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I am replacing my front springs and do not know anything about spring pads. I see that there are a number of thicknesses. Did a search and I found a few statements around ride height and corner balancing.
For front springs, are they necessary, and if so, what thickness of spring pad is everyone using?
Al in the interest of speed, I would think it better to lower the car by reducing the ride height by losing the pads than to try the corner balance thing with goober rubber pads.
RP
Patton wrote:
[quote]Al in the interest of speed, I would think it better to lower the car by reducing the ride height by losing the pads than to try the corner balance thing with goober rubber pads.
RP[/quote]
I would think that something needs to be in there to keep the spring from dropping out. I am not trying corner balancing right now just replace. But speaking of balancing, if I loose both the front pads, what does that do to the front/rear weight distribution?
With the springs/shocks we run, I believe the springs are completely unloaded when the car is jacked up. I know my car is that way and I assume everyone else’s is too.
What I’ve done is put two zip ties through the convenient holes in the lower spring plate to keep the spring in roughly the correct vertical orientation.
The savvy thinkers among you might realize that if you turn the wheel when the car is jacked up, and don’t return the wheel to the original position when you lower the car down, then the spring will have rotated relative to the top spring plate. This can, in extreme situations, get the spring all catty-wumpus with the top spring plate with predictably annoying or worse results.
A good rule of thumb is always straighten the wheels before jacking the front end and re-straighten them before lowering it back down, or if not, then reach up there and visually align the spring plate with the spring.
A very large amount of time on this forum has been devoted to Horse Power and and engine upgrades. And there is very little about how to make your car handle. But our cars are really momentum cars. OK yeah, maybe not to the same degree as a Miata, but any attempt at driving an E30 like a big-bore racecar will net you poor results.
The rules of the class and the suspension kit chosen do not permit a major amount of set up. And the E30 Chassis is not overtly sensitive to minor tweaks like said Miata.
However there are always advantages in all aspects of suspension development and setup. This includes in corner weighting.
For Spec E30 we are limited to creatively moving weight around in the car. IMO this is best done if you remove weight from the specified OEM places with careful planning while building the car, rather than arbitrarily yanking crap out while building it… This fore-planning will serve to set you up in terms of weight distribution more effectively than just adding lumps of lead to the foot-well of your car after the fact.
Springs pads do offer a chance at small benefits in handling that may or may not work for you and your car.
See this article for more information:
http://grassrootsmotorsports.com/articles/understanding-corner-weights/
I have been doing a bit of reading and it appears that with corner balancing increasing a pad thickness will have an effect on that corner and the opposite corner. As the weight “pivots” on the other two corners.
““In its simplest form, corner balance is best illustrated by a 100 pound box being carried by 4 equally sized men. Each man caring 25% (or 25 pounds) of the total load. This would be an equally distributed, or balanced load. If one of the 4 men, lets call him Lew, steps on a stack of bricks his corner (the LR corner or C) of the box will rise. The opposite corner of the box (the RF corner or B) will lower due to the increased load imposed by Lew. The two guys at the remaining corners (A and D) are now taking a free ride and the poor guy at the right front corner (B) is stuck carrying 50% of the load instead of his previous 25%.””
However this does not address the front to rear change with adding only front spring pads. If one were to insert a spring pad which increases the ride height in the front, what does that do to the weight distribution in the rear?
Al, this is going to contradict my email to you earlier today, but here goes.
Imagine a car on a flat surface. The mass of the car could be considered to be concentrated at the center-mass and the force vector would be vertical. Now lift the front of the car 30deg. Now the vertical vector at the center mass is pointed 30deg towards the rear wheels and 30deg away from the front. That means that when you raise the front wheels, weight is added to the rear wheels and removed from the front.
I just reread my book on “handling”. It does not address the idea of increasing the height of front only or rear only. I would interpret that as meaning no one is interested in doing that. My suggestion would be to pull the pads so the car is as low as it will go. Then I’d look at moving weight to the rear with a spare tire, or whatever. Last I’d look at corner balance.
Great clear article kgobey, thanks.
Not seeing much around front to back balancing in any handling guides using spring pads or ride heights. Seems that the consensus is to remove all the sping pads in order to lower the car in the interest of speed. Once lowered,shift weight around and then if you want to try corner balancing, only then would you start playing with pads.
Thanks all,
Ranger wrote:
Great in theory, but some quick trig shows that if you raise the front of the car one full inch it will only move the center of mass rearward by less than .25 inch. That would shift a total of roughly 6 lbs from front to back. Probably not worth a 1" lift for 6lbs.
Matt
Matt H. wrote:
[quote]Ranger wrote:
Great in theory, but some quick trig shows that if you raise the front of the car one full inch it will only move the center of mass rearward by less than .25 inch. That would shift a total of roughly 6 lbs from front to back. Probably not worth a 1" lift for 6lbs.
Matt[/quote]
Wasn’t trying to advocate the idea. Just seeing if I could recall enough HS physics to get to the right answer.
When BW corner weight & balanced my e36 M3 with JRZ’s, they did it by adjusting height with the spring perches. It was SCHWEET! really made the car feel like it was on rails.
Seems to me with a combination of pads and weight shifting on our “fixed” setup would work best… my .02 cents.
Ranger wrote:
At the Labor Day race at Barber, I had a push that developed in the latter half of each session. It was worst mid-corner in the first caroussel (I think they call 'em turns 2 & 3).
We raised the rear either 1/4 or 1/2 turn on the spring collars (different suspension on the Miata, but same theory). No more push. I can’t do the math, but I can tell you how the car behaved.
Rake is definitely something to have in your toolbox, but if you haven’t set a good baseline with equal cross, good alignment, no bar preload, etc., you are wasting your time worrying about rake.