Ditto. Same boat as Frist350.

 

The info I have on those springs has them at 625/700, which is data that Nissan Motorsports didn't want to come out since they declined to tell me the exact rates first hand. The 690/690 figure was also mentioned in the same timeframe that I got my rate info, though the 625/700 rate came from more then one source that I felt were both more reliable. Long story short, can you please rate test them so their isn't any question about the numbers?

 

Curious, what do you get as the wheel rates front and rear?

Just using spring rate I take your 50% increase to mean
314lbs ^50%= 475lbs front
342lbs ^50%= 513lbs rear (not sure which oem rear spring your working with, 342lbs or 427lbs).

 

^ those numbers are pretty close to the Nismo S-Tune coilovers spring rates:

F: 436 lbs/in
R: 498 lbs/in

However w/ only a .8 " drop there's not much camber to be gained.

 

I just had my car aligned yesterday and I wanted to put an end to the speculation around the ralationship between camber and toe. Here is what we found on my car:

Adding 1.5 degrees of (neg) camber toed each wheel in 1/16". I was hoping that adding camber would add some toe out, but no such luck. Looks like my street setting has 1/8" more toe out than my track setting. Oh well, my front tires still last me 20k+ miles.

As far as testing spring rates. I've been told by a reliable source that they tested in the 680 range front and rear. Mynismo.com also lists them at 690 F&R.

 

Without going into the motion ratio calculations involving the angle of the springs, arms, anti-dive, etc., a ballpark estimate is .625 of the front spring rate and .550 of the rear spring rate.

The rear wheel rate on a 350Z is softer then the front rate given equal springs. So, a 690 front spring works out to a 431 wheel rate and a 690 rear spring works out to a 380 wheel rate. Also, based on an eyeball of the spring position and suspension geometry, both the front and rear suspension on a 350Z have an increasing wheel rate in bump with the front increasing at a faster rate then the rear.

EDIT: If someone has actually done the motion ratio calcs I would love to see them. The above is based on quick measurements made when my car was on the lift.

 

In response to some posting above here are some numbers that I measured with my Z.

The front end gains 1deg of camber per in. of bump....... .8 lower equals .8 deg more neg camber.......LS-1.8 RS-2 based on average static numbers

More camber will produce toe in, BUT lowering the car will produce toe out....about 1/32 out per side per in. of drop.....up to 1/16 out per in. per side with more travel. The rear gains toe in with bump....starts at 1/16 per in. and goes to 3/32.

The motion rates (as I measured and averaged them over full travel) are.... .688 F and .649 R (measured at center of spring)
theses rates with #690 springs equal at the wheel....326.6F 290.6R
stock revised...........146.3F 189.9R

The one thing that is easy to miss is that the Z relies on the front bump stops for spring rate. It is common for manufacturers to use soft springs for ride comfort along with a progressive bump stop that engages early to control big susp. movement. I haven't rated mine YET.

John, Your guestimates are close to what I figured when I did natural frequency calculations for my car. F w/850=2.3Hz Rw/600=2.1Hz
In reality the rear is too stiff (read SCARY) for a typical auto-x lot. It would proably be close for road course use.

mike

BTW BSP was 4.5 sec faster than SM2 at nationals .....WOW......maybe it's time for a supercharger.

 

Good info. The motion ratios are pretty close front to rear and the early engagement of front bump stop now has me understanding why Nissan went to higher rear rates on the later cars. Personally I've never been comfortable using bump stops as a suspension tuning tool, but that's probably due to ignorance.

 

These are some pics of my upper bushings.

The reason I put a hex on one end and used a set screw in the arm is for easy camber adjustment......in case I started killing my street tires.

John, the arms are boxed up and I'll ship them out Mon. I can't find my notes on when the stock bump stop contacts from stock height, but at my ride height it's only about 5/8 of wheel travel. What do you think of these tire temps? 43 psi F 29psi R -2.5LF -2.7RF -2LR -2.2RR

122 123 131LF..... 127 128 132RF..... 116 119 125LR..... 122 123 124RR.....All read from outside to inside.

 

Not hot enough. If possible, get the tires into the 150 to 170 range for autox. Maybe drop the pressures 2 psi all around. Not knowing the course layout I'm guessing it was mostly left turns or the finish had a left which makes your asymetric camber work. You could even stand the rights up a couple tenths.

But, again, I haven't seen the course and the most important turn(s) might be a right onto a longer straight.

 

Hoosier A6's get greasy if they get too hot. Ideal is 140-150 (according to Hoosier) Those temps were after 1 run on a 31sec course. Yes, it was mostly left turns.

BTW If you make upper bushings like mine, the set screw would be a lot easier to get to if it were on the bottom.

 

when you make these, could you make me a set as well?!?! just let me know how much it'd be...I'd really love to see how these work

thanks!

 

I'll probably make a few sets once the prototypes are on my car and tested a bit. I don't like to test on a customer's car.

 

Hippie, can you explain how you adjust those? I like the fact that I can easily adjust my evos for street and track use.

 

If you rotate the bushing 180 deg it lengthens the upper arm (ball joint to pivot point) and reduces neg. camber. I can't tell you exactly how much b/c I haven't done it.....street tire wear isn't that bad. I "think" it would reduce neg camber by 1.2-1.5 deg.

John, you should have the arms Friday. Also, you mentioned my asymetric camber........that's not on purpose. I just got as much neg camber in the front as I could and then matched the split in the back.

 

What keeps the bushing from rotating under normal use. Is there a locking mechanism?

 

Usually its an interference fit or you can use a set screw.

 

Bringing this back because I'm after some clarity.

when I math out the motion rates you list above I don't get the same wheel rates you do.

.688 X 690lbs= 474.72lbs
.649 X 690lbs= 447.81lbs

If I switch to 1 -.688 = .312 then x 690lbs, I still get 215.28lbs.

Are you really sure about the rear numbers? Isn't the distance spread between the center of the spring to the wheel hub greater in the rear vs the front? your numbers show a 3.9% differance. When I measured things 4 years ago, the rear motion rate was about 16% less then the front even when I factored in a 10 degree angle correction for the front. I really don't mind being wrong, but I'm working on something where I need very accurate starting figures.

 

When figuring wheel rate you must square the motion rate before multiplying by the spring rate. The reason is because you are doing the math for two motion rates at once.....pounds of force and inches traveled.

spring=690 lbs/in........690 X .688 (lbs rate) X.688 (in. travel)....326.61 lbs/in

I'm not going to guarantee that my numbers are perfect, but I'm confident that they're within a couple percent. I measured them the easy way in my garage.......1" travel at the wheel = X travel at the center of the spring or coilover.....averaged from 2" of droop to 3" of bump.

mike

 

Offset Hydlar bushing update... Sorry, haven't got to them yet. Hippie's control arms are still sitting in the box in my office. I will probably be doing some suspension work on my 350Z in February and I'll make the offset bushings then.