Jump to content
SAU Community

Recommended Posts

ok.. for all you suspension gurus..

weres the perfect roll centre position on a r32 gtr. front and back.

ie.. below the road, on the road, or at the middle of the wheel etc etc. (at a sitting position,not tilting(static roll centre)

cos im gonna start having a play with it to get some more corner speed and reduce my spring rates.. :D

or.... should i basicly return it to where the factory had it ? (before i lowerd it)

any input is welcome is a think thisa area is almost always overlooked :yes:

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/
Share on other sites

ok... i did a search and revealled that yess it changes when you lower the car.

well darrr

i need to know WHERE is a happy meduim for roll centre placement front to back.

as in front 20mm above the ground, rear..50mm aboove he ground etc etc

hope this makes sence.

the reason for this topic is that we (my work) are partly preparing a s14 for "production sports" and as it sits 50mm lower than stock the front roll centre is 1 METER BELOW THE GROUND..

at stock height it is pretty much at the surface. (without puttling on a 100% leval surface with laser angle guages etc etc)

not at all desirable :D

thanx :yes:

so summing up what IN THERORY is a good position for the centres

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2315326
Share on other sites

Theoretically the best location for the roll centre is slightly below the centre of gravity.

When you change the ride height, you change the c of g, however.

When you change the ride height, you change the suspension geometry which changes the roll centre.

When the car rolls, you change the suspension geometry, which changes the roll centre.

The front roll centre will be at a different height to the rear roll centre to help transfer load away from the front tyres when cornering.

If someone has set a roll centre to be a metre below the ground they will be cornering the car on its door handles.

What you need to do is measure up & model the suspension geometry as a first step...

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2317053
Share on other sites

ok... i did a search and revealled that yess it changes when you lower the car.

well darrr

i need to know WHERE is a happy meduim for roll centre placement front to back.

as in front 20mm above the ground, rear..50mm aboove he ground etc etc

hope this makes sence.

the reason for this topic is that we (my work) are partly preparing a s14 for "production sports" and as it sits 50mm lower than stock the front roll centre is 1 METER BELOW THE GROUND..

at stock height it is pretty much at the surface. (without puttling on a 100% leval surface with laser angle guages etc etc)

not at all desirable :O

thanx :O

so summing up what IN THERORY is a good position for the centres

SK, rule of thumb for McPherson struts. Space the lower control arm from the upright by the amount you have lowered the car. This returns the lower control arm to the same angle as it had before you lowered the car too much.

SK tip, don't forget to correct the bump steer.

What are doing about the rear?

:O cheers :P

Edited by Sydneykid
Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2317276
Share on other sites

djr81. yess im aware of all this thanx but i need a xxmm etc etc not "its differant.. higher roll centre at the front ,lower ????

yeap. s14 front end is crap. (for lowering) that was doing the corect mesurements and using a angle guage and making a scale drawing..

of the top of my head the arm centreline sits at 6 deg up (noooo good) following directions from a book called "how to make your car handle" i forget the author

sk.. i was thinking of doing that to the front. easy as. (thanx phuil ryal:P)

rear.. hmmm well i dont want to have to buy ikea formular lower arms c

as there REALLY EXPENCIVE but it would be easy to just make up a variety of spacers for them. i think replacing the outer joint with a sperical ball joint seems the only practical way.

but yeah i think lowering the outer lower balljoint seems to de the go. but.. il have to draw them to see if a upper arm pivot adjustment is more feasable

yeah bump steer corection goes with out saying i spose. front and rear?

im gonna do some drawings and see if i have to lower the outer arm end the same amount as the cars been lowerd?

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2318932
Share on other sites

Dave,

I am a little confused - are you asking after the S14 or the R32? Because answers to the question will be different depending on which car you are looking at.

On the assumption it is the R32:

Mostly making suspension adjustments amount to trying to reduce the worst effects of the limitations of the stock suspension eg too little camber compensation in roll on the front end of the GT-R and too much on the rear.

If you are talking about the GT-R don't worry about the rear end too much - focus on the front as that is where the gains are to be made.

With regard to the roll centres (Note plural). The idea is to incline the roll axis (an imaginary line plotted between the two centres) forward. This allows a transference of load away from the fron end of the car and hence reduces understeer. This is the reason R32's are sensitive to rake.

How are you going to measure your centre of gravity? I ask because it is the roll couple you are really chasing rather than just the roll centres.

Edited by djr81
Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2319722
Share on other sites

yeah im talking about the 32.

so i should aim for making the roll centre of the front higher than the rear?

this is my main question.. ^^^^^^^^^^^^^^^^^^^^^^

the purpose for me carieng out this adjustment is purly to reduce roll. and soften it up so i can carry more corner speed. rather than stifening it up so it goes slower :wave:

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2327124
Share on other sites

Run it at 355 mm centre of wheel to guard at the front and 345 mm at the rear. Use a 24 mm solid front adjustable stabiliser bar on the softest setting. A 24 mm solid rear adjustable stabiliser bar on the middle setting. The rear spring rate needed is ~250 lbs per inch (4.5 kg/mm), the front is ~400 lbs per inch (7.2 kg/mm). Set the rear subframe alignment bushes to the "all round setting". Try for 6.5 degree of positive caster on the front, with 3.5 degrees of negative camber and 2 mm of toe out each side. On the rear, 1.5 degrees of negative camber with zero toe out.

