Another Euro Eibach review + track eval

[tcpsoft]

I thought it may be time for me to contribute now that I have some experience with the Euro Eibachs on both the street and track. I was going to just add a comment on another Euro spec review but I started getting off topic so I figured a new thread was in order.

I got the Euro Spec Eibachs last month (April) as something to hold me over until I can get a set of coilovers (patiently waiting on the Ohlins…) because I wasn’t fond of the gap but didn’t want the car slammed and wanted something that was track-worthy. The Exiges I had came with Eibachs standard and were very capable so I figured it was a good bet given the relatively low cost. I also ordered from Baan Velgen on a Sunday night and they were at my door on Thursday.

I installed the fronts when I received the shipment last month and the rears last week (split it just due to time) and didn't initially get an alignment. I was, however, very diligent in getting the rear bolt aligned to where it was pre-spring install. I knew the alignment would change with the springs even if everything was set exactly pre-install, but I figured this would get me around until I could get an alignment.

Similar to another poster on here the car had a bit of a drifty tendency on those big sweepers afterward, but then a used Cayman I had was the same way the first time I drove it hard. I got an alignment on the Cayman and it was a totally different driving experience afterward. I just got an alignment on the M3 and it definitely felt better after the alignment, but it does *seem* lighter in the front. Another car buddy, who also has a F80, did the ever scientific stand-on-the-spring-and-see-which-is-stiffer compression test and the Eibach appeared to compress less vs stock. However I agree it does feel softer at high speed. At low speed in a parking lot the Eibachs seem stiffer Valving on the dampers not matching the spring rate closely enough?

Now, just speaking theoretically is a softer front spring a bad thing? I'd say with the amount of stock understeer the car has, probably not (if nothing else changes.) I just had the car at VIR with the Euro Eibachs this past weekend and the car was still very solid - still understeering but a lot of it was me going too hot into some corners and temps close to 90 degrees.

So what's my final verdict? It may feel a little lighter in the front but the car seems to stick at least as well as the stock suspension. Interestingly enough, I’ve been tracking cars at VIR for 8 years and have never been on the South course until this past weekend. If I had been on the South course before I would have a better idea of old vs new, but the two common elements to the South and Full courses, turn 10 and Oak Tree, were very stable at speed. I'm looking forward to going to the track with these springs again and giving them more of a shakedown.

-Tom

[tcpsoft]

One of the guys that co-owns the garage I was able to use had his set of F80 H&Rs still in the box, so I thought it was a great chance for a photo op and comparison of the stock springs, Euro Eibach, and H&R. The rear spring picture is just Eibach vs H&R as I didn't change the rears that evening (it was already midnight when we finished the front....)


^^ Front H&R, Euro Eibach, Stock



^^ Rear H&R, Euro Eibach

[tcpsoft]

And the requisite side pics. The fronts have about three weeks and 500 miles and the rears one day and almost no miles in these pics (so may still settle a bit....) I was in a hurry and the full side pics ended up washed out, so we have front and rear half closeups.

[Jaymax85]

So these springs seem to not be a performance upgrade.. Looking forward to pics

[Racer20]

It may feel softer because lowering the car also lowers the roll center, so even though the vertical stiffness is increased, the roll stiffness may actually be less than stock unless the spring rates are *significantly* higher than stock.

I don't know anything about the euro eibachs, but that would explain what you're feeling.

That whole "lowering screws up geometry" thing is actually true.

[CanAutM3]

Originally Posted by Racer20

It may feel softer because lowering the car also lowers the roll center, so even though the vertical stiffness is increased, the roll stiffness may actually be less than stock unless the spring rates are *significantly* higher than stock.

I don't know anything about the euro eibachs, but that would explain what you're feeling.

That whole "lowering screws up geometry" thing is actually true.

Wouldn't the center of gravity be lowered by the same amount as the roll center? The distance between the two should remain unchanged and therefore not affect roll stiffness (assuming same spring rates). Am I missing something?

As another question for you, there have been numerous debates regarding constant rates springs vs variable rate springs. Can you share your point of view on the two?

[CanAutM3]

OP, thanks for sharing your experience.

I have been on the fence regarding the Eibachs for a while now. I also find that the cars sits a little too high and would have like the slight drop provided by the Eibachs. However, changing spring rates without changing damper rates goes against much of what I believe in, hence my hesitation.

[Racer20]

Originally Posted by CanAutM3

Wouldn't the center of gravity be lowered by the same amount as the roll center? The distance between the two should remain unchanged and therefore not affect roll stiffness (assuming same spring rates). Am I missing something?

As another question for you, there have been numerous debates regarding constant rates springs vs variable rate springs. Can you share your point of view on the two?

I don't know the geometry in detail enough to say for sure, but in many instances, no. The CG drops by the same amount that you lower the car, but due to how the angles work, the RCH drops lower.

