Track Width and 4-link

[BBPanel]

Have a 55 Chevy setup many years ago w/Alston ladder bars and it is back-halved. Distance between rails is 26". Its Pro-Street all the way. It looks like I could probably convert it to a 4-link w/o too much effort but is it worth the trouble? Car will be a cruiser primarily and fair weather only.
I guess my first concern is the track width - any rule of thumb that need be adhered to with a 4-link?
A TQ Arm isn't out of the question either but would like to address the 4-link specifically. -Bob

[Ron Sutton]

I'm a little unclear on the question about track width. Are you asking if the 4-link influences the proper track width of the tires? Or are you using the term track width in asking how wide to place the 4-link?

[Ron in SoCal]

Welcome Ron! About time...

[Ron Sutton]

Thanks SoCal Ron. Should I be NorCal Ron? LOL

[BBPanel]

Originally Posted by Ron Sutton

.... Are you asking if the 4-link influences the proper track width of the tires? Or are you using the term track width in asking how wide to place the 4-link?

I guess I used the term track width to define the distance between the ladder/4-link bars. I assume the distance for ladder bars is not particularly important because its primarily a straight line suspension. But people run the 4-link because it articulates better when doing things other than going in a straight line. The stock frame rails are ~40" apart and many people run 4-links with the stock frame. If I convert to a 4-link the distance between them will be >14" narrower. Will this impact the effectiveness of the 4-link? There has to be some distance where its impractical and I'm trying to determine what that might be.

[Ron in SoCal]

Originally Posted by Ron Sutton

Thanks SoCal Ron. Should I be NorCal Ron? LOL

Just be yourself and we'll all benefit.

[Ron Sutton]

Now I understand. Thanks for clarifying.

The further outward you place the suspension pieces, the more control they have. This is most critical with shocks, and to less degree with springs ... but also applies, to a lesser degree, to suspension arms that act as "levers".

You stated earlier that the frame width is 26" between the rails. Assuming your frame width is 2" (correct me if I'm wrong) ... that makes the frame rails 28" center to center.

If you're able to place your 4-link under the frame rails, 28" center to center will be very good. Something to ease your worries a little bit ... the narrower the 4-link is ... the better it articulates (rotates within the chassis).

In fact, in monster tire Pro/Mod drag cars ... where the tires are so mondo wide ... the space for the 4-link ended up pretty narrow. This was such a problem that drag chassis builders had to start adding sway bars ... in drag cars. :-)

-------------------------------------

On another note ... or two ...

1. I suggest you figure out how far outward you can mount the shocks & springs. Get away from how drag race car builders do this (on the back of the 4-link). The wider you can mount the shocks (and springs if coil overs) ... the better the motion ratio ... and the better control the shocks will have on the rear suspension. If the springs & shocks are separate & you have to choose ... shocks further outboard trumps springs. Really push the packaging of this to get the max.

2. If you really want your rear suspension to articulate ... even better than the 4-link ... and if you're NOT going to drag race it HARD (High hp, slicks & high rpm launches) I would suggest you consider a 3-link with a panhard bar. Another option, if you're going to drag race it still, would be a triangulated 4-link. It can be as strong as a regular 4-link, but with one set of bars angled together to form a triangle ... allows it to act "similar" to a 3-link in terms of increased articulation ability.

Again, not trying to take you off track. Just want you find what's best for your situation.

Best wishes !

[BBPanel]

Originally Posted by Ron Sutton

......If you're able to place your 4-link under the frame rails, 28" center to center will be very good. Something to ease your worries a little bit ... the narrower the 4-link is ... the better it articulates (rotates within the chassis)....

Hmm, that seems a little contradictory - move them outboard and under the frame rail but narrower is better?

I could probably locate the lower bar under the frame rail but what about the upper - it couldn't be in the same vertical plane - is that a problem?

As for the triangulated 4-link, i thought there were some guidelines on the ratio of the lengths of the upper and lower bars (I don't recall what they are) and very narrow frames don't work out well. Is that true?

All in all it sounds like if I replaced the ladder bars w/4-link in the same location they are now its not a problem. -Bob

[Ron Sutton]

Originally Posted by BBPanel

Hmm, that seems a little contradictory - move them outboard and under the frame rail but narrower is better?

I could probably locate the lower bar under the frame rail but what about the upper - it couldn't be in the same vertical plane - is that a problem?

As for the triangulated 4-link, i thought there were some guidelines on the ratio of the lengths of the upper and lower bars (I don't recall what they are) and very narrow frames don't work out well. Is that true?

All in all it sounds like if I replaced the ladder bars w/4-link in the same location they are now its not a problem. -Bob

Sorry if I my post wasn't clear. I didn't say narrower is better. It's not. Narrower simply offers more articulation (roll within the chassis) & wider offers more control. The lower bars affect roll steer the most. The width, angle & length of the lower bars all affect roll steer. 28" wide is fine & will work well, providing all the other suspension components & geometry are correct.

Having not seen your frame layout, I couldn't recommend the best layout. If you post some photos, we may be able to offer ideas.

Having upper bars on different vertical plane is not a problem. Mounting them inside your frame rails (therefore narrower) would allow the rear suspension more articulation (roll within the chassis).

There are guidelines on the ratio of the lengths of the upper and lower bars on triangulated & parallel 4-links. But if you ask 6 different designers/engineers, you'll get 6 different opinions based on their experience, or lack of. There is no absolute ratio.

[BBPanel]

Not the best picture but ....: