Bump steer question

[72bluNblu]

Those 1.12 bars must make your front end stiffer than a wedding pecker.....hope not to offend, just a common technical term used in most hot rod shops

Not at all. Sure, it's much stiffer than a stock A-body (which are laughably soft and undersprung) but with a nice set of Hotchkis fox shocks the car feels just like a modern musclecar. For the street they're fine, I suspect if I started doing road course stuff with softer compound tires I might actually have to upgrade again.

 

[autoxcuda]

Those 1.12 bars must make your front end stiffer than a wedding pecker.....hope not to offend, just a common technical term used in most hot rod shops

I run 1.14” MP bars.

.81 MP drag bars are rated 90 lbs/in wheel rate
1.14 MP bars are rated 350 lbs/in wheel rate

I’m almost exactly 4 times as stiff as a drag bar. And think, there guys out there with 1.24” t-bars !

At 1” compression or rebound I’m about 1/32” bump steer

At 2” compression or rebound I’m about 1/16” bump steer

....Not bad

 

[72bluNblu]

I run 1.14” MP bars.

.81 MP drag bars are rated 90 lbs/in wheel rate
1.14 MP bars are rated 350 lbs/in wheel rate

I’m almost exactly 4 times as stiff as a drag bar. And think, there guys out there with 1.24” t-bars !

At 1” compression or rebound I’m about 1/32” bump steer

At 2” compression or rebound I’m about 1/16” bump steer

....Not bad

Not bad at all!!!

My 1.12's are "only" 300 lbs/in.

1.24? I've heard that some of the old track cars swapped their torsion bar anchors over to C-body anchors so they could run bars larger than 1.24". The A, B/E body hexes are 1.25" so the max diameter is 1.24". Some of the C-body cars had 1.41" hexes, so if you swapped to those anchors and pivots you could run a 1.4" bar.

 

[HemiDenny]

Not at all. Sure, it's much stiffer than a stock A-body (which are laughably soft and undersprung) but with a nice set of Hotchkis fox shocks the car feels just like a modern musclecar. For the street they're fine, I suspect if I started doing road course stuff with softer compound tires I might actually have to upgrade again.

your roads are glass compared to what we have in the rust belt. I've run the bigger bars....they rattled my teeth on the bumps. And Ohio is smooth compared to Michigan where the potholes can gobble a car up.

 

[72bluNblu]

your roads are glass compared to what we have in the rust belt. I've run the bigger bars....they rattled my teeth on the bumps. And Ohio is smooth compared to Michigan where the potholes can gobble a car up.

California roads are like glass ?!!

I will say I rarely disagree with your posts 100%, but that sir is total bullshit. Have you even driven in California? Because I've been to Michigan. And the roads here aren't better.

Consumer Affairs agrees, worst roads in the US? Michigan #10, California #11. And California has 2x as many miles in poor condition as Michigan does. Seems like that would be worse...
Worst Roads in America, Ranked | ConsumerAffairs

Business Insider says California is #7 for worst roads. Michigan? Didn't make the top 12.
Rhode Island has the United States' worst roads — here's how other states rank

American society of Civil Engineers ranked California 3rd worst in 2017. Michigan? Again, not on the list...
Infographic: The Worst Roads in the USA

 

[brian6pac]

In the stock car world we got the camber where ever we needed it for the track, got the caster where ever we needed it, and the toe and we always got 0 bump steer. We did it be shimming the outer tie rod up or down. It's not that hard if you do it alot like every race day, the car always got hit, jammed into the wall or something. You learn how to do it. So you guys that say it can't be done are wrong. It is a lot harder with tapered tie rod ends but with hiem joints its a lot easier.

 

[72bluNblu]

In the stock car world we got the camber where ever we needed it for the track, got the caster where ever we needed it, and the toe and we always got 0 bump steer. We did it be shimming the outer tie rod up or down. It's not that hard if you do it alot like every race day, the car always got hit, jammed into the wall or something. You learn how to do it. So you guys that say it can't be done are wrong. It is a lot harder with tapered tie rod ends but with hiem joints its a lot easier.

“In the race car world, where we tuned the car every time we drove it specifically for the exact track conditions we were going to have that day, and never drove the car for even two seconds on the street, we did stuff you’d never do on a car you were going to drive on a public road”

We’re not talking about stock cars bud. You even admitted you can’t exactly do what you just claimed with a standard tie rod end, which is what most of the cars here have including mine.

Be realistic. What you can achieve on a race car is a completely different ball game from what’s a good idea on a street car. And frankly, I’m talking about street cars and don’t give a single crap about race-only cars, whether they only go straight or only turn left.

