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Old 11-10-2010, 10:07 PM   #1
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Default Spring length..Short travel

This is a potentially dumb question. Sorry, but I'm still learning. I'm hitting the bumpstops on my rear coilovers when I go over medium to large bumps. Can I remedy this with longer or stiffer springs? Currently the springs are 6in, and I was thinking of stepping up to a 7in spring. The rear rates are 6kg/mm or 336 lbs/in. Or is this not even a spring problem at all, and the dampers are just under damped?
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Old 11-10-2010, 10:09 PM   #2
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it would help if you specified what you have now
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Old 11-10-2010, 10:13 PM   #3
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Stance GR+ : puts on flame suit :

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it's in my sig
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Old 11-10-2010, 10:18 PM   #4
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increase ride height
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Old 11-10-2010, 10:20 PM   #5
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I have many times now. Spring preload is separate from ride height adjustability.
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Old 11-10-2010, 10:27 PM   #6
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increase shock length and then decrease preload. voila, same ride height with more bump travel.
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Old 11-10-2010, 10:39 PM   #7
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wait.....

So you mean you can change the "full extension" length of the dampers themselves which then allows you to increase the height of the adjustable collar at the bottom of the spring without increasing the height of the car?

OK, I checked the website, this is what I came up with.
They are height adjustable via brackets at the top or bottom of the assembly This allows you to lower or raise the car while the damper remains at full extension which therefore also allows you to change the preload independent of ride height.

OP, is this correct?

So to confirm, you have installed the suspension at any random ride height, and then set the car down so that the full weight of the corner of the car is on the suspension. You then adjusted the spring collar upward until the damper was at full extension and no more (which would give you the most suspension travel without any preload) At this point, you adjusted the ride height via independent ride height adjustment to your liking.
And you're still hitting hard on bumpstops?
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Old 11-10-2010, 10:39 PM   #8
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Quote:
Originally Posted by Y8s
increase shock length and then decrease preload. voila, same ride height with more bump travel.
This is where I'm confused. I was thinking the exact opposite, by thinking to just preload the **** out of them to get more travel. I might actually be retarded and just don't understand coilovers at all; which is why I'm asking y'all.
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Old 11-10-2010, 10:41 PM   #9
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My post above is only partially correct, disregard the part about moving your spring collar up with weight on the suspension.

When you're preloading, you have the wheel in the air and damper at full extension while moving the spring collar upward, correct? (i.e. the spring isn't sitting 'loose' on the damper before you set the car down)
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Old 11-10-2010, 10:54 PM   #10
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Quote:
Originally Posted by fooger03 View Post
My post above is only partially correct, disregard the part about moving your spring collar up with weight on the suspension.

When you're preloading, you have the wheel in the air and damper at full extension while moving the spring collar upward, correct?
Correct. I actually had them corner balanced at a local shop. Still hitting bumpstops. If you look at the pic I posted, you can see that the rear springs are actually two different lengths. Stance sent me another spring to match the shorter spring. I didn't know any better and just went with it, not realizing the difference it might make. This is the main reason why I was thinking it was a spring issue. Most of the Miata guys that run Stance slam their cars or use them for drifting. Neither of these crowds really care about suspension travel. I'm guessing they just thought I was going to do the same.
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Old 11-10-2010, 11:03 PM   #11
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Ok, now I think we're getting somewhere. I just wanted to make sure that you weren't cheating yourself out of damper travel by letting the weight of the car set the spring into place.

You were pretty much on cue, lets start by increasing the hell out of our preload. How much have you compressed the spring preload? If your spring rate is 336lb/inch, then first try compressing your spring with preload by at least an inch. That should require about 200lb or so of force at the hub to get the suspension to move at all, if that doesnt work, you might try a compression of up to 1.5 inches, I suspect that 2" is probably pushing your luck, but you may as well give it a try if nothing else works. My springs arent preloaded, and I'm only running 300s, but They're quite a bit longer than yours IIRC, length is certainly your next step.
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Old 11-10-2010, 11:07 PM   #12
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My springs, for reference to length.

Specs:
425lb/in 7" front,
300lb/in 8" rear
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Old 11-10-2010, 11:11 PM   #13
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I appreciate the help. I'm not sure exactly how much I've preloaded the springs already. I'll check it out tomorrow after work and see if I can get some more preload on the springs and if that even helps at all. Thanks.
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Old 11-10-2010, 11:29 PM   #14
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Can someone explain what preload does in regards to ride quality?
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Old 11-11-2010, 12:19 AM   #15
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oops I meant shorten bodies and increase preload.
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Old 11-11-2010, 05:35 AM   #16
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chricto, would you mind measuring the shock shaft length (the chrome piece at full extension to the top threaded portion of the shock) as well as the shock body length (usually threaded and black... since you are all the way down into the lower cup/bracket, you can get an idea without removing the shock at all). A rough estimate is all I am curious of.
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Old 11-11-2010, 06:33 AM   #17
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Quote:
Originally Posted by wannafbody View Post
Can someone explain what preload does in regards to ride quality?
Nothing.

OP, the reason you are hitting the stops is because, if that's your car in the sig, your **** is way too low. Preload is meaningless since once you put the weight on the car its completely overcome. The issue is ride height. Granted, they are kind of the same thing since the only thing you can do to adjust either without changing springs is by moving the lower perch, but conceptually pre-load only matters when the suspension is at full droop. 100lbs of preload, 200lbs or preload...it disappears once you put 500lbs of car on it.

To ride that low and still have travel, you'll need shorter shocks. If it weren't for those crazy upper mounts you'd be on the stops at rest. Actually, you might be on them at rest even with those mounts.

Raise the car and have actual functioning suspension, or lower it and look cool. Your choice.
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Old 11-11-2010, 06:38 AM   #18
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^That's what they were discussing how the shock length is adjustable separate from the pre-load adjustment. Because of this, I think if his spring is at least seated correctly at full droop, the shaft travel is just too short. Longer top hats won't even help in his case, and neither will raising the ride height-- as shaft travel will remain the same no matter what height he is at.
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Old 11-11-2010, 09:27 AM   #19
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Quote:
Originally Posted by chricto View Post
Stance GR+ : puts on flame suit :







it's in my sig

I'm willing to bet with those rear mounts, that you're coil binding and not close to hitting the bumps.
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Old 11-11-2010, 09:42 AM   #20
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Quote:
Originally Posted by SignOfZeta View Post
Nothing.

OP, the reason you are hitting the stops is because, if that's your car in the sig, your **** is way too low. Preload is meaningless since once you put the weight on the car its completely overcome. The issue is ride height. Granted, they are kind of the same thing since the only thing you can do to adjust either without changing springs is by moving the lower perch, but conceptually pre-load only matters when the suspension is at full droop. 100lbs of preload, 200lbs or preload...it disappears once you put 500lbs of car on it.

To ride that low and still have travel, you'll need shorter shocks. If it weren't for those crazy upper mounts you'd be on the stops at rest. Actually, you might be on them at rest even with those mounts.

Raise the car and have actual functioning suspension, or lower it and look cool. Your choice.
Sign, not sure if i fully understood your post, I might be arguing your own point back to ya, look at the picture of OPs coilovers. On each damper, you'll see two adjustment collars. By turning the collar at the top, you can raise and lower the bottom of the spring. If we assume that the damper is forced to full extension while we're still raising the bottom of the spring, then we are effectively adding 'preload' (except you are right in that it only raises or lowers the car until the damper is at full extension with weight on the suspension). Now look at the bottom collar on the coilover; by adjusting this collar, the ENTIRE spring and damper assembly is raised or lowered independent of the lower shock mount. In this case, the lower shock mount is merely a bracket, and not permanently connected to the damper as in most applications.

So yes, OP can change ride height and preload independently if he wants to believe stance, realistically, though, he's not changing preload independend of ride height; but rather, he is changing damper travel independent of ride height. - that is to say, he can raise or lower ride height without affecting suspension movement.

Last edited by fooger03; 11-11-2010 at 09:58 AM.
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