BC Racing Coilover Settings

[bmchi]

Hey Guys,

i Thought I've seen a thread on here where everyone could share BC racing coil over settings but couldn't seem to find it.(was possibly another forum ). This will be a good reference point when mucking around with out setups.

So thought I'd start a new one. Post your coil type (BR, ER etc), Spring rates, ride height, preload and damper settings and state what your settings are for e.g track, everyday driving, comfort, hill runs/spirited drives

Cheers

[ralt]

Hi.
You may have problems getting settings out of the racing guys. What you want is closely guarded and if successful after trial and error and cost why would they tell you. Read some books and do it yourself you may realise how satisfying it is.

[Magpie]

Happy to provide an answer, however what works for one may not work for somebody else. By the way for preload do you mean corner weight? FUrther, these will be changing soon and can be tweaked on the day depending on conditions. I'm yet to change dampers or springs at the track, yet...

Type - BC ER's. Modified to have the front reservoirs mounted remotely inside the engine bay.

Front
Spring Rate 10kg
Ride Height (pinch rails) 108mm
Rebound - 6 clicks from hard
Bump - 4 clicks from hard

Rear
Spring Rate 8kg
Ride Height (pinch rails) 115mm
Rebound - 5 clicks from hard
Bump - 3 clicks from hard

Use - track only

Other questions that would also need to be asked:

1. Alignment
2. Tyres
3. Tyre pressures (hot/cold)
4. Drivers skill

[wasp47]

Had a set on a Skyline, was more than pleased

[beavis]

What magpie posted is a good place to start.
It does depend on your tyre, the track surface, and your cars setup/weight/swaybars.

Post some more detail on your specific car and we can make some further suggestions.

[bmchi]

Thanks guys,

Just thought it would be good to share for reference points.

Just put a set of BC BR coils on my NB but haven't set ride height, preload or damper yet.

Will have a play and let you all know how i go, setting out to get something for daily dirving it (so comfort) for now till i get it to the track!

Preload as in how many mm the spring is precompressed by the cuff/ring thing without any load bearing.

[Magpie]

Good explanation of preload

[bmchi]

anyone got the 8/6k br set of coilovers?

I'm just playing around with ride height, apparently your suppose to leave at least 25mm of thread in the lower mount. Must be what the holes are for.This doesn't leave me with much height! there is about a 60mm difference in strut height between the BC coilovers and my king springs/stock shock's.

does anyone know if you can lessen the thread from the top half where the spring cuff without screwing around with the preload?

[ManiacLachy]

Don't set the height by the bottom mount. The bottom mount is used to set shock length. You want the shock length to be so that under full compression, the wheel is able to move as high into the wheel arch as possible without the tyre hitting the liner - you need to remove the spring to find this setting accurately.

Then you set the ride height by adjusting preload on the spring.

[Magpie]

The bottom mount is used to set shock length.

1. Remove dampers
2. remove springs, bump stops and disconnect sway bars
3. install damper back in, install wheel
4. jack up wheel to where either the wheel hits the wheel arch or the damper lifts the car
5. adjust the lower collar (damper length) so that the tyre just touches the inside of the wheel arch as the damper is fully compressed
6. install spring/bump stop
7. measure adjusted damper and remove the other side and match the length
8. set ride height by adjusting the spring perch
9. attach sway bar
10. rinse and repeat steps for the rears

[Red_Bullet]

Dammit, now I gotta redo it the right way.

[ManiacLachy]

1. Remove dampers
2. remove springs, bump stops and disconnect sway bars
3. install damper back in, install wheel
4. jack up wheel to where either the wheel hits the wheel arch or the damper lifts the car
5. adjust the lower collar (damper length) so that the tyre just touches the inside of the wheel arch as the damper is fully compressed
6. install spring/bump stop
7. measure adjusted damper and remove the other side and match the length
8. set ride height by adjusting the spring perch
9. attach sway bar
10. rinse and repeat steps for the rears

I need to keep this list, and the video handy. I might book mark this thread! Perfect instructions.

Yes, this adds time to your install, but you will have the optimum amount of shock travel, regardless of the height you end up using. There is a lot of miss-information out there on coil-over installs, most tell you to set height by the lower collar because it's quicker and easier, but it's not best.

[Magpie]

Dammit, now I gotta redo it the right way.

I'll contradict myself now. I will also add that I used to do my dampers this way and thought that it was the ONLY way to do it,
you live you learn! http://mx5cartalk.com/forum/viewtopic.php?p=744117#p744117. Must thanks Shane for his post on the subject many years ago!



The above method is good for most users and they will never know the difference, further the suspension is not pushed to it limits all the time so the occasional 'rub' will be tolerated. Further, the use of hard and long bump stops reduce the risk of damage if the damper does 'bottom' out. Why do damper companies recommend this method, well it is quick and easy to do. I have had this exact conversation with BC Racing.

Example:
10kg spring free length 180mm
3mm 'preload' will place 30kg of force on the spring. This will also exert the exact same amount of force in the opposite direction, pressing back against the force being applied to it. Spring length is now 177mm
Assume 250kg of corner weight is now applied to that spring. This will cause the spring to be compressed by 25mm.
HOWEVER, there is already 30kg of force being applied to spring, hence the 250kg becomes 220kg ADDITIONAL weight on the spring.
Therefore the spring is only compressed 25mm and the damper only moves 25mm...

Hooke’s Law: F = -kx
F = Force, aka Restoring Force (Weight)
k = Spring Constant (Spring Rate)
x = Distance Spring is Displaced From Equilibrium (Compressed or Stretched)

HOWEVER, if you want to maximise the amount of suspension travel you have and get the best possible performance you need to set the damper length FIRST then adjust the ride height with the spring perch. You have to forget the word "preload'.