BC Coilover Preload Adjustment

fxlr8

fxlr8

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ADJUSTING BC COILOVERS (PRELOAD)

TOOLS:
SUPPLIED SPANNER WRENCH’S


SAFETY:
ALWAYS USE QUALITY JACKSTANDS WHEN WORKING UNDER YOUR VEHICLE.
NEVER WEAR LOOSE FITTED CLOTHING AROUND A RUNNING MOTOR.
ALWAYS WEAR SAFETY GLASSES.
PLEASE STAY SAFE.

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1. RAISE YOUR CAR ON JACKSTANDS AND REMOVE THE WHEELS.

2. CLEAN THE COILOVER THREADS WITH COMPRESSED AIR AND A RAG BEFORE MOVING THE LOCK RINGS.

3. LOOSEN LOCK RING (B)
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4. LOWER SEAT (A) SO THAT THERE IS NO TENSION ON THE SPRING.
5. NOW RAISE (A) BY HAND UNTIL IT TOUCHES AND HOLDS THE SPRING FIRMLY IN PLACE WITHOUT PUTTING TENSION ON THE SPRING. (THIS IS KNOWN AS A 0 PRELOAD).
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6. RAISE (B) UNTIL IT TOUCHES (A).
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7. TAKE YOUR SPANNER WRENCH AND RAISE (A)(WHICH IS NOW PUTTING TENSION ON THE SPRING) UP 5MM (TOP OF (B) TO THE BOTTOM OF (A)). THIS IS KNOWN AS A 5MM PRELOAD (WHICH IS WHAT BC RECOMMENDS FROM THE FACTORY).
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8. AFTER YOU GET YOUR 5MM PRELOAD RAISE LOCK RING (B) BACK TO (A) AND TIGHTEN THE TWO TOGETHER.
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9. YOU ARE FINISHED.
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I spent so much time reading about adjusting these springs elsewhere, but reading your instructions in 30 seconds makes everything so clear. Great job! :tup:
 
Nice write up! I installed my BC's this weekend, I ordered 12k for the rears and 10k springs for the front as many have stated that the standard kit with the 8k's up front were not enough. The fronts were pretty much a nobrainer as far as the preload, and I have all four corners to the height I need. The problem is that the rear springs still do not seem as stiff as the front. I'm not sure if I adjusted the preload correctly on the rears and need some clarification. In the post I have read they say to lower the ring until the spring is loose in the perch. How loose? And then raise until the spring it tight but not compressed, then move 5mm more. The problem is that it is very hard to judge where the spring is tight but not compressed. Should the spring just barley wiggle in the perch when loose, and tight to where it can't budge when tight? Then adjust the 5mm? Could someone please expand in more detail exactly how to adjust the preload on the rears? Thank you in advance!
 
The spring will always wiggle a little bit in the rear. You're putting a smaller diameter spring in a bucket designed for a much larger one. It shouldn't be loose, but if you pull on it, you can move it a little bit. On the rear, the height adjustment is the same as the preload, so it's trickier. I didn't even worry about preloading the rear because it's always under tension and it will depend on how your shocks are set. I set my shocks on basically the lowest setting so full extension on the spring bucket is reduced some. With the way mine is set up, there is always tension on the springs. I've got mine bottomed out on it's lowest setting and there is still some tension on the spring.

Preload doesn't affect the spring rate at all, BC's are linear springs. So compressing it doesn't change the spring rate. I'm having the same issues where it feels like the FX blows through the travel on both front and rear, but more so on the rears. The rears always felt softer than the front with OEM, H&R, and now BC's. It's the suspension design. I have my shocks set on maximum damping right now, but am awaiting 12k front and 14k rear springs. Hopefully that will help.
 
So now that my springs are set to the proper ride height. My question is as follows:
Raise the shock til the spring is loose. How loose?
lower the shock til the spring gets tight. How tight?
Also, correct me if I'm wrong, the rears are essentially the same. The only difference being the spring and the shock are separate instead of one peice. The settings should be the same principle and order?
1. Spring for ride height
2. Shock for preload
3. knob for dampening
 
The shock shouldn't be where you set the preload. On the front, the shock is used for height adjustment. You turn the threaded body up or down to adjust height. The 2 locking collars are for preload. On the rear, it's different. The spring isn't sitting on a threaded body so adjusting the locking collars will adjust preload and ride height. Adjusting the shock body on the rear will not change the ride height. It will adjust the limits or your travel, ie. mine are set so low that when I jack the car up, the wheel doesn't sag that much because I've topped out the shock and that prevents the spring bucket from coming any lower.

Best way to imagine it is this. On the front, if the spring was a solid 8" long pipe that did not move, you could still raise and lower the front end by turning the threaded shock body on which the spring sits. On the rear, if the spring was a solid 8" piece of metal that did not move, adjusting the shock body would not raise or lower the car since the spring isn't sitting on that shock body. Rear isn't a true coilover.

Don't sweat the preload too much. It will just minimize any clunking noises, but it doesn't really affect performance. Some of the hardcore stance guys remove their rear locking collars entirely on the G to get lower. The shock prevents the spring from falling out. On a previous car, I had Ground Control coilover sleeves. Since they just sat on a shock, i couldn't preload them, turning the collars affected ride height. Mine were set very low (so low that when I jacked the car up, there was about 4-5" of gap between the spring and top mount. I could remove them without a spring compressor. Other than some horrendous clunking noises on slow speed turns, no issues and I had those on for probably 50K miles.
 
