Rack and Pinion Steering

[christineman]

what is bump steer?

[DEEPNHOCK]

what is bump steer?

Definitions of Bump steer on the Web:

• Bump steer is the term for the tendency of a wheel to steer as it moves upwards into jounce. It is typically measured in degrees per metre or degrees per foot.
  en.wikipedia.org/wiki/Bump_steer
• The tendency of a vehicle to suddenly veer or swerve to one side when hitting a bump or dip in the road. The condition is caused by uneven toe changes that occur as a result of the steering linkage or rack not being parallel with the road surface. ...
  www.worksperformance.com/html/glossary_2.html
• Refers to changes in wheel alignment (toe, camber and caster) as the wheel moves through the suspension range. Wheel alignment is set with the car stationary, so bump steer affects must be properly considered to ensure that suspension movement does not cause adverse changes in handling or grip.
  fmgracing.com/racing101.php
• The tendency of the steering to veer suddenly in one direction when one or both of the front wheels strikes a bump.
  www.autozone.com/autozone/repairinfo/common/repairInfoMain.jsp
• A change in toe caused by the suspension moving up or down. Bump-steer is built into the geometry of the suspension and steering system, and occurs independently of inputs from the steering wheel. ...
  www.steeda.com/news/tech_articles/suspension_definitions.php

[PackardV8]

Thanks, Jeff, for the clear and concise search and summary.

Each of these definitions should begin with: "Bump steer is a very scary, often dangerous result of ill-considered steering system modifications."

jack vines

[PlainBrownR2]

I've had a couple of experiences on the Lark with bump steer, and this is an all stock suspension too. A few years ago we had part of our road all tore, so in a couple of spots we had transitions from all gravel to asphalt. The sections were left unattended long enough for the passing cars to where a couple of nice potholes in the gravel when it went to asphalt, and to add to the fun, they were on a gently banked curve, so it required a little turning of the steering wheel. Anyway, if I wasn't mindful of that spot, and I bounced through the potholes at road speed just right, the potholes would violently pitch the wheels and send the car all over lane. This was on a stock vehicle with stock suspension, if an individual isn't careful on the install, like it was mentioned, this situation could get amplified on a vehicle with a modified suspension.

[sbca96]

I could swear that I posted on this thread, but now I dont see it. At any rate
what would be VERY interesting to arrange (somehow) is a comparison test
between the "modernized" Studebaker front suspension head to head against
a rebuilt/upgraded (like Packard mentioned) stock setup. Basically putting
the debate to end by seeing just how much better the chop-n-weld modern
setup does when run through a Motor Trend/Car & Driver style road test. It
would be an educational experience for all. One would expect improvement
after dumping all that coin, but how much of it is only by comparison to being
totally clapped out from years of neglect and abuse? Will we see slalom
numbers that blow your mind with C4 bliss, or marginally better, or worse?

So .. lets find out? Who has a nicely done C4 or other type Studebaker that
they will put-up-or-shut-up against a nicely done "Packard-style" stocker? We
need comparable tire/rim packages and etc. Lets do it people ... its time for
the talkers to walk the walk.

Tom

[junior]

So .. lets find out? Who has a nicely done C4 or other type Studebaker that
they will put-up-or-shut-up against a nicely done "Packard-style" stocker? We
need comparable tire/rim packages and etc. Lets do it people ... its time for
the talkers to walk the walk.

Tom

Although this sounds like fun, how feasable is it...there are just too many variables to control, unless someone is willing to take their Stude with a perfect front suspension and steering system and cut it up to install a more up-to-date system. Even is someone was willing to do this, raw numbers and data do not tell the whole story...what about subjectivity issues such as ride harshness, tracking ability, steering feel etc, etc, etc. Add to this the problem of running in a controlled environment where the test was done at the same place, same weather conditions, humidity, road surface temp etc, etc, etc. Without addressing these issues, any 'winner' of this contest would always be challenged by the 'loser' based on the unfairness of too many variables not being controlled. Junior

[sbca96]

Obviously the two cars would have to meet up at the same location. If I'm not
mistaken, there are a few cars on this thread that have a modern suspension
grafted on. RoadRaceLark actually competes and has a stock configuration. I'd
put up my Avanti once I get it where I want it, but it goes back burner often. It
also stands to reason the two cars need to be simular models.

Tom

[Dan Timberlake]

Steering Rack travel - I just measured a Volvo 940 at ~ 7 inches at the steering arm tie rod end, full left to full right. Like most RWD Volvos they turn pretty sharp ( ~ 32 feet between curbs, 109 inch wheel base

Dan T

[ralt12]

You won't find any of the "modernized" cars with a comparable wheel/tire package.

[Jerry Forrester]

Steering Rack travel - I just measured a Volvo 940 at ~ 7 inches at the steering arm tie rod end, full left to full right. Like most RWD Volvos they turn pretty sharp ( ~ 32 feet between curbs, 109 inch wheel base

Dan T

That might work with 'Quick Arms' but if I remember correctly the original Studebaker tierods travel 8 inches.
I'll have to look for a deal on the Volvo rack. I wonder what kind of pressure they use, will they accept a GM pump?

[sbca96]

You won't find any of the "modernized" cars with a comparable wheel/tire package.

Why is that? Whats the point in putting a Corvette suspension on if you are
going to run 15 inch balloon tires after? I have 17 x 8 rims with 245/45R17
tires on my Avanti, this is the same size tire my 2004 GTO has. I have 13"
rotors up front, with two piston calipers from a 2004 Mustang Cobra. Once
I get back to the project, it will get the matching 11 inch rear discs. I plan
on going with the T-bow sway bars or equiv, Bilstein shocks all around, and
quick steer arms. I am tossing around a redesigned upper control arm. So
there's your rebuilt/upgraded Studebaker .. w/modern wheels .. one would
hope the modernizing guys are making use of their investment the same ...

