[N54th]

For those with coilovers and custom spring rates; what is your current and past setups? Considering 8.5k front and 13.5k rear. Reason why I'm going with these specs is to stay with the 3:1 ratio of the factory springs. I can also adjust the dampening to compensate for stiffness. The spring rates on the XI model is wayyyy too soft and floaty on bumps and turns for my liking.

[Julian2485]

Originally Posted by N54th

For those with coilovers and custom spring rates; what is your current and past setups? Considering 8.5k front and 13.5k rear. Reason why I'm going with these specs is to stay with the 3:1 ratio of the factory springs. I can also adjust the dampening to compensate for stiffness. The spring rates on the XI model is wayyyy too soft and floaty on bumps and turns for my liking.

I have 6k/18k to stick with oem 1:3 ratio for my xi

[000ooo000]

How is 8.5k front 13.5k rear a 3:1 ratio? Am I missing something?

Originally Posted by Julian2485

I have 6k/18k to stick with oem 1:3 ratio for my xi

How does that feel? I feel like 18 would be too stiff but idk?

[Julian2485]

Originally Posted by 000ooo000

How is 8.5k front 13.5k rear a 3:1 ratio? Am I missing something?

How does that feel? I feel like 18 would be too stiff but idk?

It feels good honestly. I'm running the ycw coilovers with Swift springs

[000ooo000]

Originally Posted by Julian2485

It feels good honestly. I'm running the ycw coilovers with Swift springs

Is it pretty neutral? Im confused because I know stock is 1:3, but most coilover spring rates seem to be 1:2 (which would cause more understeer?)

[Julian2485]

Originally Posted by 000ooo000

Is it pretty neutral? Im confused because I know stock is 1:3, but most coilover spring rates seem to be 1:2 (which would cause more understeer?)

Yes it's more neutral feels way better

[miker2013]

Originally Posted by N54th

For those with coilovers and custom spring rates; what is your current and past setups? Considering 8.5k front and 13.5k rear. Reason why I'm going with these specs is to stay with the 3:1 ratio of the factory springs. I can also adjust the dampening to compensate for stiffness. The spring rates on the XI model is wayyyy too soft and floaty on bumps and turns for my liking.

i wish we knew what the spring rates were for the stock xdrive springs?

having said that, i have a set of koni yellows (paired with stock xdrive springs) with adj damping set at 1/2 from full soft and they could be set even stiffer to match the springs which actually appear to be at least average stiffness maybe stiffer

i agree stock xdrive is floaty and too much body roll, but i think the main issues are the shocks and the roll bars

[000ooo000]

Originally Posted by miker2013

i wish we knew what the spring rates were for the stock xdrive springs?

having said that, i have a set of koni yellows (paired with stock xdrive springs) with adj damping set at 1/2 from full soft and they could be set even stiffer to match the springs which actually appear to be at least average stiffness maybe stiffer

i agree stock xdrive is floaty and too much body roll, but i think the main issues are the shocks and the roll bars

Stock is 145/460lb/in for a frequency of roughly 1.21/1.35hz.

[N54th]

Originally Posted by Julian2485

I have 6k/18k to stick with oem 1:3 ratio for my xi

Originally Posted by 000ooo000

How is 8.5k front 13.5k rear a 3:1 ratio? Am I missing something?



How does that feel? I feel like 18 would be too stiff but idk?

Sorry meant 1:3 ratio not the other way around. All the XI models have the same spring rates. I'm now thinking I should go with 9k/14k.

[N54th]

Originally Posted by Julian2485

It feels good honestly. I'm running the ycw coilovers with Swift springs

Springs and valving makes all difference. 18k is 1008lbs/in. but in reality it's less than that since the rear suspension is not a true coilover.

[000ooo000]

Originally Posted by N54th

Sorry meant 1:3 ratio not the other way around. All the XI models have the same spring rates. I'm now thinking I should go with 9k/14k.

But 8.5/13.5 is about a 1:1.58 and 9/14 is 1:1.55. not 1:3????

