3DM TTX Öhlins Suspension for High Horsepower Applications

fmorelli

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About a year ago, I was knee deep in preparing for further power upgrades - Hydra HP650 turbos, ported head with Schrick cams, and supporting items to put us in the 600whp range. I was particularly concerned about power management and had been discussing this with @[email protected] . Barry had been doing some testing with the motorsport grade Öhlins TTX dampers, Such dampers are used on DTM touring cars, NASCAR, and the track-ready BMW M4 GT4 and BMW M6 GT3. They are effectively non-existent in street and HPDE applications. In testing, Barry found the TTX ability to manage both putting power down and handling uneven road surfaces (even apex berms) to be far more capable than conventional dampers.

Barry and I began discussing a hybrid suspension, where the rear would be built with Öhlins TTX dampers to help facilitate rear grip with the significant power increases that are planned. This effort became the basis for the 3DM Hybrid TTX Series suspensions: using Öhlins R&T front dampers to manage cost (front TTX struts add significant cost) in conjunction with Öhlins TTX rear dampers to better manage high horsepower applications. Today there are several 3DM Hybrid TTX suspensions in the wild, including on @ShocknAwe's car here on Spoolstreet, and several more in the making for other E9x and E8x customers. As well there are track car applications that Barry has built, to include E30 M3, E36 M3, E46 M3, with F2x *M235i R) in flight, etc. In many ways, this Z4 is the mule that pushed into this solution approach.

Along the way we decided to build a full 3DM TTX suspension for the Z4, to see if a full road-going TTX-based BMW suspension could be developed, and to see how far a street car’s handling capability could be realized. Though these pictures look like simple finished product, there was a lot of measurement and development work, along with a variety of parts machined and fabricated to get to achieve this configuration.

TTX assemblies.jpg


For the Z4, the 3DM TTX is an upgrade from an existing full M3 suspension with Öhlins R&T dampers. My frame of reference is far from a stock m-sport suspension. Let me jump to the punchline: in our initial 15 mile test drive on pave-in-place roads, the only way I can describe the new suspension is that it is like driving a hovercraft directly attached to one’s brain.

Simply unbelievable. First observations:
  1. The car glides over surfaces. Low-speed damping, to which I’ve never observed or given thought, is incredible. The TTX dampers take out all the little road imperfections that one typically associates to a high feedback suspension. Yet there is plenty of feedback and sensitivity - incredible low-speed damping.
  2. Road irregularities gobbled up. Barry had mentioned how well TTX dampers manage apex berms. On the road, this capability is evident with sharp asphalt irregularities, which are consumed with minimal jarring.
  3. Instant response. The car is not twitchy, but rather responds instantly to steering feedback. The switch to the F30 hub carrier certainly improves front-end geometry. I had to correct steer in several turns as I was providing too much turn-in, too soon, based on being acclimated to the previous suspension.
While undertaking the suspension, I decided to also upgrade the brakes. For the fronts we chose M3/M4 Brembos with 370x30mm rotors. For the rear, a very custom EMF-based setup, using G30 M-sport EMF caliper assemblies and 345x28mm E46 M3 CSL competition front rotors. More on the brake setup can be seen here.

In this thread, I’d like to share some photos and description of the build process. We are currently performing a round of changes, based on initial testing. We are far enough along that some public posting is worth sharing. I’m also hoping, for those with technical interest, that @[email protected] might chime in and explain why these dampers are not like traditional mono-tube shocks, and different from other brand motorsport shocks with external reservoirs, etc.

I’d like to thank @[email protected] for all his efforts on this undertaking - without his expertise this capability would be unimaginable, much less realized. Given the development work necessary to make this a functioning street suspension, I would venture to say that there are likely no street-going BMW’s with complete suspensions based on the TTX race damper technology.

A year of discussion, planning, and eight months of work. While we are not done, I can say this car drives like nothing I’ve driven before, and it was worth it.

Filippo

front struts.jpg


rear shocks.jpg
 
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fmorelli

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Nice setup. What does your ride height look like?
I'll be posting more, and we'll include ride height stuff. It's completely adjustable, obviously. One of the cool things about how the Öhlins are designed is that ride height adjustments are independent of damper stroke. So your range of adjustment does not interfere, for example, with ending up on bump stop because one adjusted the coilover (like other coilovers) to where there was little stroke range.

