Shock / Spring Tech Discussion

[Roy]

Im looking for a bit of rule of thumb to help me get my head around what i need to do with my suspension setup, my problem is i dont really have an accurate baseline.

First of all i have not had that much success finding our what spring rate my King forn springs are, and my rear Whitelien springs. Does anyone know? From what i have read around the traps 450lbs/in fronts and 200lbs/in rear springs seem to be the strating point based on ppls posts, and what some Jap manufactured kits come iwith.

Now not knowing what my springs are at the moment, i suppose i can calculate it but that means removing them . How verstaile is the bump and rebound of a Bisltein shock? I assume its been valved for the Whiteline springs, but can you up or even drop the spring rate by 25% and expect the shock to cope?!?!

LOL..having done a fair bit on vibration analysis i could probably get myself lost in some of the numbers...lol dont even know what sort of frequency you sue for general road/ track surface....but what experience have ppl had at throwing different spring rates at shock absorbers that re not able to have their rebound/damping externally adjusted?

Was looking at throwing some bigger swaybars at my car to help with roll. As can be seen in this pic with semi slick rubber in a 120km/h corner (approx)

So swaybars would help there. But also i understand that going for a bigger swaybar also influences the amount of damping required...now how this translates to a difference felt thru the seat of the pants...or in the ability of the shock to handle the higher spring rate and swaybar diameter...i got no flamin idea.

But then what about the pitch in my car under brakes...not that the rear brakes do a lot when braking, but with so much weight transfer i would think they are doing less then what would be optimum?!?!

The above pic is with street rubber stopping from about 150km/h to approx 60km/h, and the car always had a tendency to lock a rear brake:(

So this left me wanting to buy a shock absorber with adjustable rebound/damping and height so that i can have a play with spring rates and tweak the shock to suit how i like the car to feel.

Thing is talking to a few places i get different opinions. Thing is they ultimately have been trying to sell me something. So far i got a good wrap on what shock to buy and was trusting of this opinion...but bugger, the shock has just been discontinued.

So is there a question in here? How flexible would an off the shelf Bilstein be when throwing more spring and swaybar at it?

[ferni]

If your car is diving more than you'd like under braking, i think the only option is to put harder springs in the front? My car does the same thing, under hard braking, the front dives and the tail gets really loose, which means i can't really brake much into the start of the corner, i need to be pretty much off the brakes once i turn in.

[Roy]

Ok , would i be able to throw a higher spring rate at the front shock absorber and expect it to be able to control the oscillation fo the spring? And on top of that a thicker swaybar effectively has the same effect on the shock absorber as a higher spring rate. So its two fold what im asking the shock to cope with.

So is the valving of the shock that critical. Since you see the effort that manufacturers and race teams go to with damper development im guessing it does.

LOL...whicj is leading to what do you look for in a good shock. Material of construction, piston diameter, damper/rebound ajustable, or independently adjustable etc etc.

[dangerous_daveo]

Id like to know what you can actually buy... Like if I were to go serious Id want a shock that is...

Hight adjustable

Fast and slow rebound adj

Fast and slow bump adj

The little spring that goes above the main spring, etc.

I mean Roy, how far do you want to go?

I've found tho, when I had 450lbs on the front, and 350lbs on the rear, that was WAY too much, I didnt even notice the shocks had no oil, it was that stiff.

Now I have 350lbs in the front, and 200lbs in the rear. Rear tyre wear is pretty even, so its not squating too much, front seem firm, handles nice. The internals of the dampeners tho are custom made, and set up to the springs, but are not adjustable.

I found tho the thing that had the most impact was the corner balance, and rasing the car. Sounds a bit suss but I feel like part of the car now, just throw it around etc, no probs.

Id probably go for sway bars. Im finding now with the hight Im getting roll.

Different cars, different suspension set up etc, but gives you an idea on my experiences.

[Ronin 09]

*subscribe*

[Sydneykid]

Hi Roy, I think you know our philosophy pretty well by now. But just in case....

