Risking

Have it corner weighted, and make sure the corner weights are capable of giving a CG figure. My intercomp weights are capable of giving both vertical and horizontal. I wish you bes of luck with it. Good to see Simone playing around with the "black art"

Ummm the first two points are exactly what I posted earlier in this thread, I left RC at ground level and underground level out. How are you intending to work out the "ideal" roll center height when you don't know the the vertical center of gravity??? I personally don't always agree with the 15-30% guidline for roll center heights. I have my reasons which are far to indepth for this thread. there is no perfect RC height nor is there a perfect formula to calculate one. I'm still not sure how you plan to work out your final solution without all the real information you need not substituted guess'?? You need to know what the car weighs! Find someone with good corner weights and they can also tell you a very accurate vertical and horizontal CG to save you alot of calcs. You won't get that range of adjustment out of just the lower arm without some massive control arm angles. You must use both arms otherwise your going to run into all types of trouble with camber gains, bump steer etc etc. I never said anything about an extremely high RC that's close to the CG...... I said the closer it is the less roll. 170mm is a recommended starting point from my experiabce and what I know is the typical CG of an r32 GTR, it's far from extremely high. as opposed to your current 14mm roll center which will roll like a boat. If you plan to use your work on a real car like I think you plan to then you really need the right information and to incorporate all aspects of geometry not just roll centers.

Ah hu now I understand what you have done I think.... You don't want an 80mm odd RC you want a 170mm odd RC. The closer the roll center is to the CG the less roll you will have with the same springs and bars. But if it's too close you will get ubdersteer and oversteer. It's a balncing act that requires experiabce to get right there is no formula or realationship between the two that I know of. It's a drivers personal taste that determines what happens. I'd recommend for your own good you have your car corner weighted and find a set of scales that can quickly and easily calculate an accurate vertical center of gravity for you to use. Like you said what you have done is a good illustration but If you want to learn about it more you need the right info to begin with. CG is a very important input when playing with dynamic geometry like you are.

Stuffing around with measurments is the best way to learn that's for sure. Have you used susprog or just casim?? Is that last simulation your actual Car and how it's been built, is the center of gravity you have inserted the actual figure from weighing the vehicle or a calculated input?? In my oppinion for a gtr with a CG of 300mm a 14mm roll center is far too low. The roll couple is alot larger than a factory gtr. Work backwards to get the roll center up around the 170mm mark front and 260-270 rear. Depending on your cars actual COG of course. Unless you have lowered the weight into the chassis the center of gravity will typically lower in acordance to the chassis height you lower the suspension by. Also with your roll simulations remember you are only simulating the front and not factoring in the horizontal COG along the car. Your asumimg it's a 50/50 weight split which it probably is not. Rear roll center and roll couple also effect the roll you will see at the front like a post from above mentioned. I don't think casim can do such simulations?? By bringing the RC closer to the CG you can control the body roll without stiffer springs and roll bars which can limit traction.

Loffe are those your simulations or did you have them drawn up for you?? A few of your values that have big effects on RC's are substancially different to original. Did you end up correcting the upper control arm angle or spacing the lower arm only?

If they are a 997 caliper which is one of the more common 6piston brembos, it is not really worth repairing them. New callipers can be bought for a couple of hundred more than just the seals.

Wrong section I know but atleast people in here would have half and idea and a use for these. I've upgraded to a set of intercomp digital gauges so my 2nd set are for sale. They are identical to the manual intercomp bump steer gauges that sell for 470 odd bucks new. They have brand new 1inch travel dial indicators and are in perfect condition with a level bubble on the base. Comes with an alloy hub plate designed for any 5 stud Nissan. Could be drilled to suit almost anything really. They come apart into 5 pieces for easy packing into a toolbox and assembled within 30seconds. Asking $280 with the new dial indicators feel free to move this to the forsales if the mods see fit. Thought I'd post it here as it's more motorsport related and pretty specific.

it is a very indepth topic something unless your pushing a car hard and looking for the most out of is best left alone. The heights you have mentioned are around optimal for a gtr give or take 5mm. Just be sure to set the heights with a driver in the car and an average fuel load. Or ideally set the heights and corner weight the car at the same time. A slight varyiance in ride height is worth the trade off if it means you can balance the chassis better. For those worried about handling effects in all honesty unless your pushing the car hard and looking for time, a 30-35mm ride height drop is aceptable 90% of the time. While it will lower the RC and change the chassis chances are you will overcome it with sway bars like 1000's of people have done before. The expense of correcting and modifying a rollcenter height and going even further into it is not really economical when you can get a good result with a well thought out set-up that to the majority of people will drive the same as a car with 100's of development hours. Developed car will be quicker but comes back to how far are you willing to go?? My sports sedan has 1000's of hours put into r&d it hasn't turned a wheel yet. There has been several incarnations of suspension and many geometry changes made. It's still not perfect and honestly I still learn more about it every day. Your limiting factor will more so be tires etc etc before roll centers and other geometry.