We have the suspension back off now for a round of tweeking. The front struts are being further machined to better mate to the application range. Remember this is bespoke so this is literally development work to get everything to the right place. We need the strut tubes to sit a bit lower in the hub carrier. They are actually flanged so it not just clamped.

WhatsApp Image 2020-05-04 at 1.45.52 PM-1.jpg


Specific to ride height we will be matching what I had before, which had already gotten dialed in with the prior Öhlins R&T suspension. That would be 24 3/4" front and 25 3/4" rear. That's obviously not hub center to fender, but floor to fender. We've done 3 other suspension iterations on this car, and have arrived to this height on the last go-around. It is easier to keep the absolute measurement around for setup, then working accurate center-hub measurements :).

Filippo
 

ShocknAwe

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I can attest that the 3DM TTX Hybrid setup is an absolute dream. My car sits about 5" off the road surface and handles bumps drops and elevation changes better than our Porsche Cayenne with air suspension.

That should mean something.

Happy to add my install pictures including F8x front hub carrier swap and 1M front widebody to the bin here later on.
 

NoQuarter

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I'll be posting more, and we'll include ride height stuff. It's completely adjustable, obviously. One of the cool things about how the Öhlins are designed is that ride height adjustments are independent of damper stroke. So your range of adjustment does not interfere, for example, with ending up on bump stop because one adjusted the coilover (like other coilovers) to where there was little stroke range.

We have the suspension back off now for a round of tweeking. The front struts are being further machined to better mate to the application range. Remember this is bespoke so this is literally development work to get everything to the right place. We need the strut tubes to sit a bit lower in the hub carrier. They are actually flanged so it not just clamped.

View attachment 41838

Specific to ride height we will be matching what I had before, which had already gotten dialed in with the prior Öhlins R&T suspension. That would be 24 3/4" front and 25 3/4" rear. That's obviously not hub center to fender, but floor to fender. We've done 3 other suspension iterations on this car, and have arrived to this height on the last go-around. It is easier to keep the absolute measurement around for setup, then working accurate center-hub measurements :).

Filippo

Is that stock height in the rear and 1" lower in the front?
 

derekgates

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Yowza! This is incredible.

I *just* rebuilt my R&T setup and increased rear spring rate with @[email protected] and have been very impressed... Going even FURTHER?! Ooooh

The build looks top notch and the performance you are describing seems out of this world. Thank you for diving into this and sharing the results!
 
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fmorelli

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Is that stock height in the rear and 1" lower in the front?
Good question, Jim. At one point I knew the stock ride height. I don't think I have that info at my fingertips (it is buried somewhere). I just know that's where we ended up playing with the car, and that's where we ran the Öhlins R&T setup that was on there prior (hint hint).

Filippo
 
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AzNdevil

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Instant response. The car is not twitchy, but rather responds instantly to steering feedback. The switch to the F30 hub carrier certainly improves front-end geometry. I had to correct steer in several turns as I was providing too much turn-in, too soon, based on being acclimated to the previous suspension.

care to share more details on this? sounds like an interesting mod or is this a secret only for the people running this config
 

ShocknAwe

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care to share more details on this? sounds like an interesting mod or is this a secret only for the people running this config

I'll leave that up to Filippo and Barry. However I can add that the twitchiness of the E82 chassis comes from its short wheelbase and entirely ineffective damping available on most rear dampers for the E9x/E82 suspensions available.

The TTX/M3 rear has effectively completely tamed it.

No comment as to specifically why, I'm not an engineer.
 

fmorelli

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care to share more details on this? sounds like an interesting mod or is this a secret only for the people running this config
No secret. As I mentioned, the F30 front hub carriers run slightly different geometry which also affects bump steer. @[email protected] can get into more details on that if you wish. The E9x/E8x hubs bolt straight up, but you need to buy the F30 hub bolts, that mate the hub carrier to the hub - p/n 31206783065 which is the 1.5 thread version that mates to our hubs. You'll note the back of the bolt is convex. What you do have to deal with is the change in clamp diameter for the strut tube. The E90 is 52mm whereas the F30 is 57mm. So if you are running E90 strut you have a 5mm sleeve necessary. For us the 57mm size was suited to the TTX strut tube, which Barry nonetheless did some work on the lathe, and also fabricated a thin steel sleeve.

open-uri20140924-1680-1ekygpc.jpg


I've always recommended running a monoball or spherical bearing in the tension strut (the former deals with the reality of street driving better). This really helps with steering feedback and I've never found it to have undesirable manners.

