Updated 1/03/06
Just thought I'd post up some of my recent experiences of setting up the R. This is not definitive as there is no defintive suspension settings that will suit every car, driver, road and enviroment. Handling is subjective and what suits me may not suit you, when I say IMO I mean it. Its more to give other people ideas from what I've leant and pick what they like. I've tried not to get too technical except where necessary, please don't flame me for over simplifying things.
There's too much to write in one go so I'll just keep editing this post. I'll happily copy and paste in other peoples experiences so this first post is broader
Start
====
The Gtir is cursed with about 60/40 weight distribution. However, it is still actually a well balanced car from stock. When modifying your suspension, its as easy to make it worse as it is to improve it. Buying everything on the market and putting it on your car won't necessarily make things better. Subtlety is always the best policy, only make one change at a time and see the effect.Try each change on different roads and in different conditions before you can be certain its for the better.
Ride Height
========
I've done this to death in previous posts but I thought I'd review with a few rules and the benefit of my recent experiences.
-Never lower your car more than 50mm at either the front or the back. After 50mm, the control arms are horizontal and on cornering the car will induce positive camber. (the bottom of the Tein coilovers is about 50mm)
-Try to match your ride height side to side, If I put the Tein coilovers at the bottom setting, at the back one side is about 45mm drop whilst the other is 60mm, this meant one corner was never working properly.
-Ride Heights, measure your ride height from the wheel centre to the body arch. Below are a few examples:
--------------Front-----Back-
Standard: 365mm 375mm
Whiteline: 325mm 335mm
Tein Rec'd: 330mm 335mm
SR20 Race:325mm 340mm
Me current:335mm 350mm
The standard is high and quite roly poly but does give the Macpherson struts freedom to move. The more you lower the car, the less freedom it has.
Whiteline suggest a 40mm drop but my feeling is this is more for looks than handling. I also think the reason why they recommend it is because that is what they make, 40mm lowering springs. (Other like Eibach normally only make 25mm lowering sperings for example) However, taking nearly 2" from the travel of a strut that only has 4" to begin with means you'll be seeing the bump stops a lot and at that point you lose all grip and normally understeer
Tein recommend a few settings in their installation manual (though you have to translate the Japanese first). What they suggest is fairly sensible but I found the R was still in its natural understeering style again.
SR20 Race Series - There is a lot of good information from these people on the SR20 Forum as the Sentras they drive have identical front suspension to our cars. They state never to lower a road car more than 37mm as the induced positive camber and bump steer you get make handling worse rather than better. For their race cars, they actually lower 40mm at the front but less at the back. Bearing in mind what I have already said about 40mm drops, the reason these gents can get away with it is they are racing on smooth tarmac using springs that allow very little suspension movement. Most of us on the forum are not in that situation. The nose down stance improves turn in on slow corners but at higher speeds on longer corners lets the car understeer more so they can drive harder/safer.
-Me, I've tried every ride height going from nose up, full height and max drop but ended up with a similar setup to the SR20 boys. I have found the 5mm on top of the Nissan 10mm difference removes a lot of the understeering tendancies of the car. 10mm extra and the back can become a little loose on corner entry. This might be desirable to you but I found it too gung ho. The drop is 35mm at the front but as the poor winter weather comes in, I would't be surprised if my ride height goes up 5-10mm.
Ride Height Summary
Drop your ride height between 20-35mm to reduce roll and improve stability
Having the front height higher than the rear just felt wrong, I couldn't get the handling to work.
Having the front lower than the rear will improve turn in and accleration but will make the car understeer at higher speds.
Having the front much lower than the rear will reduce braking performance, make the rear loose on corner entry and can give terminal understeer.
If everything I've written just sounds like goblidygook, then don't buy coilovers, save some money and buy some stiffer 20mm lowering springs. They will reduce roll, without worsening the handling or changing the car's natural balance.
Anti Roll Bars
=========
The front roll bar on our cars is relativley thick and stiff from stock. Now in theory this will cause the car to understeer more as the front will have less weight transference than the back. Now in practice all sorts of funky things can happen. By reducing the roll on a lowered car, you are also limiting the suspension geometry changing as much that I previously said was a bad thing. I've read of some FWD SR20 Sentra racers who fit stiffer ARBs to the front to improve grip because of this effect.
Whiteline fit a smaller ARB to the R and some people like to remove it altogether. Why do Whiteline fit stiffer springs and then a softer roll bar? As ever, there are many ways to solve handling problems but for me I've used the "if its not broke don't fix it philosophy".
