Günther-C3

Hi all!
How can I determine, if I need a anti bump steer kit like VB&P provides?

Thanks, Günther

Golden

Put the car on stands, get the wishbones at the right height for normal running, measure the front wheel alignment, then lift the wheels and re-check.

You need to remove the springs so that you can get the wishbones to move freely.

Easy Mike

You can feel bump steer.

FWIW: most 68s had a stock damper to counter act bump steer, but GM discontinued it.

gcusmano74

The interesting thing about that kit is, it does not only change the bump steer. It changes the Ackerman angles; the toe-out on turns. The factory setup is very close to a parallel steer system; the toe-out on turns is very small. The bump steer kit moves the pivot point , where the tie rod end connects to the spindle, not only downward, but inward. This increases the angle at which the inside wheel turns into the turn (the toe-out). This will change the "feel" of the car when turning, as well as decreasing the toe changes when the wheels are straight ahead. So you are changing two things at the same time.
The factory race manual "Chevrolet Power" suggests the bump steer needs to be modified only on cars with a lowered suspension.
You pays yer money and you makes yer choice.

TheSkunkWorks

IMCO anyone who has gone to the trouble to properly lower a C2/C3 chassis should install the bumpsteer kit. The blocks aren't perfect, but net a substantial improvement from stock bumpsteer, nevertheless. And, yes, they also increase Ackerman, which has some pluses.

A while back Jason Staley went to the trouble of sharing the bumpsteer curves on his shark, before & after, if you want to search for it. Should you wish to measure it yourself...

http://www.longacreracing.com/articles/art.asp?artid=13

redvetracr

that is incorrect, bump steer is measured with a fixture and dial indicators.

Golden

Thank you for your pompous, self righteous correction, if you knew what you were talking about it would be something.

Bump steer is caused by the suspension not travelling in a parallel arc to the steering arm.

As such when the suspension deflects in induces a change in the tracking (toe).

This change can be measured with a dial gauge at the wheel or with wheel alignment equipment, you're doing the same thing but just using different units.

One of us is a suspension expert, I'll give you a clue, it's not you.

Mick71

Isn't that the truth! Been trying to adjust it out of my car with no luck so far...

redvetracr

really? who do you think has more wins in a C-3 vintage racer? me or you? while your at it do a search on "bump steer gauge" you might learn something.

redvetracr

read and learn the CORRECT way to measure bump steer, it`s done with a gauge.

http://www.longacreracing.com/articles/art.asp?artid=13

Golden

You've just shown your ignorance for a third time.

If you understood what you were measuring, you'd know that there are many ways of measuring bump steer, other than using a $250 gauge.

Have you not considered the foolishness of posting a link to the correct way to measure it when it's on the site of the retailer of said $250 gauge .

Bump steer is a calculation of basic geometry and as such can be measured with anything from a $50k laser system, to a $250 gauge to a piece of wood and a tape measure.

Before posting in a thread with the self righteous tone of a self appointed messiah, why don't you stop and consider the fact that; you might be wrong; there are people who know more than you; your tone is rude.

I'm afraid winning a few club races neither changes the laws of mathematics nor is a qualification in vehicle engineering.

7T3C3TTZ07

That's my understanding as well but there is always new procedures. The old bumpsteer procedures are described in the following threads.

http://forums.corvetteforum.com/c3-t...p-steer-s.html
http://forums.corvetteforum.com/c3-t...ump-steer.html

This bumpsteer procedure is not for the faint of heart but it is precise. If there is an easier, cheaper, better way as some suggest, please post the procedure and pictures similar to the old way (second thread) and the resulting graph of toe change versus vertical movement (first post). This way we Corvette enthusiasts can use either procedure.

scottyp99

Uh, oh, someone had the nerve,..............the unmitigated gall,..............the sheer temerity,..............to disagree with Golden!! What's he trying to do, get us all killed?!?!?!?


Scott

Günther-C3

Thank you guys for your informations and now I now, how important is to eliminate the bump steering.
Now I now, how to measure and determine bump steering but my last question is, how do I lower the outer tie rod?

