R32 Gtr Suspension Setup - What's Next

[MrStabby]

Currently its;

Tein coilovers, 8.2 front, 6.4 rear corner weighted. Front height 350mm, rear 340mm.

Whiteline adjustable sway bars, front full soft, rear full hard.

Whiteline neoprene? pineapples, IIRC in "traction" position. However, one of the factory subframe bushes is leaking.

Front 3 deg neg camber, rear 1.25 deg neg camber

Nismo radius rods with superpro adjustable bushes

R34 GTR rims with R specs

Ebay attessa tweaker

The car still understeers too much. What's the next step to address that? The car is not a daily anymore so comfort is less important. I've been thinking about;

- Rose joint radius rods (GTSboy seems to be a fan, understood they're not road legal)

- Softer front springs - maybe 7kg? or?

- Alloy pineapples (so the leaking factory bush no longer matters)

- Roll center adjusters - will this help front end grip if i just add them on the front?

Comments?

[GTSBoy]

Yup. More caster needed. Will give more camber in turns. Softer front springs will certainly help grip, but at the cost of body roll. Whether that is important will really depend on your application. If you're driving road/track with rapid left-right-left direction changes, you will dislike having more roll. If high speed sweepers is more your thing, then provided they're not too bumpy you'll benefit from softer front springs (and damping adjusted to suit).

Fixing up the rear subframe bushes will not improve front grip, but may increase your confidence, which can be good or bad depending on your actual talent level!

Roll centre adjusters? Dunno.

[GTSBoy]

Another thing to think about would be altering tyre pressure between front and rear. A couple less pounds can have a big effect.

And what diffs have you got?

[blind_elk]

Things that affect understeer:

reduce understeer by:

- front tyre pressure : higher

- rear tyre pressure : lower

- front tyre profile : higher

- rear tyre profile : lower

- front camber : more negative

- rear camber : less negative

- front springs : softer

- rear springs : stiffer

- front bar : softer

- rear bar : stiffer

[MrStabby]

Yup. More caster needed.

If I go more castor, will that cause upper control arm bushes to flog out? Lots of people seem to have problems with them, but i've been ok so far on stock castor (noltec upper arms). IIRC stock castor is in the 3-4 deg range right? How much do you suggest?

Would the extra rigidity of the rose joint arms be beneficial even it i dont pull in more castor? (less loss of dynamic castor?)

AFAIK they're stock diffs. I *think* i can notice the rear tightness in carparks, but could be my imagination.

Re tyre pressure - does that imply I need to measure temperature across the tread. or just play around with it to see what happens?

Thanks!

[White GTS-T]

Where abouts through the corner is the car understanding? Entry, mid, exit?

[blind_elk]

With the attesa tweaker, have you read Julian Edgar's article on his early attempts to build such a device? Quite interesting how attesa works.

After what I said above, I would recommend taking a bit of camber out of the arse end, to 1, maybe even .75 -ve. And pump an extra 2psi into the front tyres.

[White GTS-T]

Also what toe F & R are you running?

[MrStabby]

Where abouts through the corner is the car understanding? Entry, mid, exit

I'm going to say entry. It could be I dont really know what im talking about.

Toe is zero front, and IIRC zero at the rear too.

BlindE - i read an old ?autospeed? article about it, is that the one? The tweaker makes a huge diff compared to stock. Don't know how much better the ruzic etc ones are. However, there's too much understeer when no power is applied.

[KiwiRS4T]

I run 6deg caster cornered great with 3deg neg front camber and 1.5 deg rear (that's on a Stagea mind you).

[White GTS-T]

I would start by running some toe out on the front, that will help with turn in. Run some more positive castor and soften the dampers on the front (if fitted)

[GTSBoy]

If I go more castor, will that cause upper control arm bushes to flog out? Lots of people seem to have problems with them, but i've been ok so far on stock castor (noltec upper arms). IIRC stock castor is in the 3-4 deg range right? How much do you suggest?

Would the extra rigidity of the rose joint arms be beneficial even it i dont pull in more castor? (less loss of dynamic castor?)

AFAIK they're stock diffs. I *think* i can notice the rear tightness in carparks, but could be my imagination.

Re tyre pressure - does that imply I need to measure temperature across the tread. or just play around with it to see what happens?

Thanks!

