The two springs are separated by a spacer or guide or whatever you want to call it. On the damper body is a stop that limits the travel of this spacer/guide. The effect is that of a dual spring rate - softer when that spacer/guide is away from its travel stop, firmer beyond the point where that spacer/guide hits its travel stop.
Not the same effect as a single softer longer spring.
Not even the same effect as a dual-rate or progressive-wound spring. With this arrangement, you can adjust where that travel stop comes in contact, and that changes the point in the suspension travel at which the completed assembly changes from the lower to higher combined spring rate.
You can also individually change the short high-rate spring and the long softer spring in order to further fine-tune the behaviour of the completed assembly. Can't do that with a single dual-rate spring because you are stuck with the relationship that is built into the way the spring is wound.
I should add that this is a racing application, because you would not build a production vehicle that way. For a production vehicle, the ride and handling people would figure out a consensus opinion and build a single progressive-wound spring that acts the way they want, to save $$$ on the production line.
Yes but these are different than dual spring rate, when the wheel is on the ground, the orange springbis compressed 100% coil binded. Hence ita flat coil profile.
Its purpose is to guide the main spring when in full droop so it never comes loose.
But why not just put a longer spring with some anount of preload ???
It's still a dual spring rate ... but with a very low initial rate.
A longer (single-rate) main spring would result in a different ride height and/or require a different spring rate for the main spring to be used ... not the same.
Shortening the travel of the shock body so that it simply doesn't have as much droop travel (basically, let the wheel come off the ground, since it is hardly being pushed down anyhow) would have a closer outcome, but presumably that wasn't desirable for some other reason, or it was too hard to achieve (requires internal modifications to the damper).
A higher spring rate means it compresses less when loaded by the same car weight. The ride height would be too high if you turned up the bottom adjuster nuts until the black spring was up against the top mount.
There are only two ways to get rid of that orange spring. Run a softer spring rate that can be longer or raise the vehicle.
One reason to use a very low rate spring in series with another coil spring is to stop the springs jumping out of the spring seats when it goes wheels free, such as on a 2 post hoist or when changing a tire or over a whoops. I suspect that is the case here, the orange spring looks very soft indeed. progressive springs are a bit of a pain for production as you may be able to hear coil clash.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
We're looking at an aftermarket coilover kit- not a component engineered to an OEM level of detail.
That helper spring is there because the company making this kit wanted the kit to lower the car. That requires a stiffer spring rate so that the car doesn't destroy itself. That in turn requires some method of keeping the spring seated when the suspension is unloaded, and that flat-wire helper spring is the cheapest way to do it.
So how would the basic problem here be any different at the aftermarket level than it would be for the OEMs? The soft region needs to be really soft so that it doesn't materially affect ride height.
The only real difference I'm hearing is that the company making this kit wants to offer a range of ride heights and spring stiffnesses that no OEM would ever choose for regular production.
What OP initially asked for would have involved very different rates, different enough that you would not have been able to pack enough closely spaced coils into the available space to give him what he wanted (a very low spring rate outside of normal rebound travel). Tapering the wire itself to cut down on the number of soft-region coils or spacing the upper coilover mount down to eliminate the helper spring entirely would likely bring on more problems than would be solved.
The difference is that at the OEM level, you would choose a ride height regime for the damper that corresponds to the spring length and rate chosen, so that there is no need for doing something to stop the spring from coming adrift of its mountings. Basically if you wanted that ride height, you would select a shorter damper so that the suspension is physically prevented from extending that far.
Odds are, the selected ride height for that aftermarket coilover is way out of bounds (too low) for the design of the suspension anyhow, so in reality, at the OEM level, you simply wouldn't lower the vehicle that much.
Not quite how it works Brian. Sometimes you need a very long rebound travel, longer than the travel from wheels free to design height, at the desired linear rate, can provide while remaining engaged in the spring caps. The ride guys and off roaders will always push for more rebound travel, while the ride guys also want a comfy ride. Handling just say get your shit together give us a spring rate, we'll just use sta bars. Which the off roaders don't like, they want stiffer springs, not sta bars, for rock hopping. And so it goes.... As it happens I represented all 3 of those camps on the program coming to you soon, so all contradictions were internalised. And we ended up with variable rate springs primarily to stop the springs falling out.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
True ... although the OEM variable-rate springs that I've seen don't have an initial rate seemingly close to zero (negligible) like those in the original photo.
Mercedes did the opposite to pass a CV shaft through the spring on their W124 AWD implementation. there's a length at the normal pitch and then a half turn that leaves a few inches open for the shaft to pass thru the coil to the hub.
