At the bottom of this discussion, find a SurveyMonkey link.
Background.
Our front springs are 315lbs/in and rear 575lbs/in. Eibach, Ground Control, Bimmerworld, and Pro3 all like ~400 front and 600-700 rear.
There is some consensus that one can detect a change in spring rate when one makes a change of ~50lbs/in. Change of less than that can’t be detected.
Our springs are a wear item. BW says that once we note that other cars seem to be riding higher, we should change our springs. Therefore a lot of us are due for a spring replacement.
All spring rates discussed here are compatible with our Bilstien Sports per BW, GC, and Bilstien. No change in struts/shocks is contemplated in the hypothetical scenarios that I dreamed up.
SpecE30 bleeds racers to SpecE46. A common thread is that the stiffer SpecE46 suspension “feels like a race car.”
This is not an attempt to shove an unwanted change down the throats of the community. This is an attempt to better understand what the community wants. Don’t get over-excited by a simple attempt to get your opinion.
Front springs can be removed by dropping the strut down out of the camber plate. The rear spring can be removed by simply unweighting the suspension and prying out the spring. Both tasks are easier tho with the $15 Harbor Freight spring compressor.
- Front spring scenario. We have a number of approved kits and 2 approved venders. Cost is ~$300. Spring rate 375lbs so it would be a perceivable change. There’s a number of variations of the kits to accommodate those that want to cut and/or weld the adjuster to the strut, and those who don’t. The former solution is a bit more robust. There’s a kit for conventional coilover camber plates, and a kit for those of us that have “Spec” camber plates. The difference here is that Spec camber plates were made for the OEM tophat and therefore shove the spring top hat down an inch or so. Ride height would have a minimum spec. This would be an “allowed” not a “required” suspension change to accomodate those whom, for whatever reason, didn’t want the hassle.
The easy route for current builds would be the no weld/cut kit designed for the Spec camber plate. The logical route for new builds would be the weld/cut kit designed for conventional, also cheaper, coilover camber plates.
Installation cost. If you got the non cut/weld kit when installing the coilovers would be like swapping springs. It would easily do-able in an evening. It would be unreasonable for a shop to charge >2hrs labor.
Advantages:
Camber and caster would become far more adjustable because the OEM tophat would go away. You could get more camber then you’d need. This would level the playing field between cars that could get lots of camber/caster and those that can’t.
No more encouragement to bend struts. Some race classes allow bending and welding struts. This works, but since it’s not allowed in our class, if your strut “gets bent” there’s no welding allowed to reinforce your weakened strut. It’s a problem when the rules encourage folks to weaken suspension members.
Some drivers complain that their car rides higher then others for no obvious reason. Adjustable ride height fixes that.
Reduced roll creates more even tire wear which lengthens the life of our tires.
There is some consensus that this change would bring us in the ballpark of the optimum E30 spring rates.
Reduced bleeding drivers to SpecE46 because our stiffened suspension reinforces our big smiles.
Drivers that have big corner weight problems can mitigate problem.
Disadvantages.
Most drivers will feel that they “have to” open up their wallets. Even tho the change from 315lbs to 375lbs/in is little over the detectability threshold, there is sure to be a perception that in order to be competitive, you have to do it. This is somewhat mitigated by the need for many of us to swap out our springs anyhow. Also, drivers that did not want to go to the stiffer front spring certainly wouldn’t be forced to.
Change is bad. No sarcasm intended, I entirely agree that one should be wary of changing something that is reasonably successful. Perfection is often the enemy of good enough.
- Rear spring scenario. A single kit. Adjustable height. Spring rate would go up slightly to 600lbs/in. The higher spring rate won’t be detectable. Cost ~$250. This would require a rear height spec. This would also be an “allowed” not a “required” change.
Installation. Easy. If a shop charged you >90min labor, they charged too much.
Advantages.
Our rear springs only have about 1.5" of travel because most of the coils are bound up when the car is at rest. H&R says that the reason for this is to ensure the spring doesn’t escape when the trailing arm is unweighted. With so little travel, our rear suspension binds up whenever the car loads up significantly. Obviously infinite spring rate is bad. This is common when bounding over a gator, or when the combo of lat g and vertical g force it. For example, if I have a passenger at Road Atlanta, my outboard rear spring binds up in turn 1. A side affect is that the bound up spring acts as a fulcrum and puts huge forces on the trailing arm pivot points. This is cited as a cause of our problems keeping rear alignment settings. Coilovers would not be mostly bound up at rest, would therefore allow more travel, and these problems would go away.
Since the change in spring rate is below the level of detectability, there should be no perception of “I need to do this in order to be competitive.”
Fixes complaints re. cars riding higher than others.
If we’re going to do a rule change on something as significant as suspension, better to do it all at once.
Same mitigation of corner weight problem above.
We avoid having to negotiate with H&R to make available a “rear springs only” kit.
Fill out the survey pls. By all means add your thoughts to this thread.
