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Rear Coilovers Spring Rates too soft? (ST-X / KW or BC Coilovers)

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667 views 7 replies 5 participants last post by  Chrisjames654  
#1 ·
I’ve just about hit a wall (figuratively speaking) deciding which coilovers to purchase for street and occasional auto-x use for my ‘13 Focus ST.

I’ve settled on 3 options:
  • BC Racing BR’s with custom rates
  • ST-X Suspension Technique’s (KW’s little cousin)
  • ST XTA (rebound adjustable)
Here’s my conundrum..
  • The rear FoST springs are a divorced setup, and I’ve read here that we need to account for the motion ratio by multiplying spring rates by 0.49 to get their effective / actual spring rate at the wheel
  • OE spring rates are stiffer in the rear (confirming this theory)
  • Yet 90% of coilovers are softer in the rear, supposedly just matching standard suspension designs of most cars, and/or possibly to maximize ride quality
  • I’ve seen a few actual mentions of autocross people say to go stiffer in rear based on real-life experience to preserve OE balance, encourage rotation of car, and minimize understeer

So my decision landed on getting some BC BR series at 7K F / 8K R which are pretty close to stock balance, while keeping the ride civil on street.
Image


  • But then… I noticed ST-X / ST XTA coilovers get rave reviews and some people say they’re superior to BCs
  • One post said he went from BC extreme lows to ST’s and the car handling was far better
  • I even called Suspension Techniques North America, and the ST’s have the same softer springs in the rear (400 F / 176 R progressive)
  • One review on CJ pony said his ST drives great but the rear felt a little loose, hinted at needing a rear sway bar with ST-X

Analysis Paralysis. I wish I could try the options on and go drive all, but here I am..

——————
Does anyone have experience / can talk to any of these options?

BCs with Custom Rates (7k/8k)
ST-X
ST-X with Rear Sway
KW’s
——————
 
Z
#3 ·
Lol going from BC extreme lows to blown stock shocks would be a massive improvement in handling.

YCW here. Love em.

@freakin_elrod I believe runs the Fortune. If i was going to do it again, I'd run those.

The Fortune's have the sway bar endlinks relocated. With the YCW (and ST among others) pulling the camber back results in the endlink hitting the frame. Quite annoying.

I run 8k front 11k rear.
 
#4 · (Edited)
Ok great info, thanks. I feel like many people like the initial turn in response of the upgraded 7K Front springs on most standard coilovers, but maybe don’t realize the 5K rears are too soft for more demanding driving.

I think that eliminates ST (suspension techniques) and KW’s from the list for me, unfortunately.

New list where I can customize springs:
YCW $1600
BC DS $1400
FA500 $1900

Fortune auto seems to hold the trophy all around, possibly because of the digressive piston
 
#6 ·
I ended up with BC racing DS due to the digressive piston, 7k front / 8k rear. Felt a tad understeery and I read good things about bigger rear sways so I installed that as well and it turns great. I’m going to track it soon and try it out, I may/may not bump springs by 1-2k depending on how track day goes. Will report back.
 
#7 ·
Curious on this as well. I currently run B14s for daily driver/uncompetitive AutoX, and the spring rates have so far done me well (can’t remember the exact rates, but I think it’s something to the tune of 4.5k F / 5k R.

My question is although you can certainly drive around it, one problem I’ve noticed is the stock rear sway bar is very hard to figure out. This was my first time driving at/over my limit, and I found it extremely hard to tell how much the rear end could take before it snaps and slides out. From what I know, swaybars and spring rates affect the handling/ride quality in similar ways, and each one needs to be balanced out to counteract changes made to the other component. I’d imagine that going with significantly higher than stock spring rates, you’ll need to make at least 1 sway bar change - prolly a good idea to have a rough idea of how before you pick spring rates. Swapping out the rear bar would be the preferred method IMO, both because it’s easier to swap and gets rid of the unpredictable factory bar.
 
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