As far as variable rate springs go, I think linear rate is better purely from a handling standpoint. But there are many other factors that make progressive rate springs a better option (or sometimes the only option) for a street car. Ride quality is only one of the factors, but definitely a big one.

The linear vs. progressive rate decision is one that has to account for a huge amount of factors, from the load carrying capacity of the car to the durability of the wheel and tire and body to the assembly method in the plant. Quite often that decision is made very early on when the car is first being designed, and well before the ride engineers get their hands on it.

[Warranty P]

I don't get it. You put in new springs and they make the car under-steer more and yet you feel they are as good as stock?

[Racer20]

Edited my post above to answer your question about variable rate springs.

[tcpsoft]

Originally Posted by jawwadh

So these springs seem to not be a performance upgrade.. Looking forward to pics

Honestly, I wasn't expecting an upgrade in anything but appearance but I was pleasantly surprised that they were competent at the track.

Pics updated

[tcpsoft]

Originally Posted by Warranty Pussy

I don't get it. You put in new springs and they make the car under-steer more and yet you feel they are as good as stock?

I never said the car understeers more now, it said it *still* understeers. I was expecting worse performance but was pleasantly surprised.

Originally Posted by CanAutM3

Wouldn't the center of gravity be lowered by the same amount as the roll center? The distance between the two should remain unchanged and therefore not affect roll stiffness (assuming same spring rates). Am I missing something?

As another question for you, there have been numerous debates regarding constant rates springs vs variable rate springs. Can you share your point of view on the two?

I know this question was directed to the other post, but I switched to a variable rate spring on the MINI I had and was not happy with it. The crispness seemed to be gone and it felt softer - which it was at low speed. I understand the reasoning behind variable rates, but I don't think I'd want to try them again.

[CanAutM3]

Great thread. Thanks for the pics, they are quite revealing .

[tcpsoft]

Originally Posted by CanAutM3

OP, thanks for sharing your experience.

I have been on the fence regarding the Eibachs for a while now. I also find that the cars sits a little too high and would have like the slight drop provided by the Eibachs. However, changing spring rates without changing damper rates goes against much of what I believe in, hence my hesitation.

Thanks. I was on the fence also but I figured I'd give it a try. Compared to other M parts and accessories these are a bargain. I'm sure R&D is one of the main reasons its taking Ohlins two years to get a product out, but I expect those to be ~$4000 USD so they better be spot on.

[JTO24]

Thanks for the review! Even tho you have two photos, I'd still be interested to see a full on profile pic once the rears have some miles on them and settle fully.

[Warranty P]

Originally Posted by tcpsoft

I never said the car understeers more now, it said it *still* understeers. I was expecting worse performance but was pleasantly surprised.

Sorry, I misread your original post.

[manticor]

Damn these were the springs i was going to put on the (eventual) F80... very disappointing to hear about this floatiness. Ill say again i dont understand why kw doesnt make the V1 for this car

[CanAutM3]

Originally Posted by tcpsoft

I know this question was directed to the other post, but I switched to a variable rate spring on the MINI I had and was not happy with it. The crispness seemed to be gone and it felt softer - which it was at low speed. I understand the reasoning behind variable rates, but I don't think I'd want to try them again.

There have been numerous comments in other threads that the Euro Eibach were variable rates. However, from the pictures you posted, they seems to have a rather fixed rate (pure speculation based on the pictures). That is why I asked here.

When you purchased the Euro Eibach, did you know for sure they had a fixed rate?

[tcpsoft]

Originally Posted by CanAutM3

There have been numerous comments in other threads that the Euro Eibach were variable rates. However, from the pictures you posted, they seems to have a rather fixed rate (pure speculation based on the pictures). That is why I asked here.

When you purchased the Euro Eibach, did you know for sure they had a fixed rate?

There was something I saw that made me believe they were not progressive, so that was my expectation when I ordered.

From everything I can tell these are linear rate springs. I agree its hard to discern from the pics but in person they definitely don't appear or feel progressive.

[HamsF80]

Just a thought here; but if the spring rate increase was higher in the front springs than on the rear springs, it would cause the car to feel lighter in the front because it is shifting the balance of the car rearward.

Reason I say - I have the Euro Eibachs as well. I re-aligned the car by slightly increasing toe-in front, caster/camber unchanged since they are not adjustable on stock suspension. Rear I aligned to -1.8 degrees and 1/16th of toe. I have noticed the car pushes more now than it did with stock suspension.

I really believe the reason is that the front spring rate increase is higher than the rear springs. I didn't put my car on scales to confirm this but I would put money on it.



- Chris

[x.shell]

Can you post a side pic of the whole car?

[CanAutM3]

As a piece of info, based on info shared in the Eibach thread, it seems like the Euro Eibach spring have a lower spring rate than the OE one. This could explain the "floatiness" the OP has experienced.