400Z Track Day

[Thefunk]

Maybe they will charge you for shipping or give a discount. Ive been using the standard springs to test to figure out the rates, if you have the Swift upgrade then you will probably have to buy them. Ive been working with William on developing the 2 way and they have been nothing but amazing the whole time. They have since changed the default rear rate to 8K after my testing.

When I was talking to him prior to ordering we never discussed spring rates (I didn't know enough at the time to ask) nor did he suggest rates. I asked for the swift springs so I could avoid a manual preload. But as far as the stiffness of the springs, the only issue is my body sometimes getting launched out of the seat. I believe a proper 4 or 5 point harness will solve that. I tested the car out on some local areas that are dead at night and the handling is way better already. The car stays planted to the road, just need to keep myself planted in the seat.

 

[D2M]

When I was talking to him prior to ordering we never discussed spring rates (I didn't know enough at the time to ask) nor did he suggest rates. I asked for the swift springs so I could avoid a manual preload. But as far as the stiffness of the springs, the only issue is my body sometimes getting launched out of the seat. I believe a proper 4 or 5 point harness will solve that. I tested the car out on some local areas that are dead at night and the handling is way better already. The car stays planted to the road, just need to keep myself planted in the seat.

Exactly what I felt with the 10K rear. What you are feeling is the shock not being able to handle the stiff rate, you may also be feeling the rear shock top out as there is very little sag with the 10k. So basically the body is being flung up by the spring and the shock runs out of travel because there isn't enough sag to let the shock work in both directions. The 8K with 5mm preload puts the shock where it needs to be, lets the car squat slightly and dig out of corners noticeably harder than stock without squatting too much to induce understeer. 8K is the correct rate, the ride quality is like oem Nismo but without blowing though its travel over every double dip in the road. This is what I sent to them after 3K miles of testing.

10K Rear spring

.Low sag at zero preload so the rear suspension tops out easily over big dips, may work better with negative preload and a helper spring

.Good resistance to bottoming as spring is very stiff and has limited travel

.Harsh ride no matter what damper settings is

.Rear gets upset easily over mid corner bumps

.Limited rear squat under hard acceleration, chassis has good rotation on corner exit but can cause wheel spin

.Difficult to find a good damper setting

.I would consider this a high compromise setup


8K Rear spring

.At 5 mm preload has good amount of sag so shock is resistant to topping out

.Good ride quality

.Good resistance to bottoming

.Good stability over mid corner bumps at speed

.Easy to control the spring with damper settings, easy to find a desired damping feel. Immediately falls into desirable damping range.

.Good traction on corner exit and in straight line under hard acceleration.

.Overall a very low compromise setting, good at everything and easy to set up

 

[Thefunk]

Exactly what I felt with the 10K rear. What you are feeling is the shock not being able to handle the stiff rate, you may also be feeling the rear shock top out as there is very little sag with the 10k. So basically the body is being flung up by the spring and the shock runs out of travel because there isn't enough sag to let the shock work in both directions. The 8K with 5mm preload puts the shock where it needs to be, lets the car squat slightly and dig out of corners noticeably harder than stock without squatting too much to induce understeer. 8K is the correct rate, the ride quality is like oem Nismo but without blowing though its travel over every double dip in the road. This is what I sent to them after 3K miles of testing.

10K Rear spring

.Low sag at zero preload so the rear suspension tops out easily over big dips, may work better with negative preload and a helper spring

.Good resistance to bottoming as spring is very stiff and has limited travel

.Harsh ride no matter what damper settings is

.Rear gets upset easily over mid corner bumps

.Limited rear squat under hard acceleration, chassis has good rotation on corner exit but can cause wheel spin

.Difficult to find a good damper setting

.I would consider this a high compromise setup


8K Rear spring

.At 5 mm preload has good amount of sag so shock is resistant to topping out

.Good ride quality

.Good resistance to bottoming

.Good stability over mid corner bumps at speed

.Easy to control the spring with damper settings, easy to find a desired damping feel. Immediately falls into desirable damping range.

.Good traction on corner exit and in straight line under hard acceleration.

.Overall a very low compromise setting, good at everything and easy to set up

If 8k is the proper rate for the rear then why would they sell me the 10k springs??

 

[D2M]

If 8k is the proper rate for the rear then why would they sell me the 10k springs??

They simply didn't know, I started out with a 10K rear as well. Im guessing the are going by axle weight / spring rate chart. The front is more forgiving because of the lower motion ratio. The rear is more critical as you only have 110mm of travel as the motion ratio is close to 1:1 so it has to be optimized. I'm super OCD about chassis setup so I volunteered my time to test. Once set up correctly the shocks are awesome. RZ34 is a new chassis so as early adopters we are all kinda guinea pigs. Ask William for a discount, I'm sure he will hook you up. Sell your old springs, Swift coilover springs are universal and desirable, someone out there needs a 10K. Or maybe they will just do an exchange.

 

[Thefunk]

RZ34 is a new chassis

I know the R stands for refined but isn't the chassis the same as the 370z?

 

[D2M]

I know the R stands for refined but isn't the chassis the same as the 370z?

First apologies to the OP for us jacking his thread. Hopefully some of this information will be reinvent to him at some point.

Yes, the mounting points are the same as z34 but the weight and power are different, the power output will affect the weight transfer thus affecting the suspension. There is a limited window in the rear due to the limited travel. Most aftermarket coilovers use a similar shock body with similar travel around 110mm so once you add in a bump stop you are down to around 80/90mm of useful travel, that's about 3" ( not a lot ) Rule of thumb is %30 sag and %70 left for bump and that's what the 10K spring will give you at 0mm preload. However I found that not to be enough sag. The spring is too stiff to use the left over %70 bump travel and wants to easily top out the rear suspension. When the suspension tops out it wants to pull the wheel off the ground and when the wheel is off the ground or light you have a loss of traction. The 10K may work better with a helper spring and some negative preload but just swapping to an 8K just simply works. It puts the sag about %55 and that's enough to let the suspension work but is still very resistant to bottoming out the leftover travel.

 

[Katum68]

I have a Nismo with 6K street miles and my front pads are already %50 worn. I could see myself blowing through a set of pads in 1 track day. Luckily they are cheap. I haven't found any performance pads or rotors for the Nismo yet, so not tracking this car just yet.

Check Z1 Performance in Georgia

 

[D2M]

Check Z1 Performance in Georgia

I bought the last 2 sets or OE pads Z1 had in stock. Also got a set of lines as well. Im ready for next season, Im only planning to do 1 track day in this car next year.