 

[brian6pac]

My car has tapered tie rods and I achieved 0 toe.
I said it's just easier with hiem joints.
In post #22 he has hiem joints and can shim the inner and outer tie rods as needed to get 0 toe.
I'm not sure why you are fighting this, maybe because you can't do it ?

 

[HemiDenny]

In the stock car world we got the camber where ever we needed it for the track, got the caster where ever we needed it, and the toe and we always got 0 bump steer. We did it be shimming the outer tie rod up or down. It's not that hard if you do it alot like every race day, the car always got hit, jammed into the wall or something. You learn how to do it. So you guys that say it can't be done are wrong. It is a lot harder with tapered tie rod ends but with hiem joints its a lot easier.

Most of us are well aware of adjusting bump steer by spacing the outer tie rod up/down (and in/out) on the steering arm or changing u/p , in /out location of the inner tie rod., however, I think your zero bump steer was only in your mind, especially with the amount of travel a dirt cars suspension sees. The only way zero bump steer would be possible all the way thru suspension travel is if the three arcs (UCA, LCA, tie rod) all have the exact same length / radius.....and that, my friend , does not exist in our Mopar street cars.

 

[HemiDenny]

California roads are like glass ?!!

I will say I rarely disagree with your posts 100%, but that sir is total bullshit. Have you even driven in California? Because I've been to Michigan. And the roads here aren't better.

Consumer Affairs agrees, worst roads in the US? Michigan #10, California #11. And California has 2x as many miles in poor condition as Michigan does. Seems like that would be worse...
Worst Roads in America, Ranked | ConsumerAffairs

Business Insider says California is #7 for worst roads. Michigan? Didn't make the top 12.
Rhode Island has the United States' worst roads — here's how other states rank

American society of Civil Engineers ranked California 3rd worst in 2017. Michigan? Again, not on the list...
Infographic: The Worst Roads in the USA

I don't need a written report, I got one directly from my ***.....yes, I have driven both. The potholes on the Michigan interstates will yank the wheel right out of your hands.

The simple fact that California does not have the extreme temperature shift that the rust belt has means pavement, more importantly the base underneath does NOT shift around from the constant freezing and thawing like it does in Michigan. Then add the fact that more than a decade ago, Michigan voters removed their road taxes. Even the interstates were not maintained, yet alone the repair to any state or county roads.

Peace out, brother.

 

[HemiDenny]

My car has tapered tie rods and I achieved 0 toe.
I said it's just easier with hiem joints.
In post #22 he has hiem joints and can shim the inner and outer tie rods as needed to get 0 toe.
I'm not sure why you are fighting this, maybe because you can't do it ?

I understand the geometry. getting close, improving is a no brainer....zero thru the entire suspension travel with three different arcs is almost..... mission impossible.

 

[autoxcuda]

My car has tapered tie rods and I achieved 0 toe.
I said it's just easier with hiem joints.
In post #22 he has hiem joints and can shim the inner and outer tie rods as needed to get 0 toe.
I'm not sure why you are fighting this, maybe because you can't do it ?

In my situation I needed to move the outer up or inner down. Both those changes move the tie rod end downward on the stud.

Problem was there was no adjustment left on the stud that direction. I’m already at the bottom of the stud.



Yes, I could keep going and get more adjustment. Shim the steering box and slot the idler is one way.

This happened in our circle track car sometimes we had an adjustable Joes centerlink. So we could move the whole centerlink up or down to give all kinds of adjustment range. Then there’s adjustable idlers. And it was a fab clip so things were manipulated from the start.

I was close and I quit. Because I planned on other repairs and changes. Those would likely change the bump steer and I’d have to start again.

Need/want to change:
Spherical rod ends
Ball Bearing insert idler
Borgensen steering box
Steering box Sector support kit (shouldn’t have an effect)

 

[gm1236]

I bought a longacre gauge and tried it out today. I’m either doing something wrong or I have an issue. Here’s my findings. Seems pretty basic but maybe I’m buggered up.

- Passenger
- Compression.

.5” .055.
1”. .090.
1.5” .115.
2.0” .150

Drivers
- compression.

.5” .050.
1” .095.
1.5” .110.
2” .200[/QUOTE

Looks like this thread got away from the original topic. My experience is only on drag cars. Once you have the caster/camber where you want it, then you need to move the tie rod ends up or down to get the pivots arcs the same. I made a bump steer kit from part sold by speedway. I used Heim joints, adjusting tubes and studs that match the angle of the tie rod ends. They sell shims or you can use nuts to adjust the height. I’ll post a picture tomorrow. There is a lot of trial and error to correct this, measure make an adjustment and measure again to see the affect. Do one side at a time, unbolt the shocks and back off the t bars so you can get full travel. One tip is to take a measurement of the center of the spindle at the ride height before you take everything apart. I use the wheel well lip directly above the spindle as a reference point. It almost impossible, but if you get the arc right, you’ll have the same amount of change at the same amount of travel above and below this centerline. So say you have 0 at center and -.02 2” above and -.02 below you have the arc centered. These numbers are just for an example. Expect each side of the car to be different. Once you have both sides bumpsteer corrected you can then set the overall toe. I still don’t have mine right, but good enough.