I have concentrated on using the rear ARB to redress the front/rear balance and left the front stock.
My rear ARB is adjustable from whiteline, I have tried only 2 of the 3 settings.
The stiffest setting (the hole closest to the main bar) completely eliminated understeer but made the car loose at the rear on corner entry and exit :shock: . I maybe should have persevered with this more but after a while it became tiring driving sideways through corners. I also didn't like the way it forced the OE droplinks to a funny angle that meant the ARB didn't react linearly. This setting maybe has a benefit for high speed dry weather race use or rally driving, IMO for the roads its too severe.
The middle setting is a little stiffer than stock and what I use now. It lines up perfectly with the drop link making the ARB respond linearly again. It does exactly what it says on the tin and reduces roll at the back making the car less prone to understeer whilst not oversteering at the hint of a corner.
The final setting is probably around a stock strength again, I didn't try this setting as I just took a stock ARB off and I was concerned over the angle of the drop links when using this setting too. I will probably try this last setting in the future just out of interest but if anyone has an opinon then please post.
ARB Summary
-Again, if all that sounded too difficult to understand, save yourself some money and buy the non-adjustable rear ARB from whiteline, I bet it does 90% the same job as the adjustable ARB for the majority of road only drivers. More serious drivers might want to make the investment and I'd be interested to know how you got on.
Damper Settings
===========
Affect wheel control, comfort and dynamic weight transference, they do no affect weight transference diredtly.
Camber and Castor
=============
I won't go into explaining these as other people have done it far better.
On a stock GtiR, these are not adjustable. The level of adjustment you get depends on what equipment you fit.
Camber
=====
Camber has a direct affect on the tyre's "contact patch" (Size of the area of tyre rubber in contact with the road) for any given situation. Camber does get quite complicated the more you look into it but lets keep it simple first with a few quick definitions.
Positive camber is where the inside tyre edge is lifted relative to the outside.
Neutral or 0 camber is where the contact patch is completely flat
Negative camber is where the outside tyre edge is lifted relative to the inside.
Maximum available grip is when you have the largest amount of tyre area ni contact with the ground.
Positive camber is always rubbish unless you only ever drive round left or right handed corners!!
Neutral camber is best when you want to accelerate or brake in a straight line.
Negative camber is best for cornering as at high G, the car tyre flexes more weight onto its outside edge amintaing a neutral contact patch..
Clear so far? lets complicate it again.
Static camber
=========
Settings
Nissan OE
Front 0.45deg to -0.5deg
Rear 0.35 deg to -0.55deg
Whiteline
Front Road -1.5deg
Rear Road -1.25deg
Tein Settings
Front 1.15deg to +/-0.75deg
Rear none given
Dynamic camber
===========
Unfortunately for us, the R uses Macpherson struts that are simple and cheap to manufacture but provide rubbish dynamic camber. As the suspension compresses, the geometry chnages and you get positive induced camber. Some multi link suspensions add negative camber as the wheel compresses but not us. The level of induced camber is dependant on the amount of compression and it is possible to measure and plot this at various points to generate a "camber curve"
This camber curve is as important as the static camber as it shows how your car will respond under driving. When Nissan "designed" the camber curve on our cars, it was based around a specific ride height.
When you lower your car, you will increase the static negative camber but you will be on a lower part of the camber curve so your car will loss more camber relativley under roll.
Still with me :lol: :? :? :lol:
In short, you want to minimise camber change.
Have the geometry closest to the height where Nissan designed it means you'll get the least camber change for a given amount of compression. This means... don't lower your car more than 40mm. It might look like you've got loads of camber but as soon as you turn the wheel you'll get less! The point at which this phenomenon accelerates is once the lower wishbones go past horizontal, any further compression just piles on the positive camber.
Race cars get by the problem of camber curves by having ridiculouslt stiff springs so the suspension geometry never really changes but for a road car this is not an option.
Castor
=====
Standard settings on a Sunny are 0.3 to 2.0 degs. The Whiteline kit reduces lift/dive by changing the lower arm position and in the process adds around a degree of castor. Whiteline state their caster setting as 2.5 to 3.5 degs but it is essentiallt fixed..
IMO, this is still on the low side for a performance car, my daily driver the MR2 has adjustable castor and those in the know wind it up to the max at 5degs and it does improve the straight line stability and front end grip. The main downside is a heavier steering wheel but at this level of castor, the car still had a good "feel" and doesn't want to go straight a head all the time.
