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Old 11-28-2012, 03:50 PM   #1
dreadpirateroberts
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E30 BMW drag suspension setup

So, i was thinking about the similarities between the E30 BMW and GTO suspension... e30 bmw has a remotely similar suspension setup to our cars - semi trailing arm. differential is bolted to the subframe. seems they have no toe link, however.

http://www.speichers.com/e30_suspension.htm

Then, I thought, somebody somewhere has drag raced an E30. So I did some google-fu.

take a look at this E30 and it's setup, and tell me what you think.

http://forums.eurocca.net/showthread...on(drag-racing)

looks like he did away with the rear subframe entirely. differential bolts to some kind of tubular member that is attached to the framerails, looks like?

control arms are these massive tubular constructs that attach FAR forward, perhaps where 4 link SRA arms would attach. This probably allows for some pretty massive weight transfer, excellent toe/camber control and i doubt he has any wheelhop issues.

plz discuss.
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Old 11-28-2012, 04:08 PM   #2
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Looks interesting. I have heard somewhere that the designer of the GTO/Monaro suspension used to work for BMW. But don't take my word for it. This might explain the simularities
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Old 11-28-2012, 04:27 PM   #3
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i care more about that e30 drag car setup
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Old 11-28-2012, 07:24 PM   #4
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Old 11-28-2012, 07:25 PM   #5
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Old 11-28-2012, 08:28 PM   #6
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Old 11-28-2012, 09:27 PM   #7
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looks like he also has some sort of crossmember welded in where the tubular control arms bolt to.
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Old 11-28-2012, 11:15 PM   #8
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Quote:
Originally Posted by jpvulpes...View Post
looks like he also has some sort of crossmember welded in where the tubular control arms bolt to.

Yes, that crossmember is effectively the same as the GTO cradle.
Probably a few pounds lighter, and performs the same function.

I'm not familiar with this suspension....it is difficult to see a clear advantage
over the existing GTO suspension though.

edit: I do see one...let's play find Waldo. Who can identify the capability this
suspension has that is missing from the GTO.
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Last edited by magnum-gto; 11-28-2012 at 11:26 PM.
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Old 11-28-2012, 11:52 PM   #9
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mounting points on the same centerline? just a guess.
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Old 11-29-2012, 01:58 AM   #10
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Quote:
Originally Posted by magnum-gto...View Post
I'm not familiar with this suspension....it is difficult to see a clear advantage over the existing GTO suspension though.

I would think this suspension would maintain a totally constistant wheel geometry throughout the suspension travel from this design.

I would also think a significantly longer control arm mounted farther up the body of the car would not only help with wheel hop but also far more importantly weight transfer during launch. I think you would get a much better "tire hit" with a longer control arm.



i also want to be sure you we are both talking about that rectangular bar that sits farther up the car and sits under the driveshaft when we're talking about the "crossmember", not the tubular frame that's bolted to the differential...

Last edited by dreadpirateroberts; 11-29-2012 at 02:02 AM.
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Old 11-29-2012, 02:07 AM   #11
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Then again a longer arm may only really be of benefit when used with an SRA...
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Old 11-29-2012, 07:49 AM   #12
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Quote:
Originally Posted by magnum-gto...View Post
edit: I do see one...let's play find Waldo. Who can identify the capability this
suspension has that is missing from the GTO.

I see complete adjustability of the control arm locations.
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Old 11-29-2012, 08:57 AM   #13
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I've wondered why we insert bushings into the rear diff bracket and not make a solid mounting bracket. Bolt it to the diff, then bolt it to the frame.

I guess for NVH reasons, but people go to solid motor/trans mounts and say there isn't a lot of added NVH.
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Old 11-29-2012, 09:07 AM   #14
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Quote:
Originally Posted by 05raptorle...View Post
mounting points on the same centerline? just a guess.

Probably, but we have no way to prove it.
There is something else.
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Old 11-29-2012, 09:09 AM   #15
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Quote:
Originally Posted by jpvulpes...View Post
I would think this suspension would maintain a totally constistant wheel geometry throughout the suspension travel from this design.

I would also think a significantly longer control arm mounted farther up the body of the car would not only help with wheel hop but also far more importantly weight transfer during launch. I think you would get a much better "tire hit" with a longer control arm.



i also want to be sure you we are both talking about that rectangular bar that sits farther up the car and sits under the driveshaft when we're talking about the "crossmember", not the tubular frame that's bolted to the differential...

We are speaking of the same item. The cross member we are referring to
holds the trailing arm bushing mounts.

Last edited by magnum-gto; 11-29-2012 at 09:17 AM.
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Old 11-29-2012, 09:12 AM   #16
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Quote:
Originally Posted by MuhThugga...View Post
I see complete adjustability of the control arm locations.

Correct!
That little feature affects the car's launch significantly.
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Old 11-29-2012, 09:16 AM   #17
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Quote:
Originally Posted by smitty2919...View Post
I've wondered why we insert bushings into the rear diff bracket and not make a solid mounting bracket. Bolt it to the diff, then bolt it to the frame.

I guess for NVH reasons, but people go to solid motor/trans mounts and say there isn't a lot of added NVH.

Our 8.8 mount is solid......but then being deaf can have some advantages.
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Old 11-29-2012, 09:20 AM   #18
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Quote:
Originally Posted by jpvulpes...View Post
Then again a longer arm may only really be of benefit when used with an SRA...

Arm length is much more critical in SRA applications, and have a totally
different function.
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Old 11-29-2012, 09:31 AM   #19
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Quote:
Originally Posted by magnum-gto...View Post
Arm length is much more critical in SRA applications, and have a totally
different function.

I was thinking that might have been the case after all. Ladder bar or links in an SRA would transfer torque from the axle assm. to the chassis, helping to transfer weight. I assumed from the e30's wheel stand something similar was the case, but once thought about it, i couldnt see how the forces applied could make it do that, since these control arms are not linked to the diff or axles in any way.
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Old 11-29-2012, 09:32 AM   #20
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Quote:
Originally Posted by magnum-gto...View Post
That little feature affects the car's launch significantly.

Plz splain more lucy
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Old 11-29-2012, 09:39 AM   #21
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Quote:
Originally Posted by jpvulpes...View Post
I was thinking that might have been the case after all. Ladder bar or links in an SRA would transfer torque from the axle assm. to the chassis, helping to transfer weight. I assumed from the e30's wheel stand something similar was the case, but once thought about it, i couldnt see how the forces applied could make it do that, since these control arms are not linked to the diff or axles in any way.

You are correct on all points.
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