THIS WRITE-UP HAS BEEN BROUGHT TO YOU BY YOUR FRIENDS AT WWW.INFINITISCENE.COM

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)


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).





6. RAISE (B) UNTIL IT TOUCHES (A).




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).




8. AFTER YOU GET YOUR 5MM PRELOAD RAISE LOCK RING (B) BACK TO (A) AND TIGHTEN THE TWO TOGETHER.




9. YOU ARE FINISHED.

 

Nice writeup.

Why 5mm of preload? What spring rate is that based on?

 

Hmm so did I adjust my coilovers incorrectly? I dropped my car using A and B only. Am I supposed to use C to adjust height?

 

5mm was recomended from the factory...i guess for the street use.... and you use "A" to adjust the preload on the spring..."B" keeps "A" nice and tight..."C" you loosen and then use "A" to lower or raise your car and tighten "C" again to keep it their lol

 

Loosen C and adjust with A? So basically its the threads that move?

 

Yes, into the base to lower out of the base to raise. Then re-tighten C to keep it there.

 

^Good stuff! Im DEFINITELY gonna give that a shot when I get a chance to!! My ride has been way too soft. Cant wait to feel the difference! (no homo)

 

Are your springs linear or progressive? A truly linear spring will not see a spring rate increase from adding preload. I'm pretty sure those collars on the coil overs should be used to adjust ride height, and then corner weights. If your springs are too soft, buy stiffer springs.

 

Linear if im not mistaken. My rears have no preload on em what so ever. There was a ton of slack on it. A ton of play. Fronts seem fine; its the rears that need to be addresses so im thinking setting preload to zero at least would cure the soft ride.

 

I've been running 0 preload for 30,000 and had no issues at all. Ride feels excellent. I wouldn't be willing to try this again. I'm done with experimenting, lol.

 

This thread from another forum explains it pretty well. Look at the post that starts "Preload is one of the tougher spring concepts to visualize"

In summation, when adding preload, you add ride height until your springs no longer sag when your car is lowered off the jacks. If you have a 500 lb/in spring and preload it 2.5 inches on the front of a Maxima, you have a force of 1250 lbs in the spring. Because the Max weights approximately 1000 lbs on each front corner, there would be no sag. Not only that, but the spring would not start to compress until an additional 250 lbs acted on it. This is bad. But most times it never gets to this.

To learn more about linear springs, check out Hooke's Law.

The bottom line, the spring rate of a linear spring will never increase by adding preload.

If you think your rear is too soft (bottoming out/too much body roll), get some new rear springs. Hyperco makes good springs. There are other manufacturers as well. Search around.

 

I have BC Racing Coilover, im having hard time loosen up the (B) lock rings, and it stuck. I try PB Bluster no clue still, and is that mean after spraying PB Bluster we have to clean it with brake cleaner?

 

Hahah this happened to me on my Tein Basic....
I sprayed 1 can of PB blaster and half can of wd40 and 3 guys with gehtto ehomemade extension spanner wrench...

 

Preload is spring rate dependent....I personally used 0 on my JIC FLT A2

 

Sorry for the newbie question, but I'm new to coilovers, this does have to been done when everything is bolted on right?

 

yes

 

Yes. You could do it before, but you'll end up re-doing it once installed on the car as you cant replicate suspension droop w/o the coilovers installed.

 

Anybody know how to do pre-load in the rears n changed height? I'm confused since rears is independent suspension setup. I know I need 9pm of preload to the spring but I just don't know how to do the rears one.

 

It should be the same, IRS or beam axle.

 

Wait a minute so u don't add pre-load to ur jic? Like mine when I reset it to 0 then I add 5mm of pre-load to the springs.

My rear making squeaking sound when hitting bump is that me my rears are blown n also I'm using the digit scale when I set 5mm on them do we used outier measure or interiors measure on the scale?

 

AFAIK, JIC says 0 preload (just make sure the spring touches both perches when the car is in the air). Preloading linear springs = bad idea for handling.

 

U mean jic are linear spring? I'm learning.

 

Yes. Progressive rate springs usually require some preload (helps avoid hitting the bump stops)

 

Today I went through problem will I was trying to lower the car in the FRONT, but I did loosen up C collar the put spanner on the A collar n put right to left but after that is didn't lower the car at all. Am I suppose to loosen the strut bolt that hold the strut in place?

 

you have to turn the whole strut when the C collar is loose. the A collar itself wont lower the car.

 

So basically I'm loosen up C collar n loosen up 2 bolts that connect the strut in place n plus lossen up endlink bolt to?

 

No. Loosen the C collar, and spin the whole threaded assembly so that both the A and B collar are closer to the C collar. No need to undo the whole assembly. This is why these struts have threaded bodies.

Were I you, I would find a local race shop and let them handle it.

 

I can't let my shop do it bec there cross-threaded my coil. So I'm trying to do it myself.

So lossen up C collar then move the thread by hand or spanner? If I put spanner on the thread won't I strip it?

My question is how the strut gonna move if A n B collar are tight each other unless I loosen up the bolts behind the brake?

 

As long as the C collar is loose and the A+B collars are locked to each other, Turning them [A/B] with a spanner wrench will spin the entire shock assembly with A+B together. It's the same thing as unbolting the strut bolts and spinning the entire bottom section except the threaded strut section will spin instead of the bottom section below C. This is how you adjust the height without loosening up the strut bolts.

I actually discovered this by accident.

 

i wouldnt put any preload on your car. Its going to cause it to get bouncy.

 

so are the bc (br type) linear or progressive. haven't seen any documentation with the stuff that came with mine. Nor did it say anything for the preloading.

 

From the pic they have on their site, the spring is linear.

 

Because of the equal spacing? So, would would progressive springs be the ones where the spaccing gets smaller on one end of the coil?

 

The coil gets larger in diameter as it goes up on progressive rate springs. Linear have a set diameter the whole way up.

 

spacing, not diameter. very few springs have multiple diameters, and that's usually to increase travel before coil bind. not necessarily anything to do with rate.

 

Most progressive rate coilovers have tapered springs, at least that I've seen Matt. The only ones I know of with varied spacing is the PSS9/10 from Bilstein.

 

great write up