Help Understanding LSD

Neek

I tried using the search function but haven't really found my answer. I also watched a bunch of youtube videos on how LSDs work but they seem to only tell me how LSD's mechanically work or how it works in general but not necessarily how the setting/tunes impacts the behavior of the car.

I bought a OS Giken 1.5 Superlock LSD from another user who said he had it tuned (by OSG) for AutoX. He said that means it was tuned to have less decel lock.

1. What does that mean then for how the car behaves?

2. How would this be any different from the factory setting which is for I think a typical track car?

3. Or should I just msg OS Giken directly to get an explanation?

2011 Nismo#91

You're not finding the answer you want because it's not an easy question. Less deceleration lock means it's closer to an open diff when you are braking. Not sure of the reasons for autocross to need that because I don't have much experience with autocross. Less lock would seems to mean in that you would have a harder time to clock up the rear coming into a turn and less easy to slip/rotate which probably isn't too useful on small tight tracks.

I read a few books and have a decent amount of seat time and am only grasping the basics of what all this body and suspension tuning means on the track.

"Autocross racing places very high demands on the differential because the corners are much tighter in radius than road courses. This places an enormous burden on the chassis and differential to apply power on corner exit." So sharp turns would quickly lock up the inside wheel listing traction and braking power way too soon. Less lock more traction more deceleration in less time win.

Neek

So by reducing the decel lock, it reduces the window where the inside wheel locks up during a turn(?), allowing the LSD to adjust the speed of the wheels while decelerating, meaning more traction in tight corners = quicker times?

Rusty

On decel. You have less lock to allow the tires to rotate freely from each other. When you apply power. The diff begins to lock up.

Too much lock will give you weird handling. Entering a turn, lift off the gas. The front of car will be pulled into the turn. Step on the gas, and the front will go straight.

Learned this with a Detroit Locker, and a 100" wheelbase vehicle.

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Neek

Is there a negative of having it tuned this way?

Rusty

No. Not really. A lot depends on your driving style, track, etc.

When you install it. Make sure you use the OS Giken gear lube. Otherwise, it will be noisy.

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cv129

I’ll put in my 2 cents. In general, all other things equal, I think:

Exaggerate a bit to make my point...a 100% decel lock means both tires are forced to rotate the same speed during deceleration/off throttle, it will make the rear act like little more like a pivot, and less willing to rotate (therefore front being pulled into corner like Rusty said). It will be more pronounce in slow speed, tight corners. So I would think it’s not desirable for autocross.

Now if you have a rear end that’s all over the place, bumpy surface in a high speed braking zone, a high decel lock may help calm the rear end down during braking, making the rear end more predictable.

But of course, like others said, a lot also depends on driving style, and perhaps power level. A driver that prefers to use sharp steering input and heavy jab braking may partner better with a high decel lock versus smooth driver with gradual steering input and linear braking style.

Then again, handling is a package deal...at any one moment rebound, compression, camber and toe curves, LSD, all work together.

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Neek

Thanks all for the info!

Got it I'm a pretty casual driver with just spirited driving in the canyons. No plans to take it to the track or autox anytime soon. Just wanted to understand what I can expect from the LSD.