Suspension Theory: HLSD?

[OptionZero]

As a I understand it, my new HLSD re-directs torque on throttle to the tire with the MOST grip. In practice, this means the outside tire recieves power when throttling while turning.

I was thinking of how best to optimize this effect. To be effective, the rear tires need traction, or any power is useless, regardless of how good its distributed left and right. This would mean relatively softer rear end, so during power on the weight shifts rearward, meaning more weight on the tires, meaning more grip. That is good.

Next, both wheels need to be on the ground- while the HLSD helps solve the problem of the inside wheel having less traction, if the inside wheel is nearly off the ground, or at worse, peeing in the air (3 wheeling), then the HLSD will still result in hopelessly lost torque.

Thus:
Run a relatively softer DAMPER setting in the rear, so weight transfer is still going from front to rear; run a stiffer rear sway and strut bar setting in the rear to keep the rear end FLAT, and therefore kill left/right weight transfer.

Normally, as I understand it, people don't like to run a stiff rear setting because of the sudden and dramatic oversteer that snaps into effect. The Damper settings on most coilovers already have softer rear spring rates.

So I'm just trying to logic this out; am I on the right track?

I can't afford set of sway bars yet, and my only adjustability is on my KYB AGXs , which is pretty piddly, so I probably can't play around with settings too much...

Does anyone else have any insight? I don't really understand the effects of rear camber in turns (I know front negative camber helps turn-in...right?), caster, and toe in/out

[ultraDorksGarage]

edit: sorry for the novel that goes round in circles, ive had a few budweisers already><.

congrats on getting the hlsd in, i just got around to doing mine last night.

getting the power down earlier(and hopefully having more exit speed) is supposed to be improved by a lsd, not tune suspension to make even more acceleration capacity because u have a lsd. on a road course, a non drift clutch lsd(where driver prvents tires from spinning...) is designed to make u understeer slightly coming out of the corner(so much ample rear traction combined with 2 wheels spinning at same rate makes front plow out of corner rather than rolling), SO ANYWAY, if u make rear squat more, ull understeer like a snow plow. even though hlsd gives alot less understeer than a clutch type, it still will widen radius if not understeer.

according to most drive/engineering books, a hlsd will actually make your car feel like it is rotating harder, kinda like the gyro effect similar to being on a bike and accel out of corner....uve prolly noticed this in the way the car feels like it takes a second set mid corner as u start to accell. i noticed this in my car, and also notice it in my brithers s2000. but this is very negligible.

the hlsd is supposed to be a more reliable, durable, lsd. the draw back of a clutch type is the lock/unlock can unsettle the car in critical areas. hlsd hasnt shown me anything like that yet. although its not as positive of a lsd as a clutch type, but braking is alot more natural feeling than a clutch type.

personally, i did some testing and ended up going up dramatically on the rear dampening force.... i found that on limit-power, instead of the tires just smoothly breaking loose, at the limit the car wheel hops. outside tire is loading/unloading. i still havnt gotten it tuned out yet, but just wanted to letcha know. corner exit is a little snappy, i am prolly gonna follow C Smith's advise and go with less caster and more front rebound dampening. my rear subframe bushing are giving me some crappy wheel hop though, the oscilations are making me queesy><

in theory, the hlsd setup is the same as a clutch type lsd for raod course except u can run caster slightly more straight up(turn in with hlsd is already sharper than a clutch type, kinda like an open diff, but corner exit is not as understeer prone as a clutch type too).

supposedly hlsd's work out better because, for 1, it wont wear out, 2 its less jerky/quirky. downside...it weighs a ton, the inertia effect and the extra drag of the 101 gears internally slowed my car down some. i misshifted twice today because of the inertia effect. u wont lose anything on braking, and tighter corners will have lsd action vs the clutch type will just unlock or wheelspin on a tight switchback.

[OptionZero]

wow. Thanks, i'll have to read that a coupla times to digest it =P

[s14srpilot]

Why don't you just stop "talking" about it. Just do it so you can feel your way through.

"Don't think, feeeel!"
-Bruce Lee

[OptionZero]

Who says I won't? Track day is May 14th at Thunder Hill. Drive up here and teach me something if you're so smart.

Whats wrong with trying to learn by asking others?

[MakotoS13]

dude, drag racers have been doign exactly what you're talking about for decades.

[ZK]

Jon, that NASA event require a NASA membership? If not I might want to sign up for that too. I need some seat time and unwind the motor some more. :)

It's on a weekend too. Most of the track events are on weekdays which kinda suck.

[OptionZero]

yeah, you need NASA membership, its $40 i think

Makoto:
Drag racers use HLSD's? I thought they use some sort of 1-way differential

[thx247]

With the KYB spring rates I'd probably just adjust them as stiff as they go and then reduce to try and balance the car. Not sure how an S14 drives so I can't comment on what the HLSD will do for you. You'll notice it most on turn 2 when you start using the throttle to control the turn of the car. Other turns on Thill...8 can probably be taken nearly flat out or flat once you get comfortable tracking out.

