twitchy steering

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Cravin'sCuda

Cravin'sCuda

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I have rebuilt the complete front end of my car -I'm using a 73+ front disc setup, used all Moog parts, edelbrock shocks, big block t-bars. I have had it aligned by supposed persons that know how, but driving it down the road and hitting any small grooves,ruts or inperfections in the road seem to make it go all over the place-no single hand steering. I dont know if this would be consider bump-steer. The car does have the quick ratio power steering which I think make it feel worse. Would this be an alignment issue or something else I'm missing?
 
Cravin'sCuda said:
I have rebuilt the complete front end of my car -I'm using a 73+ front disc setup, used all Moog parts, edelbrock shocks, big block t-bars. I have had it aligned by supposed persons that know how, but driving it down the road and hitting any small grooves,ruts or inperfections in the road seem to make it go all over the place-no single hand steering. I dont know if this would be consider bump-steer. The car does have the quick ratio power steering which I think make it feel worse. Would this be an alignment issue or something else I'm missing?
Click to expand...

Can't tell you exactly what's going on but here is some interesting reading.


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

What size tires are you running on the front? If they are the narrow "skinny" tires that is just normal. Another thing is running bias ply on the front and radials on the back will have ill effects. Have you talked to the guy who aligned it about the situation?
 
sounds like the wrong spec's were used,you should be able to get spec's from someone on here,6pakdemon2go should be able to help or redhot one of our newer members,he does all my front end alignment work
 
Cravin'sCuda said:
I have rebuilt the complete front end of my car -I'm using a 73+ front disc setup, used all Moog parts, edelbrock shocks, big block t-bars. I have had it aligned by supposed persons that know how, but driving it down the road and hitting any small grooves,ruts or inperfections in the road seem to make it go all over the place-no single hand steering. I dont know if this would be consider bump-steer. The car does have the quick ratio power steering which I think make it feel worse. Would this be an alignment issue or something else I'm missing?
Click to expand...

The factory spec probably isn't appropriate given the changes, not to mention modern tires.

Compared to the factory specs, you want it set to more positive caster (2.5, 3, 4 or more degrees), and a small amount of negative camber (0.5 degrees). You also want both sides the same.

You did replace the strut rod bushings, and install the big washers the correct side out?
 
I'm running 225/45/17 goodyear responsedge tires up front, I'll have to check the strut rod washers, I dont remember. I dont have the spec sheet anymore but I'll ask the other members for the specs and read the bump steer article. Thanks.
 
Just wondering how your car drives on a smooth road?

If your answer is that it drives good......then I would first.....

Re-Check all front end components, nuts, bolts etc. for tightness. Including the large bolts for the LBJ to spindle.

It does sound like a bump steer problem, but your front tires are quite wide (IMO) and could be causing this issue also. That's alot of meat w/ a very small sidewall tire. Do you have another set of wheels/tires that you can take a test drive with by any chance?

My 3 cents.........:read2:
 
6pk2goDemon said:
Just wondering how your car drives on a smooth road?

If your answer is that it drives good......then I would first.....

Re-Check all front end components, nuts, bolts etc. for tightness. Including the large bolts for the LBJ to spindle.

It does sound like a bump steer problem, but your front tires are quite wide (IMO) and could be causing this issue also. That's alot of meat w/ a very small sidewall tire. Do you have another set of wheels/tires that you can take a test drive with by any chance?

My 3 cents.........:read2:
Click to expand...


Bump Steer has to do with the inherenet suspension geometry. It's not from worn or incorrectly installed parts. You modify it by modifing suspension components and moving the geometry around. It's not something that get fixed with an alignment or fixing parts. The term bump steer gets frequently incorrectly used.

Every time a car is twitchy or loose it is NOT always Bump Steer. In a production car that doesn't have a custom spindles, complete front end, etc the twichy-ness is rarely going to be from real bad bump steer. There's is some other issue going on.

When you say you put on "Quick Ratio Steering" which one? The power steering kind with the longer pitman arm is 12.7:1 ratio. The manual steering type is a special gear steering box and it is 16:1 (same ratio as std power steering).

The combination of quicker steering, low profile tires, stiff shocks, slightly higer rate spring is going to translate more road feel and inperfections back to the driver. There's a trade off between Sporty handling and Cadilac ride.

Would be real helpful if you had the alignment specs. If they went with near 0 or negative caster that will add to the twitchy-ness especially with your mods.

A combination of a 12:7 ratio power steering setup, low profile tires, with zero caster would make for a twitchy deal. I know people that have restored many AAR/TA with the factory 12:7 ratio steering and actually don't like it and think it's twitchy.
 
A loose component on a front end will indeed cause a "feeling" like and best described as a "bump steer".

