Effects of spring preload on handling and ride quality

[DRIFTEADOR]

I have read the suspension FAQ and found nothing on spring preload. BTW, many of the links, namely the grassroot ms articles, are dead and so are all the pics.

Also ran a search and came up with an thread that basically just said, don't preload them, with nothing to back up why it shouldnt be done.

I just bought a set of coilovers and was planning on install them today but I'm curious as to how I should preload them.

I figure the stock shocks are preloaded (havent taken any meaurements but I'm guessing a good 2") for a reason so 0 preload doesnt satisfy me.

On another note, I'm surprised I couldnt find shock dynos for anything other than spl/kts. I beleive Koni and eibach will dyno them for free as long as you pay for shipping.

[Onizuka]

Well, for the most part its because adding pre-load only shortens total spring travel. This is because most coilovers come with liniar rate springs (they exert the same amount of force no matter how compressed or streched out they are). Now if it had progressive rate springs, adding preload would be effective in raising spring rate without having to buy another set of springs.

Somebody correct me if my logic is wrong

[DRIFTEADOR]

linear means that it'll compress a certain amount for every X amount of weight. for example a spring with rate of 300lbs/in (i like using standard units for simplicity ) and 600lbs of load will compress the same two inches from its original size whether it's preloaded or not (unless it has already been preloaded/compressed more than 2 inches in which case it won't compress anymore). preload doesnt change the length/weight at which it begins compressing.

and since when is longer spring travel better for handling (smooth surface)? the reason people get those crazy 12k springs is so the spring doesnt give as easily. if you meant shock travel, preloading a lowered car actually allows more travel before bottoming out

preloading affects how much force is used to decompress on the rebound.

[Onizuka]

Edit: Snip snip away with the mis-information

[DRIFTEADOR]

i may be wrong, but common sense tells me the force required before binding occurs will be the same preloaded or not. reason is because a preloaded spring will no longer compress an inch with 300lbs, it will not compress another full inch until theres 600lbs on it.

however, that wasn't my concern, i'm not trying to change my spring rate, I'm trying to find the most comfortable preload setting for an occasional track car...and in the process learn what/how different preload settings affect comfort and handling.

[Onizuka]

Edit: Snip snip away with the mis-information

[DRIFTEADOR]

now i'm just repeating myself...if the 300lbs/in rated spring is already compressed one inch before the car is on it, it will not compress any further if that corner of the car only weights 300lbs. It will compress one more inch over the preloaded inch, for a total of 2" with 600lbs on it. The same 2" that it'd compress with the same 600lbs if there was no preloading.

if preloading makes the shock rebound faster, like i think it does, it will make a difference. it affects ride quality on bikes, I don't see why it wouldn't on cars.

[Onizuka]

I see the light. And you only had to explain it to me three times I was a little too absorbed with the spring rate constant. J-spec bows to your knowlege (heck I should be the one asking you questions)

I think with motorcycles preload effects ride quality more because it is able to completely unload either wheel with relative ease, making that preloaded travel a larger part of of the overal suspension dynamics. Preload is also how they adjust ride height, seems like a double edged sword to me.

However, now concidering, if traveling on a sub-par highway at 60+mph with a sunden drop in pavement, preload could dictate the speed that the car recovers from down-up motion after the bump. I was reading whiteline's FAQ and they say they put only a very small amount of preload on their coils, just to keep them from moving around on the perches. However, I replaced stock struts for my freind 2 weeks ago on his saturn and the springs were preloaded a good 1.5 inches at least. How would you begin to even tune for preload? Only posible on a shock dyno or is more of a feel thing. Ive done single adjustable damper and camber tuning at the track, but we never touched on preload.

I guess it would help to have seperate compression and rebound damping adjustment if your going to be messing with preload.

[DRIFTEADOR]

a shock dyno probably wouldn't say much, much like it won't tell you what spring rates should be used, I think it depends more on the weight supported by the spring and rate used rather than the shock.

I was hoping someone had already messed with preload but i guess not. I'll be doing some trial/error on the ol buttdyno to see what feels best both on the street and track and i'll post the results if anyone cares.

OT, has anyone used aftermarket tender springs on their coilovers?