Spring rates for aftermarket springs?

[optronix]

Generally after trying a search and coming up with little useful results, I figure a thread is worthy. There are a few threads for individual springs out there, but it would be nice if all of it was in a single location.

I actually have purchased Eibach PRO-KIT springs and have an appointment to install next week, but I don't actually know the exact spring rates for them, and they don't appear to be listed on any vendor storefront or the company website. I swear I've seen it posted somewhere before but if anyone out there knows the spring rates for any given set of aftermarket springs, post below and I'll update this first post.

Plan eventually is probably to do Ohlins, but clearly springs are a much lower barrier to entry so figure I'll start there for ~1/10th of the cost. Just curious about spring rates is all.

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[Integra23]

Here's info from Honda Product Type R

 

[Victorofhavoc]

I've found with springs and coils that often the rates aren't published by the manufacturer and resellers just make assumptions or use posted numbers that are incorrect. Happened even with bilstein coils from what I've seen. Ohlins is typically accurate though.

If you have dimensions for the spring though, it's pretty easy to calculate. Thickness of coil, number of coils, diameter of the spring, and free length are typically all you need.

 

[koatic]

I was not going to lower my DE5 because I have had so many problems with having lowered cars in the past. My civic hatch has had the eibach pro kit with the eibach struts for many many years and have sagged to about a 2.5 inch drop. Curious about the lifetime of aftermarket springs.
Eibach has limited lifetime warranty but I didn’t keep my proof of purchase.
H&R springs only have a two year warranty.
I am at this point planning to keep the DE5 for quite some time but have started to get annoyed at the factory gap. Starting to look at springs and while I have done all my own mods I am looking at getting a shop to do the springs. Anyone done their own springs on DE5? Was very simple on 5th gen civic. I was quoted $530 labor to install springs by local shop.
any pros or cons of different springs on DE5’s greatly appreciated.

 

[optronix]

I was not going to lower my DE5 because I have had so many problems with having lowered cars in the past. My civic hatch has had the eibach pro kit with the eibach struts for many many years and have sagged to about a 2.5 inch drop. Curious about the lifetime of aftermarket springs.
Eibach has limited lifetime warranty but I didn’t keep my proof of purchase.
H&R springs only have a two year warranty.
I am at this point planning to keep the DE5 for quite some time but have started to get annoyed at the factory gap. Starting to look at springs and while I have done all my own mods I am looking at getting a shop to do the springs. Anyone done their own springs on DE5? Was very simple on 5th gen civic. I was quoted $530 labor to install springs by local shop.
any pros or cons of different springs on DE5’s greatly appreciated.

There are a few threads on here that do a decent job at showing visual examples of the various springs out there. I'll do a quick rundown off the top of my head of what I recall the general consensus to be for various springs I was considering; hopefully compete with something an AI would spit out.

Spoon Sports- was my first choice, but availability may be limited. Expensive at ~$650 vs most other options falling in the ~$350 range, but owners have raved about the ride quality and on-track performance. Spring rates according to the resources in this thread suggest are substantially higher than the OEM and Eibachs, but are progressive rate so ride quality is not severely impacted. Introduces a "reverse rake" where the rear appears lower than the front, but apparently this has been revised in later versions according to at least one forum member on CivicXI. The same forum member fabricated a shim that can correct the rake issue if you have the earlier versions.

Eibach Pro-Kit- extremely popular option, and what I ultimately went with. Availability and price are good. Ride quality is excellent; best way I could describe it is OEM+. Not significantly harsher than stock, but noticeably more firm in a good way, no rubbing or crashing whatsoever. Aesthetics also excellent; car looks like it should have from the factory.

Eibach Sportlines- lower drop than the Pro-Kit. Haven't heard many reviews on ride quality or performance but they appear to be only slightly less popular than the Pro-Kit so I'm sure someone can chime in who has direct experience, I know they're out there.

Swift- to my eyes, they offer the best visual appearance, with a slightly lower drop than the Eibach Pro-Kit and Spoon, not quite as low as the Sportlines. Some forum members have complained about harsh ride quality.

H&R- probably the most conservative option with the least amount of drop and the most compliant ride quality. Instructions do not require cutting bump stops, whereas all other spring options (that I'm aware of) do.

Fortune auto offers an adjustable spring perch but I wasn't interested. The guys at ACH garage have an install video but that's about all I know about them.

I'm pretty sure there are RSR and Whiteline options but again, didn't investigate.

That's about all I got.

 

[StingertimeNC]

I did the install of the Prokit with the help of a mechanic friend. With another set of hand you can do it. A lift makes it way easier of course. We did it the "easy" way, based on a youtube video of a guy doing his FL5 in his garage. Here's the Vid. It worked exactly as described. I got alignment done immediately, then checked about 4 months later and still good.

