BMW M5 Forum and M6 Forums banner

Bilstein B8 Ride Height/Spring Info

41K views 87 replies 21 participants last post by  thrty8street 
#1 · (Edited)
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)**

-------------------------------------------------
 
See less See more
3
#2 ·
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.

 
#7 ·
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.
 
#3 ·
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 it’s one that I personally like and I don’t feel that it looks too low. Note that the stock front/rear stagger is eliminated.

 
#4 ·
Marko360
Bilstein B8
InTrax Springs

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

Very similar results to christic’s above. Note that Mark’s car has retained a touch of the front/rear stagger as compared to Chris’, 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 InTrax’s 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

 
#5 ·
Dinan Springs + Bilstein B8

I’m 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 nightkrawler’s thread:

 
#6 ·
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!
 
#9 ·
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.
 
#10 ·
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.
 
#13 ·
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
As another data point, I was looking through ISTA/D documentation for something else and stumbled across some ride height specifications. FWIW, the BMW method of measuring ride height is the same as I mentioned above: from 6:00 to the peak of the arch.

I'm very surprised at how low the specification is for the rear? All specs have a +/- 10mm tolerance per the document. Verified the same numbers from the last TIS update in 2007.

Food for thought I guess.

RF: 605mm
LF: 605mm
RR: 578mm
LR: 578mm
Stagger: 27mm lower in rear
 
#14 ·
When mine were first installed, the ride height looked "about the same" to me. Subsequent measurements and eyeballing confirmed that it was up somewhat at both ends. My headlights project down the road to what seems to be the exact same distance, so I ASSume that the front/rear rake is roughly the same as before, with both ends coming up slightly. Wish it wasn't so as I really like the stock ride height, but it doesn't really look "wrong" either as it now sits. And the results are fantastic when it comes to the driving. MUCH better damping than the shot stock Sachs units, less squat, less body roll, all while improving ride quality - no harshness, none of that "Bilsteins are too stiff for me!" noise that you hear at times from some.

Bilstein did indeed start listing these as proper for the M5, whereas a few months ago, they had no fitment for the E39 M5, only for the other 5-series models. One of the vendors (ECS I believe) was who claimed that the rears had been revised and these were indeed now intended "only" for M5 use, and not the other 5-series models. But apparently the part number, which is "newer" than the old longer one, is not THAT new, and has been in use for several years. I reached out to Bilstein via email and asked a very clear question about the situation, and they responded with some nose about "please provide the year, model & engine" before they were going to respond - all of which was clearly explained in the initial inquiry. Idiots.
 
#16 ·
Great feedback - I've used the B8 on a variety of other cars and I've always been impressed with the performance and the ride quality. Looking forward to trying them out on the M5!

It would be great if Bilstein could provide us with a solid answer to this. I'll try to contact them as well and see if I have any better luck. There's gotta be someone at Bilstein who knows WTF is going on - it's just a matter of finding that person, I guess.
 
#15 ·
Looking over Turner Motorsport coilover area and I came across this:

"On the E39 we recommend a front to rear rake of .75" (higher rear)"

From measurements, Kevin's car is close to their desired rake.
 
#17 ·
Turner is suggesting a ride height in the rear that is .75"/19mm higher than the front? All the measurements here have the front higher than the rear (with the exception of christic's car which is level at all 4 corners).

I've only had one cup of coffee this morning, so maybe I'm missing something? :)

Seems like making the rear 3/4" higher than the front would give the car a definitely Dukes of Hazard look.
 
#18 · (Edited)
I think there is confusion there since the fender lip to wheel centerline distance is shorter in the rear by chassis design like most all cars. Perhaps they are referring to the measurement Dinan quotes -- the difference in distance to the ground from the lower body line (below doors) between the front most point and the rearmost point...that difference should be about 5/8-3/4" with the front lower than the rear. You achieve that range (slight rake downward to the front) by having the fender gaps (centerline to lip) about equal on the E39.
 
  • Like
Reactions: Rontgen
#20 · (Edited)
So, I called and spoke to the aftermarket division of Bilstein in North Carolina. They have confirmed that the product itself has received no technical/manufacturing changes in several years and in the event that there was a change, we should expect to see a corresponding change in the product part number.

He did mention that they have been performing fitment evaluations over the last month or so and revisions to the online catalog seem to support that. When Kevin posted his thread 2 months ago, the M5 was the only E39 that had a complete set of B8 dampers in the catalog (Reference). As of when I looked this morning, every E39 has a recommended set of B8s in the catalog.

