Can somebody explain coilovers vs spring/shock

[stephenkirsh]

So I understand what a coilover is, but I don't understand how it's much different than a normal strut. With a strut, the spring and shock are together, too.

It seems like coilovers offer lower drops and better performance? And a higher price?

I'm interested in upgraded suspension for DD and once a month autocross. I want an inch drop and no more with reasonable comfort. I live in, no joke, the lowest rated city in the lowest rate county of the entire Bay Area for road quality. So comfort is a higher priority than for most people.

Help!

[wsmeyer]

It would be interesting to hear from others but here's how I would explain it.

It's confusing because most people use the terms generally. The term "coil over" originally referred to an assembly where the coil was over the shock. Then struts came along and it all got confusing. Struts are an integral part of the suspension, usually taking the place of the upper A-arm. If you're looking at a cars suspension ask yourself:

If I take that part out could the car still be driven?

YES - They are shock absorbers.
NO - They are struts.

If you are looking at the part itself, struts usually use two bolts at the bottom to attach it to the suspension. Shock absorbers just one that allow it to rotate at the mounting point.

Nowadays when someone refers to "coil overs" they are usually talking about a setup that is height adjustable via a threaded lower body and a collar that the spring sits on, but not always. Some sets are height adjustable struts in the front, and height adjustable coil overs in the back. Others though don't have the height adjustment so would really just be struts in the front and rear coil overs.

[stephenkirsh]

I was looking at coilovers at Turner and as far as I can tell, the packages they have are the same set up in the rear; separate spring and shock.

[Vas]

A true coilover system is where the coil-spring is over the shock. Some manufacturers offer "coilovers" that mimic the factory suspension set-up where in the rear the shock is seperate from the spring. However the spring rates are very high on those systems and you have slight bending of the springs due to their location between the lower camber link and the frame of the vehicle.

Coilovers offer adjustibility of height, preload, dampening, and more advanced systems offer external fluid reserviors, camber plates and etc. Plus you have the option of choosing spring rates and the shocks usually have a bigger piston diameter.

Alot of the coilovers for BMW are not "true" due to the weak metal on the strut towers in the rear. You will likely have to reinforce that are where it bolts. However the benefit of the "true" system is that you have less stress on the subframe and the bushings.

But based on your post, it sounds like you are better off with some lowering springs and aftermarket shocks.

[stephenkirsh]

Yea I'll probably go the springs/shocks route for a multitude of reasons. I just wanted to get a little info and make sure everybody was not saying "get coil overs!!!"

[LivesNearCostco]

I was going to answer but got distracted, and now you already have the answers! My summary is that for the BMW E36/E46 world...


Almost all coilovers give you height adjustability (a few do not)
Most offer adjustable rebound, but not all. Some do 2 or 3-way damping adjustments.
Camber plates and single adjustable shocks/struts can be used with stock springs, but some camber plates only fit coilover springs
Most BMW coilovers keep the shock and spring separate in the rear but higher-end ones can often be sold as true coilovers
Going true coilovers in rear not only requires reinforcing rear shock towers, it can also cause clearance problems.
Coilovers usually allow more lowering and more bump travel on lowered car, through combination of shortened shock/strut and shorter stack height in the camber plate (instead of using OEM strut hat).


Basically you get coilovers if you want to run higher spring rates or lower ride heights than you can get from standard lowering springs, or if you need more shock stiffness than Bilstein Sports or more adjustability than Koni Sports.

Edit: Forgot to add you can get coilovers for the bling factor or just because you can, but unlike a nice BBK, coilovers are hard to see with car on the ground, so you show them off by making the car lowwwwwwwww....

[scooby24]

keep in mind coilovers, at least decent ones, don't alter the preload of the spring nor the travel length of the shock. You adjust the height of the vehicle by adjusting the perch of the spring/shock which still allows for the same amount of travel regardless of height. The car will ride the same slammed as it will jacked up like a 4x4, not taking into account the control arm geometry.

A lowering spring will alter the shock's travel length which is not ideal.

[wsmeyer]

keep in mind coilovers, at least decent ones, don't alter the preload of the spring nor the travel length of the shock. You adjust the height of the vehicle by adjusting the perch of the spring/shock which still allows for the same amount of travel regardless of height. The car will ride the same slammed as it will jacked up like a 4x4, not taking into account the control arm geometry.

A lowering spring will alter the shock's travel length which is not ideal.

Kinda lost me there. I've never noticed ones that DIDN'T reduce the travel length of the shock. Seems to me that regardless of ride height you would want the suspension to hit the bump stop at the same point and completely stop travel before any part of the suspension hits the chassis.

[scooby24]

Kinda lost me there. I've never noticed ones that DIDN'T reduce the travel length of the shock. Seems to me that regardless of ride height you would want the suspension to hit the bump stop at the same point and completely stop travel before any part of the suspension hits the chassis.

