what rate spring to use?

[ron79]

i am going to get qai pro coil overs for my 78,what spring to get the 350/450/550ibs/lbs/in, the is 3550lbs

[another69]

I have the same setup on my 69, and I think they're really nice for the money. You should know your front weight and how you plan on driving before making a choice. My front is 1770#, so I went with 350# springs, but I'll likely move up to 450# soon.

[Damn True]

78?

78 VW bus?

[Lowend]

I'm guessing you are talking about a Camaro.

I would go with the 550# springs, although those are a little on the light side for a Late 70's car (they weigh closer to 4000 lbs).

In general, not a coilover fan... but do what you will

[ron79]

sorry a 78 nova

[Skip Fix]

Weight might not be that off. My 79 Camaro I used to autocross with heavy 16x10 steel wheels , heavy Recaro seats but the rest of the interior gone most of the front bumper 5 mph bracing gone, 383 iron heads scattershield headers and exhaust weighed 3250 without me.

It used 700lbs/in on the front using "regular" springs and shocks.

[79T/Aman]

not a fan of connical coil overs they side load the shock causing leaks this may be why you can't get more than 550#

[silver69camaro]

not a fan of connical coil overs they side load the shock causing leaks this may be why you can't get more than 550#

That really depends on the quality of the shock. You can buy 2.5" coilovers in 1300lbs/in rates.

[79T/Aman]

Thats right, when the spring is only 2.5" in Dia. and the top of the spring is attached to the other end of the shock making the shock and spring move together without side loading the shock, unlike the connical springs that have 5.5" dia. and not attached to the shock this exerts much side load on the shock body.

[jerome]

I think 79T is talking about coilovers with a normal lower 2.5" seat, but with a spring that starts 2.5" (at the bottom) and widens to 5.5" at the top. I can see how this creates a side load as the motion path of the spring and shock are not perfectly in line. I had not heard of this concept before, but I don't like the idea much.

Everything else is a compromise in terms of strength:
1. coilover mounted on stock LCA is not strong due to LCA being designed for shock loads not suspension loads
2. coilover mounted on stock upper shock mount is not strong for same reason as #1. These components are designed for damping loads not suspension loads.
3. conical coilover introduces side loads to the shock as stated above

However, # 1, 2, and 3 are violated pretty often in the hotrodding world, and I suspect they largely have no ill effects, but to do it right and still get ride height adjustability you can have:

1. conventional coilovers with a redesigned upper mount and lower control arm designed for a coilover. can buy any spring rate.

2. 5.5" spring with separate shock in the middle. Using a racing spring and adjuster (available from speedway motors or afco) you can adjust height, but you have to pop a ball joint every time. You can also purchase any spring rate from like 300 to 1400.

Jerome

[amx2334]

I think your over analyzing the side load issue. Macpherson struts see "side loads" all day long without problems. Standard coil overs see side loads also.
Back to the original question I can say I see alot of #350 springs being sold because people find they needed stiffer springs.

[79T/Aman]

well there is a problem with connical coil overs leaking that's a fact, and there is no such thing as overanalyzing a problem!
Macpherson struts have the top of the spring ride on a separat spring seat that also incorporates a rubber seat limiting and absorbing the side load, a strut shock also has a MUCH larger piston rod, all this to avoid the shock taking the load and leaking, and last but not least a Macpherson strut does not use an upper ball joint therfore the strut assembly moves in a much more liniar motion, in turn not side loading the shock, now back to topic, answer was given back on post #4 and #6