 

[gm1236]

I’m not sure what I did, but if you click to expand you’ll see my reply in the above post.

 

[autoxcuda]

One tip is to take a measurement of the center of the spindle at the ride height before you take everything apart. I use the wheel well lip directly above the spindle as a reference point

Excellent tip!

It took some fiddling around for me until I realized that had to happen first.

I actual left the shock on, but unloaded the torsion bar by backing off the adjustment bolt. I did carefully measure and record the number of turns it took to back off the bolt.

I moved everything up and down with a jack. It gave me precise control and the shock kept things partially loaded.

I use a white grease pencil to write those measurements on the car. Ride height measurements on fender and torsion bar measure on the LCA.

 

[gm1236]

Excellent tip!

It took some fiddling around for me until I realized that had to happen first.

I actual left the shock on, but unloaded the torsion bar by backing off the adjustment bolt. I did carefully measure and record the number of turns it took to back off the bolt.

I moved everything up and down with a jack. It gave me precise control and the shock kept things partially loaded.

I use a white grease pencil to write those measurements on the car. Ride height measurements on fender and torsion bar measure on the LCA.

My bump steer set up looks just like yours, but instead of bolts They sell a stud, 5/8 threads 3” long and has the taper on it so you don’t have to drill out the steering arms, just bolt it in.

 

[autoxcuda]

View attachment 1715533486
My bump steer set up looks just like yours, but instead of bolts They sell a stud, 5/8 threads 3” long and has the taper on it so you don’t have to drill out the steering arms, just bolt it in.

The hotchkis setup has studs with taper on one end. Similar to yours. Commonly bought at Circle Track supply places.

I see you are running the 67-72 centerlink. Don’t know if that changes then inner tie rod pivot location slightly.

Just some thin shins can make the small adjustments needed. So many variables compounded in aftermarket parts, custom parts, factory k-members and factory frames...no two cars will be absolutely alike. We’re trying to dial something down 0.050, less than 1/16”

There’s also a Howe brand tie rod end that is fully greasable ball joint with a all thread stud. You can drill out your tapers. Or I think someone offered a cone insert.

Here’s a path to find the spherical studs:

 

[72bluNblu]

Most of us are well aware of adjusting bump steer by spacing the outer tie rod up/down (and in/out) on the steering arm or changing u/p , in /out location of the inner tie rod., however, I think your zero bump steer was only in your mind, especially with the amount of travel a dirt cars suspension sees. The only way zero bump steer would be possible all the way thru suspension travel is if the three arcs (UCA, LCA, tie rod) all have the exact same length / radius.....and that, my friend , does not exist in our Mopar street cars.

Exactly sir, well put.

I don't need a written report, I got one directly from my ***.....yes, I have driven both. The potholes on the Michigan interstates will yank the wheel right out of your hands.

The simple fact that California does not have the extreme temperature shift that the rust belt has means pavement, more importantly the base underneath does NOT shift around from the constant freezing and thawing like it does in Michigan. Then add the fact that more than a decade ago, Michigan voters removed their road taxes. Even the interstates were not maintained, yet alone the repair to any state or county roads.

Peace out, brother.

I've been to Detroit in the spring, I wasn't blown away by how bad the roads were. Don't get me wrong, they were bad. But not worse than I'd seen before. Maybe Michigan has worse road than what's in Detroit, but I kinda doubt it.

The simple fact of the matter is there are A LOT of places in California that see more snow than Michigan, and have temperature shifts that are just as extreme if not more. California is a BIG place, and it's not all beaches. Seems like it's a common misconception outside of California that it doesn't get cold here, or doesn't snow that much. Well, that's BS. Tamarack, Ca actually has the record for the highest recorded snow depth in the US at 451". Some other US-wide snow records CA holds Here's How California's 6 Feet of Snow in 24 Hours Compares to Other Snowfall Extremes | The Weather Channel

I don't know where you've been, but I will say if you spent time in the richer/tourist-y places you probably found the roads pretty nice. If you went anywhere else, like over the summit on I80, then you'd probably have a different experience.

Remember bud, we ski AND surf in California. Peace out indeed!

I’m not sure what I did, but if you click to expand you’ll see my reply in the above post.

You inserted your comments in to the quote you added in your reply. If you go to edit your comment, just copy your reply and move it outside of the " [/QUOTE] " brackets. Happens all the time!

 

[HemiDenny]

Exactly sir, well put.

well....I got one out of two right.