Thanks, Günther

Golden

OMG, please stop and step away from the sheep like mentality of having to pay $250 to measure something.

Stop trusting what you're told by pretentious blowhards who have a high school shop class understanding of what they're doing and think for yourselves.

Consider what your doing, you're just measuring toe change as the suspension deflects from it's normal ride height position.

In the same way there are many ways to measure toe, there are also many ways to measure bump steer, all you're doing is measuring toe after a fixed amount of suspension deflection.


Unless you're going to build a complex CAD model, if you're going to shim the steering you're going to be doing it by trial and error so it really doesn't matter what units you use as long as your method is accurate and repeatable.



Just to clarify, this wasn't a disagreement, Mr 'I've won a few club races and therefore know more than Adrian Newey' shouted 'YOU'RE WRONG, YOU'RE WRONG, I'VE WON A FEW CLUB RACES, YOU'RE WRONG'.

A disagreement is when two people have a valid point of view and either opinion is potentially correct. What he said is, ironically, as he used the term, incorrect.

To put it another way, imagine hypothetically the OP had asked how to measure a piece of lumber.

I suggested he use a tape measure as he may already have one and understand how it works.

The Dale Earnhardt of historic racing shouts, 'YOU'RE TOTALLY WRONG, LUMBER CAN ONLY BE MEASURED WITH A NASA ENDORSED LASER' costing $250. To prove it he suggests I go to we-build-nasa-endorsed-lasers.com for a completely unbiased article about how lumber can only be measured with their $250 laser.

scottyp99

"A disagreement is when two people have a valid point of view and either opinion is potentially correct. What he said is, ironically, as he used the term, incorrect."


I'm afraid I'm going to have to disagree with this statement. If you say the sun is going to come up tomorrow, and I say it isn't, then we disagree. Even though you are right and I am wrong.

As for the rest of it, well, I am not disagreeing with you. I think you are absolutely right. But you don't have to be such an unpleasant, abrasive, petty, person.


Scott

stpman

The 2nd link the car has been corected to 0.010" bump steer (seen it with my own eyes) and the fixture was made with of the shelf materials and a good dial indicator

gcusmano74

The flip side of this all is, if one or both of the steering arms have been bent by any sort of chuckhole, collision, etc., the car will feel more squirrelly than you can imagine. There is quite a bit of adjustment available in the tie rod ends. With a bent steering arm, the static toe could be reset to spec, and the resulting bump steer will scare the $&#@ out of you. Make sure your steering arms aren't bent, first.

Golden

No we haven't disagreed, in your scenario, you're wrong. There is no grey area, no room for discussion, just plain wrong. A failure to agree relies on no one person being factually 100% correct. In both your hypothetical scenario and redvetracr's smug ignorant bump steer comments, one party is 100% correct and one 100% incorrect.


Imagine you're in your local gas station and someone from out of town asks where the best place to eat is.

You politely suggest a well priced diner with a good selection. As you finish giving directions so some loud-mouth rushes up and shouts...

"HE'S COMPLETELY WRONG! THERE'S ONLY ONE PLACE TO EAT, IT'S $250 A HEAD BUT IT'S YOUR ONLY OPTION, TRUST ME I KNOW FOR DEFINITE IT'S THE ONLY PLACE TO GET FOOD IN THIS TOWN, THIS GUY DOESN'T KNOW WHAT HE'S TALKING ABOUT".

Now do you not think this is unpleasant, abrasive and petty behaviour?

This is exactly what 'captain I've won a few club races' did.

Now if I choose to point out what a know-nothing fool he is, I feel after his rude, aggressive attack on me, I'm perfectly justified to point out that he's an ego maniac, who has not only been rude to me, but also mislead the OP, and any other forum member reading this thread with his shouted, half baked, inaccurate BS.

TheSkunkWorks

The blocks supplied in C2/C3 bumpsteer kits are by far the easiest way accomplish relocating the outer tie rod ends. FYI, your steering ratio will end up at ~18.9:1 with OEM/R box and typical bumpsteer blocks.