Technical Front panhard rods

Ok guys, what is the definitive length of a front panhard rod ? Why do some run from one side of the frame to the other side of the front end? Then why do T-Buckets run a panhard rod from the center or so from the front spring mount when then on "32 Fords, they run from one side of the frame to the other side of the suspension? Why can't they run the same as T-Buckets?

Why the question? I recently changed the steering on my "32 Highboy. Went from a worn out Vega box to a Uni-steer rack. Never had any issues of "Torque Steer" with the Vega box but sure do now.
Simply running down the highway and accelerate to pass some slow-poke, upon stepping on the go pedal, the car torque steers to the right. Everything measures right, tire pressures are spot on. Can't believe that just by changing steering boxes this stuff happens! Any ideas? Contacted the mfg. of the new steering box and they weren't any help. My last few T-buckets I ran the panhard from from the center of the spring mount to the end of the axle. No problems. All the "32's I have seen run them from one end of the axle to the opposite side of the frame. Any ideas?

 

Length defines the arc angle... longer bar means smaller arc angle. For suspensions with significant up/down travel, this arc angle becomes important in that a larger angle creates greater side-to-side movement. For suspensions with minimal up/down cycling, this side-to-side movement isn't as problematic.

 

Simple -

Short Panhard bars, greater side to side chassis movement.
Long Panhard bars, less side to side chassis movement.

Less side to side movement is a very good thing.

Some use short bars because of packaging/space problems (normally in the back). Some use them because they don't understand the way they work and don't ask.
It's pretty simple to understand. Draw a circle, then draw a much larger circle. Imagine that the circles are the side to side movement your chassis will make as the chassis moves up and down while driving down the street and going around corners.
Again, a larger circle (longer arm) is better in ALL cases. Simple geometry.
All this applies to both the front AND the rear.

Mike

 

Speedway Motors has the perfect panard bar kit for your '32. Used one with my problematic unisteer and it cured all my steering issues.

 

longer is better. I have a long panhard bar on my '32, mounted from the steering box side of the frame to the right bat wing. The panhard bar keeps the front axle from swinging side to side in the spring shackles on a buggy spring, when the frame twists or the cross-steering box puts pressure on the tie-rod.

I had torque steer so bad that mine would change lanes, until I put a rear sway bar on it. Now it goes straight when I stab it! You might look into that on your car.

A panhard bar is not a "band-aid' like some people on here believe. It's a track locator. A very necessary part of the steering and suspension, especially with cross-steering and split wishbones.

Henry used push-pull, side steering and just pressed the shackle bushings in so tight that they dampened the swing. He was a cheep son-of-a gun, but it eliminated the dreaded death wobble!

Plus, today we way-over power our cars and everything flexes way more than they did back in the day, so we box the frames and put stiff cross members in and 4-bars front and rear, and everything changes.

Hope you figure it out!

 

When two controlling forces (drag link and panhard) run parallel and are of equal length things stay in place very well despite all the up and down action. A rack system can not duplicate this on these types of vehicle's. At least not when the other portion of the steering system of a different geometry still remains behind.

 

The panhard length has been addressed by others already.

Could be that the sloppy Vega didn't let you know that there was torque steer going on! Cross steer (whether Vega or Unisteer) does require a panhard. You might also be driving more spirtedly with your improved steering, making any underlying issues more obvious?

Enjoy the drive

Chris - (unashamed Unisteer fan!)

 

by chance did the unisteer raise or lower the angle going to the steering knuckle on the axle? and how much longer or shorter is that distance than with the vega?

Just a few things that could be effecting the geometry. A panhard should be a last resort on the front.

I do have to say a sway bar on rear makes a lot of the twist in the heavy application of the skinny pedal decrease.

 

Also consider here the difference in reversibility between rack and pinion and the former box, which was fundamentally a worm gear and sector.

 

Panhard bar,should be long if there is a lot of movemint up an down,can be shorter if very little.

