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So the long bump stud will clear a 4.0" bsp stock wheel, but clearance becomes an issue with 5.0" bsp wheel.
Can you try spacing the tie rod end downward, and see how much wheel clearance you have?
The zone is 1.25" below the arm to 2.0" below the arm, center of heim.
How much you need all depends on your caster.
You can cut off the rest of the bolt after that.
You are the perfect candidate to run that test for us, you already have the wheels.
If you can keep the heim joint 1/8" away from the wheel, that is acceptable clearance. That stuff does not flex. I ran that close for years on my race car. Never had any contact. Keep it farther from the sidewall. That flexes, a lot. I'd recommend 3/8" from that part of the sidewall.
The bump blocks move the joint inward roughly 1.25"
There will definately be a limit as to how deep a wheel offset you can run, before you are forced into the bump blocks.
The blocks can still fix most of the bump steer. But the bump line will have a very strong curve to it, it will be very ride height sensitive, and you will almost definately have to run a bump curve of your own, with a bump gauge, to center the big curve at your ride height. Installation will be fussier, but the end result is similar.
Looks like I can get roughly 1.4” of drop before the heim joint gets too close to the wheel. Oh, forgot to mention that I plan of flipping the bolt to the head being on the bottom. So the clearance issue will be the heim.
So I put in the spacer on and when bolting down it gave me an effective distance of 1.25”.
One caveat to do this is apparently the drivers side tie rod is closer to the wheel than the passenger side. Strange… Either the steering arm is bent or good ‘ol 60’s manufacturing was way off.
Question is, could I shim the drivers side steering arm??
First two pictures are of the passenger side, the second set is the drivers side.
Took it for a drive last night and it’s amazing what .6” of spacer will do for your bumper steer. Before the car was very jittery over bumps. Now most of that is gone. Next up is replacing that steering arm and getting upper tubular control arms to get more caster out of it.
Good confirmation that this works. Although I have heard it a couple of times.
Were you able to set it to my suggested settings after all? Or just partway there?
No matter how close you got to ideal, just reducing it helps a lot!
Because of the drivers side I can only get 1.25” from the bottom of the steering arm knuckle to the center of the heim joint. I’m going to either angle mill the steering arm where it mounts to the spindle, effectively pushing it out or just buy a new one. Hopefully I can put more spacer on it.
The car needs an alignment, but wasn’t going to get one until tubular control arms go on. Then I can set the alignment specs.
I am building new, front steer suspension for my vintage 1960 Corvette track car. Since I am using C-3 suspension dimensions and geometry, I though I would throw this out there. Global West C-3 lower control arms, Van Steel C-3 1" drop spindles, and Howe upper control arms. The control arms (upper and lower) define the rack length once rack height is selected. Then, the last things I fabricate are the steering arms. This allows me to set the tie rod angle while positioning the outer tie rod end vertically to eliminate bump steer. I have additional adjustment with Howe screw-in outer tie rod ends and a vertical adjustment on the ends of the Sweet Engineering rack. I will rap it up with Penske shocks and a Speedway Engineering adjustable sway bar. It is a long, slow process, but the thing should handle better than it did with the John Deere suspension.
Rack and control arms mocked up in the jig/fixture
Installed my SPC arms.
They do allow easy adjustment of both caster and camber.
They also have a 1/2" taller upper ball joint.
That is supposed to improve the camber curve.
But it may also alter the bump steer curve.
SPC arms
Camber change curve: This 1/2" taller ball joint does improve the camber change curve. At a 1.0" bump, there is a gain of .25* negative camber on bump.
There are also 1.0" taller ball joints available. Presumably those would gain .5* of negative camber.
This is very likely a good thing for maximum cornering traction.
Bump Steer Curve The taller ball joint did affect the bump curve. The bump stud required another .20" of shims, to lower it more, vs the std ball joint. (Both at 6* caster).
I know that some people have use even taller ball joints, like 1.0". So the bump correction would have to be even greater.
Basically you can not use the same amount of shims that a stock a-arm and ball joint car needs.
What happens next is a domino effect of suspension changes.
The taller ball joint makes the upper a-arm tilts more severely downward toward center.
This makes it cross the lower a-arm line plane sooner.
That means the instant center changes from ~80" to ~60"
That shorter instant center (IC) is what increases the camber gain curve.
The spindle now pivots on a different circle radius.
The shorter IC winds up raising the front roll center height (RCH).
The higher RCH, means it is closer to the center of gravity (CG). That will cause less weight transfer to the outside front tire, and more to the outside rear tire, in a turn.
That means the car understeers less, or oversteers more.
