My e-body has always had some bump steer on the open road. I have fresh front suspension components and a few after market parts (tubular upper control arms and adjustable strut rods) in it. It was this way ever since I picked the car up in 1978. At speed on a road with some good wallows (rolling hills) in it,where the car goes through 3+ inches of suspension travel, the car requires a correction input from the steering to keep the car going straight. It has improved since I rebuilt the suspension with the after market components, but it still does it.

I remember reading about the technique used to quantify and adjust the components in the Mopar Chassis Handbook, but I have never gone through that process. I'm thinking I will need remove the torsion bars (to make it easier to raise and lower the car), put two alignment roller plates to measure and chart the change in toe-in and toe-out while the car is lifted and lowered through the full range of travel. Then, using the info from the chassis book, Make adjustments to the various components in the suspension to reduce and/or limit the changes in toe as the car goes through the full range of motion.

Has anyone gone through this process? I'd appreciate any input on doing this type of corrective work.

I see that Hotchkis makes a tubular upper control arm that reduces the angular change to the spindle during up and down travel. They are proud of them at over $1k, but if it works, I would switch to them. Has anyone used them and have feedback for them?

https://www.hotchkis.net/product/do...kis-1110u-a/?mk=&yr=&md=&sm=

A friend of mine recently put an R&P steering setup in his 51 Plymouth, I have a video on how he checked his bump steer that might help you get an idea or two.

Now mind you those older Mopars have horrible bumpsteer. One time I was scooting along in my 51 into an uphill sweeping right hand turn that was slightly bumpy. The car bumpsteered itself one lane left and I was already in the left lane. Scary things.

He spent a lot of time adn effort, including making new steering arms, to sort it out. Tedious but not super difficult. The MP Chassis book gives you the how.

I went through this two years ago on my RR. I used an alignment rack to get the numbers.

I started by correcting the level of centerlink by oblonging the lower mounting hole for the idler arm, using an anglemeter from k-member to centerlink. leveled and tacked a washer on the the lower idler mounting hole.

Center the gear box with outer tie rods disconnected so box stops on the internal threads and not the knuckles. Lock the box center (steering wheel lock).

Back-off the torsion bars, lower the vehicle onto the bump stops.

I used Heim joints and circle track threaded studs. I had mine custom made, but speedway motors has a few usable pieces that are inexpensive. Make sure the taper is at the correct angle in the ball-joint hole or use reamer to correct the angle if you go this route.

Assemble and set tow at zero. Raise vehicle from the k-member one inch at a time and take a reading of toe for each tire. Track the toe chamge on a graph sheet (excel spreadsheet works well). Track toe changes till tires are at full rebound.

Heat the lower ball-joint arms with an oxy acetylene torch and a rosebud then bend the outer ball joint up or down to put the tie-rod at the correct level. Put tires back on and measure again. OR, use a heim joint and an adjustable stud.

Have your camber and caster set first before correcting bumb steer.

Bumb steer is eliminated when the inner and outer tire rod pivot point length is the same as the lower control arm to ball bushing to ball joint pivot length, and the tie rod assembly and lower control arm are parallel and remain paralle in the jounce-rebound travel.

I need to refer to the chassis book for outer tie rod level changes depending on the results of the toe change graph.

Here's an example of what I'm writing about.

https://www.speedwaymotors.com/Adjustable-Tie-Rod-Adapter-Stud-to-Heim,3333.html

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1388386/adjusting-bumpsteer-a-body.html


You will need some sort of Heim ended tie rods or drill out the taper in lower ball joint steering arm for threaded stud type tie rods. The. you want to be able to make an adjustment/correction to get the bump steer you are looking for.

