Suspension edit for the TCL BMW 2002

Suspension edit for the TCL BMW 2002Misc  1.0

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I prefer softer and livelier setup for street cars. Well, I like driving street cars and have a dozen of car mods edited to my preference. So I think it is great you made a suspension edit for the TCL 2002.

But have you thought about putting the correct suspension geometry on the 2002? I would love to have a proper semi-trail arm suspension put on the 2002, then use your softer setup. Would you like me to find a workable semi-trailing arm suspension for the rear?

The following came out of a Datsun 510 we were working on in 2023

WBCAR_TOP_FRONT=0.126, -0.008, 0.421
WBCAR_TOP_REAR=0.443, -0.008, 0.273

WBCAR_BOTTOM_FRONT=0.126, -0.008, 0.421
WBCAR_BOTTOM_REAR=0.443, -0.008, 0.273

WBTYRE_STEER=0.126, -0.008, 0.421
WBCAR_STEER=0.443, -0.008, 0.273

WBTYRE_TOP=0.04744, 0.0500, 0.0000
WBTYRE_BOTTOM=0.04744, -0.0500, 0.0000
 
Thanks. Glad you're enjoying it.

Soo... This is what I said to a friend yesterday, just before I posted the fix for the road-going 2002, from Buja:
"This one is not as easy. Simple to fix the rear squat issue, but it generates a higher speed "swerve" reaction from the rear end which needs more work. I think for now, I'm going to just retro-fit the v1.1 rear suspension as a quick and dirty fix, cos that's quite stable. I'm probably the only one offended that it doesn't match reality anyway :)" << Got that wrong :)

Now that car really used a nothing-like-reality setup, but after doing some research, I though Bazza's interpretation for the TCL 2002 was pretty accurate, within the constraints of AC's understanding of suspension fizix.
The real thing has a really beefy, box-section, angled trailing wishbone. There is no upper (second) wishbone.
The spring sits centrally in in a pocket, in the wishbone and the shock-absorber attaches behind the axle line. Like this:

1.jpg


2.jpg


My thought is that the inside leg of that wishbone is angled sufficiently to act as lateral control, and the short arc of the full deflection does not change the geometry enough to require an articulated upright, and upper lateral control arm. I think.

So, how to duplicate that in AC? It's a bit like a spread wishbone with a strut, right? I've had some experience with that kind of setup trying to cure the HSS Lotus 16's terminal rear wheel camber change in the range of suspension movement, and I ended up having to make the trailing arm quite long, very close to the inside edge of the wheel and very close to directly front/back. Which would be REALLY unlike reality for this car.

Happily, smarter folks than me (Bazza, Velo et al) have already worked this out.
You make the bottom Wishbone really accurate. Then you make a second long, narrow, wishbone, separate the hub mount points by something like the length of the "upright", and mount it's feet on either side of the axle line. The feet end up on the other side of the car, lolz. It's completely imaginary, but it controls the upper end of the hub laterally (cos AC can't understand the way BMW really did it it, requiring NO upper lateral control) almost like it's invisible.
So that's what the smart guys think. Which is why I left the TCL car alone in that respect. I'm actually thinking of using the TCL mount points as a better option on the Buja car, too. Cos that's really fantasy.

But... That all said (and sorry, I'm a wordy sod :) )
I'm very open to other ideas, and keen to give your suggestion a whirl.
So let me do that and drive it and come back to you.
PS. Off the bat, it looks quite a lot like the setup Buja tried, which yielded the rear rise under acceleration problem.
 
OK, gave it a a try.

The good news:
1. After thinking about it while driving, I really like how this mimics reality. You've made a boxy, beefy, single wishbone, just like the real thing. This is the right direction.
2. I actually prefer how the car handles with this setup. The rear slides more, but not in a wild uncontrollable way. Very predictable and controllable. I am about a second a lap slower at Red Bull Ring, however.

Now the bad news, and it's a deal-breaker, given the folks who complained in the first place.
The rear rises under acceleration. ¯\(ツ)/¯
That's so antithetical to all of our IRL experience. There would be pitchforks, I think :)

But, give it a try?
 

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  • suspensions.ini
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I downloaded your data.acd file in a version of TCL 2002 and for whatever reason came out corrupted. But if you only changed the suspension tuning, then the suspension.ini file should work. Had not tried that yet.

A couple of info here that might be useful: Arch has done E30 and is very knowledgeable in suspension modding. He pulled his E30 and other car mods from RaceDepart.. but might still be on his own site (or at least the suspension files). And here you can find a 73 2002 mod in the video description. This one I have on my CM and it has semi-trailing arm. By the way, if you have not already, use CM Showroom to visualize the suspension geometry/mounting points.

About the lifting rather than squatting under throttle, I remember running into that problem while working on 510. I forgot how that problem was solved, I think my partner did it and he use extended CSP physics. The attached suspension.ini file is the latest version. The chief problem we found was the understeer and brake lock. We worked on it for a couple of months. Made some progress but I think still has a lot of room for improvement.

Back to 2002, I drove both TCL 2002 74 and the other 73, found that the 73 understeered a lot, like the 510 I worked on. The TCL has a peakier turbo torque curve, 73 is more mild. If I were to work on it, I might start with the 73 street car body. That is just my preference. I am no longer drawn to having stickers, racing number, roll-cage in cars.

FYI, I did a few cars and posted on RD. (190E, MR-S, AW11)

I wish you luck.
 

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  • suspensions.ini
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