Help with backspace and sidewall height for 71 Chevelle.

[Chevelle598bb]

I know guys this has been beat to death but I need some advice before ordering my front wheels. I will soon be ordering a set of 19x8 intro pentia to match the 20x10 intro pentia I already have for the rear. I was wondering what a ballpark backspace would I be looking for. I am unable to measure now due to the fact that I still have not received my Ats spindles that I ordered in mid October of last year. I'm not sure when they will be here so I'm trying to get some advice ahead of time. I am also running a c6 z06 brake set up. For tires I am going to run a 255/40/19 in the front and 315/35/20 nitto invos. This is the only tire that is available in both sizes and doesn't cost an arm and a leg. This is where the sidewall comes into play. The 255/40/19 is 27 inches tall with a sidewall height right at 4 inches. The 315/35/20 is 28.6 inches tall with a sidewall height of just over 4 inches. I think I should be shooting for equal sidewall heights correct?



P.S. I have a set of 295/40/20 bfg on the rear right now and they clear with all kinds of room. Every nitto tire I have run seems to be smaller than a competitors tire of the same size. I think I can run the 315/35/20 without issue. If not they make the invo in a 295/35/20.

[67rally]

I know guys this has been beat to death but I need some advice before ordering my front wheels. I will soon be ordering a set of 19x8 intro pentia to match the 20x10 intro pentia I already have for the rear. I was wondering what a ballpark backspace would I be looking for. I am unable to measure now due to the fact that I still have not received my Ats spindles that I ordered in mid October of last year. I'm not sure when they will be here so I'm trying to get some advice ahead of time. I am also running a c6 z06 brake set up. For tires I am going to run a 255/40/19 in the front and 315/35/20 nitto invos. This is the only tire that is available in both sizes and doesn't cost an arm and a leg. This is where the sidewall comes into play. The 255/40/19 is 27 inches tall with a sidewall height right at 4 inches. The 315/35/20 is 28.6 inches tall with a sidewall height of just over 4 inches. I think I should be shooting for equal sidewall heights correct?

P.S. I have a set of 295/40/20 bfg on the rear right now and they clear with all kinds of room. Every nitto tire I have run seems to be smaller than a competitors tire of the same size. I think I can run the 315/35/20 without issue. If not they make the invo in a 295/35/20.

A little extra sidewall height in the rear will look good. I run 245/40/18's up front and 275/40/18's on the rear of my Camaro and it looks good. Just avoid a rear with less sidewall height than the front.

[Chevelle598bb]

The current rear tire I have is a 295/40/20 which is 29.5 inches tall with a 4.6 inch sidewall. I'm looking to drop down to a 315/35/20 which is 28.6 inches tall with a 4.3 inch sidewall. This will also allow me to lower the rear some more The 255/40/19 I will run in the front has a 4 inch sidewall so it is still smaller than the 315/35. Just want to make sure having equal sidewall heights won't look off or weird. Engines are what I do. I just don't have an eye for design.

[67rally]

The current rear tire I have is a 295/40/20 which is 29.5 inches tall with a 4.6 inch sidewall. I'm looking to drop down to a 315/35/20 which is 28.6 inches tall with a 4.3 inch sidewall. This will also allow me to lower the rear some more The 255/40/19 I will run in the front has a 4 inch sidewall so it is still smaller than the 315/35. Just want to make sure having equal sidewall heights won't look off or weird. Engines are what I do. I just don't have an eye for design.

Equal sidewall heights are fine, that's what you will see on any car that runs 4 matching tires all the way around (i.e. most modern cars or AWD cars). On a muscle car with staggered wheels, the rear tends to have just a little more sidewall than the front. If it's the other way around it will look weird. You should be fine.

I don't know if you are using an online calculator to figure out sidewall heights or not, but the easiest way to compare to tires is to multiply the width of the tire by the aspect ratio. In a 255/40/19 the first number is the width in millimeters, the second number is the aspect ratio, which is what percent height of the sidewall vs the width, the last number is the diameter. So your 255/40/19 is 255mm wide and the side wall is (255x.4)= 102mm tall. The 315/35/20 is 315mm wide and the sidewall is (315x.35)= 110mm tall.

If you drop down to a 295/35/20 on the rear your sidewall becomes 103mm. If you went any smaller than a 295, you'd need to go up to a 40 series tire to keep the sidewall larger in the rear than the front. I don't deal in mm (just divide by 25.4 if you want inches), but it makes for a very quick comparison between different tire sizes.

[67rally]

There's a pic on page 1 and page 3 of my build thread (link in signature) of my car with almost the same size sidewall as you are considering. My fronts have 98mm vs your 102mm (3.85" vs 4.02") and the rears on both our cars are 110mm (4.33")

[Chevelle598bb]

Very nice camaro 67rally. The wheels and tires look great.

I think the 315/35/20 and the 255/40/19 is where I need to be.

[Chevelle598bb]

Well after speaking with some of the respected a-body guys around here it looks like I may have another option to think about. I originally wanted to do a 275/35/19 in the front but intro does not offer a 19x9 wheel. They only offer 19x8 and 19x10. The a-body guys are all advising to use a 275/35 on the 19x10 which is the size I wanted anyways. I think it just may look weird with the front and rear wheels both the same width but different width tires. I also did some measuring and the 315 will be a little tight for comfort so I am going to do a 295/35/20 in the rear. Wheels and tires make my head hurt.