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26-27" tires -what rpm r u 100mph+ 13 sec guys turning?

Posted By: Dave440

26-27" tires -what rpm r u 100mph+ 13 sec guys turning? - 11/01/12 11:46 PM

Time to replace those 20 yr (new) rotted tires I got 100 miles use out of! I'm REALLY gonna try to finish it b4 ruining another set!!

I used to run 225-70r-14 tires and traction was obviously lousy. Sometimes I'd get a decent run if I just tipped in the throttle then got on it...but other times it wouldn't matter and I'd spin through first and part of 2nd. Now that I'm buying again I could use some input.

Ideally...a matched set of 4 would be easier to deal with... especially when it comes to carrying a spare tire but I may stagger them based on your responses. All of the 60 series tires on my choice list (below) are wider than the 70s series I used to run but a few of the choices are 1/2" shorter. How much more rpm would I turn through the lights with a 1/2" shorter tire? I assume that would limit mph too.

And before someone mentions it...I've messed with those rpm/mph/tire/hp/weight calculators but I'm getting crazy tire sizes due to excessive mph for my et due to traction issues on my old runs.

That's why I'm askin you guys for real world numbers.

Appreciate some feedback as far as et/mph/trap rpm from those of you with similar setups and running 26-27" tall tires.

My setup: 66 Coronet - best guess around 3600 lbs with big block, Gas shocks and pinion snubber, Eng 440 appprox 350-375hp /727 trans/lo stall converter/ 3.91 posi.

My choices below - (based on BFG TA specs chart)
USE- MAINLY FOR SHOW/STREET - OCCASIONAL STRIP

Choice1
215 65 15 front and rear
7.5" tread - 26 tall. (1/2" shorter and 3/4 wider tread than my old 70 series).

Choice2
215 65 15 front / 235 60 15 rear - 26.1 tall 8.7 tread - (rear 1/2" shorter and 2" wider than my old 70s)

Choice3
215 65 15 front /245 60 15 rear - 26.6 tall 8.5 tread
(Rear is same height as my old 70s but around 1 3/4" wider)
(I Question BFG width specs because it shows the 245 as .2 narrower than the 235)

215 65 15 front /255 60 15 rear - 27.1 tall 9.1 wide
Not 100% out of the running but Most likely. They'd clear outer wheel lips with 3/4" to spare but the 245-60s on it now are hard enough to change as it is.

Please chime in with your numbers size recommendations.

Thanks in advance,
Dave
Posted By: Joel71

Re: 26-27" tires -what rpm r u 100mph+ 13 sec guys turning? - 11/02/12 05:44 AM

My combo: 71 Satellite 360/904, 2500 stahl, 3:23 gears, right at 3800 lbs as raced. I have run a hugh amount of tire/ wheel combos on my car. I have done both 26" and 27". I have never really looked closley at RPM right at the finish line but I'm sure the 26" is putting me near or above 5K.

My car makes great torque but no upper RPM HP. Short tires hurt my quarter mile and don't help my 60ft. Depending on weather, my car is done between 5500 and 5800. On a bad day I'm right at 100 MPH, on a good day well into 103.

As long as I can get my car moving, I can get traction. I have run a 215/75/14 with no problem. I can't hit it hard off the line but once it moves I'm on the floor.

Your gearing should put you where you want to be but I would say on the upper end of that. I'm sure traction is stopping you from being in the 12s. I've been 13.06 but I'm getting close to 100% from my car since I usually run something sticky on the rear.
Posted By: patrick

Re: 26-27" tires -what rpm r u 100mph+ 13 sec guys turning? - 11/02/12 11:37 AM

tire calculators don't account for converter slip....add about 200 RPM probably for that.

is it a street car, or a street strip car? I'd go for 255/60R15 all the way around for a street car, if you want the big-n-littles look, then I'd go 255/60R15 in the back, 205/75 or 215/70 in the front
Posted By: AdamR

Re: 26-27" tires -what rpm r u 100mph+ 13 sec guys turning? - 11/02/12 03:11 PM

I would stick with the 215-70-14s which look correct on the car and get some 275-50-15 or 255-60-15 drag radials for the track
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