You will also need to buy or make a bumpsteer gauge and buy adjustment shims

Mine was fine without adjustment. BUT I accurately measured it before. No assumptions






Threaded style (Howe sells these)

If it’s a stock, the first thing to check is that the idler arm and pitman arm attachments are parallel to the ground. If the steering box mount or idler arm mount are incorrect, it’ll drive poorly. Normally if the center link is in the correct location, the factory stuff is pretty close. You can either shim the box or heat the idler arm mount to bend it into the correct position.
Doug

Back in the early 90's, I met a gent who was on King Richards team. He told me it was very common for them to heat and move the arm portion of the lower ball joints, idler and Pittman arms to get them what they were after. Frightening to hear they used a torch but it worked for NASCAR back in the day before more specialized components happened.

This. When I got my current ebody it was doing exactly like the original poster described. The center link was not even close to level. The left end of it was so high that it rubbed the left corner of the oil pan and the Pittman arm stud was really close to hitting the header. I shimmed the steering box to get both ends of the center link the same distance from the pavement. Fixed the bump steer the pan clearance and the header clearance.

Either the k member was bent or the steering box bracket was welded on crooked at the factory. The pitman arm was correct and did not appear to be bent. The k member looks like it could have hit something many decades ago. It's probably bent.

Also, I question some of these aftermarket Pitman and Idlers. I've seen different castings from the same manufacture or the years. With the low volume of sales of our 50 year old cars, I don't assume aftermarket stuff is always right.

Great information guys. Thanks for taking the time to share your knowledge!

It's also a good idea to resettle the susp, on a drive on lift loosen all A arm bushings just enough to let the bushing relax jounce the body & retorque A arms,can help elevate quirky steering/susp.

SAY IT AIN"T SO You actually think the bean counters and freshly graduated morons would start substituting parts that are "close" but not quite 100% ?
You sir are likely spot on the probable cause.
Lets suppose the following scenario,
Corporate lays off old guy that makes too much $ but knows the design parameters of earlier systems.
Corporate hires in TWO morons that are all ga ga about their new jobs. They talked a little bit about older technology in their cllasses but the main focus was on current technology (lets say rack and pinion).
Moron looks at spec's for two parts and says, WOW these are almost the same only a couple of degrees or percent different (think brake compounds percentage wise)
So he, hoping for the GOLD STAR proposes making the two parts interchangeable saving X $$ and making themselves look good
Initially the change isn't really noticed by the consumer.
Repeat the above process 5-10 times and what do we have? A hair pulling nightmare for the guy working on the classic car.
Do you think Corporate cares about some guy with a 69 whatever having an issue with their parts??
No sir, they are concentrating on 5 -10 year old cars and outsourcing as much of the MFG. as they can.
BTDT and seen it both while I was in corporate BORED room meetings and in the last 25 years of running my business.
Sorry for the long post but it's not just steering/ suspension components, it's radiator/ heater cores, Rubber compounds, friction compounds for the brakes and the list goes on.
They made 100,000's of these cars that stopped, steered, did not overheat and were reliable whether they were in The Mojave desert or Alaska. I don't recall any of the vehicles having these issues when new or even 20 years old.

And as I found out from the Pro Forged rep at the SEMA show a few years ago, this is why our ball joints etc now come with washers to put under the castle nuts.

for whatever it's worth, i put the bumpsteer correction process from the chassis manual into a PDF file for another fellow. this file also includes the graphs used to plot the bumpsteer as you correct it.
if anyone want's this file, pm me and i will send it to you in an e-mail.

Didn't the DC Chassis Book say to shim the steering box to raise or lower the inner tie rod, and to slot the idler arm mount, and weld washers over the holes to create the new mounting location? I did a lot of suspension relocation on our racecar, relocated K-frame, relocated lower control arms, relocated steering rack (Fox Mustang) and you could barely keep the car on the course if you hit the brakes in a turn. It had 1/4" toe change per inch of travel. Got it to less than .020", and it handled perfect. I made tools almost exactly like these in this post. As long as the part you bolt to the wheel hub is flat and straight, and you have plenty of weight on the base, you'll get accurate measurements.

https://www.mr2oc.com/threads/diy-bumpsteer-gauge-for-under-60.452807/