525/530:
Front: 35-114079
Rear: 24-028295

540i/M5:
Front: 35-114093
Rear: 24-028295

Note that the rear B8 damper is the same for all 4 models, which I guess isn't terribly surprising.
 
#21 · (Edited)
#22 ·
I wanted to follow up on this - I've finally gotten through my analysis paralysis and installed the Bilstein B8/Intrax combo on my 01 M5 and I'm very happy with the results. The ride height is perfect to my eye and this combo has matched the wheel gaps front and rear. Unfortunately, the rear Bilstein B8 has some dimensional differences from the stock damper that make it a poor choice with stock spring (and potentially other lowering springs), but it works very well with the Intrax rears.

The ride is a touch rougher than the stock shocks/springs, but in retrospect it's not anything I should have been overly worried about. I only notice it during slower driving (<30mph) over rough rural roads. On the highway and on smoother city streets the ride quality is indistinguishable from stock to me. The car is considerably flatter during hard cornering, which still being plenty compliant for a daily driver.

I've had them in about a month and 750 miles of mixed city/highway driving and the ride heights are as follows. Both measurements were taken while parked on level ground, full tank of gas, space saver spare tire in the trunk and nothing else in the car.

Pre-Installation:
LF: 610mm
RF: 610mm
LR: 590mm
RR: 589mm

After 1 month/750 miles:
LF: 589mm (-21mm)
RF: 589mm (-21mm)
LR: 583mm (-7mm)
RR: 582mm (-7mm)

Sorry for the terrible picture, but hope this helps anyone else who is interested in the Bilstein B8/Intrax combo!


 
#24 ·
Rontgen: Not meant to be nit-picking but why are your pre-installation ride heights slightly lower than your previous pre-installation measurements in your May 3, 2016 posting, especially in the rears. Just being curious. You mentioned you had a full tank of gas when you did your measurements last May so the measured ride height in the rear should have been the lowest.
 
#26 ·
Honestly....I don't know? I don't recall exactly where I was parked when I took the measurements in May. Maybe a different angle or not on level ground? Maybe the tank wasn't quite as full as it was this time? I'm not sure.

With the more recent measurements, I tried to keep it as scientific and repeatable as I could. I did have a truly full tank of gas for all of the recent measurements and made a point to park in the same spot for repeatability. In the end, I suspect there will be some variance from car to car, but I'd expect it to be slight
 
#27 ·
One thing I forgot to mention (and I can't go back and edit the original post) is that despite what Intrax's customer support lady told me, the rear springs are definitely progressive rate as opposed to the Dinan's linear rate.
 
#32 ·
I bought the B8's from fcpeuro and ordered my intrax springs from evolve
 
#29 ·
I ordered the Bilsteins from Tire Rack, who had the best price on them at the time. Shipping was free and they arrived quickly, as I've come to expect from Tire Rack.

The Intrax are not available from a US-based reseller. Your best bet is to order from Evolve in the U.K. While that sounds like it would be a pain, it really wasn't. Just drop an email or Mark or Paul at Evolve and they will send you a PayPal invoice. Once paid, they arrived to me in about a week or so. I have nothing but good things to say about the crew at Evolve - great communication and customer service on this transaction.

If you're in Canada, Intrax might have an in-country distributor. You could email Intrax to find out for sure?
 
#30 ·
Hi Darrell! How does your car handle on strong windy days and highway driving? And how did it handle that before the suspension upgrade? My car suffer from instability during strong winds... It walks all over the highway. Replaced front shocks with Bilstein B4 (touring) as a temp solution but I feel the car is too soft and seems to lift off a bit in the front at speed on the highway. Windy day handling hasn't improved much for me. I'm thinking of buying stock Sachs back and forget about this bs... Such a headache!
 
#31 ·
My car has always been kind of unstable in a straight line and a strong wind just makes matters worse. Living in Oklahoma means I have plenty of windy days to contend with. :) Unfortunately, the replacement of the dampers and springs did nothing to improve that so I suspect that the Bilstein B4 are not the cause of your problem and even a change to Sachs most likely wouldn't solve it either. My suspicion is that it's rear suspension related as I've already replaced everything up front. Even tightening the steering box to eliminate all slop didn't help. Actually that made the steering box a little harder to turn and it would tend to stick off-center and make the car even more unstable.