Rack with a straight axle? NO;;;;;;,If rack mounted on the frame, then two little tiny tierods off the ends of rack to the spindel steering arms must move way too much as axle stays with road an frame rolls under hard power, = "Torque Steer"< all racks do that,it's ungodly combo anyway an always poor design. The only time it dose not happen,is if there is zero body roll at power up {ha ha,only in a go cart] So for all you that love racks,go get IFS an be totaly ugly so you can keep your rack{yes I don't like racks]. Or go back to steering box an steering rod placed as it should be*. Not rocket tech. If those reading still think any of this is wrong,under stand what is going on,one side of fram is lifting,other side is going down,axle is not moving,so little tierods off rack going to act like they are shorter/more one side then other do to torque,this both makes toe in,an more on one side then other=car darts one way. NO you can not design that out with a rack on frame,but you could get super ugly by mounting rack on the axle,an get a new bad design prob,of steering shaft slider bind/too many U-joints/but at lest that will not dart if bind is tiny tiny.
Not all things sold by the so called big shops is any good. I was a tiny speedshop before I retired,some of my work was fixing screw ups from other shops. But most knew if you wanted to win races {Stockcar or sportscar} or just ride nice around south Fla. " Comp Tech"was the place.

There canbe other messed design some were in a rod,but "racks" on hot rods are most often a screw up.

 

Get a Pete and Jake's catalog. Great explaination with pictures. If you have split wishbones, hairpins or 4 bar you need a front panhard bar.

SPark

 

A good buddy had his "rack" mounted (welded) to the rear of his tube axle in his '34 Dodge. It resembled a person with three arms, was SO ugly, but had little or no bumpsteer. Of course, it steered similar to a semi with very low pressure in the tires. Just wondering why you didn't rebuild your Vega, then install a panhard bar from left lower frame to right batwing ?

 

This is exactly how I understand it to be.
(Although I don’t have a panard rod on my cross steer/split wishbone/I beam axle setup).

 

On cross steer, the drag link and panhard need to be the same length. With a unisteer you've effectively shortened the drag link, you probably need to shorten the panhard bar. The panhard being as long as possible applies to rear bars or to side steer.

Chris

 

To echo the others, longer is better.

When using a Panhard bar with cross steering, the Panhard bar should ideally be the same length as the steering cross link, and parallel to it as viewed from the front. That way the whole set-up behaves as a hinged parallelogram, which can deform without any angular change to the other two sides.

Apart from a Unisteer there are many ways of doing rack-and-pinion with a beam axle, of which mounting the rack on the back of the axle is perhaps the least elegant. The rack could be mounted across the frame behind the axle, and act on a cross-link via an idler arm; an arrangement which can be set up to quicken steering and increase lock. What I said above about Panhard bars would apply there. Or, the rack could be mounted longitudinally alongside the driver's side frame rail, and act on a fore-aft drag link. The fact that most modern racks have the pinion axis at a non-perpendicular angle to the rack would help a lot with the steering column arrangement. Or, the rack could be mounted vertically or horizontally on or behind the firewall, and act on one or two drag links via bell cranks. The possibilities are endless, as soon as you forget what sort of steering set-up a rack and pinion is "meant for". It remains to give the arrangement an appropriate look. I'd suggest that the further you take a rack and pinion out of its familiar context, the more believably phantom-historical it can be.

 

Well OK now! Last night had a conversation with some old rodders concerning panhard rods. Two of them are running deah head perches and having no problems whatsoever. Everything I have built had a panhard rod. This car had no bump steer, no radical issues with wandering or torque steer. Didn't have any issues for the first 500 or so mile with the unisteer. Then it started. This is an effort to keep things simple, that's why I'm asking questions. If the car had no issues before with the Vega box and now? The Unisteer was installed per instructions, measure -- - - measure -- -measure! From the removal of the old box to the installation of the new one, not a thing as to measurements has changed. So why now the torque steer? I don't' have any issues installing a panhard rod or even a deadhead perch. It just baffles me why it started.

One person indicated that the less side to side movement is best, so that's where the deadhead perch would come in. Thinking back, I have seen them on "32's as well as other builds. Seen some off the wall installs where I think "Rube Goldberg" was the engineer. Why didn't I just re-build the old Vega box? Was going to buy a new box seeing as how the old one came out of a bone yard. Thought I'd have a little new technology riding with the old. Everyone who is running one of the racks built for "32's just love them, at least those whom I talked to.. So why not? So I suppose I will simply get a panhard set-up and install it. And to think I was all done building this thing? Hahaha -- - - its a hotrod right? So thanks guys for the input. But one thing more, whats the opinion of deadhead perches? I love to get our local guys thinking.