All this movement affects the bump steer, increasing it again, requiring more shim.
The curve came back in the bump steer line, meaning the car now really wants a longer tie rod length, which would require moving the inner inward.
Altering the suspension location points causes a domino list of geometry changes, even affecting the handling balance and weight transfer.
Great care needs to be taken when changing suspension location points.
I am not even sure which way I want to go now.
I may need to look at RCH changes next.
Last edited by leigh1322; Mar 15, 2026 at 05:48 PM.
Leigh, this will mess with your mind - it did mine. Pretty famous car with a good track record. BUT, notice the inner control arm mounts are spaced down, which puts the pivot point well below the ball joint. This should create a very low roll center (below ground) and hurt camber gain with compression. I can't figure out what they were trying to accomplish. But I wanted you to see the drag link. It is lowered significantly, which keeps the tie rod angle in line with that of the lower control arm. What are your thoughts?
Wow.
Cool car, and mod.
Suspension design and intended compromises have changed dramatically from the "old" days.
In the old days they used to adjust the RCH a lot, as if it were a major tuning tool.
The big problem with doing that is changing any a-arm pivot location causes a domino list of changes in the suspension.
I have not seen this particular mod very often, because it causes a strong jacking effect pulling the car down in a turn, since the lower a arm is not near level.
And yes then they had to lower the inner tie rod links a lot to fix the bump steer. Looks to me like they just lined it up with the a arm.
The Shelby Mustangs and the Sunoco Donohue Camaro both changed their upper a arm mounting locations, for similar effect.
I'm looking into that now to see if I want to deviate from stock.
On our C3s, we can change both the fr & rr RCH by relocating the inner rear strut rod pivot, or the fr upper out ball joint length.
But I have also driven some very ill handling autocross cars over the years, where the guy applied "every trick in the book", and it did not work out well.
So the real question is, do I want to change the RCH height?
What are the upsides and downsides?
Wow.
Cool car, and mod.
Suspension design and intended compromises have changed dramatically from the "old" days.
In the old days they used to adjust the RCH a lot, as if it were a major tuning tool.
The big problem with doing that is changing any a-arm pivot location causes a domino list of changes in the suspension.
I have not seen this particular mod very often, because it causes a strong jacking effect pulling the car down in a turn, since the lower a arm is not near level.
And yes then they had to lower the inner tie rod links a lot to fix the bump steer. Looks to me like they just lined it up with the a arm.
The Shelby Mustangs and the Sunoco Donohue Camaro both changed their upper a arm mounting locations, for similar effect.
I'm looking into that now to see if I want to deviate from stock.
On our C3s, we can change both the fr & rr RCH by relocating the inner rear strut rod pivot, or the fr upper out ball joint length.
But I have also driven some very ill handling autocross cars over the years, where the guy applied "every trick in the book", and it did not work out well.
So the real question is, do I want to change the RCH height?
What are the upsides and downsides?
I tend to change RCH as a tuning aid. I also attempt to keep the instant center length as long as possible to slow down RCH migration with travel. I agree that changing pickup points has a lot of effects on other suspension geometry aspects (camber gain, bump steer, etc.), so I tend to overcompensate by making everything adjustable. On my last couple of track cars I use slugs on every pick-up point so I can change RCH, anti-dive, caster gain, camber gain, bump steer, and Ackermann. Set-up is always interesting. Lowering the inboard pickup of the UCA to increase camber gain was an often used trick as you describe, especially in earlier Corvettes. The only downside is that it can affect braking due to the negative camber of both wheels under compression, and while it improves camber on the outside tire in a turn, it has a negative affect on the inside tire. I prefer to increase caster - and caster gain by changing the horizontal angles of the UCA and/or LCA - so my camber gain comes in when the wheels are turned and not in straight line compression (braking). Another advantage of using the caster to create camber changes is that it increases outside tire negative camber in a turn AND decreases the negative camber on the inside tire, which is a good thing. Here are photos of some of the adjustable areas I have on one of my latest projects.
Installed my SPC arms.
They do allow easy adjustment of both caster and camber.
They also have a 1/2" taller upper ball joint.
That is supposed to improve the camber curve.
But it may also alter the bump steer curve.
SPC arms
These look pretty rugged and up to date. Other than what looks to be improved clearance, is there any reason I might want to change out the original SPC design? I have the longer ball joints too. I had them installed when I did my original bump steer check. No way near what you did here but good enough for me at the time!
The race may be on to see who gets their set first.
What isn’t fair, is you’ll have the inside scoop for when they will be available and I bet there could be a discount headed your way.
I’ll have to wait until they are available to the public and go back to eating beans just so I can save the money for a set.