Filippo
 
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derekgates

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WIN ME OVER SOME MORE, JEEZ

I will be inquiring about this soon. Turbos and oil leaks first!

I've always recommended running a monoball or spherical bearing in the tension strut (the former deals with the reality of street driving better). This really helps with steering feedback and I've never found it to have undesirable manners.

Filippo

IMG_1483.jpeg


:sunglasses::sunglasses:
 

Asbjorn

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100% agree with this statement: "I've always recommended running a monoball or spherical bearing in the tension strut." And I feel the same way about solid subframe mounts.

A few questions about this Z4 TTX baller setup:
  1. It seems this setup deletes the rear upper shock mount bushing. How is the NVH? I tried running a bearing up there and went back to stock after only one week. NVH was terrible on bad roads. Is this not a problem with your setup, or did you find some way to solve it?
  2. What spring rates did you end up with for this setup? What were the target wheel frequencies? In my understanding it is hard to achieve flatride with the Z4. Because if you increase the front spring rate, even just slightly, you end up having to run a massively stiff rear spring. Apparently this is because of the position of the rear spring and the rear-biased weight distribution of the Z4.
  3. Why no coilover rear?
  4. Obviously the damper adjustments offered by TTX-series are world class, and I assume the go all the way up to 4 way? But how did you strike the right setting on the first go? I got one-way adjustable dampers only a few months back, and although I only have 1 knob to focus on, I still haven't decided exactly what I like the most in different scenarios (street vs track vs rain etc). I find it especially difficult to balance front and rear damping, because when you drive the Z4 you sit so far back, and the right setting for the car, may not be the right setting for the driver haha. I am curious if you just made it as soft as possible for the bumps etc on the street, and then adjusted the stiffness for acceleration and cornering to somewhere in the middle to match the springs? Is there some kind of short-cut or golden rule methology for a street-performance setup?
 

AzNdevil

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No secret. As I mentioned, the F30 front hub carriers run slightly different geometry which also affects bump steer. @[email protected] can get into more details on that if you wish. The E9x/E8x hubs bolt straight up, but you need to buy the F30 hub bolts, that mate the hub carrier to the hub - p/n 31206783065 which is the 1.5 thread version that mates to our hubs. You'll note the back of the bolt is convex. What you do have to deal with is the change in clamp diameter for the strut tube. The E90 is 52mm whereas the F30 is 57mm. So if you are running E90 strut you have a 5mm sleeve necessary. For us the 57mm size was suited to the TTX strut tube, which Barry nonetheless did some work on the lathe, and also fabricated a thin steel sleeve.

View attachment 41859

I've always recommended running a monoball or spherical bearing in the tension strut (the former deals with the reality of street driving better). This really helps with steering feedback and I've never found it to have undesirable manners.

Filippo

thanks for the details! i think the struct tube sleeve is the hardest to tackle... @[email protected] do you guys offer this as a kit? thanks
 
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doublespaces

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Fantastic work, I love to see the custom effort and truly dialing things in, rather than buying the canned product off the shelf.
 

fmorelli

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thanks for the details! i think the struct tube sleeve is the hardest to tackle... @[email protected] do you guys offer this as a kit? thanks
@[email protected] is actually working on a setup that let's one run the F30 Öhlins R&T kit on the E8x/E9x, with F30 hub carriers up front. It is in flight I believe. Ostensibly you could purchase F30 front hubs (cheap, plenty in junk yards), swap hub bearings up front from the E90, use the bolts I mention, and everything bolts right up front. Rear you have to run the E9x M3 arm to have it work, but I doubt that disappoints anyone.

In the near future I don't think there will be a collar sleeve available to run the E8x/E9x struts with the F30 hub. You could certainly choose to have one machined, I suppose. It's not a particularly complicated piece.

