Bump steer on a GM A Body ?

[72mojave]

I've got a 72 Chevelle with Hotchkis upper and lower control arms, 0.5" taller upper Proforged balljoints, 1" lowering springs, and 2" factory style drop spindles. I will get a performance alignment with 4-6 degrees positive caster.

Because I keep reading about bump steer, I'm looking at the Global West revised steering arms, or the UMI or Baer bump steer rod end kit. I'll buy either if I need it. But will I need it with my suspension setup? This is a street car.

I figure enough people have done suspension modifications to the A body that there must be some general rule about when bump steer will become a problem that needs correction?

I'd like to install whatever I need to install now, rather than find out later I need an extra part and go through a second alignment. At the same time, I don't want to throw on parts that aren't going to be beneficial.

[dontlifttoshift]

Is your alignment shop capable of adjusting bumpsteer? If they can't, then it won't matter if you buy the bumpsteer correction kit or not.

The GW steering arms appear to be the simple solution here. They aren't terribly expensive and still use a factory tie rod end, if you are concerned about it that is the way I would go.

[72mojave]

Is your alignment shop capable of adjusting bumpsteer? If they can't, then it won't matter if you buy the bumpsteer correction kit or not.

The GW steering arms appear to be the simple solution here. They aren't terribly expensive and still use a factory tie rod end, if you are concerned about it that is the way I would go.

That's the direction I've been leaning for the reasons you've identified.

[UMI Tech]

Donny is correct (as usual). Some hot rod shops have the knowledge and equipment to check/set bump steer.

Adding the caster hikes the steering arms up which in turn moves pivot points from where GM intended. Our kit lowers the outer tie rod point back to stock or thereabouts. It's always better to measure.

[De-noz]

Do you "RACE" ?

[Hotwire]

If you've driven the car before these upgrades, you'll know if you have bumpsteer or not. The tendency of the wheel to go numb or jitter in your hand when you go over an abrupt bump means you have bumpsteer. As said above dialing in negative caster raises the steering arms multiplying the issue.

You could also install 0.5" taller lower balljoints to help eliminate bumpsteer as well. It took all of it out my car, seriously night and day difference. Car handles bridge abutments at 70 better than my DD Yukon.

One other question, what made you go with 0.5" taller upper balljoints? 0.9" are available and help to correct the trash geometry our front ends have.

[CapSS92]

I have a 65 Chevelle with Eibach lowering springs, CPP C5 spindles, and the cheapie tubular arms and I just installed the GW steering arms. After my alignment guy dialed it in, I definitely saw a difference. I posted a review with pics on the Summit website if you want to see what they look like compared to stock arms. Thanks.

Alex

https://www.summitracing.com/parts/gls-ss-6472gskb

[72mojave]

If you've driven the car before these upgrades, you'll know if you have bumpsteer or not. The tendency of the wheel to go numb or jitter in your hand when you go over an abrupt bump means you have bumpsteer. As said above dialing in negative caster raises the steering arms multiplying the issue.

You could also install 0.5" taller lower balljoints to help eliminate bumpsteer as well. It took all of it out my car, seriously night and day difference. Car handles bridge abutments at 70 better than my DD Yukon.

One other question, what made you go with 0.5" taller upper balljoints? 0.9" are available and help to correct the trash geometry our front ends have.

The car used to have stock control arms (but the springs and spindles are the same). With the Hotchkis arms and a new alignment the spindle geometry will change.

If I install .5" taller balljoints in the lower arms, the car will be lower. It is already 3" lower than stock. And from what I understand, .9" uppers are typically paired with .5" lowers and most helpful for track use. Again from what I understand, .5" taller upper balljoints are a good improvement for street use. Hotchkis doesn't include taller balljoints with their arms so I went one step farther than what they market. I'm pretty sure I read on UMI's website that the .5" uppers are a good match for street use, but they can certainly tell me if I missed the boat on that one.

[72mojave]

I have a 65 Chevelle with Eibach lowering springs, CPP C5 spindles, and the cheapie tubular arms and I just installed the GW steering arms. After my alignment guy dialed it in, I definitely saw a difference. I posted a review with pics on the Summit website if you want to see what they look like compared to stock arms. Thanks.

Alex

https://www.summitracing.com/parts/gls-ss-6472gskb

Great review, thanks. Everybody is backed up on making/shipping parts so hopefully I can get them soon.

[Hotwire]

The car used to have stock control arms (but the springs and spindles are the same). With the Hotchkis arms and a new alignment the spindle geometry will change.

If I install .5" taller balljoints in the lower arms, the car will be lower. It is already 3" lower than stock. And from what I understand, .9" uppers are typically paired with .5" lowers and most helpful for track use. Again from what I understand, .5" taller upper balljoints are a good improvement for street use. Hotchkis doesn't include taller balljoints with their arms so I went one step farther than what they market. I'm pretty sure I read on UMI's website that the .5" uppers are a good match for street use, but they can certainly tell me if I missed the boat on that one.

