i have a 81 z with a 3.73 rear.i have 14 inch wheels with 245 60 i think anyways its about 21 inches tall. i ran a low 14 and a high 13s. well i just bought some 15x8 rims and need to know a tire size recommendation for the rear and the front on a stock suspenson. would a taller tire on the back lower my ET? any advice thank you

Here is what I have seen happen.It was a mustang,so that may have been part of the problem.While I was racing in a series at Bandimere in Colorado,I met a few people.One guy had a 70 stang and was running 13's.Next week he showed up with some slicks cause he had tracion problems.Well,he had no more traction problems but he didn't go any quicker.His slicks were about 1 1/2 to 2 inches taller than his street tires so he did nothing for his time.He affectively made his gear ratio higher with the tall tires.My opinion.Stay with the same size O.D. tire if you can find it.I think the usual O.D is around 26 inches.Here is a trick.
to find gear ratio do this.
mph(do about 55 to 60) x 3 devided by
rpm x tire diameter

substitute your short tire with 26 instead and see what you come up with.
It all depends on what the car is used for.Do you want the wheel wells filled,ect.

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1970 Camaro RS/SS
Solo II Racer

[This message has been edited by monteZ27 (edited January 29, 2002).]

I have 245/60-14's, they're right at 25.5" OD

I had the problem monte was talking about once. With the 350 I was cutting a 9.29 8th on the radials. Borrowed some 28x9" slicks and picked up my 60ft, and lifed the front, but still ran a 9.29. That was with a 3.42 open rear. Get 26" slicks.

I have 3.73's now, and will prob get a 26x10 if it'll fit.

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Eric aka(Morkai)
'79 Z28, Silver, T-Tops, 388-roller...laying in pieces all over my shop

"186,000 miles a second, it's not just a good idea... it's the law."

Mickey Thompson makes some slicks in the 9.0x26"-14 size. It woun't affect your gearing and will give you tons of traction.
also MT's don't require hard burnouts to work. A quick buzz in the waterbox and a couple of dry hops and you are ready.

Im kinda interested in your mph and 60 foot times.

While the short tire helps you out of the hole - are you spinning? You didnt mention if you are running a slick. Or if you were going to buy slicks for the new rims.

If your spinning radials on the 14 rims - and you go to a taller tire on the 15 inch rim and then stop spinning - WELL....I guess that would be a good thing. Because now your not spinning AND your going to get better MPH due to the tall tire.

Question is - radials or slicks?

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72SS SB400 9INCH/411 2950 pounds (and dropping)
http://home.att.net/~dwwest/index.html

What RPM are you going through the traps at?
What is the "powerband" of your current combo?

You want to pass through the traps as close to the max as you can.
ex. if your engine makes power from 3000 - 7000 rpm, you want to pass the traps as close to 7000rpm as possible.

shorter tire = higher finish line rpm
taller tire = lower finish line rpm