I know an old rule of thumb is to run around 5degs castor on a road car and I know of race cars setup with twice that amount. For me, the problem is the Sunny suspension was originally designed for a 1.4LX shopping cart with manual steering where people want a nice light steering wheel so Nissan put virtually no caster in. The whiteline mod is a step in the right direction but IMO, I would like to add another couple of degrees to the front.
Toe
===
Toe is quite a subtle adjustment but can have a great affect on the "feel" of a car. it is the direction each wheel is pointing relative to the direction of the car. The wheels on each side at the front or the book should be roughly equal so both each end tracks forward even if it has a propensity to turn in or out. In simple terms:
Toe-in front: Makes the front more centered an improves stability, especially at high speed.
Toe-out front: Makes the steering more twitchy but does improve the inital turn into a corner 9The wheels prefer turning rather than going straight)
Toe-in rear: Also improves stability of thecar in a straight line but also improves the "catchability" of an oversteer
Toe-out rear: Makes the rear of the car more willing to turn so can reduce understeer but also can cause snap oversteer.
A few words of warning, incorrect toe can severly damage the feel of the car and quickly wear out your tyres. Fiddle with toe settings using caution.
Below are a few recommended specifications. What must be remembered when looking at them is the averge mechanic would consider +-6' 0 even if it is not. As ever suspension is very time consuming to setup. I personally ask for 0degs all round but ask the mechanic to err on the negative rather than the positive. I've still not finished making my toe gauges yet so I haven't played too much on the R to give any better advice.
For those who don't know, there are 60'(minutes) = 1 degree
Nissan
Front toe in: 0deg to 22'
Rear Toe in: -6' to +18'
Whiteline (road)
Front toe in: 0mm (Approx 0deg)
Rear Toe out: 1mm to 2mm (Approx -6' to -12')
Tein (Japanese is quite difficult but this looks most likely)
Front toe in: -0.05' +/-45'
Rear Toe in: -0.10' +/-45'
Nissan, Tein and Whiteline are all quite closely aligned in terms of absolute values (Centre of range). Nissan say toe in slightly, Tein say toe out slightly but you look at the range for these suppliers and there is a lot of overlap around 0degs.
Bump Steer
========
If you understood dynamic camber and the camber curve then bumpsteer is the equicalent but for toe. If you don't undestand a word I'm saying then you've done well to get this far.
Tie rods are screwed in or our to change toe when the car is static. Unfortunately, when the car geometry changes under suspension compression, the relative length of the tie rod will also change and the wheel will toe out. The opposite wheel under extension will toe in slightly too compounding the problem. Like with the camber curve, the bumpsteer phenomon is on most suspension systems to a degree but more so on Macpherson struts and worse so once the car is lowered.
The sweet spot to reduce bumpsteer is for your steering rack to be slightly above the tie rod end so you are at the start of the flatest part of the change in toe. The problem with lowering the car 2 " is you are then leaving the flatest part so every compression will again increase bumpsteer.
So how come we aren't all complaining about bumpsteer all the time then, its because when the outside wheel toes out, the driver unkowingly turns the wheel more automatically to compensate. All your doing is reducing the car's ability to tuen in.
The main time you notice bumpsteer is when you drive down a bumpy road and one of your front wheels hits a pot hole, and the car then steers on that side due to bimpsteer. It can create a very unsteady car at high speed on B-roads that is undeesirable.
If you have lowered you car and the steering tie rods are pointing up rather than down then the Bumpsteer correction kits (ignoring the rose joints) will improve this situation but these are often generic so will still not remove the problem. The first step is not to lower your car too much in the first place so you can keep the amount of bumpsteer correction to a minimum too.
Spring Rate
========
Tyre choice
=======
Tyres are THE most critical part in optimising the grip and handling of a car. I read a post from a Sentra racer who was able to lap faster on a stock (and worn) car with race tyres than his race car with stock tyres.
The problem with race tyres is they are designed for tracks rather than roads.
You have to weigh up what you want from the tyre then do a search and see what peoples experiences are:
As tyre products change all the time, what's the best tyre today won't necessarily be the best tomorrow. However, the UHP (Ultra High Performance) tyres in all the good brands are the best place to start. For what its worth, the Goodyear F1's are the best wet weather tyre, semi slicks are the best dry weather tyre. Some brands have good wear whilst others delaminate in 20 minutes on atrack. You pays your money you takes your choice.
