Chevy Impala SS Forum banner
1 - 12 of 12 Posts

Discussion Starter · #1 ·
Hey guys,

I have been reading all of the front control arm info coming out and all of the available ball joint options.

So the question is, is there really a worthwhile difference to ugrading to the 5/8 or 11/16 BJ's or is it just the lust for the best of the best?

We are talking 2/16 inch difference here.

And before you say "depends on the driving style" I would add that it is for the average guy who drives his car alot and might go to a special event sometimes and autocross.


Discussion Starter · #2 ·
When I upgraded from the 9/16" to the 5/8" I considered doing the 11/16 but with a Spirited Daily Driver with Auto Crossing in mind I didn't think the 11/16" was that much better, plus the added 1/2" drop the 11/16" would have given the front end. I didn't want my car that low.. Just my $.02

Discussion Starter · #4 ·
Originally posted by 4SSD O2:
1/2" drop? What would be the specific reason for that?

The way it was explained to me was that the Ball Joint was slightly different in height plus the material removed from the spinle to let the shaft fit in ammounted to an approx 1/2" additional drop.

Discussion Starter · #5 ·
The reason I have for wanting 11/16" is that my Caprice is a "working" Police pursuit unit. I have a healthy fear of a frontend component failing during a high speed chase. If you lose a balljoint at 70 mph on a flat autocross track, you might get injured. Lose a balljoint at 130 mph on a highway and its OVER!

Is 11/16" overkill? I don't think overkill exists.


Discussion Starter · #6 ·
I had my Arms and Spindles modified for the 5/8" Balljoints because I wanted a beefier setup for Running Road-coarses and the Silverstate Classic, my lower control arm BJ Socket was reinforced for the mod so I feel that this is totally adequite.

I didn't want to lower my front end any more for everday dirveabilty and clearance issues with my Hotchkis Springs & Setup.

You could go with a 11/16" if it give you a warm & Fuzzy, but if I wanted to beef up my frontend any more it would be with the Tubular Control Arms and the 5/8" PST Heavy Duty Ball joints, those things "the Balls Joints" are BUILT, they are going on my 9c1 in a couple of weeks.

The Tubular arms by Rustic are Really nice pieces too. :D

Discussion Starter · #7 ·
My two bits based on working in the susp-collision industry.

I have seen many broken ball joint studs over the years.
Most are broken in a single catastrophic failure during a collision. The collision is always severe enough that the broken ball stud is the least of the worries and not the cause.

The other breakage causing crashes can most always be linked to the ball joint previously being bent in a previous impact.
The stud or fracture always shows fretting , an indicator of prior movement.
The only place I could see a larger than the 5/8 stud being an advantage would be to save a spindle after the taper was damaged or in competition where stopping after nailing someone or something might lose you a race.

PusuitSS I understand your feelings but I feel if you make ball joint torque checking part of your maintenance schedule 5/8 ball joints are not going to let you down.
Granted if you are in pursuit and need to keep going after hitting stuff hard maybe the 11/16 would afford you more insurance but studs usually break "right now" in the collision or miles down the road. If you are driving after a hit that hard there could be many parts at risk.

One other thing to consider. We all do upgrades to our cars but are there any legal issues for you in your line of work and the usage of your car, welding to lower control arms, fitting joints that are not designed for your car and reaming the spindles out to fit the tapers? (Which make them technically weaker due to less meat around the taper)
In my area welding on a lower control arm would be instant fail on an MVI.
I am not saying there is anything wrong with a properly modified or fabricated arm but you might have legal ramifications if there was an accident.
Just my thoughts,

Discussion Starter · #8 ·
I will admit that the 11/16 LBJ may be bigger than what's really "needed" for our cars. But I think the benefit of serviceability has merits. A LBJ is not something you swap out every 5,000 miles... but it's nice to know that you can remove/install the part without having to remove the arm. If there were threaded 9/16 and 5/8 LBJ available.... I'd offer those on the arms too for this reason.

