Thread: Rearend links- 4 link, 3 link, parellel, angled???

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Last project, I made my own. Scroll down here to see the Moog #MOK6137 bushing for the lower front control arm on a Chevy pickup. That's what I used. Made my own arms and pressed 'em in.

Don't want any of that poly-shmoly crap.

http://www.autopartswarehouse.com/se...76%20Chevrolet

MD, just to throw one more setup into the mix, have you considered quarter eliptic rear springs and a four bar setup? Posies says you can use the spring as the bottom bar if you want, but we elected to use two bars per side. It is a pretty short, simple setup.

Don

We use the delron bushings all the time. They deflect enough for a decent ride.But rubber is the best riding material, But they dont last for a long time. I like the delron myself, Good ride quality.

Techinspector. I know what those are. I went to that auto parts site and looked at those bushings. How would I find the dimensions on those? I do have an auto store that lets me go through the boxes Should I do that? It takes a little time, but I usually find something that will work.

Don, I have the quarter eliptical springs and was going to do that but I came up with a nice pair of QA1 adjustable coilovers. Being the cheapskate I am with time and money (mostly time in this case) I have chosen the coilovers.
Are your bushings Poly or rubber?

Thanks guys

It's all a matter of personal choice and the intended use of the vehicle. If I'm going to build a car that has to perform well at the drag strip or on a road course and hold the supension geometry close to the design figures, then I might use harder material to facilitate that.

But on the street, I will not tolerate the harshness of materials other than rubber. The same way I will not tolerate a shift kit in an automatic transmission on the street. Having my head jerked back on every shift is not my idea of driving pleasure. I'll tolerate it at the drags because that, in my opinion, is what a shift kit was designed for in the first place and I only have to tolerate it for 2 shifts on a 3-speed box.

Here's another for instance on the OEM bushings, these are for a Chevelle upper link at the rear. Go to the boneyard and buy an upper link. Beat the bushing out of it and closely measure the i.d. at both diameters (there's a step in there). Machine a bushing tube to replicate the measurements of the OEM piece. Weld the bushing to your link rod. Buy these Moog bushings at your parts house. Press in new Moog bushings. Fabricate mounts to accept Moog bushing bolt. Enjoy.
http://www.autopartswarehouse.com/de...QQMOK5161.html

Bottom line: If you are able to tolerate some harshness in the ride quality and it is important to you to hold the design dimensions close, then use the Delrin bushings you have. If you're inclined toward a smoother, quieter, more compliant ride quality and holding the design dimensions close is not that important to you, then fabricate some bushing tubes and use the Moog rubber units.

Don, I
Are your bushings Poly or rubber?

Thanks guys[/QUOTE]


Rubber. BTW, those arms you built really look professional.

Don

Originally Posted by Itoldyouso

Don, I
Are your bushings Poly or rubber?

Thanks guys

Rubber. BTW, those arms you built really look professional.

Don[/QUOTE]

There are Poly, why? What do you think?

You can see the bars in these shots.
Can I have the upper bar a little inboard from the lower bar?

You can also see the transmission tail shaft, and the yoke on the rearind pinion shaft. Both are mocked up at ride height, but pinion angle is not yet determaned. You can imagine the driveshaft connececting the two.

What do you think about this?
Does this look too extreme?

Its interesting having large rear wheels and a low motor with a short driveshaft.

Yes I did ask this question on another forum, but I have to ask all my friends. Thats just the way I am.

Thanks

In the first picture, are these the angles you intend to use on the upper and lower links? If so, the instant center will be below ground. Did you not understand anything I explained from Billy Shopes writings?

If this is ride height, I would be concerned with u-joint angles through suspension travel. Especially in compression. I would think the triangulated 4-link would fit your application better than the parallel setup.

What's the angle ° of the engine/ trans.?

Sorry Deuce, didn't see your post 'til after I did.

I just grabbed some magnets and stuck the bars whereI could on the way out the door last night and snapped some pics.
Yes Techinspector, I read all of Billy Shopes stuff, twice! I am still trying to understand all of it, but I am getting it, slowly. I have started a scale drawing to help me work it out. For instance, how do you locate the upper and lower bar locations on the rearend?

The real reason for propping the bars up was to ask, can the upper bar be inboard (closer to the center of the car)from the lowwer bar? (see pic below)

The angle of the trans is about 6 and the pinion is a little less in thse pics is about 4 . I am thinking I need to lower the front of the motor and then lower the pinion some to match the angles. This would reduce the angles of both u joints.

Duece, I could go triangled 4 bar but the upper arms would still be short and at a pretty steep angle to meet the frame behind the seats. Just cant move the seats forward any more. What do you think about that?

Sorry for being such a lamo but I am getting it.
Thanks for all your help.

dog, I went back and read my post and it sounded like I was being condescending when I asked if you didn't understand. That was not the way I meant that question at all. I probably don't understand what I'm doing and have just been lucky.

Question from your post:
For instance, how do you locate the upper and lower bar locations on the rearend?

They can be anywhere you want them to be, within reason. Your drawing looks reasonable, with lower rear pivot about 8" from the ground and upper rear pivot about 16" from the ground. At least, that's what it looks like to me. Anyway, here's a quick drawing to 1/8 scale with 28" rear tire, 24" front tire and 110" wheelbase. I put in 3 instant center lengths....60" (minimum you want to use), 70" and 80". If a guy wanted to make front attachment points for each instant center, he could experiment. I laid all the instant centers on the squat/anti-squat line. You can put them over or under the line to alter the behavior of the car if you wish. The solid lines are the 60" instant center lines, the dotted lines are the 70" instant center lines and the dash-dot lines are the 80" instant center lines.

Using 12" links, the front attachment points are as follows from the ground with the three different instant centers.....
60" top bar 15.040", bottom bar 8.600"
70" top bar 15.492", bottom bar 8.780"
80" top bar 15.944", bottom bar 8.960"

Using 16", 20" and 24" link lengths will of course alter the distance from the ground to the front link pivot points. I have no idea what length you can squeeze into the car.

This is just measuring off my 1/8 drawing with a dial caliper and multiplying times 8, so it is only close, not dead nuts. You, of course, will do your own drawing and arrive at your own figures. You can mount the front attachment points off any length instant center you want, even extending it out in front of the car. You can also use any % anti-squat you want by dropping the instant center below the squat line. I forget now how many attachment holes there are in a pro car, but I think I have seen as many as 96 different combinations and it has been said that only 2 or 3 of them will work in any given car, depending on wheelbase, instant center length, etc., etc.

Thanks Techinspector, You have realy helped me understand this.
I have spent a few more hours on Billy Shopes site (thanks to your condescending answer ) and am starting to have a working knowlage of how it all works. Now with knowing that the 2 pivots on the rear end can be just about anywhere, within reason, I can start doing some calculations with different instant centers, % of rise or squat and bar legnths.

By gosh, I thinik I'm gonna get this figured out!

First though, I have to solve my driveshaft problem. With the engine and trans where I want them, I have a 15* working angle on the u-joints. Thats not gonna work, so I am tilting and raising the motor and that will change the CG.

I am the kinda guy that has to know the how and why things work, then I can build with confidence.

Remember the "How and Why wonder books"? I loved those books as a kid and had to have them all.