Th Dude

Getting the power to the ground is the goal.
Minimizing the is the key.

Currently have 9x17 rears with 255's and an OPEN differential.

Which will be more effective... Adding an LSD or using 11x17 rears with 315's?

I realize the easy answer is "both". Both, in time, yes...but until then, which first?

Abiding,
D

Jim R.

Derek,

I had 255's with a limited slip diff, and nothing but wheelspin with aggressive throttle in 1st, 2nd, and 3rd. I went to 295's, and while it is better, right foot control is a must for 0 to whatever accelleration. I can still vaporize the 295's/lsd with a heavy foot, but I don't know how 315's would work. Also 5spd vs auto makes a big difference due to gearing.

We have different power delivery curves and boost methods, but I think the results will be quite similar at comparable boost levels. Boost is boost.

Jim R.

mark kibort

for street, bigger tires, for racing probably close to equal. I raced on an open diff for a very long time, and the switch was very pleasantly surprising. generally, i had no problem puting the power down with the open diff, as long as i was pointed straight. putting the power down during and out of the turn was tricky. bigger tires is the best overall change, as it helps handling a bunch.

MK

Adam C

I accelerate way faster now and get a hookup easily with 315s. It helps that I already have an LSD but the tires make a world of difference.

mspiegle

the TYPE of tire is important too. I've personally had very good luck with the BF Goodrich T/A KD. Very sticky for a street tire.

Gretch

Even with 275 Hoosiers, Gretch smoked the sneakers in the first three gears, and she pushes with both feet.....I put street tires on because my drives are long and I didn't want to get caught by the rain or the constabulary, running the track tires. (Kibort got them). I have gone as wide as I am gonna go, (limited by my choice of wheels). I looked for over a year and a half for Cup 2 18's. I finally found them and they are Gretch's choice of mule. You can always overpower one or more components of your drive train.....better the sneakers than the clutch or tranny.....

Jim_H

No doubt.

Th Dude

Interesting feedback...thank you.

Gretch makes a good point about increased power and stress relief.

FWIW: The poll is about equal.

Jim bailey - 928 International

Going from a 8.7 inch tread to a 11 inch tread which depending on the tire brand is about what you are talking about you are adding about 25% more tire. Getting both tires to work (limited slip) you should get about 50% more tire working. The benefit is most noticed when getting on the gas in a corner where the inside rear wheel is unloaded. I watched Andy K. smoke one rear tire from corner to corner at The Streets of Willow. In a straight line drag race even an open differential will power both wheels if the traction is pretty equal but when one lets loose it is all smoke and little forward movement. I put a limited slip trans into the old very brown 1980 and it is slightly faster at the Streets BUT BIG BUT I only have 200 HP at the rear wheels. Yet it still is a couple seconds a lap FASTER than Andy's times.

Th Dude

So, I think I'm starting to get the picture...

Best way to get the power to the ground in a straight line is a larger wheel/tire fitment. This should assist in improving 0-60 and 1/4 mile times.

Best way to get the power to the ground through turns (especially left ones) is the addition of an LSD. This should assist in improving track times.

Thanks again to all for the input and lessons.

PorKen

What about an add-on electronic traction control system?

sublimate

Why left turns?

Th Dude

I figured because the drive wheel is unloaded (less loaded) through left turns, no?

GoRideSno

No Jim, you are just a lot of seconds faster than me!

Andy K

sublimate

I don't think there's a bias towards either wheel. Whether you're turning left or right the inside wheel is unloaded and loses traction. In fact in right turns the traction on the inside wheel (right) should be even less because there's no weight or the driver on that side (for LHD cars).