FAQ - Suspension - Setting up the handling
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
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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
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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.
