Coilover question???

[juveteach]

Hello All,

I have a question about coilovers.
"If my desired ride height is 16.5"-17.5", should my choice of coilovers meet in the middle of this desired height"?
My choice of C/O's are QA1 DR 8855P, the compressed height is around 13" and extended is around 19". Will this be ok or should I regroup and go in another direction?
Also any ideas on spring rate? It is a 68 Camaro (see my other thread in regards to the car..85 Vette rearend in 68 Camaro)

Any input will greatly be appreciated.
Thanks

[ProdigyCustoms]

We can help you out with the shock for that. But spring rates are going to be dependant on the width of the rear mount, angle of the shock.

We have done a few of these C 4 rears and can GUESS pretty close. I can tell you the spring rate are going to be pretty high.

Cal me monday.

[aosborn]

The best bet for determining shock travel is to move the suspension to full compression (to the bump stop) and record the dimension between the mounts and subtract a given amount depending on the amount of expected compression of the bump stop (softer bump stops compress more, some hardly compress at all). And then subtract another 1/4" or so to make sure the shocks won't bottom out. That is your compressed dimension.

Then set the suspension at ride height and record the distance between the mounts.

I usually like to have 60-70 percent of the shock travel available for compression and the rest for droop. With those two dimensions you should be able to determine what length coil-over to purchase.

Keep the compressed dimension in mind also when looking at springs. Note the stacked dimension in the spring specs, (the dimension where all the coils bind or touching each other) and make sure that dimension is smaller than the distance between your spring seats at full suspension compression (usually not a problem).

As for spring rate, you need to have corner weights or at least axle weight divided by two, and the leverage ratio at the minimum to calculate. The leverage ratio is the distance between the center of the tire to the lower shock mount divided by half the track width in your case will get you close. And you need to determine the installed height of the spring.

Take the corner weight, multiply it by the lever, and find a spring that will get you that figure at the proper installed height and you'll be at a reasonable starting point. If the coil-overs are mounted at much of an angle (I usually install mine at the same arc the axle moves in) go to the next stiffer spring when ordering.

I could make a guess at the rate, but doing it the way I layed out above will give them kids a much better education!