BC Racing Spring Rate recommendations.

[Sushzzz]

So I'm looking to order the the BC Racing ER-Series for my Nismo. Im looking for daily driving comfort with compress/rebound adjustability. The default rate is
F - 10KG | R - 5KG:
Front can be swapped for 12/14/16/18kg
Rear can be swapped for 5/6/8/10/12/14/16/18kg (5kg seems very soft?)


I had BC Racing DR-Series, default SR, on my 350z. They where amazing, completely changed the the drive characteristics of the car in a good way.

Any Suggestions before I buy?
https://shop.bcracing-na.com/products/22-nissan-400z-true-coilover-rear?variant=43922050089216

(Related Question)
Does anyone know why the default rear spring rate for the True coilover (5KG) and the OEM type (9KG) are different ?
https://shop.bcracing-na.com/products/22-nissan-400z-true-coilover-rear?variant=43922050089216
https://shop.bcracing-na.com/products/2022-nissan-z

 

[VR30Infection]

There is a difference between spring rate and “wheel rate” which is what is important. Wheel rate is what is seen at/ effects things at the wheel. It is what is felt and what matters. In a suspension system you have a pivot point where the suspension arms connect to the chassis and then you have a given distance from that point to the spring, and then from the spring to the wheel. If the spring were connected to the wheel then the spring rate and wheel rate would be the same. On the rear suspension of the Z the spring is inboard from the wheel and therefore the spring has to be stiffer at this in board position in order to give you the same wheel rate as a car setup with a true coilover rear because the true coilover has the spring closer to the wheel. This difference is called a motion ratio.
As far as suggestion goes, it really depends on what you’re after. What one person considers great, another person could think is way to stiff.
I hope this helps.

 

[Sushzzz]

There is a difference between spring rate and “wheel rate” which is what is important. Wheel rate is what is seen at/ effects things at the wheel. It is what is felt and what matters. In a suspension system you have a pivot point where the suspension arms connect to the chassis and then you have a given distance from that point to the spring, and then from the spring to the wheel. If the spring were connected to the wheel then the spring rate and wheel rate would be the same. On the rear suspension of the Z the spring is inboard from the wheel and therefore the spring has to be stiffer at this in board position in order to give you the same wheel rate as a car setup with a true coilover rear because the true coilover has the spring closer to the wheel. This difference is called a motion ratio.
As far as suggestion goes, it really depends on what you’re after. What one person considers great, another person could think is way to stiff.
I hope this helps.

Man thank you! That makes alot of sense, great explanation on the why the true coilovers vs OEM type has a different default SR. Im looking to go with a true coilover, but still not sure on the SR to go with.

 

[FSUZ33]

There is a difference between spring rate and “wheel rate”...

This is something cool to know, so I want to make sure I understand.

I realize it depends on the position of the springs, but specifically on the RZ34,
if I want to change to a true coilover rear and want the same compression feel ("compression force"? not sure what to call that), I would need a softer "spring rate" on the coilover because of the location of the spring itself?

#Physics ... and we haven't discussed the geometry differences and the effect on compression and rebound damping

On another note, has anyone determined the stock spring rates for the NISMO?

 

[VR30Infection]

As far as the compression and rebound damping goes you would be forced to trust the company you are going with, in this case you would be trusting BC to properly set the valving on the shock itself to work properly with your chosen spring rate and spring location.
And yes. For a given feel you could have 2 identical cars and have one setup with a divorced rear like stock and the other would have coilover rear and if they both drove the same and felt the same, then the one with the coilover rear would have a lighter spring rate to accomplish this.

 

[ForSale24]

So I'm looking to order the the BC Racing ER-Series for my Nismo. Im looking for daily driving comfort with compress/rebound adjustability. The default rate is
F - 10KG | R - 5KG:
Front can be swapped for 12/14/16/18kg
Rear can be swapped for 5/6/8/10/12/14/16/18kg (5kg seems very soft?)


I had BC Racing DR-Series, default SR, on my 350z. They where amazing, completely changed the the drive characteristics of the car in a good way.

Any Suggestions before I buy?
https://shop.bcracing-na.com/products/22-nissan-400z-true-coilover-rear?variant=43922050089216

(Related Question)
Does anyone know why the default rear spring rate for the True coilover (5KG) and the OEM type (9KG) are different ?
https://shop.bcracing-na.com/products/22-nissan-400z-true-coilover-rear?variant=43922050089216
https://shop.bcracing-na.com/products/2022-nissan-z

I went with Fortune Auto "500s" my spring rates are 11 and 4. this is a True Coilover fitted to a 2024 MT Proformance.... 4 and 11 does sound soft on paper but the ride does feel stiffer than OEM, just a touch(my dials are all turned to the softer side) ... my only two guesses are (1 the spring itself is moved outwards because of the stock divorced set up like VR30infection was saying so a stiffer spring is not needed to keep the "same" ride quality.... and or (2 Fortune Auto uses a "digressive piston" set up vs "linear pistons" like (BC) the rest of the industry.....also, to determine the stock spring rates for the NISMO? i would try to make a new post to get a quick response... otherwise it might already be in another thread

 

[Murix]

There are several threads asking for the stock NISMO spring rate and thus far none have been answered.