Then adjust the camber for even tyre temps. If it needs more than 4 degrees negative camber on the front, then you don’t have enough bump valving in the shocks.

Once you achieve even tyre temps, then you can adjust the stabiliser bare to achieve the handling balance you like. If it still understeers on corner entry, try another 2 mm of toe out on the rear. If you get mid corner understeer and the front tyre temps are even, then increase the rear ride height, 5 mm is usually enough. If it power oversteers and the rear tyres temps are even, then back off the rear bar I hole. If it still power oversteers then change the rear subframe setting to “max traction”.

“Take 2 panadol and call me in the morning”

:wave: cheers :laugh:

Edited by Sydneykid
Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2327176
Share on other sites

ic.

thanks for that.

heres my curant setting.

front=

9deg caster

3deg neg camber

1mm toe out each side

8kg springs with bilsteins (nismo kit.old one)

whitline 24mm adj bar. softest setting

rear=

2deg neg camber.

2mm toe in each side

7kg rear springs with bilsteins (old nismo kit)

whitline rear bar softest setting

5mm rake (front lower)

the car is taily as f**k. removed the rear bar and it slightly improved.

turn-in is really sharp. mid corner oversteer

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2327203
Share on other sites

changing the springs is not an option yet.

its easier for me to adjust the roll centre, well i wanna get it in the ball park. but noone seems to know or have actually done this on a skyline :wave:

FRONT ROLL CENTRE HIGHER OR LOWER THAN THE REAR ROLL CENTRE?

sorry for caps. but this is ALL i need to know at the moment. as im ready to adjust :laugh:

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2327225
Share on other sites

changing the springs is not an option yet.

its easier for me to adjust the roll centre, well i wanna get it in the ball park. but noone seems to know or have actually done this on a skyline :kiss:

FRONT ROLL CENTRE HIGHER OR LOWER THAN THE REAR ROLL CENTRE?

sorry for caps. but this is ALL i need to know at the moment. as im ready to adjust :wub:

The rear spring rate is way too high, hence the oversteer. Changing the roll centre will accomplish nothing. It’s not a geometry issue, it’s a tyre contact patch issue. The tyres are skipping from bump to bump. Changing the roll centre will not affect this.

:) cheers ;)

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2328202
Share on other sites

changing the springs is not an option yet.

its easier for me to adjust the roll centre, well i wanna get it in the ball park. but noone seems to know or have actually done this on a skyline :dry:

FRONT ROLL CENTRE HIGHER OR LOWER THAN THE REAR ROLL CENTRE?

sorry for caps. but this is ALL i need to know at the moment. as im ready to adjust :D

Lower.

Sorry.

LOWER.

