Just installed BC Coilovers and Spacers.

reissgrant

reissgrant

Member
- Just installed BC coilovers and H&R spacers (30mm front and 25mm rear). Running 9 clicks from hard in front, and all the way hard in the rear. You guys who changed the springs to different rates, where did you get your springs from? Not sure I am happy with these 8kg fronts and 12kg rears.
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Swift & BC offer different rates. I'm running 10/12. Feels pretty good. A little soft at times, but car can be thrown around and is controllable on rough roads
 
^^ that's who I got my higher rate springs from. I went to 12/14 which at the time was the highest they made for this application. But I think now you can get higher rate ones.
 
Thanks guys, pm'd him about springs and rear camber kit.

Shadow, 12kg is what I'm going for in the front. How are you liking 12kg? Would you recommend it or something else?

Tapatalkin'
 
I did not need Camber kit. I'm still in spec.
Unless you slam it, it's not required. I think you look OK at this height
 
It's a firm ride but ok for me. Small bumps are a little harsh but big bumps and dips are fine. Keep in mind that if you up the front to 12, you'll need higher in rear to maintain balance. Rear spring rate should be 16 or higher IMO. At 14, my rear feels much softer than front but it was only option at time. It's because of suspension design.
 
OK... So I talked to the guys at BC and they said it was 8K/12K Front/Back as standard (I upped mine when I ordered to 10K/14K)... This always looked backwards to me but whatever, the specialist at BC must know what he's talking about... Then I recently talked to a member that said it's the other way around... And his logic sounded firm... But just checked my invoice and it states 10K front and 14K rear as per my custom requests...
 
8 front 12 rear is standard. Front is lower rate on strut design suspension. There are calculations that can tell you what rear spring rate should be based on front for better balance but I've never done it. I will say that I don't feel my setup is as balanced as it could be with the 12k front and 14k rear. Rear feels softer than front - if there was a 16 or 18 at the time for the rear, I would have done that.

And OP, yes mine are preloaded ~5mm or so. Preload doesn't impact the ride, it's mostly to prevent noise and potential spring bind from movement. The springs are linear so preload will not change rate.
 
shadow191 said:
8 front 12 rear is standard. Front is lower rate on strut design suspension. There are calculations that can tell you what rear spring rate should be based on front for better balance but I've never done it. I will say that I don't feel my setup is as balanced as it could be with the 12k front and 14k rear. Rear feels softer than front - if there was a 16 or 18 at the time for the rear, I would have done that.

And OP, yes mine are preloaded ~5mm or so. Preload doesn't impact the ride, it's mostly to prevent noise and potential spring bind from movement. The springs are linear so preload will not change rate.
Click to expand...
I did some calculations using a little less than our gross weight with 53% ratio in the front minus unsprung weight using the distance from the pivot to the strut with an 8" spring (3.5" strut travel) and came up with 650lb springs (11.6kg)...And that's for a street setup, not semi-race or race. Where BC arrived at 8k I have no clue...

Tapatalkin'
 
I'm curious to see if this thread/idea ever went anywhere.

The reason the rear rate is higher is because there is a different motion ratio for the rear suspension than for the front:
Automotive Spring Rate Calculator | Wheel Rate Calculator | Hyperco

So, if the FX has 50/50 weight distribution (it doesn't) you would want your wheel rate to be the same front and rear (generally speaking). But with completely different suspension designs, that will require higher spring rates in the rear to make up for a lower motion ratio back there. That's how BC came up with their spring rates.
 
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