Thread: Really need help with front radius rods.....

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Well, we definately suggested replacing that earlier setup. Some wanted you to cut all the way back to the fire wall, but you wanted the kick! While it's not what many here would build, It'll still be safer that the first go round. Try it if you've got the angle right and if you can live with it for now.. Do it. Then look at other examples and get some ideas and when you ready to make it even better, you'll have more knowledge in your back pocket! IMHO, FWIW, YADA YADA YADA...

OH, I can't tell from the picture, but make certain your using grade 8 hardware in your suspension.

Yeah I think what happened was the orignal build put the drive train to high and that is causing lots of problems.

Would any of you suggest coil overs, gas or reg oil shocks?

Deleted - no added value.

I think you're right Charlie, Roger, no added value? Hard to believe! 8-)

I believe you already have a transverse spring in the front. So you'll probably need very short oil shocks or friction shocks.

You mean Castor, Camber is not adjustable on your axle.


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Originally Posted by 34_40

I think you're right Charlie, Roger, no added value? Hard to believe! 8-)

I believe you already have a transverse spring in the front. So you'll probably need very short oil shocks or friction shocks.

I have found this article from R&C to be a good fallback in understanding the basic geometry of straight axle front suspension, the history of split bones, hairpins, why the parallel bar radius rod was introduced, why cross steering solved bump steer, etc, etc. Basic Suspension Geometry Lessons - Rod And Custom Magazine
They had a corresponding article on IFS that provides a lot of very good information, too Independent Front Suspension - Overview & Technical Specs - Rod and Custom Magazine

No--he means camber---its already built into the axle and is what it is from combo of axle ends and spindle angles---

Roger--seems to be something about my reply???

See Roger, I KNEW you had the goods! All great data/info. He'll just need time to read and digest all this. But in the mean time, he needs to decide what style he's after! He'll get there.. we always do!

Bearcamp,
I went back and re-read my earlier post and realized that I typed "camber" when my brain was thinking "caster" I sincerely apologize for any confustion my typo caused in this discussion. "Caster" - the fore/aft tilt of the spindle, measured relative to the ground; and "Camber" - the in/out tilt of the spindle/wheel relative to a flat plane through the centerline of the vehicle. I corrected my statement, and again apologize for confusing the discussion.

Originally Posted by jerry clayton

No--he means camber---its already built into the axle and is what it is from combo of axle ends and spindle angles---

Roger--seems to be something about my reply???

Jerry, as noted above I made a terminology error. As I look at a scale sketch of a traditional hairpin setup and the arc's descrbed with axle movement it's clear to me that the caster increases/decreases with movement of the axle, but the change is relatively small because both the top and bottom mounts on the batwing follow the same arc radius. However, if the top bar is longer (let's say 2" longer for point of discussion) then the batwing mount points describe two different, parallel arc's, and the measured caster angle increases more on an upswing, and decreases more on a downswing than the change seen with equal length (or very nearly equal length) top/bottom bar lengths. In my head I looked at the angle of the line through the batwing as opposed to the actual caster line, and it muddled my brain a bit. When I did a sketch it became clear. Bottom line, I think referencing the R&C tech description provides a clear, concise path for Bearcamp, and he's getting good advice about re-working his frame.

Roger---not to get in a fight--but I think that you are maybe not realizing a couple of facts about these front ends and how we got there--now there is hardly anything similar between ifs and beam axles and only a very minute differance between wishbones, split wishbones, hairpins, and parallel 4 links---

ONE factor with any suspension is that the wheel/axle DOES NOT move up and down, but stays in contact with the ground

Wishbones were split in order to lower the cars back then---

In order to adjust castor beyond what they had (remember they wanted to go from a 40mph car to a 140-200 mph car) they cut a notch out of the arms to angle the axle where they wanted it

The guys wanting lighter weight and more at track adjustment went to tubing HAIRPINS with heims so they cutadjust caster plus set axle square with driveline of car.
A car with hairpins-----does not have any different arc(concentric/parallel) for the top or bottom tube--it works as a singular unit with the batwing on the axle---now a parallel 4 link is a different story.With 4link the caster of the axle has a better chance of staying constant thru out the travel

With the split wishbones, hairpins and parallel 4 links, there is considerable binding of the front on suspension travel and also a greater need to keep the axle centered, especially with anything other than the leaf springs/shackles.

