Suspension set up with HLSD

[JohnJohn86]

I have a S14 with a KA engine with bolts ons, S15 HLSD and fully adjustable coilovers with F8K, R6K springs.

I track my car very often and mostly do grip. During SOME corners, the inside tire would spin just like the car has an open diff and I can see smoke in the back if I step on it.

This does not happen in all corner, most of the time it happens in a banked curve going uphill and only turning right!

I don't think this is normal since all the power are suppose to go to the outside wheel in a HLSD. here is a video of me doing some drifts, so I know the diff is locking very good.
http://www.trackhq.com/forums/photopost562/showphoto.php/photo/9131


Is there something I can do to fix that? swap bar? more sping rate in the front? Corner balance?

[kevtrinh]

hm, maybe try a different rear sway bar

[spool_sample]

Remove the rear sway. It causes more problems than it solves.

Take it off, and if needed, add some rear spring to compensate.

[916S14]

Looks normal to me.... but the video made my head hurt so i didnt watch all of it. Try to stiffen up your car some more.

[JohnJohn86]

So you guys think my chassis is flexing a lot and my swap bar is lifting the inside wheel and cause too little traction to lock the diff?

[steve shadows]

1. what tires are you using?
2. just grip? drop the rear sway good bye
3. leave the spring rates where they are.
4. see if no rear strut brace helps too.

[JohnJohn86]

1. what tires are you using?
2. just grip? drop the rear sway good bye
3. leave the spring rates where they are.
4. see if no rear strut brace helps too.

1. I use RT-615 for grip, and this problem got worse if I use cheap tires.
2. I sometimes do drift just for fun. The car does oversteer too much sometimes.
3. OK
4. No rear strut brace at all

[luftrofl]

I track my car very often and mostly do grip. During SOME corners, the inside tire would spin just like the car has an open diff and I can see smoke in the back if I step on it.

This does not happen in all corner, most of the time it happens in a banked curve going uphill and only turning right!

I don't think this is normal since all the power are suppose to go to the outside wheel in a HLSD. here is a video of me doing some drifts, so I know the diff is locking very good.


wikipedia says otherwise... somewhat: "For road racing, many prefer a helical limited slip differential, because it does not lock the two output shafts to spin at the same rate, but rather biases torque to the wheel with more grip by up to 80%."

I put the text that I find relevant in bold. Post a video of the inside rear spinning when you're not sliding so much because the video that you posted looks very normal to me. I don't even think it's possible to have ALL of the power go to the outside wheel.

[steve shadows]

1. I use RT-615 for grip, and this problem got worse if I use cheap tires.
2. I sometimes do drift just for fun. The car does oversteer too much sometimes.
3. OK
4. No rear strut brace at all

Add rear strut brace, get bigger rear tires and wheels.

Remove rear strut brace, If you can add a tiny bit of camber to rear wheels, since its such a short course.

If my car was on htm I would just be drifting irregardless

[cdlong]

helper springs might help too. since they help keep the wheel on the ground a little, it will add a little traction to the inside wheel and allow the diff to transfer torque to the outside.

[spool_sample]

Again: remove the rear sway. The reason why you're getting tire lift is the combination of too much roll stiffness + the crappy rear suspension design of S-chassis cars, which binds a lot and causes traction loss.

You could also get around the problem by using tender springs (or to some extent, like what cdlong said, helper springs... but those don't work as well). But leaving the rear sway in place will still cause binding and removing it doesn't cost anything...

[JohnJohn86]

wikipedia says otherwise... somewhat: "For road racing, many prefer a helical limited slip differential, because it does not lock the two output shafts to spin at the same rate, but rather biases torque to the wheel with more grip by up to 80%."

I put the text that I find relevant in bold. Post a video of the inside rear spinning when you're not sliding so much because the video that you posted looks very normal to me. I don't even think it's possible to have ALL of the power go to the outside wheel.


My bad, I thought ALL the power goes to the wheel with most grip. It does make some sense now.

[JohnJohn86]

Again: remove the rear sway. The reason why you're getting tire lift is the combination of too much roll stiffness + the crappy rear suspension design of S-chassis cars, which binds a lot and causes traction loss.

You could also get around the problem by using tender springs (or to some extent, like what cdlong said, helper springs... but those don't work as well). But leaving the rear sway in place will still cause binding and removing it doesn't cost anything...


Thx, I will try it out this weekend in Street of Willow without sway bar

[cdlong]

You could also get around the problem by using tender springs (or to some extent, like what cdlong said, helper springs... but those don't work as well).

what's the difference between tender springs and helper springs?

nevermind, google is my friend. apparently tender springs are stronger but still softer than the main springs. terminology difference, but the concept is the same.

[Jung918]

If you search in the motorsports sections, someone had a fix to the problem. I believe he went softer springs on the rear.

[OptionZero]

yes

i think it was nizmo400r (user), he wasn't getting proper damping in rear

not the sway bar...its get better coils

[JohnJohn86]

I tried 2 set of coilovers (Tanabe and STD) and both do the same thing. How can a softer sping or damper fix the problem? I just cannot understand. Can you please explain?

