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The E46 touring forum. Talk about your sport wagon E46 here.

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Old 10-08-2019, 09:18 AM   #1
Kyriva
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Rear Spring Rate

I did a search (and also emailed Eibach) and was not able to find a definitive answer. Hoping someone out here has it.

I need the spring rate of OEM Sport rear springs for the wagon, compared to the spring rate of the Eibach Sportline rear springs.

From my understanding, the Sportline's will lower the rear of the car ~.75" lower than the OEM sport suspension, but is the spring rate for the Sportline greater than that of the wagon specific sport springs?

I don't care about the drop (can adjust with spring pads), I just want which ever spring that has the higher spring rate.
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Old 10-08-2019, 09:30 AM   #2
malapane
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I have subscribed to this thread. I am curious as to what you find.

I have looked into spring info before and it is very difficult to find good / accurate info. Short of buying new versions of both and measuring them, it might be tough.

I do know the tourings with sport package springs have a pretty high spring rate for an E46, as they sit low and are rated for a pretty high load capacity. They do list a different spring for tourings with and without the roof rails, so they must be accounting for additional roof load - that is standard in the US.

I bought Eibach springs for my sedan and they weren't able to help me with any useful data over the phone. They didn't even know the cross reference numbers correctly. I ended up getting exactly what I was looking for from them, but half by accident.

Good luck.
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Old 10-08-2019, 09:58 AM   #3
Kyriva
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If that's the case, my wagon must have the highest spring rate available, because they are the sport springs and the wagon has roof rails.

I know it's .75" in OAL longer (which doesn't mean much when uncompressed) and 1# heavier than the Eibach Sportline spring.
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Old 10-08-2019, 11:10 AM   #4
malapane
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Usually, I think they increase the spring rate when they make lowering springs, to avoid an increase in potential to hit the suspension travel limit (bottom out) but really, it's hard to determine what the spring rate is at comparable common range of motion when loaded. I'd be worried published specs wouldn't be too useful to determine the practical comparison.
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Old 10-08-2019, 11:22 AM   #5
Kyriva
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I see your point. I suppose I could measure the sag from 200# of ballast and compare the delta between the current wagon sport springs and the Eibachs.

Just trying to avoid installing the Eibachs just to find out they're softer than the wagon sport springs, and then I'll have to swap out the springs a second time.

Last edited by Kyriva; 10-08-2019 at 11:22 AM.
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Old 10-08-2019, 11:28 AM   #6
malapane
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I think that would be the best way to know for practical purposes. Luckily the rear springs are pretty easy to swap on an E46. The wagon isn't any different is it?
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Old 10-08-2019, 11:31 AM   #7
Kyriva
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It's just as easy on the wagon. I have the tools and means to do it, but the way I see it... doing research beforehand is much less time consuming. I could do the whole process in under two hours if need be, but the time spend would be much better spent with the family. I spend enough time in the garage as it is!
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Old 10-08-2019, 11:36 AM   #8
malapane
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Quote:
Originally Posted by Kyriva View Post
It's just as easy on the wagon. I have the tools and means to do it, but the way I see it... doing research beforehand is much less time consuming. I could do the whole process in under two hours if need be, but the time spend would be much better spent with the family. I spend enough time in the garage as it is!
I hear you there. Wish I had more info for you, but I am still curious as to what you find out.
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Old 10-08-2019, 11:30 PM   #9
Kyriva
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Got a response from Eibach USA. They had to contact Eibach EU for the answer. My question was for the spring rate on the Sportline Kit Rears.

" The rear spring rate is progressive, initial rate - 399 lbs/in, main rate - 799 lbs/in

Now to find some friends to use as ballast to measure the stock travel....

Last edited by Kyriva; 10-08-2019 at 11:31 PM.
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Old 10-09-2019, 07:02 PM   #10
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Quote:
Originally Posted by Kyriva View Post
Got a response from Eibach USA. They had to contact Eibach EU for the answer. My question was for the spring rate on the Sportline Kit Rears.

" The rear spring rate is progressive, initial rate - 399 lbs/in, main rate - 799 lbs/in

Now to find some friends to use as ballast to measure the stock travel....
Are those the same springs in the Koni kit? Just got mine--looking forward to rebuilding the entire front end and some rear stuff too.

dlm ny country
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Old 10-10-2019, 06:27 PM   #11
tr3flip
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Originally Posted by dlmrun2002 View Post
Are those the same springs in the Koni kit? Just got mine--looking forward to rebuilding the entire front end and some rear stuff too.

dlm ny country
Koni uses the Eibach Pro-Kit with their packages. However, the Pro-Kit and Sportline springs have the rear spring rate but different ride heights for the E46 non-M models.

Eibach typically increases spring rate by 10% over stock when developing springs. No confirmation on what BMW sport suspension rates are though.

-Tony from Eibach USA
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Last edited by tr3flip; 10-10-2019 at 06:29 PM.
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Old 10-11-2019, 10:49 PM   #12
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Good to know. Thanks Tony.. And Eibach

dlm ny country
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Old 10-13-2019, 09:29 PM   #13
ewcmr2
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Quote:
Originally Posted by Kyriva View Post
I see your point. I suppose I could measure the sag from 200# of ballast and compare the delta between the current wagon sport springs and the Eibachs.

Just trying to avoid installing the Eibachs just to find out they're softer than the wagon sport springs, and then I'll have to swap out the springs a second time.
Post #21 shows my diy spring rate check contraption.
https://forum.e46fanatics.com/showth...1130400&page=2
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Old 10-13-2019, 10:09 PM   #14
Kyriva
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Originally Posted by ewcmr2 View Post
Post #21 shows my diy spring rate check contraption.
https://forum.e46fanatics.com/showth...1130400&page=2
Great info!

That puts the initial spring rate of the M3 convertible at 287#/in and the iT at 357#/in, if I did my math correctly using your data.

Assuming that Eibach matched the progressive spring curve of the OEM springs, that would put these Sportlines ~10% stiffer than the wagon rear springs, and 30% stiffer than the M3 vert's springs. That's a lot of assumptions without you having a set of Eibachs to compress on your setup.
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Old 10-14-2019, 08:23 AM   #15
malapane
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That set up would work fabulously even with progressive rate springs as long as you know/use the height of spring in its installed/normally loaded position.

This is my kind of thread.
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Old 10-14-2019, 08:44 AM   #16
Kyriva
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Well, supposing our Tourings weigh ~3200# with 50/50 weight distributions and perfect corner balance, we're talking 800# a corner at the wheels. Apply the leverage ratio of .66 for the rear spring and we're talking ~1200# of preload... he's going to need more than a bathroom scale..
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