BC BR as an example since that's what I have. There are two adjustment points on the front, you can adjust the preload of the spring but to adjust the height you loosen the locking ring at the bottom of the shock and then thread the shock body further into the housing. Since the shock body height in the housing is what's moving up and down to change height, neither the spring preload nor the shock's travel length changes.

For the rear the height is adjusted by changing the height of the spring perch. The preload of the spring remains the same. You again move the shock body in the rear housing to match the spring's adjustment so the travel length of the shock remains unchanged.

See lower locking rings below. The shock body threads up and down to adjust height.

http://coilover-store.com/wp-content/uploads/2013/11/BC-Racing-BR-Type-Coilovers-BMW-3-Series-98-05-E46-.jpg

[QC_ZHP]

I may be in the minority here but my vote would go towards coilovers, esp. if you enjoy Auto-X. Once you drop the ~$800 on springs/shocks, why not pay the extra $200-$300 and get say something like BC coils which go for around $1000 I believe. Its worth the premium to have all the adjustability in my opinion. You never know when you'll change setups, wheels, etc.

I ride around on my Bilsteins dialed in at 7/8 (9 is the highest). I love it. There's a few roads around that are a handful but I tend to avoid them. I'm sure if I set the dampening to 3 or 4, it would ride like stock.

[Avetiso]

BC BR as an example since that's what I have. There are two adjustment points on the front, you can adjust the preload of the spring but to adjust the height you loosen the locking ring at the bottom of the shock and then thread the shock body further into the housing. Since the shock body height in the housing is what's moving up and down to change height, neither the spring preload nor the shock's travel length changes.

For the rear the height is adjusted by changing the height of the spring perch. The preload of the spring remains the same. You again move the shock body in the rear housing to match the spring's adjustment so the travel length of the shock remains unchanged.

See lower locking rings below. The shock body threads up and down to adjust height.

http://coilover-store.com/wp-content/uploads/2013/11/BC-Racing-BR-Type-Coilovers-BMW-3-Series-98-05-E46-.jpg
Broadway Static also does this. No change in travel/preload as a result of height adjustment.

I may be in the minority here but my vote would go towards coilovers, esp. if you enjoy Auto-X. Once you drop the ~$800 on springs/shocks, why not pay the extra $200-$300 and get say something like BC coils which go for around $1000 I believe. Its worth the premium to have all the adjustability in my opinion. You never know when you'll change setups, wheels, etc.

I ride around on my Bilsteins dialed in at 7/8 (9 is the highest). I love it. There's a few roads around that are a handful but I tend to avoid them. I'm sure if I set the dampening to 3 or 4, it would ride like stock.
This has been my reasoning as well. After diving in $700-$800 for struts/springs.... just buy coils, dude. Ride should be better and you'll be able to dial in your ride height, as well as adjust for the settling period towards your preferences.

[stephenkirsh]

The closeness in price is what made me start the discussion.

I'm still a ways away from doing that, so I guess I'll have more time to mull it over.

It sounds like there really aren't any reasons NOT to go with coilovers?

[QC_ZHP]

Exactly.

[stephenkirsh]

Any difference in how long they last vs springs/shocks? I'm guessing it varies by brand/cost?

[derbo]

The term Coilover today seems to imply a kit that includes an adjustable height spring perch with shocks/struts. The adjustable height spring perch is the common part that defines a coilover system in today's lingo. As others mentioned, usually it will have shock/struts designed specifically to the kit.

I have a Ground Control Coilover Setup:

It consist of Koni Yellows Struts in the front (missing the normal large spring perch) with ground control's spring perch sleeves to go over it. The rear is the rear shocks and a separate spring perch and spring.
http://www.nexternal.com/vacmotors/images/GC%20E46%20non%20M%20complete%20street%20-M.jpg


As far as the reasons to go to a coilover setup vs spring/shock/strut combo, here are my personal reasons:

Pros:

Height:
A lowering spring will have one height it was designed for. It is a hit or miss that you will like it at that height. Even when the spring is broken in, the spring may settle a little lower and you may not like it again. A coilover system can adjust height to your desired height and you have the option to change it.

Front inner fender clearance:
If you look at the picture below, you can see the spring and the spring perch is much larger in diameter than the ground control spring. Usually Coilover springs are 60mm or 65mm in diameter vs the much larger stock spring. This provides better inner fender clearance when running larger width rims.

http://forums.pelicanparts.com/uploads11/IMG_15461186243894.jpg


Shocks/Struts can come in flavors than allow adjustability for dampening just like coilovers as well. Koni makes custom valving shocks/struts which can come with or without a spring perch. I could piece together a bilstien shock/strut combo + H&R race springs and it could perform the same as a coilover setup. I would loose the inner fender clearance and height adjustability.


Cons to coilover setups:
Price. It usually is more expensive and chances are you will set the height a few times and never set it again. A proper setup can cost a lot and you may or may not use them all.