Discussion Starter · #9 ·
Either of the press-in balljoints can be replaced without removing the arm using OTC 7039 ball joint service set or equivalent.
I looked into ball joint sizes a while back. Something many people don't realize is that the sizes that are commonly used to ID the ball joints (9/16", 5/8" and 11/16") refer to the theread size of the nut, NOT the actual ball stud.
Since we are talking about the balljoint breaking, the failure mode is called shear and resistance to failure depends directly on cross sectional area of the ball stud. Note that the area is proportional to radius squared.
Here are the major (larger end of the tapered hole) and minor diameters from Moog tech line for the 3 ball joints:


Note that these are diameters of the ball stud right at the spindle surface. The ball stud breaking due to hard impact is going to happen at the surface of the spindle or some distance away from the spindle surface. I have the ball stud dimesions further away from the spindle written written down somewhere, but I canot find them right now. I recall that the same trend shown above held.
Note that the 5/8" ball joint is only about 10% stronger than the 9/16" ball joint.
The 11/16" ball joint is 29% stronger than the 9/16" and 17% stronger than the 5/8".
I came to the following conclusions:
1) The 10% increase in area from 9/16" does not make the 5/8" balljoints an "upgrade" worth doing. ZIP, flame suit on!

2) The 29% increase for the K-727 would qualify as an upgrade, but it is not needed as long you inspect the balljoints periodiacally and you don't plan to hit curbs during the getaway.

Just like Gerry, I am convinced that failures ouside of accidents result from the ball stud flopping around in a spindle hole that has worn loose.
Even so, I still plan to eventually make tubular arms that allow me to use a taller spinle, bigger brakes and are longer for a few reasons one of which is to allow me to use ZR1 or other vette style wheels (cheap, large diam, good quality & not bad looking) with more backspacing, 11/16" ball joints, and maybe coil-overs also. Maybe one of these years...

Discussion Starter · #10 ·
That table is hard to read. When I typed it up I added spaces to make it line up, but they disappeared...
Ok, after a couple of more edits the table is a bit more readable.

Discussion Starter · #11 ·
I still plan to eventually make tubular arms that allow me to use a taller spinle, bigger brakes and are longer for a few reasons
Are you talking about making the upper and lowers longer? I done a set that are 0.5" longer than stock... I will be running them on the racecar to widen the stance. I don't have them mounted up and into the software to see what the camber curve will look like yet... but I'll keep you posted.

I mostly agree with you on your discussion of the LBJs. However, I'll make the following points.

>>>> Yes, the press-in BJ can be serviced on the car, but not easily. The thread-in is a much simpler operation.

>>>> I agree that shear is important, but as I understand it, the larger BJ's also have a longer service life. So strength on impact is not the only benefit of the "upgrade."

>>>> You are correct that the nomenclature commonly used... 9/16, 5/8 and 11/16... only reference the nut size. But I think most people know this (or they should). And although they are not "accurate" for the stud size, they are a good representation of the increase in size and strength and correlates pretty well to the increase in shaft diameter.

That was a GREAT post by the way... I love to see it when people have really looked at the details of the matter. Are you an ISSCA member?? if so, would you consider writing an article for the Impala SScene on the data you have put together?

Discussion Starter · #12 ·
I agree with the convenience of the screw in ball joint. But the press is not that bad either considering that luckily it's not required as often as an oil change.
The reason I pointed out the ball stud vs. nut size difference is that many people use the nut size to gauge ball joint strength. Based on diameter the 5/8" would seem to be 23% bigger=23% stronger, which would be getting close to safety upgrade territory and the 11/16" would seem to be 49% stronger than 9/16".
If the 5/8" balljoint signifficantly increases the wear life of the ball joint, then it is an upgrade from durability point of view. I don't have any idea how much longer the 5/8" typically lasts, (if any).
I'm not a member on ISSCA and unfortunately I probably would not have time to write anything formal. However, if anyone wants to use this stuff, feel free to do so.
Yes, I had wanted to make control arms that would be longer to bring the bearing hubs further out to allow me to use late model vette takeoff wheels
which would give me economical quality wheels that would fit a taller spindle and bigger brakes. I was also toying with the idea of getting some used fenders and going so long with the a-arms I would have to roll the fenders to increase track width. Perhaps change upper a-arm mounting location also. I didn't work out any of the details. However, taller spindle, wider track, etc. should not be too bad!
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.