C Spanner

[Wynand]

Originally Posted by robo

Because the spring/shock combo if correct in poundage would not be in the topped out position once the car was on the floor. Thats when the adjusters take over to trim ride height.

I hear what you say Bob as well as Baz-r. I still fail to see how the coil over adjusters will lower or raise the car, or maybe age is getting to me and stupidity moves in.

On my car - I made my own coilovers with Gabriel gas shocks and spent a lot of time working out the spring rates (courtesy of Google University )which seemed to worked because my car went down exactly to the designed height. No adjusting needed and springs nicely.
It is exactly as you said Bob.

BUT, and this pickles my mind, but hear me out - as my ride is now and I put another say for instance 1" tension/260lbs on the spring with the adjuster/perch nut, yes the spring will be shorter, but because spring loading is linear and when the car lowered back on the coilover, the spring will compress to exactly the same amount again iow, the car will get back to its original height as before the additional pre-load/tension added. The only problem I see is that the spring will now feel the cars weight and the 260lbs pre-load - sensing a higher load than actual carrying - and this extra weight has to be overcome before the spring function normally again
Does this makes sense or am I missing something.

Its not that Im nit picking, but its in my nature to be able to understand why things work the way it do, and if it works in this case, it just do not add up to my math and it drives me up a wall to now why not

[robo]

Think of it like this. Just to keep it simple lets say you have the right springs and the car is on the floor. The spring is now for arguments sake 6" long, so if you screw up the platforms an inch the spring will still be 6" long but the car will go up, same thing if you lower the car. The only time you would squash the spring more is if you put more weight on the car or they had weakened and you were over compensating with the adjusters to gain ride height, the spring would then be in bind. Hope this helps.

Bob

[Wynand]

Thanks Bob, I see now.
Shorter springs will indeed make the car sit lower and by adjusting the nut upwards, will lift the car on the spring and vice versa.
But this also means the shock will never be fully extended and when the wheel goes in full droop, (shock fully extended) the spring may come loose.

My theory was based om my units that were made from gas filled shocks and my here was how I went about it.;
I put the chassis on trestles and let the suspension dropped completely and then lifted (bumped)it completely and measured the travel and searched for a shock that have the said travel and will fit fully extended and compressed.
My shocks are gas filled and usually these extent itself fully unlike hydraulic (oil) units that does not extents itself fully.

After I made the adjustable coilovers I calculated the spring length that when fitted with a little pre-tension to tighten the spring in place, so its still 20mm longer than the max droop.
Then I made careful calculations, using correction factors for shock angles etc to have the spring rate that when the car is put on coilovers, it will be at the designed ride height - shock about 38% compressed, so when the spring goes into max bump, the shock still have a little movement left. When full drooped, the shock is about 95% extended.

As said before my car sits exactly where intended - 140mm (with driver) high and the springs sensitive for any input. I hope this will give a good quality ride because the suspension has a lot of travel and the spring rate perfect for car.
I need this because the roads in my area (rural) are very bumpy and in many places, potholes the order of the day - much so for whole of SA..
Here a pic on my self built adjustable coilovers, even done the ally anodising myself in the garage