We run the softest spring rate we can and use the stabiliser bars , anti squat and anti dive to control those aspects of chassis motion.

Standard R32GTST springs are ~125 lbs per inch, Whiteline usually add ~30% so that would be ~165 lbs per inch. Kings (based on my experience will be a little higher) around 175 lbs per inch.

In the circuit R32GTST we run between 300 and 450 lbs per inch front springs and between 175 and 250 lbs per inch rear spings. The most common, as you have suggested is 400/200. We run big anti roll bars, 27mm adjustable front and 24 mm adjustable rear. Sometimes 22 mm adjustable rear if is raining or slippery/dirty tack.

With the 200 lbs per inch rear springs, we can get a bit too much squat, so we run the rear subframe bushes to give a little more than standard anti squat. If we don't it lifts the front inside wheel up on corner exit under power. This can give slight understeer which can slow the entry speed onto the straight, and we don't want that.

The 400 lbs per inch front springs are pretty good, not too much dive under brakes. If really necessary we can run a little anti dive on the front radius rod bushes. If you still have excessive front dive then I would suggest the rear brakes aren't doing enough, maybe try a higher coefficient of friction compound for the rear pads (or adjust the brake bias).

Camber, toe and caster you have prety well covered, lot's of caster and as little camber as you can get away with.

Height wise, the staying "low is slow" applies to Skylines. Don't get caught in the fashion statement, around 350 mm centre of wheel to guard is not a bad height. With 10 mm of sill rake to the front on a GTST (GTR's are best flat, zero rake). There must be enough travel to jump the ripple strips without upsetting the balance. If it's on the bump stops, it's too low.

It's shock absorber time..........

The Bilstein rebound valving controls the Whiteline spring and stabiliser bar rates perfectly. One of the reasons why Bilsteins are so good for Skylines is their multiple stage valving, add a bit more spring rate and they handle it easily. We have tried up to 550 lbs per inch in the front and the rebound is still controlled.

Bilsteins are a monotube design, so the piston area is a large as it can be for a given outside diameter. This means the maximum oil is moved for even small movements in the suspension. This is critical for heavy vehicles with lots of suspension travel and high unsprung weight (like an R32/33/34 Skyline). So I would stay away from a twin tube design shock on a Skyline for that reason.

Obviously the Bilsteins have no problems handling the 175/250 lbs per inch rear spring rate as it is only marginally higher than the Whiteline rear coils.

If you want to go over and above the Bilsteins, it becomes very expensive to get anything that is actually an improvement. Jamie Drummond (DMS) does an OK set up, Murray Coote (Proflex) is much better. Then we get to Penske or Ohlins (that's the real Swedish made Ohlins, not the Japanese ones). We run remote cannister Ohlins on the race cars, being double adjustable (bump and rebound) we can control the springs and bars with rebound adjustments. And independantly adjust the dive, squat and roll with the bump adjustment.

Sometimes the combinations of spring, bar and shock rates can get you going in big circles and my brain aches. But once you get a set up that works, the adjustments are fairly small (in a narrow window) and we don't do anywhere near the number of spring changes that we used to with single adjustable shocks.

Hope that was of some help:cheers:

PS; the Whiteline Group 4 shocks for Skylines are progressing, but I am not holding my breath.

[ferni]

I don't mean to hijack but on topic,

I have ohlins height and dampber adjustable coilovers, came with the car, I belive they are the proper swedish ones worth around 5k, not sure what the spring rates are, but don't think they are too hard judging from the ride, if i wind up the damper it does get quite bumpy for daily driving. As mentioned above i have the same problem with diving at the front of the car on the track. I have a whiteline adjustable swaybars front and rear set on hard setting, and whiteline front and rear camber kits and whiteline castor kit... as far as i know no rear subframe bushes (are these refered to as pineapples, if so why?) Haven't heard of anti dive tho? what are these? Is this something i should be looking at getting and do whiteline make them for R33 GTR?