I'm going to do yet another inspection of the rear suspension, this time with a prybar and a dial micrometer to measure deflection distances. Assuming I don't find a smoking gun there my plan is to: start with the subframe bushings, followed by the rear lower ball joints/intergal links. Then, the wishbones. I'll do them one item as a time and drive the car in between. My hope is that one of these will be that "ah ha" moment I've been looking for.

I assume you'd had the car aligned?
 
#33 ·
Interesting!! Doesn't it drive you nuts though?? In sport mode my car is more stable but I rarely drive it in sport mode unless it's too windy and I want the steering to be a little more stiff I guess which adds a little more stability. The last alignment I had was in October last year probably... One thing I noticed is that the front left side strut didn't go inside the knuckle as much as the passenger side. Did you have fitment issues with your Bilstein? Did they fit exactly at the same spot in the knuckles? The difference between both side is exactly 1/4 inch...

I will try and fit the lower arms this weekend and see how the car feels. Thrust arms were replaced late last year before the alignment along with PowerFlex black bushings... Not sure if that is causing my problems. In warm weather, the car drives much better so I don't know if those bushings are shrinking too much in the cold causing play in suspension. I have Lemforder new bushings I can press in anytime and I'm thinking of going back to stock with thrust arms... All this aftermarket bs isn't improving anything man. I need to find an easy way to press these things in while the arm is on the car... Maybe I can rent a tool.

What air pressures are you running?
 
#35 ·
I had a similar issue. Initially I replaced the entire front suspension and B8/Intrax on all 4 corners. When driving on the highway the car would still wander slightly as if it was being blown by a crosswind. I replaced the rear suspension (10 piece Lemforder) and it was cured. Doing some research here I learned this is a symptom of worn rear ball joints. It was also very noticeable going around cloverleafs at decent speeds. The car felt loose in the rear almost as if it had a rear swaybar issue.
 
#37 ·
Rontgen: I am still struggling with my math on the B8 rear shock with stock spring raising the ride height. You measured the Bilstein rear B8 shocks to be 30mm shorter than stock Sach shock. I believe you mentioned specifically that the fully extended piston rod is 30mm shorter on the B8. You also measured the spring perch to be 8mm higher on the B8 than stock. So if you mount the fully assembled B8 shock (with the compressed stock spring) to the top mounting location on the rear speaker shelf, you would have to raise the lower trailing arm about 30mm just to be able to line-up and insert the lower mounting pinch bolt. So I am struggling on understanding how a shorter B8 shock body (length from top of extended piston rod to bottom mounting point) can raise the overall ride height when compared to the much longer OEM shock. I must be missing on something here.
 
#38 ·
I think it's better to use Bilstein B6 with stock springs. I have B4 in the front but will be buying B6 for the rear and switch front to B6 later. I need to find a machine shop that can make another notch 8-10mm lower than the lowest Bilstein have on their rear shocks then I'll be set! The B8 have shorter rod and because of that it will over-compress your long stock springs and make the car really harsh and I suspect it will ride not so nice.
 
#40 ·
Having just installed Bilstein B8's as part of a B12 kit on my 03 540i M Sport perhaps I can shed a little light.

First, my car has (had) the same M5 aluminum M Sport shocks.

The rear perches on brand new B8's are still a couple of mm higher than the OEM shock. B8's for the 540 and M5 I believe list the same. But so what, match the Billies with the right spring and it's irrelevant.

The front B8 is much more a match to the original sport damper in terms of working with the factory spring than a B6 would be. You do not want B6's for this application.

Again, I installed a B12 kit, the Eibach springs are available here in the US and work and fit *perfectly* with the B8's.

Pre-install height was 606mm front, 597mm rear. As reference, I believe the 540i M sport front springs are a bit different than M5 due to slight difference in weight.

Post install height is 597mm front and rear.

If you decide to go with Bilsteins, I would pair them with Eibach's or Intrax before OEM springs. In my experience Bilsteins tend to work poorly with OEM springs with a resultant hard ride. Eibach's are perfect with B8's and matched for this car. Using the stock springs will also result in unwanted gain in ride height.

Again, Bilsteins for this car are magic, they handle way better than the OEM dampers and ride extremely well. I would not hesitate on Bilsteins for this car for a second. Floaty feelings are gone and it takes bad road and bumps without any drama.

As below, stock damper vs B8.



 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top