What spring rate ?

[z28cp]

Originally Posted by frojoe

Just to avoid misinformation, there are essentially 3 lengths of springs available for our cars and all have vastly different spring rates:

1) Stock spring (uses spring pockets on subframe as well as LCA's) I believe is in a 12"-14" range (changes depending if OEM vs aftermarket vs aftermarket lowering, etc) and are generally quite soft (200-300lb/in?)

2) Traditional design "conversion coilovers" like QA1/Viking that re-use the subframe spring pocket however have a threaded collar on the shock body to support the bottom of the spring. These are in the 10-11" uncompressed length if I remember correctly, and usually have spring rates available in the 350-550 range (for our cars 400lb/in is quite soft and 350lb/in would almost be undriveable)

3) Newer "coilover conversion" design like the Ridetech, where the spring is entirely captured by collars on the shock body and the shock itself has a Tbar mount on the bottom and a pillow ball like upper stud mount. Because the spring is entirely captured on the shock body, and has to clear the subframe as well as the LCA, the spring has to be a much shorter uncompressed length of 8" in order to clear everything (spring rates available from 500-800lb/in)

The shorter the spring gets, the higher the spring stiffness needs to be to get the same ride quality (obviously as the spring gets shorter, then available travel also decreases).

When I switched from QA1's with 10" 450lb/in springs to the same control arm setup but with 8" 700lb/in Ridetechs, for curiousity sake I calc'd that the equivalent rate of the new springs would've equalled ~430lb/in if in the length needed to fit the old QA1's.

Rod P's setup of 750lb/in 8" springs is now what I'm running, and that should have an equivalent ride feel to maybe a 475lb/in spring that is the proper length to fit a QA1/Viking conversion coilover, or maybe a rate of ~325lb/in for a stock-suspension length spring.

When you ask what peoples' spring rates are you have to take into account the length of the shock they're using, for stroke as well as uncompressed overall spring length.

-Joe

Um, spring rate is spring rate, regardless of spring length. It still takes 'x' pounds to compress the spring 1 inch.

However, the wheel rate can be affected if the top and/or bottom of coilover 'x' is mounted in a different spot than coilover 'y'.

[Vince@Meanstreets]

Originally Posted by z28cp

Um, spring rate is spring rate, regardless of spring length. It still takes 'x' pounds to compress the spring 1 inch.

However, the wheel rate can be affected if the top and/or bottom of coilover 'x' is mounted in a different spot than coilover 'y'.

exactly. The cosine between the DSE quadralink and a Ridetech airbar are night and day which is why Rod is up there at 250.



.

[raustinss]

Steve...just missed you. I was at Dasilva motorsport today hoping to see how the car was coming along. Manny said you got it yesterday oh well lol
Hope your pleased with it manny quite liked it.

[Sheck44]

Ryan, could not be happier, have been driving the car a little the last couple of days and it's absolutely ridiculous. The torque is mind blowing with this setup.

I ended up fooling around with the ride height and the compression/rebound settings and am very pleased now with the ride.

Ryan, are you going to Camaro Nationals next week in Oakville ?? If weather is good I will certainly be there

Cheers
Steve

[19,69camaro]

I have a 73 Nova iron head sbc/th350 with stock UCA/LCA but with Delrin bushings, 600lb Hotchkis springs for a BB 2" drop 12.875 Inch free height.

For shocks the are ridetech rq's and it also has a 1.25" hollow front sway bar.

My problem is this thing rides like a dump truck. I know ordered the wrong springs but I didn't notice until they were in there. Heres the thing the stance is prefect the way it sits and the only diffrence I see between bb and sb springs is a .375" height difference. Spring rate is quoted the same.

I'm pretty sure the problem is the springs since the control arms moved fine with no binding before the springs were installed and if I push on the fender the thing barely budges. There is also plenty of travel before the bump stops.

Anyone have any suggestions?

[Rod P]

there is always an installation ratio and shock angle that affects the relationship between the vertical wheel movement and the shock shaft velocity and spring rate.

The farther the shock is mounted from the ball joint and the greater the shock angle from 90 degrees off the control arm that it is mounted to, the slower the shaft will move in relation to the wheel movement and the heavier the spring needed.

[GregWeld]

There's only about 200 places on the internet to get this info.... and how to calculate it etc.

Here's just ONE


http://www.hypercoils.com/spring-calculator

[frojoe]

Originally Posted by z28cp

Um, spring rate is spring rate, regardless of spring length. It still takes 'x' pounds to compress the spring 1 inch.

However, the wheel rate can be affected if the top and/or bottom of coilover 'x' is mounted in a different spot than coilover 'y'.

That's 100% true. What I meant is the mounting spot (top or bottom) of the coil moving along the axis of the spring (spring getting shorter/longer). When the mounting point moves laterally along the control arm or inboard/outboard on the frame, the shock angle, shock rate, and overall leverage ratio all change for sure.. but I wasn't wanting to get into that.

Spring rate is spring rate, no question about it. But for the same weight on each spring (same wheel rate) so the car can be driveable, as the spring gets shorter the spring rate has to go up. If you have 2 springs both with the same # of coils & wire diameter, one short and one long, the shorter one is going to see more torsion angle in the coil wire per inch of spring length than the longer spring will. Two ways to fix this.. more coils per inch of spring length, or thicker coil diameter (or higher-strength coil material). More coils means less working travel of the spring since there's less room for the increased # of coils to compress into. So realistically, for standard spring steel material, the rate has to go up.

My main point is that if someone offers their opinion by just saying "I run 750's in the front no problem", it's pretty helpful to also say what shocks those springs are on (and thus the length of their 750# springs).. without that extra info it could be a bit misleading to someone who is asking for spring rate suggestions for their much-longer-overall springs.

Cheers,
joe