2023 Civic Si Spring Rates, Motion Ratio, Ride Frequencies, Autocross

[absolude]

Gotcha thank you

Sure, NP!
Maybe I should say that the front is slightly higher than the rear. Is this the case for stock springs???
In that case, I'd try the AFE Type R springs. Those are progressive and start from 165 lb/in., which IIRC, is the same as stock Si's rate. Thinking it'd be less bouncy on rough roads.

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[ValkenDnB]

Sure, NP!
Maybe I should say that the front is slightly higher than the rear. Is this the case for stock springs???
In that case, I'd try the AFE Type R springs. Those are progressive and start from 165 lb/in., which IIRC, is the same as stock Si's rate. Thinking it'd be less bouncy on rough roads.

Do you have a picture?

 

[ValkenDnB]

 

[absolude]

Thanks for the pic. Is the road slightly downhill?
Petty sure mine is higher in the front compared to rear.
I'll take a picture if I drive it to work tomorrow.

 

[absolude]

Forgot about this one I took not too long after install.
Maybe I should take another one in the same spot...

 

[ValkenDnB]

Thanks for the pic. Is the road slightly downhill?
Petty sure mine is higher in the front compared to rear.
I'll take a picture if I drive it to work tomorrow.

It’s up slightly. So slanted up from left to right.

 

[absolude]

According to these pictures I took today it seems to have settled in the meantime...

 

[ValkenDnB]

According to these pictures I took today it seems to have settled in the meantime...

Yeah that actually looks good. Can’t find any FK8 springs near me only FL5 unfortunately.

 

[absolude]

Yeah that actually looks good. Can’t find any FK8 springs near me only FL5 unfortunately.

Got mine used on Marketplace. I'd love to try the ones I mentioned before. These are a bit bouncy on real rough roads.

 

[Dazzling2394]

Still happy with those FK8's in place? Also, did you get anything to dial in /correct the camber up front?

 

[DYI01]

Yeah that actually looks good. Can’t find any FK8 springs near me only FL5 unfortunately.

I have a suspicion that the FL5 springs will work just fine, and might even sit a hair lower than FK8 springs will. I'm talking like 2-4mm here.

Still happy with those FK8's in place? Also, did you get anything to dial in /correct the camber up front?

I'm still very happy with the FK8 springs. All I did was pull the front camber pins before going and getting my car aligned. It for sure needs an alignment once you take apart the front end plus adding in camber, it throws the toe out just a hair.

I don't really have the bounciness on rough roads that @absolude mentions, I think the rebound damping on the OEM struts is more than capable to handle the increased spring rate for a while. The front end much firmer with the stiffer springs, but I would never characterize it as bouncy. If you've ever ridden in a car with some blown out dampers, you will know what I mean. I'm sure over the lifetime of the vehicle it's likely reduced the lifespan of the front struts, but hopefully Koni or Bilstein will have some good options in the future.

 

[absolude]

I don't really have the bounciness on rough roads that @absolude mentions, I think the rebound damping on the OEM struts is more than capable to handle the increased spring rate for a while. The front end much firmer with the stiffer springs, but I would never characterize it as bouncy. If you've ever ridden in a car with some blown out dampers, you will know what I mean. I'm sure over the lifetime of the vehicle it's likely reduced the lifespan of the front struts, but hopefully Koni or Bilstein will have some good options in the future.
[/QUOTE]

Thank you for pointing this out. I want to clarify this as best as I can.
I'm not experiencing bounciness like when the spring compresses and then moves up and down a lot, like in the case of blown or mismatched shocks.
Probably the right word is bumpy.
It's more the smaller imperfections, when I assume the spring doesn't compress, or compresses very little, that cause this very busy ride, making the car feel a bit unsettled . I'm bobbing about on rough roads a bit more than I like.
Pretty sure this is a non issue in places where the roads are good. When I'm out of Toronto is pretty much smooth sailing. Too bad my work is downtown where the roads are shitty.

This is the reason I was thinking about the AFE springs for Type R.

 

[Dazzling2394]

That almost sounds like too stiff, meaning the impact transmits and the spring is not even having time to dampen down any of the response?

 

[absolude]

That almost sounds like too stiff, meaning the impact transmits and the spring is not even having time to dampen down any of the response?

Could be. To me they feel very close to the HFP springs in my 8th gen that are around 300LBS/in.
Except the HFP kit is tuned together with the shocks and is just very firm and not bobbing about.

 

[SlowAP2]

OEM Data	N/mm	kg/mm	lb/in
Front Spring Rate	27.00209276	2.753447178	154.186
Rear Spring Rate	55.90501125	5.700724636	319.226
Front Wheel Rate	25.50155572	2.599546965	145.7231756
Rear Wheel Rate	31.46229801	3.207165954	179.7845601

Vehicle Data
Total Vehicle Weight (kg)	1339
Front Weight Distribution (%)	60.3
Motion Ratio (Front)	1.029
Motion Ratio (Rear)	1.333

For the MR, did you calculate this yourself or find a source for it? Never seen MR as being over 1, it should be under 1 AFAIK. Then wheel rate is Spring X MR^2. The math isn't mathing for me here. Even if the MR should be flipped, .971 F and .667 R, those don't add up to the wheel rates listed. Front is in the ballpark regardless since its a strut car and the MR is essentially 1, rear is where I'm more curious.

https://robrobinette.com/Suspension_Spreadsheet.htm

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