Roll Centre Adjustment On R32 Gtr

[Beer Baron]

Hi guys,

I'm interested to hear from anyone who has spent some time with roll centre adjustment on an R32 GTR and what effects it had on the handling of the car. of course for track use.

Cusco make a kit to allow roll centre changes. Costs around $1500. Pics here (it's the kit on the far right).

[djr81]

I posted something similar a while back. Got nothing by way of a reply.

I have thought about it in the interim & come to these conclusions.

Having a roll centre inclined going forward is good. It transfers load to the rear tyres & lessens understeer. Unfortunately, on a GT-R there is too much roll to begin with. So lowering the front roll centre more will only increase the cars body roll. The down side of this is less grip due to the car rolling over the edge of the tyre.

But it might just work is you can also dial in some more -ve camber at the front.

[BHDave]

Does anyone have any pics of some of these things mounted?

I just can't get my head around how they'd fit

[djr81]

The spacer goes just above bottom arm on the outside lower link. It physically moves the pivot point thus changing the inclination of the arm & hence migrating the roll centre.

Edited February 12, 2007 by djr81

[Beer Baron]

hmm, it has me interested. but I already stuggle a little with set-up. currently have

front upper arms (midori, but switching to noltec)

front castor rods (cusco)

rear upper arms (cusco)

rear traction rods (ikeya formula)

adjustable front and rear whiteline sway bars (but about to switch to cusco non-adjustable)

nismo G attack R-tune suspension (the remote canister ohlins ones, 600 different bump/rebound settings per shock - 20X30 plus height of course)

so you can see I already have a shitload of variables to deal with so I'm wondering if this is one more variable I dont need? On the other hand is it not adjustable? Ie, you just bolt it in, and it changes the roll centre but with no scope for tuning that change?

[salad]

I remember reading this thread a while ago

http://www.skylinesaustralia.com/forums/in...hl=roll++centre

Might help a little

[STATUS]

i use them on cats drift car, Moon Face Racing not cusco. The cusco are by far the better but 3 times the price.

It is very common for the roll centre to go sub terrenial when lowering and i can tell you on the S13 it made a huge differrence to the way it turned in and held poise mid corner. In a GTR i would assume a far greater benefit due to the larger mass transfers.

The CUSCO one has the advantage of radius/caster rod geometry correction also.

The MFR ones for the Front and rear are basically ball joints with 25mm extra length, the front of my car used Nagista lowers arms to combat the roll centre problem, but i gave them to Mark from exhaust tech to try in his S15., i think they are still in there.....

[djr81]

i use them on cats drift car, Moon Face Racing not cusco. The cusco are by far the better but 3 times the price.

It is very common for the roll centre to go sub terrenial when lowering and i can tell you on the S13 it made a huge differrence to the way it turned in and held poise mid corner. In a GTR i would assume a far greater benefit due to the larger mass transfers.

The CUSCO one has the advantage of radius/caster rod geometry correction also.

The MFR ones for the Front and rear are basically ball joints with 25mm extra length, the front of my car used Nagista lowers arms to combat the roll centre problem, but i gave them to Mark from exhaust tech to try in his S15., i think they are still in there.....

If you can get them for the rear & assuming they reduce the roll couple (ie raise the roll centre) I, for one, would be very interested.

Subterrestrial roll centres are a side effect of McPherson strut suspensions when lowered too far. Hopefully the Skyline suspebsion doesn't do this. Unfortunately I have been far too lazt to measure up the links & actually plot the roll centres front & rear.

Baron, what diameter are the Cusco sway bars and are they solid or hollow?

Edited February 12, 2007 by djr81

[STATUS]

Unfortunately I have been far too lazt to measure up the links & actually plot the roll centres front & rear.

Ditto

[STATUS]

If you can get them for the rear & assuming they reduce the roll couple (ie raise the roll centre) I, for one, would be very interested.

http://www.moonface.co.jp/mfr/roll/index.htm

They even have a tight ass option (sleeve)

[Beer Baron]

i use them on cats drift car, Moon Face Racing not cusco. The cusco are by far the better but 3 times the price.

It is very common for the roll centre to go sub terrenial when lowering and i can tell you on the S13 it made a huge differrence to the way it turned in and held poise mid corner. In a GTR i would assume a far greater benefit due to the larger mass transfers.

The CUSCO one has the advantage of radius/caster rod geometry correction also.

