R33 Gtr Coilovers/swaybars

[kamakazi1122]

Hi Guys,

I'm looking for a new set of coilovers and swaybars for my gtr and hopefully eliminate some understeer. Currently its stock swaybars with Tein Super Streets (4F/4R same as vspec). I've been looking at Cusco and Nismo products mainly and its lead me to a bit of a conundrum.

The nismo swaybars are about halfway between stock and cusco in size and the S-Tune coilovers are 6F 6.7R
The cusco stuff swaybars are 160% increase on front and 130% rear, with the Zero A suspesnion being 10F 8R (can get other rates), so im guessing these may increase understeer?

My issue lies in two parts 1) why do some brands run a stiffer rear than front and vice versa or even same front+rear, is the stiffer rear better to reduce understeer? 2) are the Nismo (if any) the only ones designed for use with HICAS still in place?, as my HICAS works perfectly.

I've read a few build threads here and on GTR.co.uk and peoples coil and swaybar rates arent mentioned to often. If anyone can throw some advice my way it would be appreciated.

[GTSBoy]

GTRs are understeery cops owing to the extra weight at the front, so some effort is usually spent on softening the front end relative to other Skylines. For example, where you might run 6F/4R on a GTSt, you'd go closer to same F/R or even slightly stiffer rear, exactly as you say, for the purposes of taming the understeer.

So anything that moves stiffness forward, whether it's springs or ARBs, will tend to increase understeer.

But.....there's understeer and there's understeer. For some, increased turn in and responsiveness from stiffening the front a bit might make it feel less "understeery" because the car will start to turn better. So urban roundabouts and whatnot will feel better. For others, you need to know that it won't run wide and off the track in the middle of a long and really fast corner on the track (or worse, in the hills!). In that case, you'd be careful about biasing the rates forward too much.

FWIW, even though my car is a GTSt and so doesn't directly translate, I have put 24mm bars on both the front and rear of my car. Springs are a set of Whitelines (so they suit each other - there's no wierdness hiding in there that I'm masking with the ARBs). The ARBs are set stiffest at front, softest at rear - but this should still be more rear bar than most people would run. Most would go for a 22mm at the rear and still set that softer than full. I like the balance that I have as a result - but then I hate understeer. Anyway, the point it, unless it turns it into a twitchy oversteering monster, you can probably get away with a lot more rear stiffness than a lot of people expect.

[Arkhaeon]

I think of sway bars as a fine-tuning tool - I'd suggest getting spring rates correct first, then sway bars to balance the car how you like.

In your case, probably go a heavier front spring to add response to that boaty front end, then a larger rear sway bar (relative to front; upgrade both) to dial out understeer.

I'd suggest starting with an aggressive wheel alignment however. Make the most of the hardware you have now, then base upgrades from there. Deciding on a style of driving will make the setup process a lot clearer, too. If you want to do twisty low speed stuff, your setup will differ from high speed runs.

[kamakazi1122]

Thanks for the responses guys, I'd really like to hear about what swaybars and rates people are currently running in their street and track R33/R34 gtr's

Seems as though most people like to keep their settings a closely gaurded secret

[djr81]

Hi Guys,

I'm looking for a new set of coilovers and swaybars for my gtr and hopefully eliminate some understeer. Currently its stock swaybars with Tein Super Streets (4F/4R same as vspec). I've been looking at Cusco and Nismo products mainly and its lead me to a bit of a conundrum.

The nismo swaybars are about halfway between stock and cusco in size and the S-Tune coilovers are 6F 6.7R

The cusco stuff swaybars are 160% increase on front and 130% rear, with the Zero A suspesnion being 10F 8R (can get other rates), so im guessing these may increase understeer?

My issue lies in two parts 1) why do some brands run a stiffer rear than front and vice versa or even same front+rear, is the stiffer rear better to reduce understeer? 2) are the Nismo (if any) the only ones designed for use with HICAS still in place?, as my HICAS works perfectly.

I've read a few build threads here and on GTR.co.uk and peoples coil and swaybar rates arent mentioned to often. If anyone can throw some advice my way it would be appreciated.

Most suspension suppliers default to chosing a front spring rate then knocking a kg/mm or two off it and fitting that to the rear. Nismo actually spent some time on the GTR and put a softer front spring in it. Understand too that what you want on the road and on the track are two completely different things. For the road you want a softer rear.