How do you adjust brake bias? I'm putting new pads in this weekend, RB74 front and Comp3 rears.. not sure whats in there at the moment.

you say as little camber as you can get away with - is this because if you run too much camber you don't have enough tyre on the road when braking? how do you know how little camber you can get away with?

how do you corner balance your car? From what i understand they just weigh your car on each corner, but how do you adjust it to balance it? and what real world effect does this have on a race track?

[dangerous_daveo]

...

how do you corner balance your car? From what i understand they just weigh your car on each corner, but how do you adjust it to balance it? and what real world effect does this have on a race track?

Yeah... as I think SydneyKid or Roy explained once when I asked the question. Basically think of the car like a table. If a table is unballanced it rocks, likewise with a car. Just as the car has suspension (or say a bit of carpet on the table, it sits flat) Where the corner ballance works *with hight adj suspension* is the raise and or lower corners to get the weight distribution correct, (like wise with the table, you cut bits off/add bits so its level). Im my cars case its fairly front heavy, so we were also able to bring the weight backwards a bit by rasing the front slightly more than you would a car with better balance to start with.

Real world effect is hard for me to say, as my car was raised about 40-50mm the same day, so my suspension started to work how it was intended to. But the car feels a lot more controlled. It cost me $260, which included a wheel alinement.

[ferni]

40-50mm? must of been pretty low. My car is pretty even height all the way along, i raised the front by 2cm when i first got it because it was sitting like a grass hopper...

How small of an amount can you raise/lower your suspension? is that the only way to adjust the weight balance? (besides physically removing/adding weight)

[dangerous_daveo]

40-50mm? must of been pretty low. My car is pretty even height all the way along, i raised the front by 2cm when i first got it because it was sitting like a grass hopper...

How small of an amount can you raise/lower your suspension? is that the only way to adjust the weight balance? (besides physically removing/adding weight)

My little arms at the front were ___ and they should be like / (just not as exagerated) so basically now the suspension works, before it was hit a bump, in to positive camber. Really I dont give that much of a rats what it looks like. Winners always look good

Just get them to lower corners rather than raise them I guess...

[Sydneykid]

I don't mean to hijack but on topic,

I have ohlins height and dampber adjustable coilovers, came with the car, I belive they are the proper swedish ones worth around 5k, not sure what the spring rates are, but don't think they are too hard judging from the ride, if i wind up the damper it does get quite bumpy for daily driving. As mentioned above i have the same problem with diving at the front of the car on the track. I have a whiteline adjustable swaybars front and rear set on hard setting, and whiteline front and rear camber kits and whiteline castor kit... as far as i know no rear subframe bushes (are these refered to as pineapples, if so why?) Haven't heard of anti dive tho? what are these? Is this something i should be looking at getting and do whiteline make them for R33 GTR?

How do you adjust brake bias? I'm putting new pads in this weekend, RB74 front and Comp3 rears.. not sure whats in there at the moment.

you say as little camber as you can get away with - is this because if you run too much camber you don't have enough tyre on the road when braking? how do you know how little camber you can get away with?

how do you corner balance your car? From what i understand they just weigh your car on each corner, but how do you adjust it to balance it? and what real world effect does this have on a race track?

Pineapples, because they are flat round and yellow with a hole in the middle, like a slice of Golden Circle pineapple.

Too much static camber means too little tyre in contact with the track, when you brake, the front gets even more camber (dynamic neg camber). When you accelerate, the rear gets more dynamic neg camber. You paid for 245 mm wide tyres, you might as well use every mm.

We set camber by measure tyre temperatures at 3 points across the tread, inside middle and outside. If the inside is much hotter than the outside then we have too much negative camber. If the middle is much hotter than the outside and the inside, then we have too much tyre pressure. If the outside is hotter than the inside, then we don't have enough negative camber. Simple.

You are installing new pads, what are the coefficients of friction? If you want more rear braking, go for a compound with higher CoF on the rear.