Stock BC 8/12. The stock rates are not bad, but for my setup, they don't really work. I'm low enough that I've almost worn a hole through the front fender liners. And I've already flattened my fenders and quarter panels as much as they will go without a pull and I still rub. Maxing out the damping was the only way to not blow through the travel. But now the problem is that on washboard roads, the ride really sucks since the damping is set so high that the spring doesn't rebound as quick. Plus I'm getting wider wheels soon so I need to address the suspension first.
 
Well so far I'm so so on the bc's I have never had coil overs before so I really don't know what to expect. The ride is great! I just can't get that little bit of bounce out at highway speeds. I'm also getting the extenders for the rears as I'm tired of becoming a contortionist to adjust them as my tires are to wide and rims are not open enough to access the adjusters. I will say this, with all the braces in combo with the coilovers and the AWD it handles like its on freakin rails with no body roll to speak of. With the dampening hard I would put it up against any 911 or like models in regards to handling! I guess it will take time to adjust them perfectly or they will simply grow on me. Right now I'm about two fingers from the top of the tires to the wheel well. I have done so many mods to my car, but have only posted a few pics here and there . The garage full of pics is soon to come!!! The only thing left is the exhaust, after its paid for then it's turbo or supercharger time.
 
Yeah, I can see how it would be hard to adjust the rear suspension without reaching through the wheels. I agree the coilovers improve handling on the FX immensely, but it's still not anywhere near 911 or sports car handling. The roll is much less, but drive a lower lighter sports car and the FX will feel very bulky. Compared to my 335 w/ KW V3's and all suspension upgrades, the FX feels like a monster truck. Compared to a friend's 996 Turbo or another friend's GTR, the FX isn't even remotely in the same league.
 
Well maybe mine handles better than yours, I have no doubts I can bounce the passangers head off the side window with no problem. I have driven many not only porsches, ferraris, lambos and numerous super cars in my life and my fx without a doubt handles exceptionaly well. I have yet to break the tires on it as I have on many if not all of the above stated cars. Yes, 0-60 hands down the fx is a slug, but on a super curvy road with an experienced driver the fx offers some serious competition for many much more expensive cars on the market. Heres food for thought, a new fx is about 65k, and a new 911 turbo about 120k. What is someone put another 55k in the fx? The problem with alot of so called super cars is they are not only faster, but a hell of allot lighter which means a hell of allot less traction. I had a 66 chevelle with a 396 that was scary fast, If you could get it to hook up and keep it out of the ditch. I'm not saying the fx is faster or more superior, but none the less exceptionally well built and in my book a fierce contender on a curvy road.
 
My kidos are 10kg front and rear with damping set about 30% front and 70% rear. (100% being full hard) Handling is great for its size but like you said, shadow, its not a sports car. My wife's A4 on coils, braced, with track tires puts it to shame in terms of cornering ability. Cant argue with physics...

Renhalt, which tires do you have?
 
Didn't mean to offend you. Maybe it does handle better than mine, but since we have the same suspension, it'll be close. FWIW, I can bounce passenger heads off the window in my Chrysler Sebring work car. The FX is basically a bigger, taller, and heavier G35. A G35 isn't remotely a match for a 911; the FX isn't going to do better. Just because your tires aren't breaking free doesn't mean the handling is better. There just isn't enough power to do it in a corner, especially when the FX is understeering. I can easily get my 335 to start sliding, but that's because it has 150hp more than the FX and I'm going way faster. Doesn't mean the FX is handling better.

It's just physics, the FX is big and tall. It's heavy (and no a heavier car doesn't help with cornering) and the center of gravity is higher. No way it will compare to a purpose built low sports car. Obviously ours are modified, but a stock FX pulls .79G on the skidpad. A Toyota Sienna minivan pulls a .76; no one compares that to a sports car. I absolutely love my FX, and it does handle great. But no amount of modifications or bracing will put it in sports car territory. The best way I can explain it is that in all of the other cars I've mentioned -911, GTR, M3- they corner so hard that it's scary. You can feel the pressure from the G forces. The FX doesn't come anywhere near that.

Anyways, we're just internet arguing since neither of us tracks the FX. Probably need to ask Stu his opinion since he takes his to AutoX. So let's just agree to disagree on this.

Renhalt said:
Well maybe mine handles better than yours, I have no doubts I can bounce the passangers head off the side window with no problem. I have driven many not only porsches, ferraris, lambos and numerous super cars in my life and my fx without a doubt handles exceptionaly well. I have yet to break the tires on it as I have on many if not all of the above stated cars. Yes, 0-60 hands down the fx is a slug, but on a super curvy road with an experienced driver the fx offers some serious competition for many much more expensive cars on the market. Heres food for thought, a new fx is about 65k, and a new 911 turbo about 120k. What is someone put another 55k in the fx? The problem with alot of so called super cars is they are not only faster, but a hell of allot lighter which means a hell of allot less traction. I had a 66 chevelle with a 396 that was scary fast, If you could get it to hook up and keep it out of the ditch. I'm not saying the fx is faster or more superior, but none the less exceptionally well built and in my book a fierce contender on a curvy road.
Click to expand...
 
No offense taken, I'm just saying for what it is it handles exceptionally well let's just leave it at that. When posting last night was on my 3rd 9year knob creek small batch single barrel, so please forgive the over exaggeration. :tongue:
 
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