Link to comment
https://www.sau.com.au/forums/topic/125378-roll-centres/#findComment-2328856
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • My experience with Rising Sun Exports Before agreeing to the sale I tried to do as much research as I could (obviously), his Facebook reviews are 98% and he goes Live at least once or twice a week. I contacted 2 people in the UK who had used him for their imports, both had positive feedback. His explanation and talk through of the import process was thorough, answering any query no matter how stupid it was. It felt as soon as the money was sent, communication dropped off. I asked for shipping updates every 2 weeks or so, not wanting to pester him, he never had any updates. I wasn't informed the car had been dropped off at the port, I only found out by his Facebook story. I asked for the photos taken at the port, knowing he would need some for insurance purposes. I received a few 5 second clips and that's it. When asked again, he said his staff had them. Weeks later I asked again, he tells me he doesn't have any, but does have 50 photos from the original advert. I never received them. I eventually got the documents sent via WhatsApp after I mentioned the port was requesting them. I purchased a CarVX report, to find out the vehicle is a Grade R with recorded accident damage, first recorded in 2017 when it was first auctioned. He never told me the grade, then again I didn't ask. His response was "Grade R means nothing, it wasn't chassis damage". Still, I would have liked to have been informed about it. Jon prides himself on being open and honest when it comes to inspecting cars, it's his main job doing so at the auctions for customers. When the vehicle arrived in the UK I noticed a few little cosmetic issues. It's a 21 year old car so it wasn't going to be mint condition. The side skirts are cracked on each corner and the sealant is failing. The front grill on the bonnet/hood isn't secured very well, mounting studs are missing. Both minor things, but again, it would have been nice to be told. During a Facebook Live walk around video of the vehicle, he mentioned it has a front Whiteline anti roll bar/sway bar. While on the inspection ramp, I noticed the stock item has been installed. When first questioned, his response was "the ARB? Switched? Since when, it never had them". Since sending video and photo evidence I've not received a response. I'm probably being over critical of the overall condition of an old car, but all I wanted was honesty (which he claims to have). I'm aware I wasn't his only customer, he's busy doing XYZ but other reviews praise him for great communication with regular updates and photos, I felt I didn't receive the same treatment. 
    • I was able to get some underside photos while the car was on the ramp The suspension is all Altezza/IS200/IS300 so getting part's will hopefully be less of a headache
    • Welcome to my 2004 Toyota Mark ii IR-V Fortuna (series 2) With a 1JZ-GTE powerplant under the bonnet (hood) it'll give me plenty of scope for power upgrades. For those who aren't familiar with imports, the 1JZ-GTE is a 2.5L 6 cylinder VVTi engine with a single turbocharger. This has the factory R154 5 speed gearbox, along with a aftermarket 2 way LSD differential (brand unknown). Under the arches are a set of CST Zero 1 alloys, 18x9 +30 225/40 up front and 18x9.5 +15 265/35 on the rear. The car was quite low in Japan and there's evidence of the wheels catching the rolled arches/fenders. The tyre's aren't great so I'm in two minds whether to replace both or just the tyres and put up with the wider wheels on the rear. The car still uses stock brakes with the addition of some braided hoses. The exterior is stock with the exception of a BN Sports front bumper and a replacement Fortuna grill  Moving to the interior, the steering wheel has been replaced with a dished MOMO steering wheel (which will get swapped for my Momo Tuner for the time being) Defi Link Gauges are mounted above the climate controls and on the A pillar, the Oil Temp,Oil Pressure,Water Temp and Boost gauges should help with spirited and track driving  The stock seats have been replaced with some retrimmed Recaro bucket seats. Being a larger build these are a little snug, unfortunately the orange isn't for me so I'll look into replacing these down the line. Other modifications include a twin plate clutch, Blitz intercooler, Evolve alloy radiator, a stainless exhaust with decat, HKS EVC-S boost controller and coil overs
    • Apologies for the long read My R34 GTT was up for sale at the beginning of spring due to a few repairs creeping up. The strut tops needed replacing, roof and bonnet (hood) painting (yay for 3 stage pearl) and the underside stripped and treated. I sold the car which allowed me to be in a much better place financially. Leading up to the sale I was already thinking about the replacement. In an ideal world it needed to be a good all-rounder. Something I can mess around with, modify, do track days, do the school run, go on long drives etc.  Options included but not limited to... Laurel C35, Evo 8/9, Civic FD2, Impreza Hawkeye, Aristo and even an Audi S4 Avant (I've already got the Mazda 6 wagon). But there was always one car at the top of the list The Toyota Mark ii JZX110 I found an advert on a Facebook group for an example in Japan, from a seller called Jon at Rising Sun Exports. A few messages back and forth and Jon calls me from Yokohama one morning (or afternoon in his case). He briefly explained the import process, the costs involved and a repeat of the advert. After much deliberation, the price was agreed and the sale was locked in. I've never imported a vehicle so I jumped into the unknown head first. The money transfer was completed through wise.com (fees apply), very easy to use and the money was with him within a day or two.  The car suspension was raised for the vessel and the car dropped off at the port. It was 7 weeks later when the bill of lading was received and the freight invoice sent to me, followed by the export certificate a couple of days after (both digital copies) In the mean time the port had been in contact. I needed an agent to deal with the NOVA (notification of vehicle arrival) along with the tax/duty invoice, this was £75.00. The port also had a fee of £100, I'm guessing to cover the cost of the 10 day 'free storage' and for moving the car off the boat etc. They need a copy of the vehicle invoice, freight invoice and export certificate to allow the vehicle to pass through customs. The vessel arrived on Tuesday 5th August, the tax/duty invoice was generated and sent over. This is generally tax 20% and duty 10% of the vehicle value. Although the invoice came in at a higher amount than I had calculated. Once HMRC had received the payment the vehicle could be released from customs. I thought once the tax/duty was paid you could collect at any point, that's not the case. Your agent will need to book a collection slot, I requested Thursday 7th which was accepted, with a 9:00am slot allocated. It was a 5:00am start from Norfolk heading to Southampton. We eventually found the compound, upon presenting the bill of lading and some ID they released the car (they drove it out of the compound to the front ready for us to load up). The email from the port stated each slot had a 10 minute window, which seemed abit farfetched but the staff said it's not a strict rule. We were there for approx. 30-40 mins in total. A week prior to collecting I contacted my garage and explained the situation, I was able to get an inspection slot that afternoon. For the registration, DVLA require the car to be insured, for this I used a company called Adrian Flux who can insure the vehicle using the VIN number. 
    • Hey guys, looking for these side skirts if anyone can help me out. 
×
×
  • Create New...