[MrChow]

^^ Do you know what setting preload is?

Also are you doing drifting in the video or trying to grip?

[!Zar!]

It's simple, op doesn't have enough droop.

So that's why his car is lifting a wheel. Once your wheel looses traction, it acts like an open diff.

Reset wheel travel length and preload then try again.

"Remove rear sway...bigger tires"...shut the fuck up. That's like a bandaid for a bullet wound.

haha. [email protected] tuning with strut tower braces.

[MrChow]

^^^
I mean hell I run the whiteline sway at 22mm with the stock front sway with coils and I don't lift.

[zads]

Remove the rear sway, give yourself as much droop travel as possible. Helped me for autocross/track setup.

[!Zar!]

Remove the rear sway, give yourself as much droop travel as possible. Helped me for autocross/track setup.

Removing a sway like that would only help for lowspeed without any ill effects.

[MrMigs]

Removing a sway like that would only help for lowspeed without any ill effects.

Agreed. Words of wisdom here.

Removing the rear sway will help you get rear tire grip when you're exiting corners under throttle, but remember that it'll also affect your entry and steady-state cornering, perhaps negatively (depending on your driving style).

Nevertheless, if you want to give it a try, give it a try, since it's not hard to remove/reinstall the rear sway bar.

Just watch out though - if you like to trailbrake late into corners, you wont be able to dive in on the brakes as deeply without running into some understeer.

Let us know how it goes - curious as to your results :hsdance:

[MrChow]

^^^
I remember when I had no sway bar then having one. I don't want even go back to no sway bar. But then again I haven't auto-x a lot so I mostly deal with mid to high corners with my car.
Oh yeah I remember the understeer I had without my sway bar.

[MrMigs]

^^^
I remember when I had no sway bar then having one. I don't want even go back to no sway bar. But then again I haven't auto-x a lot so I mostly deal with mid to high corners with my car.
Oh yeah I remember the understeer I had without my sway bar.

You should try taking off your FRONT swaybar...

Ah yes... I remember the oversteer I had without my front swaybar... that was fun...

LoL j/k don't do this. It's only fun for really lowspeed corners. :2f2f:

I also thought of something that MIGHT make a difference. If you have adjustable tc rods (you prolly do) then try lessening your caster setting so that when you steer in, you don't have as much mechanical weight transfer off of the inner rear tire.

Or you could try taking a different line and opening up the throttle a bit later... Maybe try late-apexing. If I remember correctly, you end up giving throttle with less steering angle, and thus you should get less oversteer.

[JohnJohn86]

^^ Do you know what setting preload is?

Also are you doing drifting in the video or trying to grip?

I have zero preload I believe, the spring is almost free to move when I jack the car up in the air.


I posted that video just to show the diff is locking in condition like that but not locking in other corners.

[JohnJohn86]

You should try taking off your FRONT swaybar...

Ah yes... I remember the oversteer I had without my front swaybar... that was fun...

LoL j/k don't do this. It's only fun for really lowspeed corners. :2f2f:

I also thought of something that MIGHT make a difference. If you have adjustable tc rods (you prolly do) then try lessening your caster setting so that when you steer in, you don't have as much mechanical weight transfer off of the inner rear tire.

Or you could try taking a different line and opening up the throttle a bit later... Maybe try late-apexing. If I remember correctly, you end up giving throttle with less steering angle, and thus you should get less oversteer.

Understeer is not fun either, I rather have some wheel spin and deal with it than mad understeer.

[steve shadows]

I don't have this understeer problem without the rear sway on s13.

I did stock from sway bar no front strut brace

Add a strut brace in rear . Remove the rear sway.

It seems to stiffen up the rear of the ass without connecting the wheels directly to each other under the car.

No understeer problems here, If anything a slight bit of oversteer (could be all the power I have though).

[projectRDM]

Removing the sway bar won't do much with such stiff rear springs. Do what others have said first, adjust the preload and dial in a little more camber. You may also want to reset the sway bar endlinks with it fully on the ground, it's possible they're overtightened, in that case they're binding under load and causing added lift.

[!Zar!]

Like I stated before which most people overlook.

When you lower your car by adjusting the mounting perch, you're raising the spindle/hub. That in turn affects your droop. By doing that, it raises the inside wheel and affects the contact patch.

In your case it's causing your diff to unload. Lets say your car had a locking diff. Then adjusting droop would be even more effective and you could control how your car handles just through that. Very effective, yet commonly overlooked.

[cdlong]

Reset wheel travel length and preload then try again.


how do you go about doing that? i have a similar problem, though much less extreme. when i put my coilovers on, i set the preload to zero with them off the car. i don't know how the shock could extend any further. i didn't try pulling them out because i though they were fully extended already.

[JohnJohn86]

Like I stated before which most people overlook.

When you lower your car by adjusting the mounting perch, you're raising the spindle/hub. That in turn affects your droop. By doing that, it raises the inside wheel and affects the contact patch.