You can buy brake bias adjusters, there are a large number of different brandss. There are however, only two basic designs, the mechanical leverage style that require individual master cylinders (one for front and one for rear). Or the hydraulic pressure limiting style, that can be used with a single master cylinder.

I assume the R33GTR has ABS, which means you can turn and brake at the same time without fear of locking a wheel. What I generally suggest is to do say 80% of the braking in a straight line and the last say 20% as you are turning into the apex. This means the braking distances are shorter (you brake closer to the corner) and you still have some weight transfer onto the front which helps with the turn in. Plus you have the stabiliser bar working on holding the inside front wheel on the track to match the amount of dive on the outside front.

This is the fastest way around a circuit and why you see F1 car and V8Supercars with the front inside tyre locked up on the way to the apex, when the driver makes a mistake and uses more than say 20% of the braking when turning.

Daveo has already used the table with one short leg analogy. Here is one I preapred earlier...

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What you are trying to do (with corner weighting) is to stop the table rocking diagonally. You can either lengthen the short leg or shorten the other diagonal legs. Either way it will stop the table from rocking. If you have a big pot of soup on one end of the table, moving it around won't stop the table from rocking.

Getting the diagonals to total the same weight is what we are trying to do with corner weighting. So whether the car has 50/50 front to rear (or left to right) weight distribution is not something you can change with corner weighting. You simply want to get the diagonals to total the same weight.

Our race GTST is 62% front and 38% rear and weighs a little over 1200 kgs. It has had all the usual stuff removed, spare wheel, jack, tool kit, boot carpet, rear seats, air con etc. Note that most of that stuff is from the rear of the car. Then I added a bigger engine, gearbox, oil cooler, FMIC, remote filter, extra 3 litres of oil in the sump, larger radiator, bigger front brake rotors, twin plate clutch etc. Most of that weight is in the front, so that's why it ends up at 62/38, it was around 59/41 standard.

You have to physically move stuff to change the weight distribution (front to rear or left to right). This is why circuit race cars have lots of stuff moved from the front to the rear. Battery, dry sump tank, oil cooler pumps, filters, surge tanks (for fuel), brake fluid reservoires, etc etc. The big one is the engine itself, it's heavy, so moving it as much rearward in the engine bay as possible can be quite worthwhile.

When you consider the driver is seated in the right hand side, you also need to make sure that there is as much weight moved to the left hand side in an attempt to compensate. So if I put the battery in the boot, I make sure it is on the left hand side. I see so many Skylines where the fuel system (pumps, filters, tanks) is on the right hand side of the boot. It may be easier to put it there, but it would be better for weight distribution if it was on the left hand side.

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Hope that answered your questions:cheers:

[ferni]

Brake pads: I believe my rear pads Comp3's are higher CoF then my fronts RB74, don't know the figures tho.

The braking 80% in a straight line and 20% (usually lighter braking) as you enter the corner, i think its called trail braking right? I have trouble doing that, because if i'm on my brakes when i enter the corner, the rear wants to come out, i believe because it doesn't have enough weight because all the weight has moved to the front of the car when braking, ie too soft front springs? and maybe something the anti squat and anti lift kits can help? Can i get these for my car? is it worth it?

So what do you adjust to balance the table from wobbling diagonally? Suspension height as Daveo mentioned already?

[pontiff]

Brake pads: I believe my rear pads Comp3's are higher CoF then my fronts RB74, don't know the figures tho.

The braking 80% in a straight line and 20% (usually lighter braking) as you enter the corner, i think its called trail braking right? I have trouble doing that, because if i'm on my brakes when i enter the corner, the rear wants to come out, i believe because it doesn't have enough weight because all the weight has moved to the front of the car when braking, ie too soft front springs? and maybe something the anti squat and anti lift kits can help? Can i get these for my car? is it worth it?

So what do you adjust to balance the table from wobbling diagonally? Suspension height as Daveo mentioned already?

Not buying the table from Sydneys would be a good start. Some of their stuff is cheap and nasty.

[GTRgeoff]

So what do you adjust to balance the table from wobbling diagonally? Suspension height as Daveo mentioned already?