Tyre pressures
==========
These are what most people with a stock car can easily and cheaply play with to affect the car's handling. There is no holy grail of tyre pressure settings as everyone has different tyres, wheels, roads and weather conditions so this is quite a general section as there are no "right" settings. Before you start though, get yourself a decent pressure gauge and/or pump. My pump is accurate to 1psi and when I filled my tyres to 34psi and checked them on the fancy digital tyre pressure machine at Tescos, they read 38psi. 4psi is the diffference between a tyre working right or understeering all over the place.
-What I can say is there are wrong settings. My mate has just bought a GT4 and was complaining of twitchy handling and mumbling about the need to change shocks springs and make all sorts of modifications. I asked if he'd checked his tyres. He found the front right and back left at 38psi whilst the other 2 tyres were 34 and 32 repectivley. He set them all to 36 and hey presto everything was fine, twitchiness gone.
-Around Winter time your pressures can start to drop if you've not checked them do it now.
-Different tyres work best at different pressures because of the following reasons:
Tyre temperatures, more pressure stops them overheating as much under load (Which is one of the reasons why you run higher temperatures at high speeds). The rubber on your tyre is designed to work at a specific temperature, changing the pressure and temperature it gets too under load will help it stay at that temperature. This is one of the reasons why race tyres are pants on the roads and why road tyres delaminate on the track.
Tyre Profile, many tyres nowadays have 3 or 4 rolling profiles to try and keep as much tyre in contact with the road for most of the time. A tyre will work well at one pressure but not another for this reason. Low profiles are a good example where they generally need higher pressures to maintain their shape under load
Sidewall stiffness, similar to the above but some higher profile tyres will sag and bag at lower pressures so you need more pressure to keep them from folding over at high speeds.
Comfort/Suspension, a tyre will only work when it is contact with the road (kind of obvious) but if you over inflate your tyres on the road, it can feel skittish over bumps and not grip as well. This is because your tyres are the first part your car uses to soak up bumps and are a very necessary part of the suspension. I once read how TVR chassis engineers preffered 15" rims on their cars as the higher profiles were an important part of the setup. They only begrudgingly moved to 17" and 18" because of fashion. If the B-roads round you are far from smooth, try dropping a few psi and you might find the tyre rolls more but overall they grip better.
-For the GtiR tyre pressures of between 30 and 38 should cover all the tyres and all the profiles. You should try each pressure for a few days and see how you get on. Increase the pressuers in 2psi increments until you feel things are not working as well. Once you've found your optimum, drop it back 2psi and double check whether it was better or worse.
-One of the most important thing you can do with your tyre pressures is adjust the cars grip and balance front to rear. In theory, rear tyre's need less pressure as they are under less load (That 70/30 weight distribution again). Putting in more pressure in than optimum should rediuce the amount of grip the tyre can provide so making the rears run out of grip before the front. This can help with understeer problems but be aware that less grip at the back might also cause oversteer problems which can be equally as frustrating. Try running the back at the same pressure, try 2psi lower and 4psi lower and see what gives you the best handling balance.
-For the standard 195/55/14 (I kid you not) Nissan recommded 36psi if I've read my Japanese correctly. My thinking is this is to solve the problem of excessive roll under cornering but also cover the driving at 120mph with 4 people and a full boot load of stuff base. Though it sounds silly, consider whether you do go blasting around on your own or with all your mates in the back before you choose optimum pressures.
-I personally run a 2-4psi difference front to back, this is beacuse I am a car geek
and when measuring the ride height I noticed with my tyres, the 4psi difference, meant the wheel centre to floor distance was the same on the front and back so the tyres had the same profile. This was my starting point for setting up the suspension. At the moment I'm running a 36psi front and 32psi rear but as the weather changes these will probably change too.
-I find on my car when the tyre pressures drop to 32psi, the handling loses its edge and the car starts to understeer more.
-For track days, consider putting an extra couple of psi in the tyres before you go on track and take a decent pressure gauge and foot pump so you can change the pressures during the day. You will also be surprised at how high your pressures will get after a session.
-For drag racing, consider dropping a few psi to make the tyre profile flatter and provide more straight line grip.
Tyre Pressures Overall
-Tyre pressures have a direct affect on the grip available from a tyre at a given temperature in given raod conditions. Knowingly running less than optimum tyre pressures on the back can help with understeer by makeing the car more prone to oversteer. However, ideally its worth optimising the grip from your tyres and using the rest of your suspension to optimise the balance.