Filippo
 

fmorelli

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Sorry just saw this - there was a flurry of alert activity on various thread, and I somehow missed this one. Comments within, I hope they are helpful!
100% agree with this statement: "I've always recommended running a monoball or spherical bearing in the tension strut." And I feel the same way about solid subframe mounts.
BMW's have always had this issue - be it the later model tension struts, or the earlier "thrust arm" (which was same thing but from behind the suspension). These bushings are the devil. On any BMW I've never found a negative to getting those bushing stiff.
  • It seems this setup deletes the rear upper shock mount bushing. How is the NVH? I tried running a bearing up there and went back to stock after only one week. NVH was terrible on bad roads. Is this not a problem with your setup, or did you find some way to solve it?
Too early to tell, as it will just need more time. I have a few tricks up my sleeve if we have issues. We basically had to go to this setup.
  • What spring rates did you end up with for this setup? What were the target wheel frequencies? In my understanding it is hard to achieve flatride with the Z4. Because if you increase the front spring rate, even just slightly, you end up having to run a massively stiff rear spring. Apparently this is because of the position of the rear spring and the rear-biased weight distribution of the Z4.
I'll let @[email protected] address this, as I think there is some all-in-one stereo stuff here. I will say the rear end of the car is stiffer. Actually it is pretty ridiculous - I'm amazed at how I can't jump up and down on the 4 corners and make anything move, yet the car rides comfortably.

I'd love to see if there are others that are doing active suspension development work on these cars. Based on your comments above, @Asbjorn, do you happen to know of anyone?
  • Why no coilover rear?
The chassis is not reinforced for that. The Öhlins adjustable ride height perches basically gives us everything we need on the adjustable aspect.
  • Obviously the damper adjustments offered by TTX-series are world class, and I assume the go all the way up to 4 way? But how did you strike the right setting on the first go? I got one-way adjustable dampers only a few months back, and although I only have 1 knob to focus on, I still haven't decided exactly what I like the most in different scenarios (street vs track vs rain etc). I find it especially difficult to balance front and rear damping, because when you drive the Z4 you sit so far back, and the right setting for the car, may not be the right setting for the driver haha. I am curious if you just made it as soft as possible for the bumps etc on the street, and then adjusted the stiffness for acceleration and cornering to somewhere in the middle to match the springs? Is there some kind of short-cut or golden rule methology for a street-performance setup?
Barry did not see 4-way as particularly useful in this application. We can upgrade the rear controls all the way to 5 levels of adjustability (blowoff valve is 5th), but for this application it becomes faires on the head of the pin. As for striking it right on first settings - several things. First off Barry has a lot of experience dialing in these suspensions, so the first pass is coming from a fair bit of prior experience. Second, the car is apart for a set of initial changes, based on our first test, so adjustments are underway. The first set of adjustments are just with an eyeball alignment, enough to get the car on the road and see where things are at. What's that saying, "it's a process". We won't know when we are done, until we are done kind of thing. First results were very promising, and that's reassuring after 8 months of work. It could have not gone that way!

I'm responding to this part because I think it is impossible to bottle up everything Barry knows and distill that into a concise explanation of how to set up a suspension based on Barry's experience. I'm sure if there are helpful pieces of information he will share them. But I also know, from my own work, that often there are questions to which the answers actually don't contribute to the desired end result (in other words, it's more inter-related). But I'm sure Barry will respond. He has custom tooling he's built, software that's been created with a partner of his to do motion analysis for suspension development. And that's just what I know ... which is probably 1/10th of it at best!

Filippo

1.jpg 2.jpg 3.jpg[/QUOTE][/quote][/QUOTE]
 
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fmorelli

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Here are a few more photos on the rear mount. I ran a 0.020" fiber board spacer between the body and mount (I use this material in guitar construction lol). I will soon "sound deaden" the shock tower, which dampens vibration. unfortunately with an eyelet design, there is no way to attach the shock mount with any compressible layer, as that interferes with torquing the fasteners. We're also in the middle of sealing all the ball joints - again street applications, so keep dust and such out of the joints is necessary.

Filippo

10.jpg 11.jpg 12.jpg 13.jpg