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      09-14-2008, 11:40 AM   #1
Radiation Joe
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Spring rates for H&R and Eibach?

Does anyone know the spring rates of the H&R and Eibach springs?

If I buy a set of springs, I want to know how they are different from what I have already.

How much stiffer are they, and are they progressive rate or linear?

Secondary, but just as important, what are the stock spring rates?

Thanks,
Joe
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      09-14-2008, 06:48 PM   #2
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I've talked to both Eibach and H&R. H&R will not give out spring rate information as they state that there is no standard for measuring spring rates and they don't want people comparing rates.

Eibach did give me numbers for both stock and their springs which I have at work and post them tomorrow. Based on Eibach's measurements, their springs are 10% stiffer in the front and 20% stiffer in the rear which I believe will reduce understeer to some degree.

Thanks,
Barry
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      09-15-2008, 04:04 AM   #3
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I wouldn't doubt that there is no standard for such a measurement. One issues is that springs are not entirely linear, meaning the spring rate can vary with deflection. However, once preloaded to the extent that most springs are in actual use much of the initial deflection non linearity is no longer present. All this aside one number, the "rate" is typically well suited for a characterization of the spring and it should be reported.

Do you think race teams know the exact spring rates they install in their cars?

Sounds a bit lame on Eibach's behalf...
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      09-15-2008, 08:53 AM   #4
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Quote:
Originally Posted by swamp2 View Post
I wouldn't doubt that there is no standard for such a measurement. One issues is that springs are not entirely linear, meaning the spring rate can vary with deflection. However, once preloaded to the extent that most springs are in actual use much of the initial deflection non linearity is no longer present. All this aside one number, the "rate" is typically well suited for a characterization of the spring and it should be reported.

Do you think race teams know the exact spring rates they install in their cars?

Sounds a bit lame on Eibach's behalf...
I assume you mean H&Rs behalf.

I wrote and then didn't post a tirade about H&R being driven by marketing rather than providing their customers with enough information to make informed decisions.
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      09-15-2008, 10:40 AM   #5
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Hey guys - well apparently I trashed the note with the specific rates for the Eibach and OEM. My memory is the following approx. numbers:

Front: Stock 154 Eibach 170
Rear: Stock ~500 Eibach ~600

Big spread front to rear....

BC
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      09-15-2008, 11:13 AM   #6
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That is a surprising spread front to rear. But remember that the front spring acts directly on the strut. The rear spring is set inward on the control arm. If I remember correctly, the wheel rate is about 60% of the spring rate in the rear and better than 90% in the front.

Still, I would have expected the front rate to be more like 250 lbs/in. I run 500 lb/in springs in the front of my e46.
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      09-15-2008, 12:06 PM   #7
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Yeah I was surprised to hear how soft the front springs are. Fronts appear to be progressive based on their shape while the rears are linear. The person I spoke to at Eibach said the springs are linear so they may be linear.

I've put approx. 200 miles on the Eibachs and I'm pretty pleased with them. Slightly stiffer ride, better body control and just enough lowering (for me). They're cheaper than the H&Rs to boot. So all in all - I'm very satisfied with my choice!

BC
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      09-15-2008, 03:02 PM   #8
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Quote:
Originally Posted by Radiation Joe View Post
I assume you mean H&Rs behalf.
Yep, another late night flu ridden typo. Thanks!
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      09-15-2008, 11:14 PM   #9
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Quote:
Originally Posted by BarryC View Post
Hey guys - well apparently I trashed the note with the specific rates for the Eibach and OEM. My memory is the following approx. numbers:

Front: Stock 154 Eibach 170
Rear: Stock ~500 Eibach ~600

Big spread front to rear....

BC
I measured and computed the rates for stock E92 springs. Wheel rates front and rear are about 200# per inch (my front wheel calculation disagrees with the one above, and it might be wrong - it's based on wire and coil diameter and number of coils, etc).

The rear spring is much stiffer but it's the spring rate measured at the wheel that matters. Because the rear spring sits about half-way between the lower control arm pivot and the wheel, the spring is compressed about half as far as the wheel moves. That means the effective spring rate at the wheel is about a quarter of the actual spring rate - the reduction is the square of the lever ratio.

My exact calculated wheel-effective rates were 202 pounds per inch at the front, 195 at the rear.
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      09-16-2008, 07:51 AM   #10
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I'm pretty sure the lever ratio is linear. Half way between the suspension pivot and the wheel translates to 50% wheel rate. If it was the square of the distance, half way would be 25%. But your numbers sound close according to my butt scale.

By the way, what were you inputs to get "exact calculated"? Without a lot of very detailed information the wheel rate calculation is just a swag.
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      09-16-2008, 09:09 PM   #11
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OEMs and suspension designers care about suspension leverage ratio (mechanical advantage) AND spring rate, which when combined give the wheel rate. Tuners who don't change the actual suspension geometry only care about spring rates as that is all thay can be changed.

Depending on suspension type, geometry and spring placement the leverage ratio can be (almost)constant, linear or non linear. Typically you can only get a rough estimate of this by a quick visual inspection and quick measurement of two distances. However, given the M3's nearly 50-50 weight balance roughly equal wheel rates doesn't surprise me.
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      09-16-2008, 11:30 PM   #12
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Quote:
Originally Posted by Radiation Joe View Post
But your numbers sound close according to my butt scale.

By the way, what were you inputs to get "exact calculated"? Without a lot of very detailed information the wheel rate calculation is just a swag.
My "exact calculated" is only the calculated result - the calculated results could (and probably do) bear very little relation to "exact real". But as a "within 20 percent" swag, the surprise was that the wheel rates were similar front and rear and that they were very close to the measured factory rates on the 4000 pound E39 M5.

Just wanted to toss another data point on the pile.
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      09-23-2008, 11:24 AM   #13
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Quote:
Originally Posted by BarryC View Post
Yeah I was surprised to hear how soft the front springs are. Fronts appear to be progressive based on their shape while the rears are linear. The person I spoke to at Eibach said the springs are linear so they may be linear.

I've put approx. 200 miles on the Eibachs and I'm pretty pleased with them. Slightly stiffer ride, better body control and just enough lowering (for me). They're cheaper than the H&Rs to boot. So all in all - I'm very satisfied with my choice!

BC
Barry,

Any pictures of your car with the Eibach drop?
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      09-23-2008, 03:01 PM   #14
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Quote:
Originally Posted by Sedan_Clan View Post
Barry,

Any pictures of your car with the Eibach drop?
+1

Barry, I'm also curious as to why you say the fronts are non-linear but Eibach says linear. Are the coils closer together at one end or are the pretty evenly spaced? I know H&R are linear.


Allen
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      09-23-2008, 09:18 PM   #15
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Quote:
Originally Posted by MVEED3 View Post
+1

Barry, I'm also curious as to why you say the fronts are non-linear but Eibach says linear. Are the coils closer together at one end or are the pretty evenly spaced? I know H&R are linear.


Allen
I'll take some pics this weekend and post. The fronts looked progressive to me because of their shape but you're right. The spacing of the coils is a better indicator of the linearity rather than size of the coils.

Thx,
BC
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      09-26-2008, 07:17 PM   #16
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I was told by Tire Rack K&N are progrssive. I think we should wait as they also weren't sure if the lowering would bottom out the shocks, but I don't think so. This car after being on the track twice with less than 3K on it - I guess I'll wait and see, but for now not too impressed.
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