To be conituned
Jim
Just thought I'd post up some of my recent experiences of setting up the R. This is not definitive as there is no defintive suspension settings that will suit every car, driver, road and enviroment. Handling is subjective and what suits me may not suit you, when I say IMO I mean it. Its more to give other people ideas from what I've leant and pick what they like. I've tried not to get too technical except where necessary, please don't flame me for over simplifying things.
There's too much to write in one go so I'll just keep editing this post. I'll happily copy and paste in other peoples experiences so this first post is broader
Start
====
The Gtir is cursed with about 60/40 weight distribution. However, it is still actually a well balanced car from stock. When modifying your suspension, its as easy to make it worse as it is to improve it. Buying everything on the market and putting it on your car won't necessarily make things better. Subtlety is always the best policy, only make one change at a time and see the effect.Try each change on different roads and in different conditions before you can be certain its for the better.
Ride Height
========
I've done this to death in previous posts but I thought I'd review with a few rules and the benefit of my recent experiences.
-Never lower your car more than 50mm at either the front or the back. After 50mm, the control arms are horizontal and on cornering the car will induce positive camber. (the bottom of the Tein coilovers is about 50mm)
-Try to match your ride height side to side, If I put the Tein coilovers at the bottom setting, at the back one side is about 45mm drop whilst the other is 60mm, this meant one corner was never working properly.
-Ride Heights, measure your ride height from the wheel centre to the body arch. Below are a few examples:
--------------Front-----Back-
Standard: 365mm 375mm
Whiteline: 325mm 335mm
Tein Rec'd: 330mm 335mm
SR20 Race:325mm 340mm
Me current:335mm 350mm
The standard is high and quite roly poly but does give the Macpherson struts freedom to move. The more you lower the car, the less freedom it has.
Whiteline suggest a 40mm drop but my feeling is this is more for looks than handling. I also think the reason why they recommend it is because that is what they make, 40mm lowering springs. (Other like Eibach normally only make 25mm lowering sperings for example) However, taking nearly 2" from the travel of a strut that only has 4" to begin with means you'll be seeing the bump stops a lot and at that point you lose all grip and normally understeer
Tein recommend a few settings in their installation manual (though you have to translate the Japanese first). What they suggest is fairly sensible but I found the R was still in its natural understeering style again.
SR20 Race Series - There is a lot of good information from these people on the SR20 Forum as the Sentras they drive have identical front suspension to our cars. They state never to lower a road car more than 37mm as the induced positive camber and bump steer you get make handling worse rather than better. For their race cars, they actually lower 40mm at the front but less at the back. Bearing in mind what I have already said about 40mm drops, the reason these gents can get away with it is they are racing on smooth tarmac using springs that allow very little suspension movement. Most of us on the forum are not in that situation. The nose down stance improves turn in on slow corners but at higher speeds on longer corners lets the car understeer more so they can drive harder/safer.
-Me, I've tried every ride height going from nose up, full height and max drop but ended up with a similar setup to the SR20 boys. I have found the 5mm on top of the Nissan 10mm difference removes a lot of the understeering tendancies of the car. 10mm extra and the back can become a little loose on corner entry. This might be desirable to you but I found it too gung ho. The drop is 35mm at the front but as the poor winter weather comes in, I would't be surprised if my ride height goes up 5-10mm.
Ride Height Summary
Drop your ride height between 20-35mm to reduce roll and improve stability
Having the front height higher than the rear just felt wrong, I couldn't get the handling to work.
Having the front lower than the rear will improve turn in and accleration but will make the car understeer at higher speds.
Having the front much lower than the rear will reduce braking performance, make the rear loose on corner entry and can give terminal understeer.
If everything I've written just sounds like goblidygook, then don't buy coilovers, save some money and buy some stiffer 20mm lowering springs. They will reduce roll, without worsening the handling or changing the car's natural balance.
Anti Roll Bars
=========
The front roll bar on our cars is relativley thick and stiff from stock. Now in theory this will cause the car to understeer more as the front will have less weight transference than the back. Now in practice all sorts of funky things can happen. By reducing the roll on a lowered car, you are also limiting the suspension geometry changing as much that I previously said was a bad thing. I've read of some FWD SR20 Sentra racers who fit stiffer ARBs to the front to improve grip because of this effect.
Whiteline fit a smaller ARB to the R and some people like to remove it altogether. Why do Whiteline fit stiffer springs and then a softer roll bar? As ever, there are many ways to solve handling problems but for me I've used the "if its not broke don't fix it philosophy".
