front and 305 rear work great. I got 200TW stickies and while i always wish i had more sidewall, the increased grip makes up for it. Makes parking lots a pain in the *** though.