Tyre selection

[Aussie Rob]

What would be the the best tyre radius for1/4 mile runs on my 64  galaxie. I have wide ratio toploader and 3.77 gears with approx 430 hp and 500 ft/lbs t. Options are 275/50/15 [26.5 ins] or 275/60/15 [28 ins] :

[plovett]

I would say the shorter tire.  A taller tire might give a bit better traction, but the change in overall gear ratio with the smaller tire would be worth it in this case, in my opinion.

With a true 430 hp and 4000 pounds you might do somewhwere between 105 and 110 mph in the quarter.  With 26.5" tires 110 mph is about 5260 rpm.  With 28" tires 110 mph would be about 4980 rpm.  The extra rpm will likely put your engine in a higher average range of horsepower.

The shorter tire is also going to be lighter, for less rotating mass to accelerate.  A lot of people get hung up on saving a few hundred grams in the shortblock, but then leave 20-30+ extra pounds in just the wheels and tires.  It makes a difference.

I say go with the shorter tire if 1/4 mile performance is the goal.

paulie

[Aussie Rob]

Thanks Paulie that makes sense, I'll just have to do some measurments as I also want to fit caltracs and have to maintain a minimum of 4 inch ground clearance[ we have some strange rules here],if I'm under this I may have to save some more pennies and go 3.9 gears and 28.

[Faron]

I always go with the tallest , then the widest and then gear it a using a 26 inch rear tire does not leave many options for a front tire, unless you want the rear to be shorter than the front   , a 275 60-15 fits nice and fills up the wheel well IMHO

[plovett]

28" tall tires would certainly fit the Galaxie's wheelwell better, and they would likely work very well with 3.91 or 4.11 gears.  That was not the original question though.

paulie

[Aussie Rob]

Thanks for your help everyone,I'll run 28's and change the gears later and thanks Paulie what you said was right about the original two choices. . 

[LuxurySportCoupe]

I'm very happy with my 28" tires. It had 26's on it when I bought it, and they didn't look right on the car.