I have concentrated on using the rear ARB to redress the front/rear balance and left the front stock.
My rear ARB is adjustable from whiteline, I have tried only 2 of the 3 settings.
The stiffest setting (the hole closest to the main bar) completely eliminated understeer but made the car loose at the rear on corner entry and exit :shock: . I maybe should have persevered with this more but after a while it became tiring driving sideways through corners. I also didn't like the way it forced the OE droplinks to a funny angle that meant the ARB didn't react linearly. This setting maybe has a benefit for high speed dry weather race use or rally driving, IMO for the roads its too severe.
The middle setting is a little stiffer than stock and what I use now. It lines up perfectly with the drop link making the ARB respond linearly again. It does exactly what it says on the tin and reduces roll at the back making the car less prone to understeer whilst not oversteering at the hint of a corner.
The final setting is probably around a stock strength again, I didn't try this setting as I just took a stock ARB off and I was concerned over the angle of the drop links when using this setting too. I will probably try this last setting in the future just out of interest but if anyone has an opinon then please post.
ARB Summary
-Again, if all that sounded too difficult to understand, save yourself some money and buy the non-adjustable rear ARB from whiteline, I bet it does 90% the same job as the adjustable ARB for the majority of road only drivers. More serious drivers might want to make the investment and I'd be interested to know how you got on.
Damper Settings
===========
Affect wheel control, comfort and dynamic weight transference, they do no affect weight transference diredtly.
Camber and Castor
=============
I won't go into explaining these as other people have done it far better.
On a stock GtiR, these are not adjustable. The level of adjustment you get depends on what equipment you fit.
Camber
=====
Camber has a direct affect on the tyre's "contact patch" (Size of the area of tyre rubber in contact with the road) for any given situation. Camber does get quite complicated the more you look into it but lets keep it simple first with a few quick definitions.
Positive camber is where the inside tyre edge is lifted relative to the outside.
Neutral or 0 camber is where the contact patch is completely flat
Negative camber is where the outside tyre edge is lifted relative to the inside.
Maximum available grip is when you have the largest amount of tyre area ni contact with the ground.
Positive camber is always rubbish unless you only ever drive round left or right handed corners!!
Neutral camber is best when you want to accelerate or brake in a straight line.
Negative camber is best for cornering as at high G, the car tyre flexes more weight onto its outside edge amintaing a neutral contact patch..
Clear so far? lets complicate it again.
Static camber
=========
Settings
Nissan OE
Front 0.45deg to -0.5deg
Rear 0.35 deg to -0.55deg
Whiteline
Front Road -1.5deg
Rear Road -1.25deg
Tein Settings
Front 1.15deg to +/-0.75deg
Rear none given
Dynamic camber
===========
Unfortunately for us, the R uses Macpherson struts that are simple and cheap to manufacture but provide rubbish dynamic camber. As the suspension compresses, the geometry chnages and you get positive induced camber. Some multi link suspensions add negative camber as the wheel compresses but not us. The level of induced camber is dependant on the amount of compression and it is possible to measure and plot this at various points to generate a "camber curve"
This camber curve is as important as the static camber as it shows how your car will respond under driving. When Nissan "designed" the camber curve on our cars, it was based around a specific ride height.
When you lower your car, you will increase the static negative camber but you will be on a lower part of the camber curve so your car will loss more camber relativley under roll.
Still with me :lol: :? :? :lol:
In short, you want to minimise camber change.
Have the geometry closest to the height where Nissan designed it means you'll get the least camber change for a given amount of compression. This means... don't lower your car more than 40mm. It might look like you've got loads of camber but as soon as you turn the wheel you'll get less! The point at which this phenomenon accelerates is once the lower wishbones go past horizontal, any further compression just piles on the positive camber.
Race cars get by the problem of camber curves by having ridiculouslt stiff springs so the suspension geometry never really changes but for a road car this is not an option.
Castor
=====
Standard settings on a Sunny are 0.3 to 2.0 degs. The Whiteline kit reduces lift/dive by changing the lower arm position and in the process adds around a degree of castor. Whiteline state their caster setting as 2.5 to 3.5 degs but it is essentiallt fixed..
IMO, this is still on the low side for a performance car, my daily driver the MR2 has adjustable castor and those in the know wind it up to the max at 5degs and it does improve the straight line stability and front end grip. The main downside is a heavier steering wheel but at this level of castor, the car still had a good "feel" and doesn't want to go straight a head all the time.