In your case it's causing your diff to unload. Lets say your car had a locking diff. Then adjusting droop would be even more effective and you could control how your car handles just through that. Very effective, yet commonly overlooked.

Can you please explain what is droop? I have zero pre-load in my sping and I adjust the height with the bottom mount now. Should I have some pre-load and lower the bottom mount more to keep the same height?

[MrChow]

argh...
http://splparts.com/doc/SPLCoilover/default.htm

Just try to add some preload. I dunno 1/2 inch of preload all around and drive. Try stuff out. Read that it.

Here something to note. I've set and reset my preload over 14 times till I found a good setting.

[HaLo]

I had the same problem with my S13.. the problem is with the short negative travel of your suspension. Get some helper springs and put that on... it should help.. you really have to soften the rear.

[!Zar!]

To optimise your suspension setup you would need to give up the option of being slammed. Because you lower your car by taking away/lowering the preload collar and raising the lower shock perch.

By lowering the perch, it raises the wheel which changes your stroke.

If you want to fix it then raise screw the perch down and try about half an inch of preload up front and a full inch in rear.

[jmauld]

Again: remove the rear sway. The reason why you're getting tire lift is the combination of too much roll stiffness + the crappy rear suspension design of S-chassis cars, which binds a lot and causes traction loss..


What binds in the rear?

[98s14inaz]

argh...
http://splparts.com/doc/SPLCoilover/default.htm

Just try to add some preload. I dunno 1/2 inch of preload all around and drive. Try stuff out. Read that it.

Here something to note. I've set and reset my preload over 14 times till I found a good setting.

That link is a great read. I learned something new.

[a_ahmed]

Agreed. Words of wisdom here.

Removing the rear sway will help you get rear tire grip when you're exiting corners under throttle, but remember that it'll also affect your entry and steady-state cornering, perhaps negatively (depending on your driving style).

Nevertheless, if you want to give it a try, give it a try, since it's not hard to remove/reinstall the rear sway bar.

Just watch out though - if you like to trailbrake late into corners, you wont be able to dive in on the brakes as deeply without running into some understeer.

Let us know how it goes - curious as to your results :hsdance:

Can you explain this further? I am running a rear sway but I consider to remove it after seeing some of the more successful setups without them.

How does it affect it? I've never run without it... my car is stored indefinetely until winter is over and maybe more not sure yet.. so can't test :)

How does it affect mid-high speed cornering? High speed straight line? Etc...

[jmauld]

Can you explain this further? I am running a rear sway but I consider to remove it after seeing some of the more successful setups without them.

How does it affect it? I've never run without it... my car is stored indefinetely until winter is over and maybe more not sure yet.. so can't test :)

How does it affect mid-high speed cornering? High speed straight line? Etc...


It's easy to test to get a feel for what it does. Just unhook one endlink and the swaybar will not have an effect your handling. (other then the slight weight penalty of carrying it around)

[AceInHole]

You'll also have a tad more suspension bind/ resistance on one side vs. the other. It's not a huge deal though.

+1 for no rear sway. Really lets you plant power, especially as your grip limits increase. Sprung right, the car is extremely predictable.

[Petoria]

How new is the dif? A worn out hlsd will start to act like an open diff. Other wise play around with some settings till you find the right one for you. :hsdance:

[AceInHole]

An HLSD shouldn't really "wear". The helical gears themselves are what apply pressure to transfer torque. It's not like a clutch diff where there's a friction surface to wear out, or a viscous diff which can just break down chemically.

[MrMigs]

Can you explain this further? I am running a rear sway but I consider to remove it after seeing some of the more successful setups without them.

How does it affect it? I've never run without it... my car is stored indefinetely until winter is over and maybe more not sure yet.. so can't test :)

How does it affect mid-high speed cornering? High speed straight line? Etc...

Well, if you remove your rear sway, you'll more-or-less reduce your roll resistance in the rear when your car is shifting weight from left to right or right to left (lateral weight transfer)

It doesn't affect any straight line performance.

Just give it a try, and you'll see what I mean. It's a lot harder to rotate the car using your brake pedal without a rear sway bar. You'd have to compensate with a brake bias adjuster or by running pads in the rear with more friction. But nevertheless, if you don't drive this way, you probably won't notice too much... or maybe you will - just give it a try and find out for yourself. :hsdance:

[heychris]

After watching the vid I would be removing / disconnecting the rear sway bar

An old 4x4 trick is to disconnect it at the links for offroad (more spring articulation) and reconnect it for onroad...:fart:

Whatever you do TAKE (and store) EFFING NOTES, so you can revert back to a previous setting that worked FOR YOU !!
GL
CH



[quote=zads;1687599]Remove the rear sway, give yourself as much droop travel as possible.

[Petoria]

An HLSD shouldn't really "wear". The helical gears themselves are what apply pressure to transfer torque. It's not like a clutch diff where there's a friction surface to wear out, or a viscous diff which can just break down chemically.

My bad had a brain fart and was thinking about viscous.:keke: