Question: Tire size suggestions

[Positronic]

I have 4 silver like new a-mold wheels, 9.5 width, for my 96 CE that I'm going to use to replace the ones I have cause they are in better shape and need size help on the tires. My current setup is 8.5 in front 9.5 in rear. I'm looking at 285's on all fours since that's the stock rear size on my car currently, but I know the z51 package had 275's all the way around. Should I do 275 in front 285 in the rear, keep them all the same, or is it personal preference and nothing will affect handling?

 

[Tuna]

With the same size wheels all around, I'd put the same tires all around. The antilock braking system likes that.

You could put 275 or 285 tires on all 4 corners - kinda depends on which 4 you can find and how much.

 

[jmhorn52]

The previous owner of my car put 275/40-17 all round on it. car handles and drives great.

 

[Toms007]

The high performance suspension, Z07 & Z51 cars came with 275's all around. That's the way my 94 came equipped. You could go 285's, but I'd do the same at all four corners.

 

[Tuna]

Up to 1992, the C4 with the 17" wheels came with 275's all around. Some owners complained that the C4 was twitchy or hunting all the time and wanted a more stable ride. GM decided that the base C4 in 1993 and later would get the 255/285 arrangement. This made the base C4 more stable. The 255 and 285 are about the same diameter, so they didn't need to reprogram the anti-lock braking system. The late ZO7 or Z51 C4s got the 275s all around.

With my old 92 C4, I used 3 different tire sizes: 275s all around, 285s all around and finally 275 fronts and 315s on the rear. The idea was to get the tire size I wanted and keep the diameters close.

 

[Positronic]

How did the car handle with 285s all the way Tuna? I think I may go with that.

 

[Hib Halverson]

The base C4 suspension was retuned for 1993. The goal was to improve ride and steering feel.

Front wheel width was an inch less. Wider tires on the rear. More narrow tires on the front. Larger rear stabilizer bar.

The goal was to get the steering feel and car balance of the base coupe to be more like a ZR-1.

Replace the 255/45s in the front with 285/40s and you will disturb that steering and balance. The tire change in the front may make the car look better, but the car may handle worse at the limit, not better. First problem is the 285s on the narrow front rims. Second problem is the much wider tires in front with the bigger rear stab. bar.

I'd either leave the tire sizes alone or upgrade to the 275/40s all around, the wider front wheels and the 22mm rear stablizer bar.

 

[Positronic]

The base C4 suspension was retuned for 1993. The goal was to improve ride and steering feel.

Front wheel width was an inch less. Wider tires on the rear. More narrow tires on the front. Larger rear stabilizer bar.

The goal was to get the steering feel and car balance of the base coupe to be more like a ZR-1.

Replace the 255/45s in the front with 285/40s and you will disturb that steering and balance. The tire change in the front may make the car look better, but the car may handle worse at the limit, not better. First problem is the 285s on the narrow front rims. Second problem is the much wider tires in front with the bigger rear stab. bar.

I'd either leave the tire sizes alone or upgrade to the 275/40s all around, the wider front wheels and the 22mm rear stablizer bar.

The wheels I am putting on will be 9.5 width, that's including the front, so I will not be mounting a 285 on a 8.5 stock width.

 

[93Rubie]

You'll be fine with 17X9.5's with 275or 285's at all fours. No need for the smaller rear bar. My 93 was fine with this setup and my stock rear 24mm bar. It will still understeer, just a bit less than the stock 255/285 combo. Factory errors on the side of understeer and lots of it. Understeer is safe, your car will still be quite safe at the limit.

Then I did a more aggressive alignment, and each step took a bit more under steer out of the car. Stock C4's under steer like pigs.

I finally quit messing around and did the full Z07 spring and sway bar swap. BIG, no, HUGE difference in handling. Still understeers but its a gentle push NOT a plow like the stock FE1 springs/bars. Car is VERY stable at the limit and controllable. I do a LOT of auto-x so I think I can safely say this about my 93 Corvette.

Truth be told, unless you get crazy with the rear roll stiffness (which you will NEVER do it with stock FE1 rear spring and 24mm bar) the rear end won't jack. If it jacks you get oversteer and funny handling. Other than that, a C4 will always under steer, the suspension is setup (design/geometry) in such a way that it does this.

 

[Positronic]

Thanks for the info. I'm mainly going to be cruising the streets and an occasional cruise in this summer so I'm not looking for a finely tuned setup, just something that's not going to give me any minor handling issues. These wheels look a heck of a lot better than my old ones so I'm looking forward to getting everything put on.

 

[Tuna]

How did the car handle with 285s all the way Tuna? I think I may go with that.

I didn't notice much difference between the 285s and the 275s.

 

[Schrade]

Where in NC are you there Posi?

I've got 2 G/Y 275's ZR40 with over 1/2 tread that you can have for the cost of a Happy Meal...

ed.:
And 2 F1's, 315 x 35 x 17, about 70% tread, for a little more than a few HM's...