Since its your first day I wouldn't expect you'll be able to really pay attention to the HLSD and how it impacts your driving compared to how you the driver impact your driving. There is too much to learn to pay close attention to the difference the HLSD will make.

If anything, with a stock KA on Thill and an HLSD...when you get off the brake and on the gas you can get on it quicker than you think you can. Almost stomping it even

[OptionZero]

Yeah, I noticed that just driving it around down- where before I had to kinda gas on entering a turn aggressively, then let off to rotate the car...i add mroe throttle and the car rotates like there's a pole down the center axis...beautiful feeling.

but you're right, I'll be learning how to drive, if anything, not so much specific parts. I'm pretty nervous actually.

Turdz drove my car and loved it, even the shitty metal master pads. I can't wait to see what it's like with real pads, fluid, and new rotors.

[SequenceGarage]

If anything soften up your rear sway bar. The way sway bars work is they lift up the inside wheel to bring the entire car down. If you're cornering hard with very short stroke suspension (like my D2s) the inside wheel will pickup sometimes and you will be left with tire spin. I would suggest a normal setting as far as shock stiffness, without too much preload (about 5-10mm spring compression).

Good luck man

[OptionZero]

hrm, i never thought of a rear sway bar like that. I imagined it forced both sides to stay down...in contact with the ground

[ZK]

Sway bar makes the other side of the car do the same as one side. So if one side wheel goes up, the other one does too.

A large sway bar in the rear makes the car handle more neutral because it makes the rear loose traction so you turn faster.

[ultraDorksGarage]

If anything soften up your rear sway bar. The way sway bars work is they lift up the inside wheel to bring the entire car down. If you're cornering hard with very short stroke suspension (like my D2s) the inside wheel will pickup sometimes and you will be left with tire spin. I would suggest a normal setting as far as shock stiffness, without too much preload (about 5-10mm spring compression).

Good luck man

other than tightening the d bushings, the sways arent adjustable are they, and in tightening the bushings it actually prevents rotation like spring, not like anti-swaybars... its a rotational resistance and not a torsional resistance. (resistance through the bushing is like adding dampening and will affect both sides, not allowing both sides to be moved upwards(and downwards for that matter), where more bar in the form of torsional resistance uses one wheel for leverage on the other)

but yes, i dont like antisways bars. or at least too much of them.

ive had to increase rear rebound dampening to reduce wheel hop/tramp. next on the list is removing the toe in on the rear that made open diff drivable. i think its making hlsd snappy feeling.

[jmauld]

Stiffer swaybar bushings change the amount of deflection between the bar and the mounts. They don't really prevent the bar from rotating.

[ultraDorksGarage]

Stiffer swaybar bushings change the amount of deflection between the bar and the mounts. They don't really prevent the bar from rotating.


>.> i said tightening them up, not changing them???? in reference to the fact that unless we are changing parts, theres nothing u can do to run heavier rear bar...

[jmauld]

How are you going to tighten a bushing?

Squeeze it? With the amount of leverage that the suspension has on the rotational center of the swaybar, I don't think you could squeeze it tight enough for it to have the effect that you are talking about. However, you could probably squeeze them enough to make them act like stiffer poly bushings.

[ultraDorksGarage]

How are you going to tighten a bushing?

However, you could probably squeeze them enough to make them act like stiffer poly bushings.

sort of, try it and u will see a slight difference,its minimal at best, but that was part of the point, my point being unless u change the bar or mounting locations, it wont change bar rates, just preloads, and reducing deflection on an antisway bar has small effects on overall balance of a car unless bushings were crap to begin with.

over tight bushings wont deflect that much less, just have a static resistance. im not saying u are supposed to over tighten a bushing. just that if u do u will notice a difference. try it. honestly, rubber ones have more change do to overtightening than poly ones.

even try things like tightening end links while car is on ground vs in the air, it has alot to do with preloads.

the post i was originally replying to was about softening rear sway. and i still dont see how u could do that unless u 1 have an expensive adjustable bar, 2 have several bars to choose from.

in either case, i envy you..

[jmauld]

the post i was originally replying to was about softening rear sway. and i still dont see how u could do that unless u 1 have an expensive adjustable bar, 2 have several bars to choose from.

in either case, i envy you..

Or you could unhook it like I have. Although, I don't plan on leaving it that way. I'm just going to go back to the stock bar when I get a chance to swap the rear ST bar to the wife's 240.

[ultraDorksGarage]

Or you could unhook it like I have. Although, I don't plan on leaving it that way. I'm just going to go back to the stock bar when I get a chance to swap the rear ST bar to the wife's 240.

lol, nice...

i don't like bar and all, but have never even thought about running without one. lol.

[SequenceGarage]

Yea I agree man, but if you had something like a whiteline sway bar that was adjustable, you could loosen it up as much as possible to prevent the sway bar from lifting the inside wheel as much as possible.

If you have stock bars, like you said, there isn't much you can do other than deal with it and adapt. The wheel shouldn't lift off too much anyways, maybe if you clip the curbing at apex but you dont need to come onto the throttle until a little after that anyways. The only place i'd see areal problem is if you were autocrossing and had a car that tended to lift up the inside wheel.