Bilstein B8 Ride Height/Spring Info - BMW M5 Forum and M6 Forums
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post #1 of 67 Old 3rd May 2016, 04:55 PM Thread Starter
Rontgen
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Bilstein B8 Ride Height/Spring Info

In preparation for an upcoming suspension refresh on my Beast, I've gathered some info that I wanted to share with the group and hopefully spur some conversation and additional data points. THANK YOU to the following members for taking time out of their lives to take a couple measurements on their cars and contribute: @KevinC , @christic , and @marko360

My Story:

I've owned my 01 M5 for nearly 2 years and from the beginning, the one thing I disliked about it was the handling. I came from the E46 M3 camp and had become accustomed to the tight and responsive steering, lack of body roll, and confidence in a bumpy corner that the E46 chassis delivers. Unfortunately, my M5 exhibits lazy steering response, lots of body roll, and feels like a boat in rough seas on a rough freeway off-ramp. I've recently developed a bad ball joint on my pass-side lower control arm, so I've decided now is the time to step it up and improve the handling of this otherwise magnificent car.

Due to a variety of factors that are outside the scope of this thread - I made two decisions:

- I wanted a conventional strut/spring combo rather than an adjustable coilover
- I wanted Bilstein dampers rather than Koni

Now that I've decided on dampers, that left me with one decision point left...Springs:

There appears to be several spring sets available for the E39 in general, but only a couple for the M5 specifically. I'm focusing on two sets in particular: Dinan & InTrax

General Info:

Dinan Performance Spring Set for E39 M5: Dinan Performance Spring Set
Available From: Dinan directly or several of their authorized distributors
Price (as of May 2016): $308, free shipping

Linear Rate Springs
Front Spring Rate: 197 lb/in
Rear Spring Rate: 250 lb/in
Advertised lowering: 0.25" / 6.35mm


InTrax BMW1251: InTrax Racing
Available From: Evolve in the UK or InTrax direct in Holland. There are no US distributors for this product, per InTrax customer service.
Price (as of May 2016): $350 shipped to the US (Evolve)

Linear Rate Springs
Front Spring Rate: 191 lb/in
Rear Spring Rate: 228 lb/in
Advertised lowering: 1.18" / 30mm

Aside from the obvious difference in how much the InTrax lower the car vs. the Dinan, it's also worth noting that the Dinan springs are approximately 3% stiffer up front and 10% stiffer in the rear.

Ride Heights:

The ride heights are listed above, so what's the problem?

Bilstein B8 are a nitrogen-charged, high-pressure monotube damper. Due to the internal pressure, it's very well documented that these dampers add a touch of ride height to most cars when installed. Combine that with the fact that the E39-specific rear dampers allegedly have the spring perch in the wrong spot and you can see that trying to calculate ride height from a pile of specs is tough.

As a means of establishing a baseline of sorts, here are some measurements from my 36K-mile 2001 M5. My car is completely stock with the exception of Dinan mufflers in the rear, and a steel space saver wheel/tire in the trunk. Measurements were made with a full tank of gas and sitting on level ground.

RF: 612mm
LF: 612mm
RR: 596mm
LR: 596mm
Stagger: 16mm lower in rear



---------------------------------------------------------------

A note on ride height measurements: The conventional means of measuring this on our cars has been to measure from the center of the wheel/hub to the top (12:00) position of the wheel arch. While this certainly works in theory, I've found in practice that it introduces a lot of variables that make it tough to compare results from one car to the next. While watching a video on YouTube from Redish Motorsports in the UK, the owner James measured ride height differently and I think it's a more accurate, repeatable, and easier measurement to make. The caveat here is that you must have stock Style 65 wheels...

The idea is to measure from the wheel arch to a fixed point on the wheel. The center is a great point in theory as it allows people with different wheels to compare. The reality is that it requires some "eyeball" work and depending on how two different people eyeball it, you may come up with different measurements. The way I've listed measurements here is shown below:





Measuring is a piece of cake - just hook the end of the tape between the wheel & tire, make sure the tape passes through the center of the BMW Roundel, and read the measurement at the arch. **If you would like to convert these measurements to the "wheel center" method, just subtract 246mm (the radius of the Style 65 wheel)**

-------------------------------------------------

- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK

Last edited by Rontgen; 3rd May 2016 at 04:57 PM. Reason: Clarity
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post #2 of 67 Old 3rd May 2016, 04:55 PM Thread Starter
Rontgen
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KevinC
Bilstein B8
Stock springs

RF: 617mm (+5mm)
LF: 617mm
RR: 608mm (+ 12mm)
LR: 608mm
Stagger: 9mm lower in rear

These measurements confirm that the B8 do add some ride height and the reduced stagger shows there may be some validity to the rear perch height variance.


- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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post #3 of 67 Old 3rd May 2016, 04:55 PM Thread Starter
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Christic
Bilstein B8
InTrax Springs

RF: 590mm (-22mm)
LF: 590mm
RR: 590mm (-6mm)
LR: 590mm
Stagger: 0mm

These measurements show a substantial drop from stock, but itís one that I personally like and I donít feel that it looks too low. Note that the stock front/rear stagger is eliminated.

Want to lower car - oem feel-img_0476.jpg

- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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post #4 of 67 Old 3rd May 2016, 04:56 PM Thread Starter
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Marko360
Bilstein B8
InTrax Springs

RF: 592mm (-20mm)
LF: 592mm
RR: 587mm (-9mm)
LR: 587mm
Stagger: 5mm lower in rear

Very similar results to christicís above. Note that Markís car has retained a touch of the front/rear stagger as compared to Chrisí, which could possibly be explained by a variety of reasons: fuel tank level, cargo in the trunk, suspension bushing condition/preload, etc.

In the end, I think InTraxís 30mm drop claim is overstated for these cars, particularly when combined with the B8. If we average the two datapoints we have, the InTrax lower the car 21mm F / 7.5mm R


- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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post #5 of 67 Old 3rd May 2016, 04:56 PM Thread Starter
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Dinan Springs + Bilstein B8

Iím posting this as a placeholder in hopes of finding someone with this combo who would be willing to take the following measurements:

RF: ? mm (- ? mm)
LF: ? mm
RR: ? mm (- ? mm)
LR: ? mm
Stagger: ? mm

Picture from nightkrawlerís thread:


- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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post #6 of 67 Old 3rd May 2016, 05:04 PM Thread Starter
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If anyone else would like to contribute ride height measurements for STOCK or Bilstein B8 (with any spring), please PM me and I'd be happy (and gracious) to add them to this thread.

If you have Koni and would like to do the same, please PM me and I'd be happy to start another thread just like this one. I'd like to try and keep this thread contained to just the Bilsteins to avoid confusion.

Thanks!

- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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post #7 of 67 Old 3rd May 2016, 07:43 PM
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Quote:
Originally Posted by Rontgen View Post
KevinC
Bilstein B8
Stock springs

RF: 617mm (+5mm)
LF: 617mm
RR: 608mm (+ 12mm)
LR: 608mm
Stagger: 9mm lower in rear

These measurements confirm that the B8 do add some ride height and the reduced stagger shows there may be some validity to the rear perch height variance.

Rontgen: Are you suggesting that the latest version of the rear B8 shock still has the spring perch located too high ? I was under the impression from KevinC posting that Bilstein has made changes to the location of the rear spring perch on the B8 shock and took care of the high ride-height issue.
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post #8 of 67 Old 3rd May 2016, 08:20 PM Thread Starter
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Quote:
Originally Posted by garry_lay View Post
Rontgen: Are you suggesting that the latest version of the rear B8 shock still has the spring perch located too high ? I was under the impression from KevinC posting that Bilstein has made changes to the location of the rear spring perch on the B8 shock and took care of the high ride-height issue.
Well, I'm being very careful how I word it since I don't have a B8 and a stock strut here to compare. At some point in the not-so-distant future I will have both on hand and will take some measurements to see once and for all.

I thought the discussion in Kevin's thread ended with some pics from 3+ years ago that showed the same part number that Bilstein recently recommended (meaning that perhaps the new part number is not actually a new part)? Or did I misunderstand?

- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK

Last edited by Rontgen; 3rd May 2016 at 08:29 PM.
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post #9 of 67 Old 3rd May 2016, 08:31 PM
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Thank you for the footwork.


I will be doing suspension sometime near future...good data points.


Just a side note that may have no bearing on the M5;
My 2002 530i (which is flawless other than a tiny leak in rack/pinion right boot) about a year ago I did Bilstein parts as the shop said it would set with nice gaps and handle "on rails". Well, I love the handling...not track ready but good compromise with touring (its my long road trip car...cant park the M5 just anywhere). The issue it is sets HIGH. You can see the shocks if you bend down. Wasn't happy with the larger than OE gaps.
Just tossing it out there if the Bilsteins has any similar effect on M5s.
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post #10 of 67 Old 3rd May 2016, 08:47 PM Thread Starter
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Quote:
Originally Posted by AllesklarBMW View Post
Just tossing it out there if the Bilsteins has any similar effect on M5s.
It's my understanding that the Bilsteins have this affect on most, if not all cars. I remember reading several places (to include Bilstein's own FAQ), that it was perfectly normal to have a slight increase in ride height. Obviously that affect is more dramatic if you're replacing older suspension parts and so on.

I've run Bilstein B8s several times in the past and always been very pleased with them (although never on a BMW). In every one of those instances, they were paired with aftermarket lowering springs so it was impossible to say how much the Bilsteins raised the car as compared to stock.

- Darrell

2001 M5 - Jet Black / Black Nappa
Dynavin N6, Dinan Exhaust, AutoSolutions SSK
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