Springs are shorter and not all coilover setups will have 2-way height adjustment to minimize lack of preload when jacking up the car. My setup does not have pre-load but I do not see it as a problem unless I happen to launch the car into the air and my springs do not properly seat back when land.. :eeps

Possibly quality loss on cheaper coilover setup:
Since coilovers are all the rage now, there are cheaper alternatives brands and not all are made with the best quality in mind. Some may have great quality and great pricepoints but I personally have no knowledge in this department. They are out there but it would involve some research from you. :)


Anyways, enough blabbing. I like coilovers for the ability to adjust height and better inner fender clearance. It's also nice that the shocks/struts usually are valved to the spring rates provided in the kit. I usually get a coilover set that has camber plates and rear reinforcement plates so its easier to install. Stock stuff comes out, new stuff goes in without swapping any hardware besides bolts/nuts.

IMO, if your budget lets you. I would go with a coilover setup. If you know you want a specific height and you do not wish to deal with multiple spring setups to get there, it would be the best route to go. I would pick a setup with adjustable dampening too since we all know it can get pretty harsh out here in the city. ;)

[JKO_ZHP]

Subscribed/bookmarked.

I've heard that shocks/springs is the DD option....but more coilovers are now also DD-able and can be adjusted for track use.
Also have been told that unless you off-road your E46 or drove into a volcano, the (structural integrity? of the) springs should be fine, and at most, only the shocks need to be replaced. Which means cost of shocks alone < coilovers.

[3ZHP]

Dinan Tech-Tip Tuesday; Coilovers
http://dinancars.com/tech-tip-tuesday-ep-3-coilovers/


Sent from my iPhone using Tapatalk

[stephenkirsh]

"Springs are shorter and not all coilover setups will have 2-way height adjustment to minimize lack of preload when jacking up the car. My setup does not have pre-load but I do not see it as a problem unless I happen to launch the car into the air and my springs do not properly seat back when land.. :eep"


Can you talk about that more? What's preload and why does it matter?

[scooby24]

"Springs are shorter and not all coilover setups will have 2-way height adjustment to minimize lack of preload when jacking up the car. My setup does not have pre-load but I do not see it as a problem unless I happen to launch the car into the air and my springs do not properly seat back when land.. :eep"


Can you talk about that more? What's preload and why does it matter?

Preload is compressing the spring before installing it in the car. It doesn't matter as long as it's not preloaded beyond what the car would put on the spring anyways. If you preload beyond the car's load, you've effectively increased the spring rate...and that can have dramatic consequences depending on how much preload you put on it. You could make the car extremely stiff, have excessive rebounding and basically launch the car off every bump...depending on how bad it is. You don't want to preload unless you know what you're doing.

[stephenkirsh]

So is preload determined by the equipment or the installation process?

[scooby24]

So is preload determined by the equipment or the installation process?

Equipment and install...varies from front to rear. You preload the spring by adjusting the spring perch on the front coilovers.

On the rear, you preload by adjusting the height of the shock in the housing to "pull" the rear swing arm up, compressing the spring when the car has no load on it.

[LivesNearCostco]

What Scooby24 said. My coilovers (most BMW coilovers, I would say) don't allow the strut or shock length to be adjusted so you can't adjust preload independently from ride height. If you make the ride height high enough, that can put preload on the springs, but in most cases probably not more than the spring would compress under the car's static weight. Therefore, effectively no preload for performance purposes. As mentioned the BC Racing, Fortune Auto, and I think TRM coilovers ones allow preload adjustment.

Strut/shock height adjustability also allows the bump travel to stay the same as ride height is changed, but many of the non-height-adjustable coilovers accomplish this by simply using shortened struts and shocks to work in the expected (lowered) height range, so they don't have to design a threaded shock body with two height adjusters (one for spring, one for shock). <Edit: This means you might not be able to raise the car all the way up to stock ride height, or if you can you might preload the springs, but nobody who wants coilovers or lowering springs wants to be at stock ride height, right?>

Preload serves one purpose beyond handling... prevents springs from rattling around when car is on lift or jacked up or if you go over a big enough bump to get two wheels airborne. In my car if I lift one wheel in a corner, the spring should still be tight because of the swaybar, but if I removed the front swaybar or jack up both front wheels, the front springs are loose. Same in back when I tried 6" springs--the rear shocks are shortened but if rear height adjuster was low enough, rear springs would rattle around at full droop (which almost never happens while driving). <Edit: Went back to 6.5" rear springs, so they're under a bit of tension at full droop and don't rattle around as long as shocks are still connected. But I have a modest drop--if I lowered it a lot more, the rear springs could get loose if booth rear wheels are at full droop.>

Use of a tender spring can keep springs snug at full droop without increasing effective spring rate. One reason stock springs are so tall and progressive is that allows them to have lots of bump travel, not get loose, and still offer a comfy ride all at once--they're almost like two springs in one.