Racers with back halved cars.Tire size questions.

[bignastyGS]

What size slicks are you running? I have 15x14 wheels and the tires suggested by S&W are 31x18.50x15. I was looking at tires on line and it suggested 31x14.50s for 14 inch rims. What do you suggest? Car is a 70 Skylark with a S&W frame and will have a Ford 9 inch. Should I get the 14.50? or 18.50's?

[ric]

I am running 14x32 slicks, tubeless, on 15x12 rims. I am pretty sure the rule of thumb is the tires can be 2" wider than the rim. Big Vito to run over an 18" wide tire...GEEZ we'll call it a Fred Flintstone car. I really don't think you need that wide of a tire. Go with the 14.5 tire. Also too wide of a tire will slow you down as you have more rolling resistance and weight.

[99nhra]

The 18.50 they're talking about is a dot tire. they go by sidewall not tread like slicks. My 65 cutlass with s&w back half had 14x31x15 on 14" rims.

[ric]

The 18.50 they're talking about is a dot tire. they go by sidewall not tread like slicks. My 65 cutlass with s&w back half had 14x31x15 on 14" rims.

I see said the blind man:Dou: :grin: Thanks for the correction Jeff.

[bignastyGS]

Thanks guys,
I questioned the guy and he kinda came off as a Chevy type guy. I have been looking at the 14.50's and he threw a curve ball at me. I told him this is going to be a drag only car and he went on about if ever I decided to street car thing it...etc.I just want to make sure I do this right the first time and dont have to do over things.
2 more questions now.How do I determine axle ratio for what I need? and what brand tires are good? I am unsure of the compound thing at this point. Need to do more investigation..

[ric]

Pat

To determine your axle ratio you first need to know your estimated or exact hp, type of trans & stall of your convertor and your red line on your engine, plus weight of the car and exact tire height you will use. All these factors effect what ratio you will pick.

You need to plan it out on paper first. Example with my 4.30's I go through the traps at 7,000 rpm which on the dyno is a hair above my max hp. My convertor of course if it were tighter the rpm's would be lower. But if I had an engine making peak hp at a lower going through the traps, my ratio would be different.

So first you have to plan out on how fast you want to go, and figure on paper your entire combo.

As for types of tire....pick your poison, they are all basically the same, as for compound, again it depends on your combination. A lighter car can use a different compound than a heavy car. Because a lighter car doesn't need gobs of torque getting out of the hole fast, where as a heavy car does.

[bignastyGS]

Rick, What is your backspacing on your rims? My ralleys are exactly 15 inches wide from rim lip to lip.The BS is 7 7/8 on the back and 7 1/8 from the front. Still waiting on S&W to give me a housing total length.as well as axle length.