 

[Frenzal]

Had so much problems with Eibach springs in the past that I'll stay OEM from now on.

Same with KONI sports shocks.

Even if they have a lifetime warranty, when a part fail, you'll have to wait for 2-4 weeks to get a new one, and you'll have to pay again for installation. So you'll loose usage of your car for a while each time a part fail. Don't expect any Eibach spring or KONI shock to last more than 10 years in your car sees winter and road salt.

Would be another story if you live in a hot climate without snow and salt.

 

[Integra23]

I was not going to lower my DE5 because I have had so many problems with having lowered cars in the past. My civic hatch has had the eibach pro kit with the eibach struts for many many years and have sagged to about a 2.5 inch drop. Curious about the lifetime of aftermarket springs.
Eibach has limited lifetime warranty but I didn’t keep my proof of purchase.
H&R springs only have a two year warranty.
I am at this point planning to keep the DE5 for quite some time but have started to get annoyed at the factory gap. Starting to look at springs and while I have done all my own mods I am looking at getting a shop to do the springs. Anyone done their own springs on DE5? Was very simple on 5th gen civic. I was quoted $530 labor to install springs by local shop.
any pros or cons of different springs on DE5’s greatly appreciated.

Its a pretty easy job. Just rent a spring compressor at your local auto parts store. If you have an impact it does make life easier. I did it in the drive way in a few hours on Jack stands.

 

[Victorofhavoc]

I did the install of the Prokit with the help of a mechanic friend. With another set of hand you can do it. A lift makes it way easier of course. We did it the "easy" way, based on a youtube video of a guy doing his FL5 in his garage. Here's the Vid. It worked exactly as described. I got alignment done immediately, then checked about 4 months later and still good.

There are several mistakes made in this video, but chief among them is the use of the impact to loosen the strut mount bolts, strut shaft bolt, and spring compressor.

I fully understand wanting to be quick and being careful about being quick, but if your bolts are a bit more stuck or you go just a tad too fast you could damage the strut mount, damage the strut, or injure yourself by launching the spring around from the compressor. Always use hand tools in these areas to loosen, then an air or battery ratchet to speed things up. An impact is the wrong tool.


Also, I'd steer clear of any true progressive springs. They're not as big of a handling detriment on active electronic shocks as they are on standard gas shocks, but electronic shocks still don't quite pair up as the rate of compression changes frequency, while the factory electronics expect the frequency to be linear progression. They'll adjust a bit, but not perfectly and hard driving at the limit (on track) can lead to bump understeer or bump oversteer.

Dual rate springs work okay since the upper portions of the spring are typically there for just slop, nothing else. They have their own limitations, like noise, shorter life, and still having some progressive tendency, but they're definitely better than true progressive.

With any lower spring there's always the geometry change to account for to rebalance handling and grip later, especially if you cut bump stops and don't add an anti roll bar.

 

[StingertimeNC]

Good info. I didn’t know any of this. So are the Eibach pro kit springs decent in your opinion? I also added the Eibach rear sway bar. Looks like they are progressive springs.

 

[optronix]

I think it’s a fair assessment that swapping springs only is not ideal for track performance. Many would argue that springs with factory dampers would actively hinder performance. Personally I don’t think I’d agree… and I think most folks agree that the extra camber you get with springs (in the rear at least) would net some performance benefit. But end of the day I’m not a mechanical engineer; as long as the car is not made unsafe, I’m fine with the better “feel” on the street, and the aesthetics, which is pretty much what I bought them for. What I won’t attempt to argue with is that I’d be looking at coilovers if I was dead set on improving track performance. There are obvious cost and ride quality implications to consider there though, which is why I figured I’d give springs a shot before ponying up $4k for coils…

TL;DR, springs are a fun OEM+ type mod, but I wouldn’t expect to see performance impacted severely positively or negatively.

 

[Victorofhavoc]

I think it’s a fair assessment that swapping springs only is not ideal for track performance. Many would argue that springs with factory dampers would actively hinder performance. Personally I don’t think I’d agree… and I think most folks agree that the extra camber you get with springs (in the rear at least) would net some performance benefit. But end of the day I’m not a mechanical engineer; as long as the car is not made unsafe, I’m fine with the better “feel” on the street, and the aesthetics, which is pretty much what I bought them for. What I won’t attempt to argue with is that I’d be looking at coilovers if I was dead set on improving track performance. There are obvious cost and ride quality implications to consider there though, which is why I figured I’d give springs a shot before ponying up $4k for coils…

TL;DR, springs are a fun OEM+ type mod, but I wouldn’t expect to see performance impacted severely positively or negatively.

So here's exactly the argument of how they affect performance; the McPherson strut suspension gains negative camber as it compresses until the outer ball joint is level to the inner joint/pivot point. At that point, additional compression begins to create positive camber gain.