The balance you are trying to get is between mid corner balance (its a GTR it will understeer in spite of anything you may try - it is just the amount that changes) and corner exit balance (usually oversteer as the ATTESSA isnt as good as it should be). The point to note is that on a 32 (with a less responsive attessa) Nismo use a softer rear spring for traction. If you can get away with more front torque on corner exit (by using an attessa controller) you can use a softer front spring for better front grip.

Sway bars can then help a little further - same philosophy - just for tuning. Soft front hard rear. Good luck trying to compare a Nismo rate to a Cusco rate to a Whiteline rate, however they all speak different languages.

Wheel alignment is the least effective tuning tool. So comes last.

[kamakazi1122]

Thanks mate, I did some research and it seems the Cusco 30mm hollow rear bar is just about equivalent to a 23mm whiteline solid bar in terms of stiffness due to sidewall thickness and material. So the 24mm whiteline bar on the hardest setting appears to be the stiffest rear swaybar I've found thus far.

having left the HICAS in place which appears to differ from what most people do I'm wondering if I should go with what Nissan/Nismo seem to do standard and keep the rear spring same /or just higher than the front.

I'm trying to save myself the time and money of having to go through heaps of combinations to find what I want

[djr81]

Thanks mate, I did some research and it seems the Cusco 30mm hollow rear bar is just about equivalent to a 23mm whiteline solid bar in terms of stiffness due to sidewall thickness and material. So the 24mm whiteline bar on the hardest setting appears to be the stiffest rear swaybar I've found thus far.

having left the HICAS in place which appears to differ from what most people do I'm wondering if I should go with what Nissan/Nismo seem to do standard and keep the rear spring same /or just higher than the front.

I'm trying to save myself the time and money of having to go through heaps of combinations to find what I want

Well firstly I doubt that a 23mm solid bar would get near a 30mm hollow bar unless the level arm was massively shorter or the wall thickness was very thin. So I am going to go out on a limb and say wherever you got that from is spouting nonsense. I changed a rear Whiteline for a Cusco and the Cusco is stiffer.

I cant answer you second question for you. It depends on how much stiffer you are prepared to/wanting to go and it depends on what type of spring you have. If they are (for arguments sake) 65mm id springs they are cheap as chips and easy to swap out. If they arent it is harder and more expensive.

For what it is worth there is nothing special about Tein or Nismo S tune shockers anyway.

The HICAS is really neither here nor there. I ditched mine because it didnt help and frankly the back end can be steered with the throttle pedal. Dont need a heap of computers to do that for me. But again it depends on what you are after. On the road on road tyres is different from on the track on track tyres.

If you want an opinion (worth every cent you pay for it) 10/8 as a spring combination is just stupidly hard and will shit you to tears. Go softer.

[GTSBoy]

Just on bar stiffnesses.......assuming same material and same arm length, then the following numbers are instructory as to how stiff various bars will be relative to each other.

24^4 (that's 24mm raised to the fourth power) = 331776 arbitrary stiffness units.

32^4 = 1048576 arbitrary stiffness units

So a solid 32mm bar is 3 times the stiffness of a 24mm solid.

This is where it gets interesting. A 32mm bar with 1mm walls is (32^4 - 30^4) = 238576 = 72% of the stiffness of a 24mm solid.

A 32mm bar with 2mm walls is 433920 = 130% of the stiffness of a 24mm solid.

A 32mm bar with 3mm walls is 591600 = 178% of the stiffness of a 24mm solid.

So as djr81 said above, you'd have to have a very thin wall 32mm bar to match a 24 solid. And there is a very rapid change in stiffness as the walls get thicker. Also, the material used to make the bars is not going to have a very big effect. There's only so many different materials suitable for making springs out of (ie that have decent fatigue life and so on) and they don't have a massive variation in modulus of elasticity.

Also.....how the hell do you bolt a 32mm bar to a Skyline? At the rear it would be so fat that it would probably rub on the tailshaft. At either end of the car it would be hard to arrange for brackets to bolt it to the body. Do they have a special bracket that comes with it?

[Arkhaeon]

Also.....how the hell do you bolt a 32mm bar to a Skyline? At the rear it would be so fat that it would probably rub on the tailshaft. At either end of the car it would be hard to arrange for brackets to bolt it to the body. Do they have a special bracket that comes with it?