Has anyone actually ever calculated factory GTR roll center heights, instantaneous centers, roll axis etc etc??? I can tell you that the factory front roll center of a GTR is typically 80-85mm. Lowering the car by 1 inch normally drops 12-13% off the centers height (my own R&D). So you end up with a roll center of roughly 9-10mm. Still positive but close to going negative. Quickly showing why excessive lowering screws everything up. All those "roll center correctors" are only a part solution. If you lower a GTR by 30mm and fit a 30mm roll center corrector under the front uprights you correct the roll center by 6-7% generally. The upper arm needs to be corrected to rectify the problem properly. Bearing in mind this all all static calculations, Roll centers have not even started to move around the car dynamicly yet, roll axis and couple are not even considered either...... Alot of people have the general oppinion that a car set-up with the rollcenter at the same height is the center of gravity should handle well. Couldnt be more wrong, a car with RC and CG at the same height WONT roll at all and will simply slide. Normally we set a car up so the roll center is lower than the CG. For a good reason. The higher the CG is compared to the Rollcenter the more "leverage" the weight has and the more body roll you will get. This is roll couple. To smaller distance and you create an oversteering pain. To large and you have a body roller that your forever adding more spring and bar to try and correct. Noramally by lowering roll centers you end up raising the roll couple. Typically and for simplicities sake(so many variables) by the same % you lowered the RC . So lower the RC by 10% you raise the roll couple by 10%. Inducing 10% more leverage and 10% more roll. 10% more spring is now required to get the roll back to how it was before you changed the RC. (Again its not always a linear ammount but too indepth.) A low roll center induces body roll and vice versa for a higher RC. If you dont move the Roll centers together it can and will introduce under and over steer. Lower the front roll center by say 10% you have now got to increase spring rates by 10% to get back to the original ammount of body roll (assuming linear rates/RC for ease) Lower the rear roll center by 5% and do the same with the springs. The front of the car now has more tendancy to roll than the rear. So in a corner the front will not resist the body roll as much as the rear. The rear will take on more of the rolling forces and as a result increase its weight transfer. Leading to only one thing, oversteer. Most people try and dial this out with roll bars a very common problem on GTR's when lowered and not set-up properly, but the solution is to fix the roll center problem you created first. Ive been setting-up race cars and road cars for a while and have built my fair share. I have my own equipement (C weights, alligner, bump steer guages, Susprog modeling software etc etc) so I have managed to aquire a fair ammount of data and experiance with the GTR and GTS-t chassis. Im sure someone will sit down and google search the net to blow holes in what Ive said, because someone else uses different terminology etc but there is a little of my knowledge about the concept from first hand experiance. There is little information about roll center effects and so forth so hopefully that helps I wouldnt normally go into this kind of discussion due to the vast ammount of oppinions surrounding the topic. Every engineer or "expert" if there is such a thing has their own view. Please do bear in mind what ive written is only just touching on the surface when it comes to geometry and RC's etc. There is FAR too much to consider in writting it down. Dynamicaly everything changes again. I spent an entire day with another forum member last weekend doing practical excersises, calculations and so forth. If he reads this im sure he will comment on what he took away from the day.

It will be a front wheel bearing. When your loading up the wheel bearing and applying the brakes the movement in the bearing is causing pad knock off, with your foot on the brake you feel it as brake shudder.

Are they a 2 piece rotor you have?? I know the greddy kits use a strange PCD with their 2 piece rotors. The last set I did I ended up using a HSV 330mm dba 5000 series rotor and machined up a pair of hats to suit them. Replacement is a very simple task next time around.

As I said mike any time at all, and thanks for the kind words. Hopefully during the few hours you spent here you took away a few ideas. I will update the thread very shortly mate, there is a heap to be seen. If you do want photos of something specific that you didn't get to take just let me know.