When dealing with a car that has had the geometry altered as the poster has mentioned, there are many scenarios that come into play.

The width of the front tires is also in question....IMO
 
being you haven't done anything radical to the front suspension it doesn't seem like a big problem with bump steer,more of a problem with not enough caster,sometimes when switching to the bigbolt pattern disc brakes it makes it hard to get the front end to desired caster settings and the use of offset upper control arm bushings may be needed,I'll get with jim(redhot) and see about getting him to post a reply to this,he's very familiar with the a body front ends and the big bolt conversion.
Cravin'sCuda said:
I have rebuilt the complete front end of my car -I'm using a 73+ front disc setup, used all Moog parts, edelbrock shocks, big block t-bars. I have had it aligned by supposed persons that know how, but driving it down the road and hitting any small grooves,ruts or inperfections in the road seem to make it go all over the place-no single hand steering. I dont know if this would be consider bump-steer. The car does have the quick ratio power steering which I think make it feel worse. Would this be an alignment issue or something else I'm missing?
Click to expand...
 
waggin said:
being you haven't done anything radical to the front suspension it doesn't seem like a big problem with bump steer,more of a problem with not enough caster,sometimes when switching to the bigbolt pattern disc brakes it makes it hard to get the front end to desired caster settings and the use of offset upper control arm bushings may be needed,I'll get with jim(redhot) and see about getting him to post a reply to this,he's very familiar with the a body front ends and the big bolt conversion.
Click to expand...

I agree, there's nothing too radical there. Just stock abody parts. Check the basics.

I've got big bolt pattern disk but I do have the offset bushings so I can get a lot of caster. I think you could still get 1-2 postive degress with a stock setup. My 68 Dart have BBP conversion and doesn't have offsets and gets 2.5 positive caster. The BBP has the same geometry so I don't know why it would be though to get caster.

Looking at his profile pictures he's running power steering. So if it's true quick ratio long pitman arm, that's 12.7:1 ratio. That's quick. Many new performance cars are 14:1. And he's got an aftermarket steering wheel that's smaller diameter than stock. Looks like a 15". That reduces leverage and give you a "feel" that it's even a quicker ratio.

Edit: if you put the longer pitman arm on, did you put the longer idler on too?
 
The car has the power steering set-up that someone else installed in its history. I'm not sure what ratio-but its approx 3.5 turns lock to lock. I searched every where for the alignment specs and could not find and I usually keep that stuff. I do not have the offset bushings. This weekend I'm going to go over the front end again to make sure I did not miss anything. I used the idler and pitman for a 68 barracuda as I changed the K frame to a 68. What specs would you guys recommend, Thanks for the help.
 
Cravin'sCuda said:
The car has the power steering set-up that someone else installed in its history. I'm not sure what ratio-but its approx 3.5 turns lock to lock. I searched every where for the alignment specs and could not find and I usually keep that stuff. I do not have the offset bushings. This weekend I'm going to go over the front end again to make sure I did not miss anything. I used the idler and pitman for a 68 barracuda as I changed the K frame to a 68. What specs would you guys recommend, Thanks for the help.
Click to expand...


3.5 lock to lock is the std power ratio.

The fast ratio power steering takes a longer pitman arm that is tricky to put in an a-body with 340 exhaust manifolds, but you can't use them with header.

.5 degrees negative camber
1/16" toe in
as much caster as posible up to 4 degrees positive

Those are pretty low profile tires.
 
Those are indeed low profile tires. One of the things I have run across over the year is that square shouldered tires are MUCH more sensitive to grooves in the roadway. With different tread widths fore and aft, there are two sets of tracks going down the street looking for longitudinal trenches and lines in the pavement for crawl up or follow.

Secondly, there is such a thing as too much negative caster. It's great for sharp turn in but it can make the front end hunt like a coon dog. It's not a reassuring feeling when you're cooking into a corner and wanting to kill a lot of speed before initiating the turn.

Any work done on the rear suspension? How are the bushings? To keep the axle consistently under the car consider using either a Panhard (track) bar or a transverse Watts link.
 
check your steering box adjustment, too tight it will fell twitchy, too loose and
car will wander on uneven roads.
 
If there is to much camber to begin with, it only gets worse when the suspension compresses and does the 'plastic cup' move with the tires. take two plastic cups and put them on an axle of some sort and roll it accross the table. now do the same without an axle and you will have a pretty good visual. Excessive camber makes the front (or rear for some) fight each other and dart all over the road.
 
I think 72 Demon meant "negative CAMBER" -- nobody is suggesting running negative CASTER (except the factory <g>, and then only a tiny increment).

If you don't know the alignment specs, just take it back to the place that did it and have them put it back on the rack and give you the printout (which they should have done in the first place). Then have them go with what autoxcuda said...
 
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