 

Dead perches were designed for roundy-round dirt track racing to keep away from the dreaded death wobble in high speed cornering. During spring flex, the length change is absorbed at the opposite end where the shackle is, keeping the axle from swinging from side to side.

Usually the dead perch is placed on the right hand side for obvious reasons.

 

Figures, although my full midget ran torsion bars, there were a couple really old cars that still ran springs and that's where, if I remember rightly, seen them but didn't give them a second look. Apparently there are quite a bunch of hot rodders who use them. I just ordered a panhard rod with the goodies, a Super Bell item. I guess some use them, the deadperches, because it may be simpler to install? I can see where I will be having quite the conversations with some of the guys. Thanks for the input.

 

I reckon something has worn out or broken and I'd start the search at the rear end!

Chris

 

^^^^^^For left hand drive cars only ?
Placed on left side for right hand drive cars ?

 

Actually for left hand turns to keep the outside tire firmly planted on an oval track. The inside tire tends to float with less load on it and can move around some. Think of a sprint car in a corner.

 

I go along with Happydaze. If something changed 500 miles after you changed to Unisteer, then I'd look into something else. I doubt that it's the Unisteer box causing the problem.

Look for broken or worn suspension bushings (front and rear), bolts that may have come loose or broken, etc. I've seen steering boxes come loose after a fresh install.

Also, Unisteer isn't totally a rack and pinion in the sense that you have two tie rods and independent suspension. It's sort of a hybrid, but because of it's mounting characteristics, it acts more like the Vega box than a rack.

Seriously, I'd be looking into a rear anti-sway bar. That will stop the torque steer, because it keeps the rear from squatting on the right and the frame from twisting and lifting on the left front, and steering the car.

Look at some rear coil sprung drag cars (think of Chevelles and 442's, etc.). When they drop the hammer, if they don't have a working rear anti-sway bar, the left front lifts in direct proportion to the amount of squat in the right rear.

If they are set up right with a rear anti-sway bar, both front wheels will come up evenly and set down straight and they don't have to counter steer.

 

Thanks for all the in-put. No, there isn't anything worn out. No loose bolts anywhere. The Uni-steer isn't any higher or lower than the original layout. The angle / level of the drag link is the same as the steering arm on the Vega box. The rear panhard rod is in place and functioning. Just took it off the stands. We will see what happens when I install the new front panhard rod. Super Bell item / Pete & Jakes. One thing I did notice, the So-Cal Steering Damper appears to have leaked out all its fluid? Actually took it off to check it. Can't do that when its installed. What's interesting is that all cross steering systems should have a pan hard rod. This one never had one. It did steer like a go kart on the highway. Input from brain to steering wheel to change lanes, and so it happens! QUICKLY! So the goodie is supposed to get here next week and I will post later on how this thing is handling and if the panhard rod cures the Torque Steer. Again, thanks for all the thoughts and opinions.

Jon & Ollie
Purveyors of Fine Texas Snake Oils

 

Dead perch setup on a 1964 sprint car. Will always force the axle to scrub one direction, not such a big deal on a dirt track, not the best answer on the street in my opinion.
My '32 frame has a panhard bar. Right batwing to left side of frame.
SPark

 

Hey, fellow Texan rodder, do you live near San Antonio ? Just wunnerin'.

 

Naaa- - - Amarillo where the sign for Libers to keep going outa Texas was recently seen by Vega! Boy was that a good one! Was on Fox national News too!

 

Hey -- - ran one on my Midget. Was a 3 bar car but needed a panhard rod. Car was set up loose and I drove where I wanted, being mindful of traffic that is.

 

I assume you are using the Unisteer rack and pinion that bolts in place of the Vega box and has one drag link that goes to the passenger side spindle, and a separate tie rod joining both spindles. Is this correct? If so, the drag link will be shorter than the one used with the Vega box.

To achieve the least possible bump steer, you must run a panhard bar that is the same pivot-to-pivot length as the drag link. The two parts must be parallel and as close to horizontal at ride height as you can get them.

Don't even consider using a straight axle with a frame mounted rack with separate tie rods to each spindle. This would guarantee massive bump steer and an evil handling car.

 

Interesting discussion. I enjoy reading answers from experienced hot rodders. ?. Would there be much benefit from say making an adjustable front panhard bar mount so you could fine tune it ? Would you feel the effects from minor adjustments ? Thanks

 

Hopefully the first quote above answers the second one.