Ball joint question

Shocks, Springs, Brakes, Frame, Body Work, etc

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exhaustgases
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Ball joint question

Post by exhaustgases » Fri Dec 26, 2014 2:22 am

I saw a post on some other site about pull apart ball joints, I'm curious what others feel about them? These are joints that have all the sprung load pulling them out of the socket.

governor
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Re: Ball joint question

Post by governor » Fri Dec 26, 2014 1:04 pm

Never seen a sprung pull apart ball joint, but I use rebuild-able take apart Howe Racing ball joints that have no pre-load built in. There are some
other mfg of racing ball joints that you can also change the pin to repair when damaged or to change roll centers.

So what is your application? Hope this helps.

https://www.howeracing.com/p-7932-howe- ... -k727.aspx

Gov
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Brian P
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Re: Ball joint question

Post by Brian P » Fri Dec 26, 2014 5:30 pm

I believe I saw the same thread on the same other site. By "pull-apart" it means the lower control arm has the spring pushing it down, and the ball joint is in "tension" because the lower control arm is on the bottom of the knuckle so that the ball is "trying" to be pulled out of the socket by the normal loading. All I know is that lots and lots of upper-and-lower-arm front suspensions have been like that over the last several decades, which would suggest that as long as the various components are sized properly, it's not a big problem.

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Re: Ball joint question

Post by Krooser » Sun Dec 28, 2014 5:15 pm

A lower ball joint that positions the 'ball' above the spindle is commonly called a 'loaded' joint as it carries the weight of the front suspension. One that has the spindle above the joint is 'unloaded'. Many older GM cars used the 'loaded' type… Buick, Cadillac, etc.

Back when I attended both GM Training School and Hunter school in St. Louis (late 60's) there was a different term used but I'll be darned that I can remember it.
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Re: Ball joint question

Post by exhaustgases » Wed Dec 31, 2014 3:15 pm

The application was the older generation 1 LS400. I saw a picture of a newer one where they (the engineers) got smart and flipped the ball joint so the loading kept the ball in the socket.
"They done it like that for years" Problem there is, it doesn't always mean it is the correct way to do it. What I see is a lot less surface area having them be in pull apart mode. And since less metal is there to hold the weight on that area of the socket as well as the stud and the nut having all the weight and shock load, there is just not much safety margin if there is any sort of fatigue. If the ball is in the other position everything is plus plus, example was it is like installing a trailer hitch with the ball upside down! I'm sure a normal person would want that tongue weight holding the hitch on the ball and not trying to pull it off the ball! I know the Mercedes CLK430 has a funky lower ball joint that is at least loaded correctly, with McPherson strut systems the lower ball joint is not loaded and is basically an idler.

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Re: Ball joint question

Post by Olefud » Wed Jan 07, 2015 12:51 pm

Having the ball joint in "tension" rather than "compression" would not be good competition practice.

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Re: Ball joint question

Post by exhaustgases » Thu Jan 15, 2015 3:41 am

Olefud wrote:Having the ball joint in "tension" rather than "compression" would not be good competition practice.
What about good engineering practice?

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Re: Ball joint question

Post by Brian P » Fri Jan 16, 2015 6:11 pm

Olefud wrote:Having the ball joint in "tension" rather than "compression" would not be good competition practice.
Yet lots of cars, including lots of cars that are used in competition, have ball joints that way.

As long as the components are designed properly, it's not a problem.

How about the Chrysler/Dodge Viper ... https://images.search.yahoo.com/images/ ... mp=yhs-001

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Re: Ball joint question

Post by Brian P » Fri Jan 16, 2015 6:13 pm

Early Camaro:

Image

Dan Timberlake
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Re: Ball joint question

Post by Dan Timberlake » Sat Jan 17, 2015 2:44 pm

I think it falls into a category like redundant or fail safe design.
Given the choice, adding redundancy for free seems like an easy answer. Do it.
Some industries insist on redundancy.

Redundancy is about the only value of cotter pins, nylok nuts, loctite etc. Properly designed, installed and torqued fasteners don't loosen, and a cotter pin won't keep a badly designed or installed fastener from loosening. But if something goes wrong a cotter pin will keep the nut from leaving town for a wile and letting the tie rod end or airframe control linkage run wild.

If the other site was eng-tips I posted a bunch of pix of Hondas that had separated ball joints. The issue was separation due to extreme wear, not the strength of the stud or joint itself.
Not inspecting suspensions for wear is a root cause that //seems// like it could and should be avoided.
In a few instances ( one first hand) the car had been thru a state inspection within a few months of the failure. In those cases it is hard to say if the inspection was criminally sloppy, //OR// wear is not easily detectable with traditional methods. Jacking under the control arm is quick and easy and on those Hondas /should/ unload the lower ball joint to reveal looseness because the spring load is applied thru a clevis to the lower arm.

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Re: Ball joint question

Post by Ernie » Sat Feb 28, 2015 7:59 pm

Hello all,
Over the last 20+ years or so OEMs have been focussed on removing friction from joints in suspension and steering systems. This allows more consistent performance for damper and bush tuning by not having to factor in a wide range of joint friction outcomes.
With ball joints in particular this usually involves the incorporation of nylon or similar material as a bearing surface on the ball. Compare the friction of a modern mass market OEM joint to a 70's/80's joint and you get the idea.
Great idea and means the dynamics guys have one more way to deliver a more refined and better performing mousetrap.
Unfortunately, should the lubricant in a tension style joint become contaminated over time (spit rubber boot?), the road grit will quickly embed itself in the grease and erode the nylon bearing leaving unwanted clearance and a gritty paste creating more still more clearance.
Over time the nylon material may disappear leaving metal to metal contact. If this is not identified during routine maintenance service by a skilled technician the end result may be separation.
You will notice that very few OEMs now used ball joints in tension.

Larry

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Re: Ball joint question

Post by SLPRACINGENGINES » Tue Mar 03, 2015 11:54 am

i dont understand why or what benifit they would be from this..ive build racing chassis for 35 years.the lower the friction..the better you are..i may not be understanding the type suspension that you are dealing with.

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Re: Ball joint question

Post by exhaustgases » Wed Mar 11, 2015 4:21 pm

And then so, with so little surface area the in tension ball joints would of course wear out faster then? I think an all round bad design choice, agreed?

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Re: Ball joint question

Post by Olefud » Thu Mar 12, 2015 6:30 pm

Brian P wrote:Early Camaro:

Image
The load is carried on the lower BJ, i.e. in compression. The upper is for lateral location.

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Re: Ball joint question

Post by Dan Timberlake » Sat Mar 14, 2015 1:00 pm

In the Camaro example the ground pushes upward on the tire, then the wheel, then the axle.
The cr's weight pushed downward on the top of the spring, then the lower control arm.
The result is the lower ball joint "ball" stud is in tension, and the ball is forever trying to wear it's way out of the ball joint socket.

Two examples in this image. IN one the tapered ball joint stud points upward. in the other it happens to point downward.
Attachments
ball joint load.gif

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