Setting Coilover Preload

[Jono.c]

G'day guys


I've got a pair of BC Racing BR's (mx73) to go into an Ra65 with 8kg springs.

I've seen various figures and formula's for the perload adjustment..

The most common is 5mm. This seems a lot to me..


Is anyone able to tell me the correct formula or figure for this setup? AFAIK they're just the standard 200mm length springs


Cheers

[jondee86]

BC recommends 5mm preload from finger tight. That is really only enough to make sure everything stays tidy when a wheel comes off the ground, and allow for a little bit of spring settling. Actually, I don't really know why a spring should "settle" after a certain amount of use, but apparently they do

Cheers... jondee86

[Z2TT]

I too need info about Setting coilover Pre-load but on a Dual Spring Setup. I've been told the Pre-load affects the way the unit behaves during rebound, however am not sure.

Should Pre-load adjustment be used to even out height differences on each side due to weight difference after the car has been lowered using the same Adjustments on the threaded section/body of the unit? why and why not? While adjusting height with even increments I am left with two sides of different height, and have used Pre-load to even it out, is this the correct way or should I just adjust the strut length more on one side to even out the height difference and keep pre-load on both sides the same?

[dnegative]

Pretty sure the manual that came with my BC recommended 0 pre load, wouldnt really want to add to it

[jondee86]

Winding up the preload sits the car a little higher, and changes the ratio of bump stroke to rebound stroke. For example, say a shock has 70mm of total travel, and the spring rate is selected to give 40mm of bump and 30mm of rebound with the factory recommended preload. If you add another 10mm of preload, the car will now sit 10mm higher, and you will have 50mm of bump and 20mm of rebound. Too little rebound will result in the wheel coming off the ground which will generally mean loss of grip.

You should set the preload equally on both sides, and adjust the height/corner weighting with the strut length adjustment.

Cheers... jondee86

[oldcorollas]

it's not really preload... just setting the height of the car
err, or maybe it is.... nm