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That shows the Guldstrand bump steer blocks from 40 years ago. Similar blocks are available from Duntov, already installed on arms, and at great expense:
These move the steering pivot point both downward and inward. The inward movement will change the Ackermann angle. I don't know if this is a good thing for C3s, or not. I would think that moving it inward would be good for autocrossing. Moving it outward might be better for certain road racing. This is why I ask.
The VanSteel solution moves the pivot point down without changing the Ackermann angle. Allegedly this is an improvement, but perhaps not worth it for a street car.
I'm thinking a hybrid solution might be the best, if I can find a cheap source of the Ackermann blocks, and adjustable-length tie rod ends (or make something with heim joints and spacers).
The VB&P kit I got looks like the Guldstrand kit. Probably that's where they got it. I plotted before and after while my chassis was up in the air without any springs or dampening. Here's what I got.
You can surely guess which line is from installation of the kit. I don't now remember what the 6-3/4 means. Likely I was smarter 10 years ago.
The Guldstrand bump steer blocks do also adjust the Ackerman angle, as they move the tie rod end inside about 1/2".
You might notice that on a race car, but I doubt you could on the street. It changes the angle of the two tires to better correspond to the angle of the turn. In essence it works for only one turn radius. You get understeer in others, which increases tire drag, and wear, and could show up on your lap time.
The drag reduction alone is worth it on a race car, to get it correct. On a street car it's worthless.
There are far easier ways to adjust understeer. And these require drilling the steering arms, so you can never go back. And you better safety wire them to ensure they do not come loose. Too many issues for me for the street.
The bump steer adjust portion however is something you can really feel. The tire rods need to be moved downward to prevent toe-in from changing on a bump or on the brakes. If you get toe-out on the brakes hard, it gets squirelly. If you get toe-in you have extra drag. If only one tire changes toe-in due to hitting a one wheel bump, the car steers right or left and that you can feel at any speed. That's the part that is well worth it to fix for the street.
I have measured the front bump steer, and it is pretty bad. Plenty enough to notice.
The bump steer/ackerman blocks only drops the tie rod one set amount, and it might be closer but will not get it right. You still need the vertical adjusters. Duntov used to sell the blocks separate if you want to go that way. Don't see that option now. But I do see they have added the Howe adjustable toe links, good move.
The thing about the tie rod end height, is every car will need a different vertical adjustment to get the toe change as low as possible. Anything that affects the height of the steering arm, or the height of the drag link, will change the required adjuster height. That means Caster affects the adjuster height, and lowering the car affects it as well. Those blocks were designed for 1970s era race cars, with manual steering and 2.5 degrees caster. They will not be at the optimum height for a modern 4 or 5 or 6 degree caster setup, with possible different lowering than a 1975 race car.
The Van Steel kit basically offers the Howe (circle track) vertical toe adjusters. You can buy those at Howe for much less. But they have gobs of choices, too many.
For some reason VS puts the Howe toe adjusters on both ends of the toe link, which is silly. There is no need for a fore and aft adjustment on the inner link. A simple ball joint is all you really need there. Maybe it makes customers feel better.
I already have tubular front toe rods with ball joints on both ends and screw adjusters, so Dan at Van Steel helped me out and sent me just the outer "Howe" vertical toe adjusters. Great customer service! And much less expensive. He mentioned I may need to shorten my tube, I'll see when I get there.
I will also measure all the toe changes, at different ride heights, caster, and toe rod heights. For my own info, as well as to publish here.
I guess I did not take a pic when the box of parts arrived, but I got these two height adjuster ends, with a variety of spacers. for about $160. To add to my tubular toe in rods. They bolt on without any permanent drilling.
I think the 6-3/4's was so that I could calculate an angular difference. I have a notebook somewhere where I probably measured the distance from the steering arm to the white board and that's how I would have calculated angles. Don't recall one way or another if I bothered, but yes Leigh1322, you notice the difference on the street.
As to Ackerman, I tried and failed to find any discernible angular difference between left and right. I suppose it has to be designed in but I failed to measure it. Probably my ignorance in setup.
Add one thing here, I kept my original steering arms just in case of I don't know what and bought another to be drilled out for the bolts for the bump steer block. That's irreversible.
Thanks for the pictures I was having trouble figuring out how the two bolts fit in a single tie rod end hole!
There are similar heim end with spacers for GM A bodies using a taller spindle to address bump steer.
It seems the VanSteel solution gives most of the benefit, and is a lot easier to implement. Since I have two cars, and already have one set of tie-rod "turnbuckles", perhaps one kit would let me fix two cars.
Their original 13" disc kits for A bodies used a second Gen F body taller spindle(I think Global started using those tall spindle those years ago with just the GM calipers 11" standard spindles and 12" B car spindles)
I had more ability to change the length of the rack to get my ball joints to the imaginary line between the upper and lower A arm pivots.
But it gives you a better idea of the goal you are trying to achieve from a geometry perspective.
This is enough parts to do two outers.
Notice the left hand thread.
I would guess the inner ones would be right hand thread and would not work as an outer.
Van Steel pic from their instructions on their kit, Tapered stud slides into steering arm with no mods to hole. Reversible.
The other advantage is there is no loss of steering ratio, unlike the Guldstrand setup, which puts the tie rod in the middle of two holes. I think the Borgeson box gains some of that back so I am unsure what I ended up with. I might rethink my setup knowing this is available and that I have the original undrilled arms.
I couldn't find that "kit" on their site. Is it necessary to call them?
I used the VB&P kit also and have had no issues with it over 20 years now. Drilled out steering arm on drill press and used thread locking compound on the 1/2" bolts. I lowered my 76 to maximize the reduction in bump steer and I am very pleased with the outcome.
Increasing the Ackermann angle improved the performance on road courses as far as I could tell, but I don't have a direct comparison to show you. Made the car feel more sure footed in the turns.
Wow. 1-3/8" is a lot!
That would shorten the tie-rod significantly, and make it's arc much sharper.
It is possible that this new arc matches better with the a-arm's arc radius better, and if the two arcs are similar, the bump steer would be reduced for a longer duration during bump. It still would only be correct for one D-height and one caster setting.
Being a very skeptical scientist, and racer, I do not take any marketing claims at face value without data. I have seen far too many bogus claims.
I still do not like the idea of drilling my steering arms unnecessarily, without knowing the direct benefit.
I guess I will have to measure one of these myself and see how well it works.
Jason Staley above has achieved near zero bump steer for the first inch of bump.
Perhaps he is willing to share his caster setting and D-height?
Last edited by leigh1322; Jan 10, 2024 at 10:42 AM.
Best Solution for Bump Steer?
