LSD vs brake lock-up testing

[nomis3613]

Hi Folks,
Testing the effects LSD Initial/Decel on which wheel locks up during braking has burped up some strange results which I thought you might be interested to see.

(all testing done without ABS)

FF
With the brake strength set so the fronts lock before the rear, no combination of LSD settings made it possible to lock the outside wheel first. Which is interesting considering that LSD can cause the outside wheel to spin under acceleration. For most settings, the inside locked first; but with high LSD Initial both wheels locked at the same time.

FR
With a rearward brake bias, the outside rear tyre always locked first(?!). I tried various combinations of Initial and Decel, but it was always the outside to lock first.

Very strange...what do you think?

 

[CSLACR]

Hi Folks,
Testing the effects LSD Initial/Decel on which wheel locks up during braking has burped up some strange results which I thought you might be interested to see.

(all testing done without ABS)

FF
With the brake strength set so the fronts lock before the rear, no combination of LSD settings made it possible to lock the outside wheel first. Which is interesting considering that LSD can cause the outside wheel to spin under acceleration. For most settings, the inside locked first; but with high LSD Initial both wheels locked at the same time.

FR
With a rearward brake bias, the outside rear tyre always locked first(?!). I tried various combinations of Initial and Decel, but it was always the outside to lock first.

Very strange...what do you think?

I did notice when tuning a 4WD increasing front decel didn't seem to have much, if any effect.

I'd say it all comes with a decade old tuning setup that PD keeps recycling.

 

[ampire]

I've gotten the best results for rear wheel drive with a "symmetrical" LSD setup built around something like:
Initial: 9
Accel: 18
Decel: 18


Otherwise, it seems that the transition from acceleration to deceleration in the corner results in under-steer and tire smoke.

I run front brake bias, usually front: 5 rear: 3.

 

[nomis3613]

^ cool. Do you know whether it was the inside (or outside) wheel that was smoking when you had too much (or not enough) LSD Decel?

 

[Johnnypenso]

I've gotten the best results for rear wheel drive with a "symmetrical" LSD setup built around something like:
Initial: 9
Accel: 18
Decel: 18


Otherwise, it seems that the transition from acceleration to deceleration in the corner results in under-steer and tire smoke.

I run front brake bias, usually front: 5 rear: 3.

Recently I've done the same thing for most cars in general, FWD, RWD and 4WD. I find it smooths out the transitions between brake/coast/accel and brake/accel, stablizes the car at all points during cornering and helps with trail braking as well.

 

[CSLACR]

FF
With the brake strength set so the fronts lock before the rear, no combination of LSD settings made it possible to lock the outside wheel first. Which is interesting considering that LSD can cause the outside wheel to spin under acceleration. For most settings, the inside locked first; but with high LSD Initial both wheels locked at the same time.

A thought, firstly I believe the "initial" is exactly as described in game, the amount of slip that must occur before the lsd accel and decel will activate.

Given that theory, it would make sense for the outside to always lock/turn red first, without a high initial. With a lower initial, by the time the decel lsd activates, the outside wheel has already locked, and turned red.

 

[Sail IC]

One explanation could be that ..... When a tire turns red, it doesn't necessarely means the tire is locked or severely skid, it is just loaded very hard.

I race with ABS=1. When braking hard and too late into a sharp corner whilst turning, the outside front can go "red". But the car is still turning, so the tire does not skid, its just loaded very hard (too hard for good tire wear).

When reading some posts, I think sometimes when stated a tire turns red it gets misinterpreted as the tire skids but in its really overheated for good tirewear.

Just my two cents.

 

[nomis3613]

I did notice when tuning a 4WD increasing front decel didn't seem to have much, if any effect.

Cool, thanks I'll keep an eye on that. Speaking of 4wd, instead of just using separate FF and FR cars I should also test 4WD. Cheers 👍

A thought, firstly I believe the "initial" is exactly as described in game, the amount of slip that must occur before the lsd accel and decel will activate.

Given that theory, it would make sense for the outside to always lock/turn red first, without a high initial. With a lower initial, by the time the decel lsd activates, the outside wheel has already locked, and turned red.

I was expecting the inside to lock first because it has no load so it handle as much braking. How come you think the outside would lock first?

Also, I find it very strange that it's the outside on the rear, but inside on the front that's locking. Any thoughts?

One explanation could be that ..... When a tire turns red, it doesn't necessarely means the tire is locked or severely skid, it is just loaded very hard.

I race with ABS=1. When braking hard and too late into a sharp corner whilst turning, the outside front can go "red". But the car is still turning, so the tire does not skid, its just loaded very hard (too hard for good tire wear).

When reading some posts, I think sometimes when stated a tire turns red it gets misinterpreted as the tire skids but in its really overheated for good tirewear.

Just my two cents.

I agree that red doesn't always mean locked. But in this case I have the skid marks to prove it's lockup under brakes!

 

[CSLACR]

Cool, thanks I'll keep an eye on that. Speaking of 4wd, instead of just using separate FF and FR cars I should also test 4WD. Cheers 👍


I was expecting the inside to lock first because it has no load so it handle as much braking. How come you think the outside would lock first?

Also, I find it very strange that it's the outside on the rear, but inside on the front that's locking. Any thoughts?

The outside front spins faster then the inside when you're turning, so until a wheel starts to lock, the lsd should send more power to the outside.

I have been tuning a 4wd car tonight, I found a high front initial makes the car under-steer more when braking, as does decel, though higher decel with lower initial results in the * rocking motion I hate.

I usually don't go into "realism" thoughts for tuning in GT anymore, it's only important I know what each does in the game to me anymore, I've found it helps my tuning greatly.

 

[nomis3613]

The outside front spins faster then the inside when you're turning, so until a wheel starts to lock, the lsd should send more power to the outside.

Ahhh... makes sense.

So I re-tested with a Gallardo. Unfortunately no amount of stupid brake setting / ballast / mismatched tyre antics could get it to lock the rears before the fronts. But anyways, same results as before: at the front it's always the inside first, at the rear it's always the outside. More importantly than trying the different car, I also compared Sports Soft and Racing Soft. Same result.

Interesting results, I've got no idea what it means though!

 

[CSLACR]

Ahhh... makes sense.

So I re-tested with a Gallardo. Unfortunately no amount of stupid brake setting / ballast / mismatched tyre antics could get it to lock the rears before the fronts. But anyways, same results as before: at the front it's always the inside first, at the rear it's always the outside. More importantly than trying the different car, I also compared Sports Soft and Racing Soft. Same result.

Interesting results, I've got no idea what it means though!

The rest of the car setup should have a play here, over-steer should make what you're experiencing happen, and under-steer should make the outside front go red first.
In theory, with enough under-steer on braking, the rear should lock and/or turn red at the same time.

In any case, under braking, the outside tires always have the most weight, so the natural tendency should be outside first, regardless of lsd efficiency, because the brakes have tenfold the stopping power of engine braking, which is all lsd can control.

Overall balance, weight distribution, and over-under steer should have the final say on what tires go red first, lsd has a much bigger role in acceleration, where there is not a looming giant force (brakes) coming into play.

 

[nomis3613]

Yeah, I indirectly was messing with the grip balance when trying different tyres and ballast. Even when I could barely keep the car on the track from all the oversteer, it was still locking the fronts first. Argh!

 

[CSLACR]

I have a Ferrari tune that locks the rear first if your turning hard.
It'll be up pretty soon @ 600PP Racing Medium.