The MFR ones for the Front and rear are basically ball joints with 25mm extra length, the front of my car used Nagista lowers arms to combat the roll centre problem, but i gave them to Mark from exhaust tech to try in his S15., i think they are still in there.....

thanks trent that is some good info. I'm thinking that this may be worthwhile now that most other aspects of the suspension is covered. my last bits will be rear lower arms and possibly front lower arms. I alread have hicas disabled too. as the car is lowered I think the roll centre adjustment could be worthwhile. I'm still really keen to hear from someone who's done it on a 32 though. judging from daves thread it seems not many people have bothered on a 32.

[djr81]

http://www.moonface.co.jp/mfr/roll/index.htm

They even have a tight ass option (sleeve)

Do they have an English option? Can't make head nor tail of that lot.

[Beer Baron]

Baron, what diameter are the Cusco sway bars and are they solid or hollow?

firstly quit the laziness! pull a finger out and measure (so I dont have to) lol.

lucky for you I brought the cusco 2007 goods master to work today so I can answer that question.

they are:

front: 20mm id, 24mm od (and quoted as 192% stiffer than stock) hollow.

rear: 25.4mm id, 30mm od (and quoted as 162% stiffer than stock) also hollow.

both are not adjustable.

I've felt them and they are shitloads lighter than the whiteline ones. I am hoping they are a bit less stiff as well. Since I've switch to the nismo/ohlins dampers they are running 10kg front srping and ~9kg rear spring so I want to go to a lighter (less stiff) bar. going to try the cusco ones, and if they don't work either the nismo ones, or go back to my stock ones.

From my people in japan they tell me the order of stiffness of the big brand japanese stabilizers is: ARC-Cusco-Nismo. and price wise cusco is the cheapest, then ARC I think, then nismo.

Trent, thanks for the link. I will have to look into pricing some of those up.

[STATUS]

I know rear is a big issue on all skylines, i remmeber talking to the owner of NAGISA in japan (Nissan R34 Skyline GTR (R34) - Current record holder, Central Circuit Super Lap) and he as well as SUNLINE MFR all do kits for the rear. CUSCO is the only one i know that does a bolt on for the front. most are complete arms.

http://www.nagisa-auto.com/

Edited February 12, 2007 by URAS

[Beer Baron]

Do they have an English option? Can't make head nor tail of that lot.

lol, time to study up the ol' kanji! or at least some kana. most of it's kana anyway. if you click on the pics it will take you to the application and retail price listings.

[djr81]

From the blurb they look like the lessen the front roll couple (ie raise the roll centre). Which is good in one way - makes for less front roll & therefore better front tyre grip.

On the flip side you don't get the weight transfer to the rear which may well promote more understeer.

You would therefore have to expect the better front tyre camber outweighs the lesser load transfer front to rear....

[STATUS]

From my people in japan they tell me the order of stiffness of the big brand japanese stabilizers is: ARC-Cusco-Nismo. and price wise cusco is the cheapest, then ARC I think, then nismo.

I have my NISMO power book handy if you need some specs, its a bit dusty so i should open for a good reason.

[Sydneykid]

Basically these kits are not actually designed for “modifying” the roll centre. They are designed to “put back to standard” (or close to standard) the roll centre after you have lowered the car too much. That’s why they work so well on the McPherson strut front end cars like S13/S14/S15, they give back the standard roll centre. Simply put, Nissan were right in the first place.

If you are looking at correcting the roll centre, then you need to also be conscious of the anti squat geometry in regards to the radius rods front mounting. It may be necessary to also correct that at the same time.

With GTR’s you have to contend with the added complication of front drive shaft angles when you lower them too far.

The best answer = don’t low it too far.

cheers

[STATUS]

Basically these kits are not actually designed for “modifying” the roll centre. They are designed to “put back to standard” (or close to standard) the roll centre after you have lowered the car too much.

Glad you added that, i take it for granted people would assume as such but yeah, well said.

[Beer Baron]

lol, yeah got the nismo book at home somewhere! but I'm pretty sure the nismo bars are not as stiff as the cusco ones. and I think the whiteline ones are far stiffer than any of them (except maybe the ARC ones).

to be honest the whiteline ones worked very well with my old set-up which was bilstein shocks with eibach springs. the fairly light springs were complemented nicely by the big bars (rear on full hard, front on medium), but with the new ultra high srping rates I feel it's a bit too stiff, and some lighter bars will bring it back into balance. if it's no good I'll just put the rears in the front and buy some 7kgs or 8kgs for the rear.