Andrew, both the individual corner heights and the anti-roll bar balances are adjusted to achieve this. Chris at centreline will be your guy.

[Sydneykid]

Brake pads: I believe my rear pads Comp3's are higher CoF then my fronts RB74, don't know the figures tho.

The braking 80% in a straight line and 20% (usually lighter braking) as you enter the corner, i think its called trail braking right? I have trouble doing that, because if i'm on my brakes when i enter the corner, the rear wants to come out, i believe because it doesn't have enough weight because all the weight has moved to the front of the car when braking, ie too soft front springs? and maybe something the anti squat and anti lift kits can help? Can i get these for my car? is it worth it?

So what do you adjust to balance the table from wobbling diagonally? Suspension height as Daveo mentioned already?

Usually the Whiteline stabiliser bar upgrade for an R33GTR is 24 mm front and 22 mm rear. Is that what you are running? Since you are suffering throttle off oversteer, then softening the rear bar will help, as will adding a little more negative camber on the rear. A small amount of rear toe in, say 2mm per side, will also reduce the instability.

Oh, I just had a thought, none of our cars have HICAS, it is the first thing I remove. Do you still have functioning HICAS on yours? If so that's the primary reason for the power off oversteer. HICAS is not your friend on the track or the road, loose it.

Are you using the gearbox to slow the car as well or just brakes? This can cause instability in the rear, my suggestion is to try brakes only, then select the correct gear for the corner.

Adjusting the spring seat height adjusts the weight carried by each wheel.

I wouldn't ever recommend fixating on the front spring rate being too low, it may be that the rear spring rate is too high. The above adjustments will tell you if that is the case.

[TurboX]

Roy I guess you did not respond to my message because you dont want my headaches ;-)

So I will hijack your thread (sorry Mate;-) by asking what can I do about my JIC pillowball Adj Coilovers to make them more comfortable on the normal roads while still being OK on the Track?

I dont know what the spring weights are but can you measure or change them, or is it possible to revalve the shocks without modifying the springs to make them more bearable on the road?

[Sydneykid]

Roy I guess you did not respond to my message because you dont want my headaches ;-)

So I will hijack your thread (sorry Mate;-) by asking what can I do about my JIC pillowball Adj Coilovers to make them more comfortable on the normal roads while still being OK on the Track?

I dont know what the spring weights are but can you measure or change them, or is it possible to revalve the shocks without modifying the springs to make them more bearable on the road?

You can get the springs rates measured, most good suspension shops have a coil rate tester. Or if you tell me the wire diameter, the coil diameter and the number of coils I can work out the spring rate for you. Just post the dimensions up.

[ferni]

I believe they are 24mm front and 22mm rears, whatever is in the handling kit from whiteline...

I still have HICAS, i know lots of people remove that when getting on the track, but i didn't realise/think it would cause my rear to lighten up that much when entering a corner under brakes... so i guess that will be the first thing i try. I'll also try setting the rear bar to a medium setting... negative camber i run around -1.8 on the rear and around -2.2 on the front... I also think i have about 3mm toe in on the rear, none up front...

When approaching a corner i'm normally hard on the brakes while heal-toeing, i'm pretty sure i use mainly brakes to slow me down not gearbox/engine - maybe 80/20 brakes/engine...

First thing on my list is to get rid of the HICAS and soften the rear swaybar, thanks

[Ronin 09]

Hi SK, what sort of spring rates would you recommend to start with for a R32GTR? A little heavier than GTSt I imagine, say 450 and 300lbs?

PS running semis

[Sydneykid]

Hi SK, what sort of spring rates would you recommend to start with for a R32GTR? A little heavier than GTSt I imagine, say 450 and 300lbs?

PS running semis

The rear of am R32GTR doesn't weight much more than the rear of an R32GTST, so we run a rear spring rate that is much the same ie ~250 lbs per inch. The front is around 12% heavier, so your estimate of 450 lbs per inch is a good place to start.