When you lower the car (without changing the suspension pickup point on the subframe) you gain negative camber because you've compressed the suspension some along its natural path. The same negative gain you'd have if the car leaned in that direction when turning, by that same amount.

If you cut your bump stops, you've moved the range the lower control arm will travel, which means more positive camber gain than you'd have from factory. That also means at the absolute limit of travel the lowered and cut car will have more positive camber than the factory setup, which is not good for performance.

You can counter the drop by increasing the spring rate so the car leans less and hopefully limits the travel to before the control arm passes parallel, or at least limits it to factory range as much as possible. The grippier the tire you out on, the less chance you'll prevent that roll since more grip means much more lateral g to push the car over. This is why, typically, to make a lowered mcstrut car go fast, you MUST add a front antisway bar to reduce that roll even further, or you must increase the spring rate further. The problem starts to become too much spring or too much bar reduces overall grip because nothing is helping "press" the weight of the car down into the tire efficiently over rough/imperfect surfaces.


My recommendation is to keep as close to factory height as possible and increase spring rate based on the tire you want to run, while also increasing camber to meet the tire's specific requirements. That will lead to best performance per buck you'll get out of a stockish platform. Otherwise if you want to improve suspension performance AND aero performance by being lower, you'd have to change the suspension pickup points, add a lot of castor, add a lot more static camber (while also doing an anti roll bar), or change dynamics drastically at the rear end (since it behaves differently).

However, for most people's aesthetic, road friendly, and budget friendly goals, I realize the above isn't always feasible. So if you're going to lower your car for appearance but want to bring the performance back in line, your best option is to increase negative camber even further than stock can do (the strut pin pulled is a good start, but more is likely necessary if you go very low (like 25mm lower) and cut bump stops. Then make sure you're picking a dual rate spring or a custom rate spring with a helper and likely add an adjustable arb if you're going to have very grippy tires.

Hope that helps . Pretty much all of this is covered in more detail in this article, https://nasaspeed.news/tech/suspens...-track-performance-for-strut-suspension-cars/

 

[Integra23]

So here's exactly the argument of how they affect performance; the McPherson strut suspension gains negative camber as it compresses until the outer ball joint is level to the inner joint/pivot point. At that point, additional compression begins to create positive camber gain.

When you lower the car (without changing the suspension pickup point on the subframe) you gain negative camber because you've compressed the suspension some along its natural path. The same negative gain you'd have if the car leaned in that direction when turning, by that same amount.

If you cut your bump stops, you've moved the range the lower control arm will travel, which means more positive camber gain than you'd have from factory. That also means at the absolute limit of travel the lowered and cut car will have more positive camber than the factory setup, which is not good for performance.

You can counter the drop by increasing the spring rate so the car leans less and hopefully limits the travel to before the control arm passes parallel, or at least limits it to factory range as much as possible. The grippier the tire you out on, the less chance you'll prevent that roll since more grip means much more lateral g to push the car over. This is why, typically, to make a lowered mcstrut car go fast, you MUST add a front antisway bar to reduce that roll even further, or you must increase the spring rate further. The problem starts to become too much spring or too much bar reduces overall grip because nothing is helping "press" the weight of the car down into the tire efficiently over rough/imperfect surfaces.


My recommendation is to keep as close to factory height as possible and increase spring rate based on the tire you want to run, while also increasing camber to meet the tire's specific requirements. That will lead to best performance per buck you'll get out of a stockish platform. Otherwise if you want to improve suspension performance AND aero performance by being lower, you'd have to change the suspension pickup points, add a lot of castor, add a lot more static camber (while also doing an anti roll bar), or change dynamics drastically at the rear end (since it behaves differently).

However, for most people's aesthetic, road friendly, and budget friendly goals, I realize the above isn't always feasible. So if you're going to lower your car for appearance but want to bring the performance back in line, your best option is to increase negative camber even further than stock can do (the strut pin pulled is a good start, but more is likely necessary if you go very low (like 25mm lower) and cut bump stops. Then make sure you're picking a dual rate spring or a custom rate spring with a helper and likely add an adjustable arb if you're going to have very grippy tires.

Hope that helps . Pretty much all of this is covered in more detail in this article, https://nasaspeed.news/tech/suspens...-track-performance-for-strut-suspension-cars/

Well there is a solution to this...
https://spoonusa.com/spoon-zero-bump-steer-kit-front-civic-fk8

 

[Victorofhavoc]

Well there is a solution to this...
https://spoonusa.com/spoon-zero-bump-steer-kit-front-civic-fk8

4mm correction. Not much considering most springs take you 3-5x that, but it's certainly better than nothing at all. It sounds like they're looking to correct at only the extreme end of the motion path when shortening the bump stop. So if you only cut the bump stop 4mm, this probably makes sense to limit the upper range of motion of bump action and limit it to factory position and factory toe change.