Completely understand. The 0.5" taller lowers will lower the front end by 0.5".

What you have now will slow the camber gain down so it won't go as negative as factory, it's good. Did you ever notice when you jacked your car up and the suspension drooped how much the bottom of the tires pooched outwards? Made the car look pigeon toed, that's what we're correcting.

The 0.9" taller uppers do help to correct the camber so you get negative gain on compression. I measured -3 degrees from complete droop to full compression with taller upper and lower installed. Our front ends are not designed with any type of handling in mind. I made the quick diagram below to help people visualize the issue on the a-bodies. It's not to scale but gives you a good idea of what you're doing adding the recommended parts.
red = frame
dark blue = a-arms
orange = spindle
aqua blue = increased height needed to correct the geometry

The upper and lower control arm pivot points are spaced further apart than the spindle's balljoint pivots. The diagram on the left is showing stock geometry. With the shorter spindle side it creates a trapezoid that forces the top of the spindle outwards during compression. This is exactly what you DON'T want to have any hopes of turning. The diagram on the right is our front suspension with the spindle height corrected, either through the use of a tall spindle OR taller balljoints. This spaces the pivot points out to match the control arm's pivot points creating a parallelogram, meaning it cancels the negative camber on compression.



This is stock suspension *with poly bushings and all new joints* with positive camber on compression. Mine were cambering out so bad they rubbed bare spots on the outer fenderwells and smoothed the lettering on the sidewalls.



Here's the car with tubular lowers, SPC adjustable uppers, 0.9" taller upper and 0.5" taller lower balljoints installed. Completely transformed the car into something you want to drive instead of fear of death.

[72mojave]

Maybe it was Proforged who I saw recommending the .5 ball joint on the upper for street use. Below is a response to someone's question on the Summit website (72 Cutlass, same as a 72 Chevelle).

They do recommend the .5 ball joint on the lower too. I could do that, but I'd have to add a .25 shim to the coil spring to bring my ride height back up .5 and I'm not sure it's worth the hassle to change the ball joints and add shims. I'm mainly interested in avoiding bump steer at this point. This is a 100% street car. (409 sbc, Richmond non-OD 5 speed with 3.28 first gear, 2.73 12-bolt posi. Good out of the hole and low rpms at 75 mph.)

https://www.summitracing.com/parts/pof-101-10473
Hi Matt, Thanks for reaching out to us on your Cutlass, we appreciate your interest. In answering your question, it really depends on what you are doing with car, road racing, auto crossing, drag racing or just spirited driving occasionally. For racing purposes, the 09' is perfect, for spirited driving the 05" is the one you want. Part# 101-10016 is the .5" tall and part# 101-10473 is the .9" tall and we recommend that you replace the lower ball joint with part# 101-10014 when using either one. Keep in mind that these ball joints will lower your car even more. Hope that helps Matt.
Proforged Chassis Parts Answer - 3/9/2020

[Hotwire]

As long as you're addressing the problem anything will help. I doubt you want to wrestle with the springs to add shims so the arms would be the way to go in this instance.

Fixing the bumpsteer will also help your 60' as it will keep the tires aligned when you pull the front end. :D

This video opened my eyes and made me realize what was going on with my turd. Always had to stay on point when driving it to keep it between the mayonnaise and the mustard. Full video is educational, 2:40 mark shows what's happening.

https://youtu.be/aLFD16A2sRg

[72mojave]

This video opened my eyes and made me realize what was going on with my turd. Always had to stay on point when driving it to keep it between the mayonnaise and the mustard. Full video is educational, 2:40 mark shows what's happening.https://youtu.be/aLFD16A2sRg

Yup, that video is what made me interested in the arms in the first place.

[c4racer2]

I have a 65 Chevelle with Eibach lowering springs, CPP C5 spindles, and the cheapie tubular arms and I just installed the GW steering arms. After my alignment guy dialed it in, I definitely saw a difference. I posted a review with pics on the Summit website if you want to see what they look like compared to stock arms. Thanks.

Alex

https://www.summitracing.com/parts/gls-ss-6472gskb

It's amazing what modern suspension design can do for these classic cars. I swear my 71 Camaro with DSE arms, hotchkis springs w/ bilsteins and solid body mounts along with welded in SFCs rides nicer on the highway and handles those bumps better than any other car I own - even the M5! Amazing.

[Hotwire]

*** I bought this Stage III set up 5 years ago from SC&C.. I would check out what's the latest going on over there. I read that SC&C has been having trouble getting the parts to the people who paid the full price for them.. I sure do hope this works out. They have been a very big help to so many people over the years.. ***

His site has been taken down, might could send him a soap on a rope.

[c4racer2]

they went out of business from what I heard.