Drove to Detroit a month ago....the potholes on I-75 will cause lane changes you were not planning on. We freeze / thaw in Ohio too which requires constant upkeep and rebuilding of the interstates. Difference in Ohio (and California) is we have been maintaining our roads all these years.....Michigan quit more than a decade ago due to their tax revolt. Just the way it is.

 

[brian6pac]

In my situation I needed to move the outer up or inner down. Both those changes move the tie rod end downward on the stud.

View attachment 1715532860

Problem was there was no adjustment left on the stud that direction. I’m already at the bottom of the stud.



Yes, I could keep going and get more adjustment. Shim the steering box and slot the idler is one way.

This happened in our circle track car sometimes we had an adjustable Joes centerlink. So we could move the whole centerlink up or down to give all kinds of adjustment range. Then there’s adjustable idlers. And it was a fab clip so things were manipulated from the start.

I was close and I quit. Because I planned on other repairs and changes. Those would likely change the bump steer and I’d have to start again.

Need/want to change:
Spherical rod ends
Ball Bearing insert idler
Borgensen steering box
Steering box Sector support kit (shouldn’t have an effect)

O.K. so you need to move the steering arm up.

 

[brian6pac]

Most of us are well aware of adjusting bump steer by spacing the outer tie rod up/down (and in/out) on the steering arm or changing u/p , in /out location of the inner tie rod., however, I think your zero bump steer was only in your mind, especially with the amount of travel a dirt cars suspension sees. The only way zero bump steer would be possible all the way thru suspension travel is if the three arcs (UCA, LCA, tie rod) all have the exact same length / radius.....and that, my friend , does not exist in our Mopar street cars.

Sorry if I did not specify the exact set up. I have modified steering arms, pinto rack out front, other than that it is stock. I have 3/4" bolts in the upper bumper to stop the drop so the car doesn't lift all the way through the travel but it only stops about 1" of drop. It has most of the travel and it has 0 toe change all the way.

 

[HemiDenny]

Sorry if I did not specify the exact set up. I have modified steering arms, pinto rack out front, other than that it is stock. I have 3/4" bolts in the upper bumper to stop the drop so the car doesn't lift all the way through the travel but it only stops about 1" of drop. It has most of the travel and it has 0 toe change all the way.

My guess is you did 2 things
1) mimicked the arc of the LCA with your the tie rod assembly which is good, but IMO, only part of the puzzle.
2) limited travel to minimize the bump steer thru normal (not limited) travel and with its limited suspension travel, you also eliminate / minimize the effects of camber change on the toe.....another piece of the puzzle.

Your set up sounds similar to the way the early 70 Pro Stocks w/ racks set up their race fronts....limited the travel to achieve minimum bump steer. Joe Pappas, who crewed on the 72-73 Mopar Missile Duster, told me they literally ran on the stops....about 1" of travel that was due to the deflection of the (then) rubber (shortened) stops. With rear steer spindles and steering arms swapped / modified, Ackerman sucked, but they were more concerned with straight line performance. They would spend a whole day on the front end addressing bump steer constantly making sure the wheels stayed as straight as possible.

Butch Leal told me he and Ron Butler would also spend a day to achieve very minimal (never zero) bump steer with their only way to keep the bump steer number low was to limit suspension travel to around 2" total.....they had to have some travel, Butch always had the nose in the air.

I just like to add to the discussion. If what you do works for you....I'm good with it.

 

[brian6pac]

I just learned back in the day that The 4 link cars and I should say ladder bar cars were going fast with out front end lift and that they were cabling down the front to stop the suspension from extending all the way. That stopped the upward motion and turned it into forward motion.

I read the mopar racing manual front to back in the early 80's and that is how I set up my car, I plotted the charts that I made many copy's of so I could draw lines on them.
It was definitely a project back then and It worked out well, the toe out in turns is off a little but it is real close, It was way off at first and that was fixed by moving the steering arms out. Now we were back to fixing the bump steer. After many hours it turned out right and It was a good learning experience.

Any one can do it if you learn the geometry of how it works and how to change it.

 

[HemiDenny]

I just learned back in the day that The 4 link cars and I should say ladder bar cars were going fast with out front end lift and that they were cabling down the front to stop the suspension from extending all the way. That stopped the upward motion and turned it into forward motion.

You have a very good point which makes me curious .....did the suspension get limited first to limit bump steer or was it for improving the motion forward. I know two guys that were there and I will ask both. Butch will give the short answer....Joe the long technical version.

looks like a two-fer to me.

 

[brian6pac]

It does toe in hard at the most drop with out the bolt stops just as it hits the bumpers, it hits the bolt stops about 1" less drop than hitting the rubber stops so it still has a lot of travel.