 

[optronix]

So here's exactly the argument of how they affect performance; the McPherson strut suspension gains negative camber as it compresses until the outer ball joint is level to the inner joint/pivot point. At that point, additional compression begins to create positive camber gain.

When you lower the car (without changing the suspension pickup point on the subframe) you gain negative camber because you've compressed the suspension some along its natural path. The same negative gain you'd have if the car leaned in that direction when turning, by that same amount.

If you cut your bump stops, you've moved the range the lower control arm will travel, which means more positive camber gain than you'd have from factory. That also means at the absolute limit of travel the lowered and cut car will have more positive camber than the factory setup, which is not good for performance.

You can counter the drop by increasing the spring rate so the car leans less and hopefully limits the travel to before the control arm passes parallel, or at least limits it to factory range as much as possible. The grippier the tire you out on, the less chance you'll prevent that roll since more grip means much more lateral g to push the car over. This is why, typically, to make a lowered mcstrut car go fast, you MUST add a front antisway bar to reduce that roll even further, or you must increase the spring rate further. The problem starts to become too much spring or too much bar reduces overall grip because nothing is helping "press" the weight of the car down into the tire efficiently over rough/imperfect surfaces.


My recommendation is to keep as close to factory height as possible and increase spring rate based on the tire you want to run, while also increasing camber to meet the tire's specific requirements. That will lead to best performance per buck you'll get out of a stockish platform. Otherwise if you want to improve suspension performance AND aero performance by being lower, you'd have to change the suspension pickup points, add a lot of castor, add a lot more static camber (while also doing an anti roll bar), or change dynamics drastically at the rear end (since it behaves differently).

However, for most people's aesthetic, road friendly, and budget friendly goals, I realize the above isn't always feasible. So if you're going to lower your car for appearance but want to bring the performance back in line, your best option is to increase negative camber even further than stock can do (the strut pin pulled is a good start, but more is likely necessary if you go very low (like 25mm lower) and cut bump stops. Then make sure you're picking a dual rate spring or a custom rate spring with a helper and likely add an adjustable arb if you're going to have very grippy tires.

Hope that helps . Pretty much all of this is covered in more detail in this article, https://nasaspeed.news/tech/suspens...-track-performance-for-strut-suspension-cars/

I'm not sure quite what it is exactly that makes my brain slowly turn off when reading about suspension physics. I'm not denying that I might just be dumb, but I think it's more that I feel like you just kind of have to be a true expert to really be of much use when it comes to topics like this. Kind of like, I have to feel like I know virtually everything about it or I may as well know nothing.

I'm in a technical field by trade and oftentimes I realize that there are certain things that I would just have to truly bench myself to learn (e.g., assembly for reverse engineering malware comes to mind...) and without a practical requirement it will remain one of those things that I wish I knew but never could muster the energy to actually learn to a functional extent. Suspension design is another one of those things, to me at least.

In other words... I feel like I can follow that article well enough... but extracting practical knowledge that will help me figure out ideal suspension configuration for my street car? Not much help to be honest.

I also am not the biggest fan that the article seems to exclusively reference 30+ year old cars (the article was written over 10 years ago...), and refers to "modern" suspension design as being in the 70s and 80s. It's good fundamental information, but I feel like I personally would benefit more from a similar article that was more specific to our cars, specifically the DE5/FL5, because I think there's enough nuance to justify that, as from all the marketing and media noise around the topic, this "dual axis" design is apparently some sort of breakthrough anyway.

All in all, what will end up being my approach to all this is to see how this setup with the Eibachs hold up to this coming Saturday's autocross. I've said before, I'm not actively going for class-based competition; I'm just trying to see how close I can come to the guys who take this shit really seriously. If that makes sense.

I actually did NOT pull the strut pins- I decided I'll probably end up doing the Whiteline camber kit eventually anyway so I didn't bother telling the shop to pull them (I still don't think they would have done it anyway but that's another story...). So right now my car is sitting at ~1.5 degrees negative camber in front, ~2.5 degrees out back. Bump stops were cut by 20mm front and rear as per the instructions from Eibach. If my times start sagging, and I don't feel like I have as much control of the car as I've gotten used to with the stock setup, then I'll get the Whiteline camber kit sooner rather than later, and probably a rear anti-roll bar. I don't think I'm going to screw with the front. At least not until a refreshed article comes out, or someone can explain it to me like I'm 4 years old on how it's still relevant to our cars' specific suspension geometry.

Also FWIW, Zygrene as always has amazing track content that IS specific to our cars, and his latest vid he feels like his car is dialed in better than it ever has been, and he's running the Whiteline kit and -4.2 degrees negative camber up front. No other suspension mods other than the Ohlins coilovers (with pre-production rates that I'm also waiting to become available...). When I get more serious about taking the car to an actual race track on a routine basis, pretty sure this will be my move.

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