I know an old rule of thumb is to run around 5degs castor on a road car and I know of race cars setup with twice that amount. For me, the problem is the Sunny suspension was originally designed for a 1.4LX shopping cart with manual steering where people want a nice light steering wheel so Nissan put virtually no caster in. The whiteline mod is a step in the right direction but IMO, I would like to add another couple of degrees to the front.
Toe
===
Toe is quite a subtle adjustment but can have a great affect on the "feel" of a car. it is the direction each wheel is pointing relative to the direction of the car. The wheels on each side at the front or the book should be roughly equal so both each end tracks forward even if it has a propensity to turn in or out. In simple terms:
Toe-in front: Makes the front more centered an improves stability, especially at high speed.
Toe-out front: Makes the steering more twitchy but does improve the inital turn into a corner 9The wheels prefer turning rather than going straight)
Toe-in rear: Also improves stability of thecar in a straight line but also improves the "catchability" of an oversteer
Toe-out rear: Makes the rear of the car more willing to turn so can reduce understeer but also can cause snap oversteer.
A few words of warning, incorrect toe can severly damage the feel of the car and quickly wear out your tyres. Fiddle with toe settings using caution.
Below are a few recommended specifications. What must be remembered when looking at them is the averge mechanic would consider +-6' 0 even if it is not. As ever suspension is very time consuming to setup. I personally ask for 0degs all round but ask the mechanic to err on the negative rather than the positive. I've still not finished making my toe gauges yet so I haven't played too much on the R to give any better advice.
For those who don't know, there are 60'(minutes) = 1 degree
Nissan
Front toe in: 0deg to 22'
Rear Toe in: -6' to +18'
Whiteline (road)
Front toe in: 0mm (Approx 0deg)
Rear Toe out: 1mm to 2mm (Approx -6' to -12')
Tein (Japanese is quite difficult but this looks most likely)
Front toe in: -0.05' +/-45'
Rear Toe in: -0.10' +/-45'
Nissan, Tein and Whiteline are all quite closely aligned in terms of absolute values (Centre of range). Nissan say toe in slightly, Tein say toe out slightly but you look at the range for these suppliers and there is a lot of overlap around 0degs.
Bump Steer
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If you understood dynamic camber and the camber curve then bumpsteer is the equicalent but for toe. If you don't undestand a word I'm saying then you've done well to get this far.
Tie rods are screwed in or our to change toe when the car is static. Unfortunately, when the car geometry changes under suspension compression, the relative length of the tie rod will also change and the wheel will toe out. The opposite wheel under extension will toe in slightly too compounding the problem. Like with the camber curve, the bumpsteer phenomon is on most suspension systems to a degree but more so on Macpherson struts and worse so once the car is lowered.
The sweet spot to reduce bumpsteer is for your steering rack to be slightly above the tie rod end so you are at the start of the flatest part of the change in toe. The problem with lowering the car 2 " is you are then leaving the flatest part so every compression will again increase bumpsteer.
So how come we aren't all complaining about bumpsteer all the time then, its because when the outside wheel toes out, the driver unkowingly turns the wheel more automatically to compensate. All your doing is reducing the car's ability to tuen in.
The main time you notice bumpsteer is when you drive down a bumpy road and one of your front wheels hits a pot hole, and the car then steers on that side due to bimpsteer. It can create a very unsteady car at high speed on B-roads that is undeesirable.
If you have lowered you car and the steering tie rods are pointing up rather than down then the Bumpsteer correction kits (ignoring the rose joints) will improve this situation but these are often generic so will still not remove the problem. The first step is not to lower your car too much in the first place so you can keep the amount of bumpsteer correction to a minimum too.
Spring Rate
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Tyre choice
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Tyres are THE most critical part in optimising the grip and handling of a car. I read a post from a Sentra racer who was able to lap faster on a stock (and worn) car with race tyres than his race car with stock tyres.
The problem with race tyres is they are designed for tracks rather than roads.
You have to weigh up what you want from the tyre then do a search and see what peoples experiences are:
As tyre products change all the time, what's the best tyre today won't necessarily be the best tomorrow. However, the UHP (Ultra High Performance) tyres in all the good brands are the best place to start. For what its worth, the Goodyear F1's are the best wet weather tyre, semi slicks are the best dry weather tyre. Some brands have good wear whilst others delaminate in 20 minutes on atrack. You pays your money you takes your choice.
