Hey Al here's 4 link info

john vanlandingham Wrote:
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>
> But Mark, isn't it fun to actually have the choice
> of being able TO TRY something out after all
> these years of fixed junk?

Yeah, it's fun to think it will be better, but we'll really see after all the work is done. The stock Opel 2 link + torque tube + Panhard rod rear axle was actually pretty good for a stock axle, for handling and weight transfer under acceleration. The stock trailing links were close to level to start with, and the rear axle behaved well, with simply substituting mildly stiffer-than stock springs, and Bistein's in the stock mounts. Just plug-'n-play easy rear suspension, so to speak.

So the proof of the 4 link will be in the pudding. The real design driver was to get a different rear axle under the car for which I could get cheap rear gears and LSD's versus the old Opel Aascona/Manta A parts, not just of the sake of a 4-link. THAT's the exciting part to me. The factory teams went to a version of the 4 link for the WRC chanmp Opel Ascona's, so I presume it is equal or better. But I understood they modified this to get away from some weakness in the torque tube design, not so much for handling improvments.

Regards,
Mark B.

starion887 Wrote:
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>(due to a bump or a roll in a corner)

Yeah that's what I was after... just was curious if they were one and the same thing.. makes sense of course

> More likely this is due to inherently overly stiff
> rear suspension, that acutally leaves the road
> surface on a bump for a moment. The traction is
> lost and the truck's rear moves in the direction
> away from the forces acting on it when the
> traction is broken (like swinging out on a
> corner). Stock truck suspensions have to be a
> compromise on handling in order to carry loads.

Yeah I know this all very well.. grew up in the country and have had 9 rwd trucks/cars all solid rear axles of course.

Have you ever noticed some solid rear ends will literally throw the rear end left or right when you're going straight and have hit a bump it can even be an expansion joint in a bridge. My dakota does that fairly often.. and was curious if that's caused by the leaf spring suspension or what. I don't remember any of my cars with coils doing that.

---

Andrew M
Onterrible
30ish

Are you going with a toyota truck axle?

---

Andrew M
Onterrible
30ish

Pete Wrote:
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> But you can reduce the roll steer by making the
> lower links parallel to the ground and as looooong
> as possible.
>
>
>
> Pete Remner
> Cleveland, Ohio
>
> 1984 RX-7 reshell
> 1978

Yeah, Pete, we are going with 23.5" links (the lowers fit to the stock trailing link attach points) and starting with both links level, or very close to it. I've read all the stock car set-up stuff, thought about it, and concluded it had some serious issues for rallying. But I was asking if anyone ever messed with this in rallying, and found a good compromise. We will lose the inherent forward-bite-enhacing characteristics of the Opel torque tube with level links, and wanted any clues available ahead of time to how some upward link angle (to enhance forward bite) might effect roll steer behavior.

Thanks,
Mark B.

Regards,
Mark B.

I am unfamiliar with the Opel torque tube. I am assuming that it's a torque arm arrangement similar to a Chevette or a GM F-body. If that's the case, the instant center is more or less fixed at the forward attaching point. The angle of the lower links does play a role if they are short so the wheelbase can alter appreciably, but if they're nice and long then it doesn't matter.

---

Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

hudson Wrote:
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> Have you ever noticed some solid rear ends will
> literally throw the rear end left or right when
> you're going straight and have hit a bump it can
> even be an expansion joint in a bridge. My dakota
> does that fairly often.. and was curious if that's
> caused by the leaf spring suspension or what. I
> don't remember any of my cars with coils doing
> that.

Well, I would cautiously say yeap but not with 100% conviction. I had an '03 Dakota and it didn't bounce around too much (at least in my view), but it was the ologer wheelbase. I have attributed a lot of roll steer to the Colt/Arrow to the leaf spring set up, so it might be the same. Have you compared the lower arm effective length of the suspensions in question? I recall older Chevy trucks have some pretty long arms and coil springs, versus the fornt half of a leaf spring. One other difference is that multi-leaf springs are pretty progressive in their rate, at least when compressing. It may be that the leaf spring gets really severely mistmatched with the shock rate. Interesting to try to figure out.

Regards,
Mark B.

hudson Wrote:
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> Are you going with a toyota truck axle?
>
> Andrew McNally
> Hamilton ON
> 28

Yes, early 80's Toyota P/U from a 4WD, 8" ring geear. Thicker axle shafts on the 4WD, and a stronger center diff, versus a 2WD axle. The early 80's are 2-3" shorter than the later ones. Doing a 4 link and keeping the Panhard rod that was stock with the early 70's Opel. Also, using some Bilstein coil overs from John.

Regards,
Mark B.

Pete Wrote:
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> I am unfamiliar with the Opel torque tube. I am
> assuming that it's a torque arm arrangement
> similar to a Chevette or a GM F-body.

Yes, the Chevette rear axle and suspension was pretty much a carbon copy of the Opel.

Regards,
Mark B.

Oh, yeah now I recall another reason to not set-up a rally 4-link + solid axle like the circle track set-ups. If you look at illustration 2D in the article posted, as the axle moves up or down in that picture, look how the axle tube has to twist to conform with the movement of the arms. Than imagine a rough rally road, with one end of the axle going up while the other tries to go down. The left and right ends of the axle housing are trying to be twisted in opposite directions! The results will probably be binding in the suspension motion, and, at worst, broken link ends or mounting tabs on the body or axle. Maybe enve a twisted axle tube.

Regards,
Mark B.