Most of these older vehicles have a decent amount of camber which came about from wheel/tire size height etc and using wheels with different offsets upset the issues very quickly (death wobble)

Originally Posted by jerry clayton

Roger---not to get in a fight--but... ONE factor with any suspension is that the wheel/axle DOES NOT move up and down, but stays in contact with the ground.

A car with hairpins-----does not have any different arc(concentric/parallel) for the top or bottom tube--it works as a singular unit with the batwing on the axle---now a parallel 4 link is a different story.With 4link the caster of the axle has a better chance of staying constant thru out the travel...

Jerry,
As you said, not to get in a fight, but we disagree on a couple of points. First, when we mention movement of the suspension it is relative motion, the measurement of the wheel/axle regerenced to the frame. As you point out, the wheel stays grounded (we hope), but the relative motion of the frame to that wheel is the same whether the wheel & axle move up, or the frame moves down. I agree with your statement, but the relative motion is identical whether we say "...as the wheel moves up & down.." or as the suspension compresses and decompresses." It is common practice to raise the frame/body and then check travel and clearance by moving the axle assembly, right? Same motion, relative to one another - it's only terminology.

Second, we can solve the differential length point easily. Draw a straight line on a piece of paper, and we'll say that's the centerline of the batwing and the back hairpin mount. Now with a compass move out say 3" and strike an arc ~45* above and below that line, and then move out to a 3.25" radius and strike another arc, parallel to the first. On your first arc define two points, say 0.25" above and below the line, representing your "correct" batwing connections. Easy to see that as the frame moves up & down those two points follow that arc, and while the caster changes a bit it is not too much. If you have cross steering bumpsteer is not an issue.

Now using that lower point on the inside arc, connect it to a new point 0.25" above the line, but on the outer arc. This is the batwing connection point for Bearcamp's setup shown - the batwing is effectively rotated on the axle, tilting forward. Now as you move the frame up & down you'll see that in order to stay on the outer line the batwing has to tilt farther back on the upswing - the caster increases faster the more the rods are out of equality in length. It's a simple graphic solution that explains the point.......Or we can just agree to disagree.

Roger===there is no movement up and down at the front--only at the back--and the caster will rotate relative to the ground at about 1 degree per inch of vertical frame travel at the rear hairpin mount point---( the old 1/60 rule)

You have a mental block about this or a misconception of the real facts of basic beam axle suspension---
I read your R & C story and it jumps around so much that I don't believe the aurthor understood himself and most likely any one reading it would be confused---

With a hairpin set up you need to forget about your dancing radai because they don't exist--it matters NOT what the batwing looks like as the action is no different from just being welded to the axle like the wishbones were---the batwing just gives the builder a means of setting caster without having to build it into the arms(and a slight adjustment for wheel base or offsets of the mounting points to frame--

Choosing to disagree or not isn't what we should do here but end up with agreement on the proper and correct facts of this so readers won't be mislead about some very basic principals of suspension / steering/alignment-----

Dang, it's warm in here! Getting a bit heated!

Bearcamp, don't take it personnal! I'd suggest that sometimes other folks forget the we live in a world of compromises! You found a ride that you thought was cool and now want to make it more your own yet retain the concept(s) that you felt made it cool. No harm, No foul!

Again, I think at this point just try it out. Read / Learn get familiar with the concepts everyone else is discussing. I'm sure that in a season or two you'll get the itch to further refine your ride and then you'll be ready to really make a nice rod!

Again, IMHO, FWIW, Yada, Yada, Yada....