gearheadmb
gearheadmb Dork
10/1/16 9:59 a.m.

What is the advantage of using coilovers, instead of good quality factory style shocks and struts? Especially when they are replacing struts. They appear to be just an adjustable strut. I've been looking at CL cars (as always) and my natural inclination is to run away from cars with coilovers, the same way I run from cars with big goofy spoilers or body kits. Am I wrong for doing this? Should I be pursuing these coilover cars? Explain the tech behind these things that make them worth the money?

Trackmouse
Trackmouse Dork
10/1/16 10:32 a.m.

Coilovers allow for ride height. Ride height affects cornering performance. However, going too low with ride height screws up suspension geometry, like roll center. Screw that up and it's not worth having. Getting low PROPERLY is expensive and sometimes difficult if the right parts aren't available. Or if you can't relocate suspension mounting points. It also depends on the type of coilovers. I had some cheap, 20$, eBay coilovers on my celica with kyb AGX's. They worked great for track and autocross. They were not street friendly. Analyze what the car will do primarily. Then choose. There's no reason to go crazy expensive.

Also, it's very unusual for someone to change there ride height on a street car more than once. You get it dialed in, set it, and that's it.

Factory shocks on most cars are designed to take a beating and go a 100k miles. While this is great for the average driver, it doesn't work for a car that has had the spring rate increased. The majority of "lowering springs" also increase the spring rate beyond stock rates. This means that extra firmness need to be controlled, you can have an over damped and under damped car. Neither is fun... well, actually an under damped car is fun. But only at a stop sign when you smash the brake pedal. Lol.

Stefan (Not Bruce)
Stefan (Not Bruce) GRM+ Memberand MegaDork
10/1/16 11:06 a.m.

The real point of adjustable spring perches (which is what "coilovers" are really) is to not only allow ride adjustments (up or down as they are used on rally cars quite often as well), but to allow corner weight adjustment to help balance the static weight on each corner of the car which improves the balance and handling of the car.

This can be accomplished with spring shims or shimming the sway bar end links, without the adjustable spring perches, but it is no where near as easy or as accurate.

Another benefit is they use easily replaceable springs that allow quick and easy tailoring of the spring rate and length to the course and/or driving style.

The springs used are often smaller diameter when compared to the stock springs, especially on strut equipped cars. This can allow more room for wider rubber and/or more negative camber to help them as strut suspension has terrible camber curves.

When combined with a decently matched set of dampers, one can have a car with ideal ride height while maintaining reasonable suspension travel and the ability to adjust compression and maybe even rebound (or more as there are triple adjustable dampers).

All that said, quite a lot of "coilovers" on the market are cheap, poorly made Chinese junk bought by people who ar only interested in getting the ride height as low as possible for that race car look. So you should certainly make note of the brand of the suspension components used and how low the cars are. I would plan on replacing those parts with decent quality OE-equivalent or decent performance parts and sell the cheaply coilover stuff to someone else.

bentwrench
bentwrench Dork
10/1/16 11:54 a.m.

Also, Coilovers allow you to play with spring weights using cheaper generic springs, rather than springs that may be expensive or need to be custom made to fit in the OEM location

KyAllroad
KyAllroad UberDork
10/1/16 12:38 p.m.

Stephan (not Bruce) nailed it.

On my CSP Miata I have coilovers for all the reasons listed. The smaller diameter of the springs allows me to run 275 section tires. The increased spring rate keeps the body flat, the heavier damping controls this springs, the adjustable height allowed me to tune the corner weights.

None of that would have been possible with OEM style shocks and springs.

Streetwiseguy
Streetwiseguy PowerDork
10/1/16 4:00 p.m.

There are many good reasons to use coil overs and standard sized springs on a race car. There are far fewer good reasons to do it on a street car.

And, as was said above, there is a lot of real junk out there.

Trackmouse
Trackmouse Dork
10/1/16 4:53 p.m.

So I knew they use the height adjustment to do something with corner weights, but I don't see how that affects the corners weight, all you are doing is elevating the weight present at that corner right? Is it acting like a scale and balancing the weight front, back, side to side and diagonal? If it is, it seems like it would take a lot of ride height on the drivers side to offset the weight present there. And I've never seen a race car that didn't look even on one or more corners... not disagreeing here, just want to know the "why" (or is it how?)

NOHOME
NOHOME PowerDork
10/1/16 4:59 p.m.

In the case of most of those adds, follow your instincts. But keep asking good questions like this.

red_stapler
red_stapler Dork
10/1/16 5:07 p.m.
Trackmouse wrote: So I knew they use the height adjustment to do something with corner weights

You're adjusting the preload of the spring, so that it takes x amount of weight before it starts compressing.

Trackmouse
Trackmouse Dork
10/1/16 5:08 p.m.

Oh! We're talking preload! Ok, I thought you guys were saying the height shifts weight to another side.

Streetwiseguy
Streetwiseguy PowerDork
10/1/16 5:28 p.m.

They do move weight around, but not by moving weight... What you are trying to do, roughly, is have the tires pressing evenly upon the road. The front of your car weighs 1500 pounds. You would like each side to weigh 750 pounds, so if the right corner weighs less, you would wind the adjuster down to push that tire down harder. When you do that, though, you will also push down harder on the left rear at the same time...Its an art, really to move weight around and then know when to give up. Its also pretty amusing to watch the corner weights change as the driver leans left or right.

Then, when you are running a stock car, you start worrying about wedge, which is the diagonal measurement of the weight, biased to make the car turn left.

kb58
kb58 Dork
10/1/16 6:02 p.m.