Super pro I would not use in my lawnmower! We wore a set out in a single meeting. Duncan is correct about the owners/realationships between conpanys.

Rose joints and sphericals are the only way to go. Yes they do have a limited life span and wear out in some areas more thab others. typically if you buy budget ones they last a season give or take,if they don't break first. They also tend to push the inner sleeves out. the good Teflon versions are twice the price and last a bit longer but don't normally spit the inner sleeves out the side of the spherical. They will still break but take alot more punishment. Depending where you use them they will normally break before they wear out.

Still have a set of these to offload

I use tilton products as I have an awesome supplier for them. In a skyline we use a steel twin pedal hung box. by the time you factor in the two pedals, the mounting you need to do ( really needs to hang from a dash bar on a cage) the three master cylinders ( 2 brake 1 clutch) 3 resiviours and hoses etc there is very little if any weight saving. Using a 3 pedal tilton floor mount in my r34 which is possibly as heavy as factory system if not more.

Exactly. Change the pedal ratio and size the master cylinder properly for a setup without assistance and it works okay. You will bend tr firewall and pedal bracket if not reinforced well. Hence why most atleast buy an overhung pedal box with a 6.25 pedal ratio. It's not as simple as relocating the pivot pin to change the ratio either. The pushrods needs to remain square to the rear of the master cylinder so there is some stuffing around with cylinder mounting. Well worth the effort of going non assisted. Who ever was doing that pedal box had no idea how to set it up properly. A well done system will give you a far superior pedal feel and feedback, it's more consistant particularly when you start left foot braking, you gain proper bias control and the pedal can be styled to suit anyones driving habbits with the right masters. It took us a while to get our heads around master sizing and so forth but done right they are worth it.

You will most certainly hear back from mike. They are great to deal with

Samco radiator hoses can be bought online from Williams race services in qld. Email [email protected] very helpful and a distributor for samco.

I've neve seen a lock bar bar the weighs 6-8kgs! Even a solid bar in that length would not come close reading his post I'd say his never weighed anything accuratly! A chromolly bar can be made but will cost you 3 times as much and with the ammount of material in it there will be stuff all weight saving. I use Molly daily for suspension and cage work, for a lock bar just buy an ordinary one and spend the money Saved on fuel!

They are 997 Porsche cup car callipers and brembo 380*36mm rotors. Have you found a set of rims to fit yet pete??

Wanting to buy a pair of r34 2 door tail lights GTT or GTR doesn't matter. Even slight damage is okay they are only to use a moulds for a sports sedan. Willing to pay postage etc

You don't. "pillow balls" are just a laymans term for a spherical bearing. The spherical bearing or "pillow ball" is fitted into a camber plate and widely used on mc strut systems for camber adjustments. Most high end shocks like sach, proflex etc all recommend the use of sphericals in the mounting plates instead of rubber or nylon etc. Also alot of Jap manufactures use sphericals in their skyline tops. HKS and cusco are two that come to mind in their better models. We use sphericals or pillow balls in all of our lower control arms, upper control arms for wishbone conversions and cockpit sway bar adjustment systems.

To start with of from an engineering point of view you have to ask about design and rod ends you probably shouldn't be playing around with it. Don't buy cheap rod ends!!!!! Use ONLY good quality teflon/stainless end at least. Teflon/4130 end are available as well. They can be bought metric but imperial are easier to source and more widely used 3/4unf MALE joints are what you should be using for any lower control arm and 5/8 unf for most other things. Do not ever cut a thread into a control arm and screw the rod end into it directly. Biggest no no of all. Machine up a sleeve that is a neat interferance fit into the tube and leave a step atleast half the length of your rod end length. Drill and tap the thread into your sleeve then weld the sleeve into the control arm. Allows a far greater wall thickness of the threaded section and a smaller wall thickness tube to be used For the arm. For the outters don't use rose joint ends. Use spherical bearings and machine up a sleeve with a circlip groove to retain them. Spericals in a sleeve are far stronger for a single application ( you have two inners and one outter on a lower arm for example) and it allows the arms end to penetrate into the sleeve ad be welded far better I use 1inch 4130 for pretty much everything except front lower arms.

Come set-up on of my race cars with the Track= Sway bars hard as possible method, lay out a few laps and then ill show you how a "softer" properly done car can be atleast 3 seconds a lap faster.