Tyre pressures
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These are what most people with a stock car can easily and cheaply play with to affect the car's handling. There is no holy grail of tyre pressure settings as everyone has different tyres, wheels, roads and weather conditions so this is quite a general section as there are no "right" settings. Before you start though, get yourself a decent pressure gauge and/or pump. My pump is accurate to 1psi and when I filled my tyres to 34psi and checked them on the fancy digital tyre pressure machine at Tescos, they read 38psi. 4psi is the diffference between a tyre working right or understeering all over the place.
-What I can say is there are wrong settings. My mate has just bought a GT4 and was complaining of twitchy handling and mumbling about the need to change shocks springs and make all sorts of modifications. I asked if he'd checked his tyres. He found the front right and back left at 38psi whilst the other 2 tyres were 34 and 32 repectivley. He set them all to 36 and hey presto everything was fine, twitchiness gone.
-Around Winter time your pressures can start to drop if you've not checked them do it now.
-Different tyres work best at different pressures because of the following reasons:
Tyre temperatures, more pressure stops them overheating as much under load (Which is one of the reasons why you run higher temperatures at high speeds). The rubber on your tyre is designed to work at a specific temperature, changing the pressure and temperature it gets too under load will help it stay at that temperature. This is one of the reasons why race tyres are pants on the roads and why road tyres delaminate on the track.
Tyre Profile, many tyres nowadays have 3 or 4 rolling profiles to try and keep as much tyre in contact with the road for most of the time. A tyre will work well at one pressure but not another for this reason. Low profiles are a good example where they generally need higher pressures to maintain their shape under load
Sidewall stiffness, similar to the above but some higher profile tyres will sag and bag at lower pressures so you need more pressure to keep them from folding over at high speeds.
Comfort/Suspension, a tyre will only work when it is contact with the road (kind of obvious) but if you over inflate your tyres on the road, it can feel skittish over bumps and not grip as well. This is because your tyres are the first part your car uses to soak up bumps and are a very necessary part of the suspension. I once read how TVR chassis engineers preffered 15" rims on their cars as the higher profiles were an important part of the setup. They only begrudgingly moved to 17" and 18" because of fashion. If the B-roads round you are far from smooth, try dropping a few psi and you might find the tyre rolls more but overall they grip better.
-For the GtiR tyre pressures of between 30 and 38 should cover all the tyres and all the profiles. You should try each pressure for a few days and see how you get on. Increase the pressuers in 2psi increments until you feel things are not working as well. Once you've found your optimum, drop it back 2psi and double check whether it was better or worse.
-One of the most important thing you can do with your tyre pressures is adjust the cars grip and balance front to rear. In theory, rear tyre's need less pressure as they are under less load (That 70/30 weight distribution again). Putting in more pressure in than optimum should rediuce the amount of grip the tyre can provide so making the rears run out of grip before the front. This can help with understeer problems but be aware that less grip at the back might also cause oversteer problems which can be equally as frustrating. Try running the back at the same pressure, try 2psi lower and 4psi lower and see what gives you the best handling balance.
-For the standard 195/55/14 (I kid you not) Nissan recommded 36psi if I've read my Japanese correctly. My thinking is this is to solve the problem of excessive roll under cornering but also cover the driving at 120mph with 4 people and a full boot load of stuff base. Though it sounds silly, consider whether you do go blasting around on your own or with all your mates in the back before you choose optimum pressures.
-I personally run a 2-4psi difference front to back, this is beacuse I am a car geek
and when measuring the ride height I noticed with my tyres, the 4psi difference, meant the wheel centre to floor distance was the same on the front and back so the tyres had the same profile. This was my starting point for setting up the suspension. At the moment I'm running a 36psi front and 32psi rear but as the weather changes these will probably change too.-I find on my car when the tyre pressures drop to 32psi, the handling loses its edge and the car starts to understeer more.
-For track days, consider putting an extra couple of psi in the tyres before you go on track and take a decent pressure gauge and foot pump so you can change the pressures during the day. You will also be surprised at how high your pressures will get after a session.
-For drag racing, consider dropping a few psi to make the tyre profile flatter and provide more straight line grip.
Tyre Pressures Overall
-Tyre pressures have a direct affect on the grip available from a tyre at a given temperature in given raod conditions. Knowingly running less than optimum tyre pressures on the back can help with understeer by makeing the car more prone to oversteer. However, ideally its worth optimising the grip from your tyres and using the rest of your suspension to optimise the balance.
To be conituned
Jim
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