I was going to reply to this and then got massively sidetracked. So there are a few replies above this one that cover a lot of what I was going to say. Basically you need to wind on as much caster as you can. That's typically in the 5-6° region. I don't have my catser rods as short as it is possible to make them because I feel it makes the front suspension bind up too much, plus I get some rubbing.

I also suggest a little toe out. Certainly up to 1° at the front will make it more willing to turn in. It will not actually reduce understeer once into the corner though.

Toe out at the rear will make the rear more willing to come around. So it will be less settled, more twitchy and active. That will make it behave as if it has less understeer. Whether it is faster or not will agani depend on how good you are I suspect.

[djr81]

For all the castor enthusiasts (fkn drift has ALOT to answer for, this being just one thing) a stock 32 GTR runs, wait for it: Fk all camber. 3 degrees and forty minutes. Trying to run more puts the top, outer link out of alignment and if you run a rose joint castor rod you will screw the bushes once per track day. If you want more castor you need to modify the top link and the mounting point on the chassis not just wind up the rose joint as many people do.

All castor is is more camber when the wheel is turned. As most GTR's are underbraked anyway you dont need the castor to pick up the camber, you can just run more camber. It is just that the drift nuggets like it as it means they can let go of their steering wheels and freed from the muppet behind the steering wheel their cars will return to travelling in a straight line.

If you want a gain there are two things I would do as a first step:
1. Replace the the stock upper link mounting bracket with either a Nismo item or a stock item remanufactured to be like the Nismo geometry or run one of those top links with the bearing in the middle of it (which I dont much like but each to their own)

2. Soften the front spring.

Put the pineapples in the normal position, not the traction position as the thing shouldnt oversteer on corner exit anyway. If it does push more torque toward the front with your attessa do hickey.

Bottom line it is a GTR and with such awful weight distribution it will understeer. You have to drive around it and make lap speed by a late turn in and early power down rather than trying to flow the thing with bulk speed at the apex. Dont overdrive the car as that prompts plough understeer mid corner and canes your lap speed.

Edited October 28, 2013 by djr81

[GTSBoy]

^ It's a valid point. Hence why I don't have my caster rods wound up to drift spec. But a little extra caster is free grip in corners without wearing out the insides of tyres while driving straight - which is a priority for my daily.

[White GTS-T]

Agreed. We stated that some extra castor will help, it's not like we said to wind in as much as possible, even couple of degrees would be of benefit. Too much castor on a drift car equals positive camber on the inside wheel at opposite lock anyway. And although its been three years since my last drift day, I do try my best to 'feed' the wheel as much as possible, but i'm not as good at it as I would like to be.

[Dan_J]

considering how cheap gk tech front RCA's are theres no point in not trying them out

you wheel track also plays a part so make sure front and rear is equal or front has more track then rear

try stock gtr front sway bar and i've also noticed once changing my worn rear sway bar bushes this made the car more oversteery

edit: make sure current castor settings are equal ( loose bolts, bent parts, bent car) as if not this also deals out understeer

Edited October 28, 2013 by Dan_J

[Roy]

Whole discussion is rather mute without knowing the tyres you run. What R-Spec?

[djr81]

^ It's a valid point. Hence why I don't have my caster rods wound up to drift spec. But a little extra caster is free grip in corners without wearing out the insides of tyres while driving straight - which is a priority for my daily.

A little extra castor drags the bottom of the front suspension forward. A couple of degrees turns out to be quite a distance. So what do you do to compensate for that? Most people do nothing and scrape the tyre on the front of the guard liner but it should also be adjusted at the top by reducing the trail on the upper link. Unfortunately there isnt anyone out there making a decent upper suspension link any more.

Oh and roll centre adjusters arent easy. They are a pain to install given how difficult it is to get the old stuff out and apart. Particularly at the rear.

[MrStabby]

If you want a gain there are two things I would do as a first step:

1. Replace the the stock upper link mounting bracket with either a Nismo item or a stock item remanufactured to be like the Nismo geometry or run one of those top links with the bearing in the middle of it (which I dont much like but each to their own)

2. Soften the front spring.

What would you go for? 6kg/ 7kg?

Whole discussion is rather mute without knowing the tyres you run. What R-Spec?

Its 'moot' not 'mute' Also - I would have thought that the type of tyres could not effect under/oversteer balance - am i wrong?

[White GTS-T]

Not really, unless you were running different compounds front to rear. But as people have mentioned, different pressures would.