Another thing is that coil overs typically have more adjustability, such as separate bump and rebound, a big deal for suspension tuning.

tr8todd
tr8todd Dork
10/1/16 6:03 p.m.

Picture in your mind a car that has more weight on the left front and right rear. It sits there teeter totting diagonally on the imaginary line between those two wheels. The car will will react differently as you corner right or left. By lowering the left front just a touch, more weight will shift to the right front and left rear. The car will be better balanced for both left and right turns now. You can also dial in the ride height you want. Changing springs is a snap. Spin the perch down to unload the spring while the wheel is in droop. Unbolt the top of the shock and let it drop down. Remove spring and insert new one. Reattach shock thru the shock tower and lower the car back down. Readjust the perch. Spring changes can be done in 5 minutes per side. Try that with stock spring mounts. You need to have access to scales to maximize their effectiveness. Once you have driven a properly set up suspension thats corner balanced with shocks valved correctly, you will never want to go back to standard off the shelf uprated springs that look sort of like the stock springs. There must be a video out there where someone balances their car on scales by adjusting coil overs. Go find it and watch it. Easier to understand by watching than by reading my lame attempt at an explanation.

RevRico
RevRico Dork
10/1/16 6:13 p.m.

For some applications, and I think this applies more here than the actual racing applications that they are made for, coilovers are just cheaper and easier to get than OEM replacements. To keep a car on the road another year or two, $250 for coilovers all around or $500+ for OEM?

There are also lot's of people buying them just because it sounds fancy when someone who doesn't know anything about cars asks what all you've done to it. Much like the people that put a 3 inch exhaust on a 1 liter motor with no turbo or intake, or the gigantic spoilers on front wheel drive cars that can barely break 100mph. It's cheap and it looks/sounds "cool" to them, whether they understand the reasoning behind or not.

Granted these vehicles have probably been abused, so best to just keep on scrolling, but you can always find a diamond in the rough. Hell, some body kits sell used for more than you can buy the car they are on.

Gearheadotaku
Gearheadotaku GRM+ Memberand PowerDork
10/1/16 6:35 p.m.

My concern with some coil over kits are the mounting load paths. The factory designed the control arms and body to bear weight at certian points and some coil over kits change that. I've seen several that move the spring from the control arm and sub frame to the strut or shock tower for example. Others now put the load onto the mount that was previously only meant for the shock.

Stefan (Not Bruce)
Stefan (Not Bruce) GRM+ Memberand MegaDork
10/1/16 8:24 p.m.

In reply to Gearheadotaku:

This is very true.

The common, lazy man approach for the rear suspension on the 924/944/968 is to ditch the torsion bars and add adjustable coil spring perches and 2.5" diameter springs to the rear shocks.

This can result in cracked shock mounts and frames.

So much for the "cheap" solution.

There's also the slightly higher unsprung weight and change in CoG.

JBasham
JBasham Reader
10/3/16 11:02 a.m.

One of the things I generally expect when I'm buying used sport sedans under $4,000 is that the dampers will be worn out and I will have to replace them with something.

Usually I'm looking to use them as DE track cars, and my replacement will be a tried-and-true aftermarket "sport" spring (like H&R) that fits the stock suspension, coupled with a "sport" damper (like Billies) that also fits and provides moderate & appropriate height adjustment. I can usually get those used for a few hundred bucks from somebody that is upgrading to four-figure $ coil-overs. A few hundred bucks is about the same price I would pay for a new set of stock dampers anyway.

But if I just wanted to drive the thing, I would be happier with "cheap" coilovers with dampers that still worked, than I would with worn-out stock dampers. Plus if the car was excessively lowered, it would be easier to back that out if the coilovers have adjustable perches, than it would be if the previous owner had cut the springs.

Mister Fister
Mister Fister New Reader
10/3/16 11:35 a.m.

Is this a joke/troll post?

Huckleberry
Huckleberry MegaDork
10/3/16 12:03 p.m.

If you have no use for controlling the ride height, rake and corner balance to get better cornering power from the chassis then a nice set of OE dampers are what you want. Buying cheap junk dampers with either approach will yield poor results.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/3/16 1:20 p.m.

I'm going to reiterate a couple of points we've already seen in this thread.

Coilovers (when put on a car equipped from the factory with struts or coil-over-shock shocks) give you the ability to move the perches. They may (but may not) use standard spring sizes. They may be adjustable. But they also may not.

That's it. "Coilover" don't mean good quality shocks, or well matched springs and shocks, or poor quality shocks, or anything else. There are excellent coilovers out there. There are steaming piles of E36 M3. The only thing you can assume from "coilover" is that the perch adjusts.

As for cornerweighting, this is laid out pretty nicely in How To Build A High Performance Mazda Miata But the best way to think of it is to equate it to making a four-legged table sit flat. If you have one short leg, then the table rocks back and forth between the short leg and the one diagonally opposite. They carry very little weight, and the other two carry more of it. Adjusting the spring perches up or down allows you to balance those "leg lengths" so the car sits balanced. Note that you cannot shift weight forward/back or side/side when cornerweighting, you can only shift it diagonally.

You're not adjusting the spring preload when you move the perches. You might be, but it's not the preload that affects the cornerweighting. It's the distance between the upper and lower perch. The car may not have any preload at all, but moving that perch will change the car's cornerweighting.

If you start with a car that does not have concentric springs and dampers, then a coilover conversion is a different thing. The 944 is an example. Puts the loads into different places, and we're talking a change in the suspension design.

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