When shooting for the best SLR would a 9 be consider your best SLR or do it even matter?

Need a little more info, like size of engine, weight of car, size of the rear tires.



Joe

As much as you can get and still hook. I run 10.53 SLR with 10.5Wx31 tire. Car has 54% on the nose. Mid 1.2x 60ft foot braking. it took awhile but it is pretty consistent.
Doug

I would agree with this but add "and not go on the back bumper "!

Really depends on weight and power. Power adder combos can and need to run lower SLR's to manage the car at the hit.

Manual or automatic?
(I suppose most are running torque converters but there are a few of us shift-lovers out there)

My new combo will have a SLR of 13.22:1... But it's a stick car.

IMO it will deped alot on the combo and intended purpose for sure. But the most you can hook up consistently for sure. FWIW the Vette is 11.3:1 and my Stratus 7.72:1. The former has been 1.13 60 and the latter 1.02, as pointed out is fairly combo dependent IMO

Many many variables. Cant single out a number, its whatever SLR the combo wants.

And if you are shoe polish racing sometimes less SLR is better.

My Dart with a Glide has a SLR 8.75 1.80 X 4.86

My old Duster has a SLR of 10.0 2.45 X 4.10

It matters a great deal. Hit the sweet spot and the rest of it becomes much easier (less difficult?).

Mine was 9.6 for what I was doing. Yours is probably different. Every combination is. Weight & bias, power, suspension, tire, track, what you are trying to accomplish, etc....

I had everything from 1.76 to 2.74 in mine with a couple of different rear ratios. A four link and good shocks will let you get more aggressive with it.

What are you using to calculate SLR ?

i always thought SLR was transmission low gear ratio times differential ring and pinion ratio.

Math
AKA, I change the low gear ratio and rear end ratio in my old NHRA legal M.W. 1963 415 HP Stocker, took out the 4.89 rear gear with the stock 2.45 727 low gear ratio = 11.98 SLR to a 4.56 rear gear and swapped the trans to a Mopar 2.77 low gear ratio which made SLR 12.63 ratio.
Those two changes made that car a lot quicker and faster
I was running that car in B/SA at that time and it had to weigh 3520 with me in it, NHRA had lower the HP factor on the 1963 low compression motors 405 HP due to them having a smaller set of carbs and a smaller camshaft than the 1964 M.W. low compression motors had
Test, test and test some more to learn and hopefully go faster and quicker

More factors besides low gear + axle, which is why some PG trans work well.
AT: add the stall ratio, stall speed, launch RPM (crankshaft inertial mass), and converter-flex plate stored inertial mass.
MT: add the launch RPM and clutch-flywheel-pressure plate stored inertial mass.

If the total is too high the car is not repeatable or violent on launch.

Torque multiplication. Which is why auto trans low gears will be ~1.80 to 2.70 and manual trans will be very high 2s and more commonly low to mid 3s.

SLR is a simple arithmetic calculation. Low gear times rear gear. A hundred other factors will determine what that sweet spot is for your situation.

The last 4 speed drag race SB 340 car I drove at the track was a 1970 Duster with a set of 5:57 rear gears with a 3.09 first gear NP833(17.21 SLR, let the clutch out at 7000 RPM and shift at 7000 RPM 3 times very quickly ), you were real busy the first 400 to 500 feet or so with that car

My GTS has a 2.66 1st gear and a 3.23 R&P in the diff. 235-60-14 tire.

Thoughts?

We changed the SLR in this car from 9.17 to 7.77 , literally no change in the ET . But now it barely picks the tires up

In a perfect world, you would take a car like yours and reduce the trans gear, and increase the rear gear. Experimentation like this would accelerate the car and help tighten the converter at the stripe. This would pick the car up on both ends as more rear gear doesnt work the converter so hard and allows it to not slip as much. Im sure you know this but just a good example for people to read. Once you get a good SLR that the car likes you play with it, you can keep the SLR but change the trans gear and rear gear. keep the slr the same and change the mechanical advantage at both ends of the track.

My opinion is your car might be faster with less SLR because wheelies are slower than wheels on the ground passes......BUT who am i to say that?>??? LOL

In the end its expensive and a lot of work, but thats how you go real fast

3.28 in trans 5.57 in Dana 18.27 SLR 9 X 29.5 tire Shift in the air.