3.15 gears. 26 or 27 inch tires?

[01GTB]

I'm probably going to buy a pair of 15x8 Weld RT-S rims for drag radials. Car will remain naturally aspirated and I have no intention of swapping the stock 3.15 gear with the automatic. Would you go with the 255/60/15 and keep a nearly stock 27" tire height, or go with the 275/50/15 and drop an inch of tire height? Not going to be able to get a pair of front runners for a while, so the stock 19x9 Brembo wheels will be run on the front until then.

 

[D.T.R]

I run 275/50/15 on my 15x8 RTSs.
I like the 26" tires on this nearly stock car... it helps waking the car up down low.

 

[SteveG@Lethal]

With a 3.15 gear, your going to want to run a 26" tall tire.

Wallace Racing - Automotive Calculators

This will solve and answer all your questions.

 

[UnleashedBeast]

Agreed, I also run a 26" tire at the strip. The last time I calculated it, it was the same as running a 3.27 gear on a 27" tire.

 

[auto02]

Went with the 255/60/15 myself on a 15x8 wheel. Definitely works better if you're playing on the street! Actual installed height was about 26.5 with 20psi.

 

[coyote302]

I will say it depend of your mod and what shift point and mph you are going at the end of 1/4 miles....if you are going 120-121 mph like mine , 27" tire will make you pass in top of 3 rd gear and that's what you want.....if you go 115 mph i will say go with 26" ...

 

[JohnRichard]

Steve at BBR gave a great link but I like this one better...

Gear Ratio Speed Calculator


Standard 6-speed manual
Gear ratios
1st 3.66
2nd 2.43
3rd 1.69
4th 1.32
5th 1.00
6th 0.65
Final drive 3.31:1

Optional 6-speed automatic
Gear ratios
1st 4.17
2nd 2.34
3rd 1.52
4th 1.14
5th 0.87
6th 0.69
Final drive 3.15:1

 

[D.T.R]

I cross the line in 3rd gear still with the 26"
The car is only trapping 117mph tho lol

 

[KrisR]

I run 26" tires at the track with my 3.15s. With my Boss manifold, the car shifts at 7500 and crosses the stripe just before the 3-4 shift. The car traps 118-119 in decent air (1000-1500 DA). With a factory manifold, shifting closer to the 7000rpm mark, the 27" might be better.