Yes, they come with new D bushes to accommodate the larger bar.

[GTSBoy]

Hmmmm. D bushes that big won't fit into the original brackets, and the brackets would be so big that you would not be able to access both bolts holding it to the chassis. That's why I asked.

[djr81]

...and they don't have a massive variation in modulus of elasticity....

Bloody engineers. FFS etc.

[kamakazi1122]

#@GTSBoy The sizing i got for the wall thickness for cusco was 1.2Xmm or close too, but that's from the internet so who knows if it's legit. by the sounds of it it's potentially slightly stiffer like #@djr81 mentioned than the 24mm whiteline.

The cusco site gives a % increase over standard of 160% for front and 130% for rear using their bars and they seem to be the only ones who do this.

[Arkhaeon]

They were saying 30mm, not 32mm. Factory rear 33GTR bushes are 26.5mm, so an extra 1.75mm on either side will definitely fit in the stock bracket.

http://www.cusco.co.jp/2013_cusco_catalog/#242/z - I think that tells us 1.0mm wall thickness.

It would be nice if Whiteline actually tested their bars. When I phoned them to ask how stiff compared to factory their S15 bars were, they got quite short and snappy, saying they don't test things like that. "Our bars are better. Made from better materials and thicker" - That doesn't help me set the balance of my car, idiots.

How the hell do they expect to know if their bars are any good if they don't test them? I can't imagine it being that hard to grab the stock bar, give it a reef, then grab the new bar and do the same thing. Surely they have the stock bar there in order to make the new one.

[GTSBoy]

A 32mm bar with 1.2mm wall thickness will be ~85% the stiffness of a solid 24mm bar, all other variables being the same. Turns out to be exactly the same as a 23mm bar.

Edit. Sorry - missed that it was actually 30. Don't know why I went straight to 32.

Anyway, to then correct the top part of this post, a 30mm bar with 1.2 wall will be 70% of the stiffness of the solid 24mm. About 82% of a solid 23mm.

Still can't see a 30mm bar fitting inside a useful bush inside the stock D bracket.

Edited December 17, 2013 by GTSBoy

[GTSBoy]

Factory rear 33GTR bushes are 26.5mm.

Not in the hole in the middle they're not. Surely that's the outside dimension of the bush.

[kamakazi1122]

Superpro site lists a whole bunch of different sizes and this ebay ad for nolathane is different again

http://www.ebay.com.au/itm/SKYLINE-SILVIA-S15-R33-R32-R34-NISSAN-REAR-SWAY-BAR-MOUNT-BUSH-NOLATHANE-42478-/321272193316?pt=AU_Car_Parts_Accessories&hash=item4acd50a124

So in summary, have we concluded that the whiteline is the stiffer rear swaybar?

Edited December 17, 2013 by kamakazi1122

[Arkhaeon]

Not in the hole in the middle they're not. Surely that's the outside dimension of the bush.

You're such a Negative Nancy! The rear sway bar is 26.5mm in outer diameter. The associated bush has a 26.5mm inner diameter. There is approximately 4mm of rubber between the sway bar and D shackle.

Now that we know the Cusco bar does in fact fit, can we get back to the topic at hand?

[GTSBoy]

Yeah, that Nolathane listing for R33 GTR shows 18mm hole for bar, which I would believe. Standard R32 GTSt rear is only 14mm (I think. I measured the one on the shed floor not long ago, but can't remember exactly. Anyway, it's skinny).

So, looking at this picture, you can see why I reckon you'd have a hard time fitting 30mm bars into any standard bracket

http://www.nolathane.com.au/images/bush_id/bush4.gif

And, yes, apart from the occasional talk of 26 or 27mm solid bars, I don't think there's a lot out there that would be stiffer than the Whiteline 24mm.

[djr81]

No. The Cusco sway bar is more likely to be of the order of 4.5mm wall thickness.

Edited December 17, 2013 by djr81

[GTSBoy]

You're such a Negative Nancy! The rear sway bar is 26.5mm in outer diameter. The associated bush has a 26.5mm inner diameter. There is approximately 4mm of rubber between the sway bar and D shackle.

Now that we know the Cusco bar does in fact fit, can we get back to the topic at hand?

The Whiteline 22mm bar is an UPGRADE from the stock bar. How could the stock bar be 26.5mm?

Edited December 17, 2013 by GTSBoy