Nice insight on spring rates for someone like me who is new to inboard springs. What is the advantage to even doing this?

 

[ForSale24]

There are several threads asking for the stock NISMO spring rate and thus far none have been answered.

Nice insight on spring rates for someone like me who is new to inboard springs. What is the advantage to even doing this?

To replace the spring buckets with new Toe arms. You need the new Toe arms, with true coilovers . Good idea to replace all three arms(traction, Toe and camber) , but the toe arms are the ones that have the spring buckets.
removing the huge buckets for (Z1 arms maybe) is a weigh savings. Along with other arms like Upper Control Arms in the front will allow for alignments to be done when you buy some crazy offset for new wheels... i halfway quoted @VR30Infection for this response. jump in if i missed anything. pics from "JonnyG"

 

[VR30Infection]

Another benefit to true coilover is the ease of adjustment.

 

[Sushzzz]

Another benefit to true coilover is the ease of adjustment.

Opposed or related to what?

 

[VR30Infection]

Opposed or related to what?

Opposed to a ride hight adjustment on top of the inboard spring on a divorced setup like stock. Now there are ride height adjustable toe arms from SPL that make it easier because the adjustment is done from the bottom and is therefore easier to get to but they aren’t cheap and as stated earlier in the thread, you don’t get the added benefit of loosing some unsprung weight which is the enemy. Really the biggest argument against a true coilover rear would be whether or not the chassis can handle the weight of the car at the rear strut tower. Many Z33’s and Z34’s and G’s have ran true rear without issue so…. The GT4 cars have true rear as well. However they also have a pretty beefy roll cage triangulated back there and are for sure helping to stiffen things up. So in this matter, everyone has to make the call themselves. I personally have talked to multiple companies about this and have decided to go true rear.

 

[FSUZ33]

Never had coilovers, or at least not adjustable. What changes the ride height? I think you can screw the threaded barrel(?) in and out of the perch, which changes ride height, correct? Does changing the spring preload adjust the ride height as well?

Also, if you go true coilovers on the rear you HAVE to change the toe arms? If so, I guess that makes sense if the OEM toe arms are just spring buckets with nowhere to mount a perch.

 

[VR30Infection]

Never had coilovers, or at least not adjustable. What changes the ride height? I think you can screw the threaded barrel(?) in and out of the perch, which changes ride height, correct? Does changing the spring preload adjust the ride height as well?

Also, if you go true coilovers on the rear you HAVE to change the toe arms? If so, I guess that makes sense if the OEM toe arms are just spring buckets with nowhere to mount a perch.

As far as changing ride height is concerned, it depends on the coilover design. Most of them are designed to use the lower mount as the ride height adjustment and the preload is used to set your droop. In a true Motorsport coilover the bottom mount is set and the preload is used for height/ corner weighting.
As far as the arms are concerned, you do not have to change them in most cases. There are tow adjustments with eccentric washers. Now you could lower the car and surpass the stock adjustment range and then you would NEED adjustable arms to get things right. Now again, you would want to change the arms to get rid of the unwanted weight.

 

[ForSale24]

As far as changing ride height is concerned, it depends on the coilover design. Most of them are designed to use the lower mount as the ride height adjustment and the preload is used to set your droop. In a true Motorsport coilover the bottom mount is set and the preload is used for height/ corner weighting.
As far as the arms are concerned, you do not have to change them in most cases. There are tow adjustments with eccentric washers. Now you could lower the car and surpass the stock adjustment range and then you would NEED adjustable arms to get things right. Now again, you would want to change the arms to get rid of the unwanted weight.

lol he is talking about a dark path my friend...(we gave you what you need for true coilovers, Toe Arms) IF you wanna go crazy: Traction arms , Toe arms, and Camber arms in the rear and Upper Control arms in the front, plus a rear anti sway bar to go with your coilovers. will make the new wheels and tires fit as clean as you need. dont ask me how i know. I just pay Z1 for my addiction/parts

 

[VR30Infection]

lol he is talking about a dark path my friend...(we gave you what you need for true coilovers, Toe Arms) IF you wanna go crazy: Traction arms , Toe arms, and Camber arms in the rear and Upper Control arms in the front, plus a rear anti sway bar to go with your coilovers. will make the new wheels and tires fit as clean as you need. dont ask me how i know. I just pay Z1 for my addiction/parts

Hey! I’m innocent and just trying to be helpful!