8.5/13.5 results in a frequency of 2.19/1.74
9/14 results in a frequency of 2.26/1.76

These are rough calculations as your exact corner weights are needed but they should be close enough. As you can see the front will be much stiffer than the rear (higher frequency=stiffer, and usually anything over 2 is racecar territory). Stock is approximately 8% stiffer in the rear with a frequency of 1.21/1.35. Remember that the stiffer end will lose traction first, which means it will be very understeer biased (which if you like I guess it's good??). Also more stiffness equals less mechanical grip all around. High spring rates are only useful if you're going to slam the car or have the grippiest biggest tires.

And keep in mind running high spring rates in the rear will need better subframe bushings because the stock ones aren't strong enough to handle it.

Personally I just placed an order for 5k/15k so we'll see how that works.

[000ooo000]

Originally Posted by N54th

Springs and valving makes all difference. 18k is 1008lbs/in. but in reality it's less than that since the rear suspension is not a true coilover.

18k will result in a wheel rate of 319lb/in, basically the true spring rate. This is due to the rear spring being more inwardly placed. It is calculated based on the motion ratio of 0.563 for the rear. So wheel rate = spring rate * motion ratio ^2. In this case wheel rate=1008*.563^2.

[Julian2485]

Originally Posted by 000ooo000

But 8.5/13.5 is about a 1:1.58 and 9/14 is 1:1.55. not 1:3????

8.5/13.5 results in a frequency of 2.19/1.74
9/14 results in a frequency of 2.26/1.76

These are rough calculations as your exact corner weights are needed but they should be close enough. As you can see the front will be much stiffer than the rear (higher frequency=stiffer, and usually anything over 2 is racecar territory). Stock is approximately 8% stiffer in the rear with a frequency of 1.21/1.35. Remember that the stiffer end will lose traction first, which means it will be very understeer biased (which if you like I guess it's good??). Also more stiffness equals less mechanical grip all around. High spring rates are only useful if you're going to slam the car or have the grippiest biggest tires.

And keep in mind running high spring rates in the rear will need better subframe bushings because the stock ones aren't strong enough to handle it.

Personally I just placed an order for 5k/15k so we'll see how that works.

What coilover kit you order and which subframe bushings would you recommend i have m3 ones in

[N54th]

Originally Posted by 000ooo000

But 8.5/13.5 is about a 1:1.58 and 9/14 is 1:1.55. not 1:3????

8.5/13.5 results in a frequency of 2.19/1.74
9/14 results in a frequency of 2.26/1.76

These are rough calculations as your exact corner weights are needed but they should be close enough. As you can see the front will be much stiffer than the rear (higher frequency=stiffer, and usually anything over 2 is racecar territory). Stock is approximately 8% stiffer in the rear with a frequency of 1.21/1.35. Remember that the stiffer end will lose traction first, which means it will be very understeer biased (which if you like I guess it's good??). Also more stiffness equals less mechanical grip all around. High spring rates are only useful if you're going to slam the car or have the grippiest biggest tires.

And keep in mind running high spring rates in the rear will need better subframe bushings because the stock ones aren't strong enough to handle it.

Personally I just placed an order for 5k/15k so we'll see how that works.

Originally Posted by 000ooo000

18k will result in a wheel rate of 319lb/in, basically the true spring rate. This is due to the rear spring being more inwardly placed. It is calculated based on the motion ratio of 0.563 for the rear. So wheel rate = spring rate * motion ratio ^2. In this case wheel rate=1008*.563^2.

thanks for your input. What coilovers did you go with? Can't believe you lose that much spring rate in the rear.

[000ooo000]

I went with the bc racing in extra low (just because even though I'm not going to slam it). Seems like the best value. And as for subframe bushings, I know that m3 aren't much stiffer than stock, but if you don't notice any bouncyness and if everything feels tight then they're probably good. I think m3 people use some pretty high spring rates without issues.
I ordered some strongflex poly ones because they're the cheapest but I hear solid aluminum ones are great as well (and like 3x the price)

[N54th]

Knowing what I've learned in this thread and doing some more research I think 6k/18k and 5k/15k that both of you are running are a pretty balanced setup and keeps the motion ratio almost the same. So I will play with some numbers and decide from there.

[000ooo000]

The only think I'm not sure of is how changing ride height/spring height or other suspension components such as subframe bushings and control arms can impact the motion ratios and whatnot.

[N54th]

I would just adjust the dampers to be on the softer side.

[Julian2485]

Originally Posted by N54th

I would just adjust the dampers to be on the softer side.

Doing that would make the ride bouncy keep adjusting till your liking