I remember when I first put the 17" wheels on, I got ripped up one side and
down the other for ruining the car, and "baby buggy" wheels and quite a few
insulting emails from some Biggs posters. Now that many factory cars have
a 18 or 20 inch wheels ... those 17s are looking pretty tiny.

I wish I had gone 18s, they would clear the upper Zerk interference.

Tom

[Bob Andrews]

Gee, Tom, I was hoping you'd get interested in doing a R&P conversion on your Avanti. I know you'd figure it out right, do the job right, and give us a detailed, step-by-step 'How To' thread with lots of pictures

I'm still mulling this over, and keeping my eye and ear open for more info. I really want P/S since I learned decades ago with race cars that while it's not needed for regular driving, it's worth way more than gold when trouble happens. All you have to do is be in an oval track race with 25 others and have someone get into you or have to avoid a crash one time and you will understand the value! Imagine entering a turn at 125-150 MPH and someone tags your LR bumper and gets you sideways... you appreciate it VERY fast. Even the Supermodifieds I love- 467 fuel-injected, engine offset far left, 800+ HP, 1850 lbs, etc. run power steering.

Even for street use, PS makes driving much more enjoyable; and is handy in parking, accident avoidance, or correcting the fishtail you get from breaking the tires loose on that 2-3 or 3-4 upshift

I have a strong upper body, but Momma, not quite as much. I want her to not only enjoy driving, I want that added measure of safety- just as much as upgraded brakes, dual M/C, seat belts, etc. Happy and safe Momma= likewise for Poppa

[sbca96]

Gee, Tom, I was hoping you'd get interested in doing a R&P conversion on your Avanti. I know you'd figure it out right, do the job right, and give us a detailed, step-by-step 'How To' thread with lots of pictures

Thanks for the compliment Bob, some people have complained I post TOO
many pictures, but since a picture is with a thousand words, I have posted
millions of words .... I dont see the R&P in my future. I dont see the merit
in the cost, and due to a popped pressure line I have already gone through
my factory power steering (some of those million words).

There are many competitive cars out there still running "old" school setups
and one has to wonder how much better R&P REALLY is when its all done
and even done RIGHT. I think if some vendor could come up with a quick
ratio power box, that would be the holy grail. I contacted Flaming River a
few years ago, but they were not interested due to the low potential sales
(I dont blame them) .

What do you plan to use the car for when its done?

Thats really the question that needs to be addressed before any money is
spent, doing a Vette suspension, coil overs, R&P, panhard bar, watts link,
or ?? is cool, but for a car that is driven twice a year to a show : worth it?

Tom

[Mike Van Veghten]

For what it may be worth -

I've done the 90's Vette front suspension swap to my 60 Lark, 2dr wagon.

1. it's not easy.
2. it's not simple.
3. it STILL requires a "MODIFIED" (shortened) R&P unit to eliminate bump steer...! If this isn't done, the handling while conering WILL be terrible....

There is NO...easy way out on this subject.
As Jack says, many ove done this R&P swap, and they will swear by it, but the way they have done the work, it creates as much or more bump steer than a stock Stude. It's plain very simple geometry, lay it out on paper, you'll see what happens when you start mixing and (trying) to match parts that were NOT designed to work together...without...somewhat heavy modifications to major parts.

Funny thing "Bump Steer" is....most don't even recoginze it while driving..! Most just put around whiout really even "driving" their cars. So in THIS case...why even bother..!
Two of the most popular 60's cars had terrible bump steer from the factory...yet thet were very popular cars. One of the cars had a fix. The road racers of the time figured out that by doing a few heavy modifications, two things happened, the tires roll camber was improoved and the other change helped the bump steer.

Can you spell, find a geometry book.....! Or recall your high school geometry...take some suspension dimensions, lay it out on a piece of paper...this part ain't that difficult. Finding parts that will "properly" work together IS.

Mike

[ralt12]

Why is that? Whats the point in putting a Corvette suspension on if you are
going to run 15 inch balloon tires after? I have 17 x 8 rims with 245/45R17
tires on my Avanti, this is the same size tire my 2004 GTO has. I have 13"
rotors up front, with two piston calipers from a 2004 Mustang Cobra. Once
I get back to the project, it will get the matching 11 inch rear discs. I plan
on going with the T-bow sway bars or equiv, Bilstein shocks all around, and
quick steer arms. I am tossing around a redesigned upper control arm. So
there's your rebuilt/upgraded Studebaker .. w/modern wheels .. one would
hope the modernizing guys are making use of their investment the same ...

I remember when I first put the 17" wheels on, I got ripped up one side and
down the other for ruining the car, and "baby buggy" wheels and quite a few
insulting emails from some Biggs posters. Now that many factory cars have
a 18 or 20 inch wheels ... those 17s are looking pretty tiny.

I wish I had gone 18s, they would clear the upper Zerk interference.

Tom

This was Tom's response to my saying "You won't find any of the "modernized" cars with a comparable wheel/tire package.".

That's the point, Tom. Most cars that have mods aren't running 1953 wheels and tires, they're running much bigger tires, at least. So when someone says--

"So .. lets find out? Who has a nicely done C4 or other type Studebaker that
they will put-up-or-shut-up against a nicely done "Packard-style" stocker? We
need comparable tire/rim packages and etc. Lets do it people ... its time for
the talkers to walk the walk."

You say we need comparable tire/rim packages, but the new guys don't run them, or because of brake sizes, can't run them.
My car is in the paint shop, and when I finish with wiring , etc. I'll be happy to walk the walk.
Not a problem.