Anyone running 20's on a 68 Camaro?

[Lawrence]

I've just bought a '68 Camaro (Its still in the US, waiting to ship to the UK where I am) with 16x8 w/4.5 BS wheels all round, 245/50 on the fronts and 255/50s on the back. I'd like to put 20x8 rims on with 245/35 or 245/30 tyres on which according to an online tyre height calculator should be within half an inch height wise. Am I missing anything obvious or should these be near identical as far as clearance, rolling radius etc?

[baz67]

Welcome to the site Lawrence and thanks for bringing some muscle cars over to the other side. You are correct with your measurments. Most of us on this site are more concerned with the overall performance package. In the grand picture you not get very good performace out of the 20s. Most of us do not care for the looks of 20s on first gen. The body is too small.
Brian

[F70t/a]

I know I seen a few guys run 20's in the rear. I think 20's will be fine if you can get a decent side wall.

[Lawrence]

Thanks for the replies Brian and Dave, what wheel sizes would you all recommend for performance reasons? I was hoping to improve the handling with the thinner sidewall, as well as make it look good. It's going to be my daily driver, so I'd like it to handle as best it can without shaking my teeth out!

[CarlC]

Here's what my '68 looks like with a 20/18 combo:



For overall performance and street drivability the 17" setup worked better for me. From a performance standpoint the 20/18 package worked fine right up to the point of losing traction. Once they started to lose traction it was all over, no forgiveness. Plus, it was scary driving the streets with them. Potholes, even small ones, had to be avoided to save the rim.

The current 17" setup on the car is by far the best. The only change that I would make for a car that was driven more would be to use the NT555 and not the RII. The 555 would be last a lot longer.

[baz67]

Holy, big picture Batman. I agree with Carl on the 17's giving you better perfomance. If you want a larger rim than a 18 does not give up that much performance over a 17. You do want some sidewall for ride and to protect the rim.
Brian

[Steve Chryssos]

Yup. These guys are right. Part of the problem is that you are suggesting fairly narrow tires. As sidewall height (aspect ratio) is indicated as a percentage of tire width, the tires you describe will have very short sidewalls.

245mm * .30 = 73.5mm (2.9" for us yanks: 73.5mm / 25.4mm/in = 2.89in).

Those are advertised numbers. The actual sidewall height may be even less. And 3" may sound like enough, but it really isn't. Better to select tires with a higher aspect ratio, more width or both.

I have 275mm/255mm 35/18 Nitto's on my car and I will readily admit (a lot of guys won't) that my car rides like a cement truck. A 245/35-20 or 245/30-20 will not ony ride poorly, you will virtually eliminate your tires as part of your car's handling equation.

If you must have "big" wheels--stick with 18's. Try to locate a 40 series tire for the rear and 35's in the front. As has already been stated, 17's with 40's all the way around will provide excellent handling and ride with an updated look. Here are my 18/35's

[F70t/a]

what if you had a 345/30/19 or a 345/25/20 and not a stiff suspension, but firm? would the handling still be as bad? I understand since the sidewall is shorter the ride will be a little rougher then say 17's or 18's. I think they need to make tires with taller sidewalls. i wish they made a 345/55/17

[Steve Chryssos]

Let's start with the math to figure out tire diameter (in inches):
345/30-19: (((345mm*.30)*2) / 25.4mm/in) +19in=27.15" dia.
The 1st part of the equation accounts for the sidewall height: 103.5mm
then multiply by 2 to add the top & bottom sections sidewall: 207mm
then convert to inches: 207mm divided by 25.4mm/in: 8.15"
then add in wheel diameter to get total diameter 8.15" + 19" = 27.15"

So this tire has about 4" of sidewall height and is 27.5" tall. Mathematically, this tire should ride well and will really fill the wheelwell. In fact you may have trouble fitting the tire on a very low car unless custom backspacing is used.
Your 2nd example has 3.4" of sidewall and measures 26.8" tall. Still a nice diameter but the aspect ratio is pushing it. The 3rd example belongs on a monster truck: It's a 32" diameter tire.

If you mess around with the formula, you can better zero in on a tire. If you want a little more sidewall, you can check into some sport truct tires, but the tread patterns may look too off-road-ish. Soft suspension and short sidewalls is typically worse than harsh suspension and good sidewall flex.

[F70t/a]

Thanks steve. that's some good info to know!!!

[CarlC]

That's one heck of a cement truck. I'd rather haul A in yours than haul 9 yards in the real thing.