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Author Topic:   Long ball joints on metric
dean_7585
Dirt Forum Racer

Total posts: 88
posted January 14, 2003 11:32 PM
I know that the longer upper and lower ball joints help roll center, but how do I know if I need them ? I'm building a new car and don't know if I should put them in now or use stock ??

powerglides
Dirt Full Roller

Total posts: 69
posted January 15, 2003 06:24 AM
Without measuring your roll center you don't know if long ball joints will help or hurt. That said, now would be a great time to check it. A 2 dimensional roll center program is a great help and fairly cheap. Just measure very carefully. I think on dirt the stock stuff works well and is easier to fix/replace. IMHO

d4490
Dirt Maniac

Total posts: 113
posted January 15, 2003 09:42 AM
I can help you figue out your roll center, for a small fee. LOL.

c21
Dirt Freak

Total posts: 346
posted January 15, 2003 10:52 AM
Unless you are willing to take the time to plot out your front suspension and correct your bumpsteer (or use a program as powerslides suggested), I would strongly advise against switching to taller balljoints (or different height spindles, etc.) unless ..... you are working with someone who has a good (verified) set-up to use.

The reasons are many: right off the bat, depending on other factors (frame height, etc.) you may create a less desireable RC location ..... but of greater concern is that you will disturb your Bumpsteer and ...taller balljoints (particularly uppers) bend much easier so your abilty to finish a race (after ANY contact)with a good set-up is diminished.

c21

Darcy
Dirt Full Roller

Total posts: 54
posted January 15, 2003 05:22 PM
i agree with c21 stay with the stock lenth ball joints we have tried the longer one and there is no advantage that my veiw

dean_7585
Dirt Forum Racer

Total posts: 88
posted January 16, 2003 12:41 AM
Stock it is !! Sounds like a lot of work.

Thanks !!!

DMS CEO
Dirt Freak

Total posts: 212
posted January 16, 2003 11:42 AM
I didnt have to change much and just used a good eye on changing mine...If you car feels as if it is skating put an upper balljoint for an 84 chevy pickup on the right front its inexpensive and easy to do. You may try cutting the center out of an old one and using the outside as a spacer between your bj and a-arm. That makes it keep its strength. Like I say, worked for me may not for you, and its cheap and easy.

[This message has been edited by DMS CEO (edited January 16, 2003).]

c21
Dirt Freak

Total posts: 346
posted January 16, 2003 01:51 PM
I wouldn't reccomend changing effective spindle height (using taller balljoints or spindles) without correcting bumpsteer, but...
... in any case if you use the tall uppers you should use the support collars that Harris sells ($7 each?). They go between the BJ and the spindle. They effectivly increase the length of the top tapered hole in the spindle providing much more support. They dont usually get damaged when the balljoint gets bent (can be reused many times).

c21

powerglides
Dirt Full Roller

Total posts: 69
posted January 17, 2003 06:48 AM
I just finished checking my roll center. On my car without tall ball joints on both the top and bottom the roll center is way to low it should be 2"-31/2" I'm using 79 chevy pickup on the top and bottom. if your top A-arm does not angle down towards the center of the frame (ball joint top at least 1 1/4"above top of pivot shaft) your roll center is probably off.

martnracn_91
Dirt Forum Racer

Total posts: 80
posted January 17, 2003 03:10 PM
I am a rookie at setups. How do you measure roll-center?

c21
Dirt Freak

Total posts: 346
posted January 17, 2003 05:39 PM
if you are really curious, you should invest in at least 1 of Steve Smith's books (almost all cover this, if you were to buy just 1 make it S192 if you were to buy 2 .... I would get S280 plus S192 if you drive a hobby or ... S280 plus S157 if you drive a superstreet or sportsman).

anyway, when most folks say "roll center" they are talking about front roll center unless otherwise specified so ... front roll center is a point that represents the imaginary point that the car's front suspension starts to pivot around as it rolls (I say starts only because the point changes as soon as the car begins to roll over).


To measure it (locate it) the most common method is to reduce your A arms to 2 dimensional lines (in front view). Where the lines for the A arms from a given side of the car converge is the "instant center". A line then is drawn from the instant center to the center of the tire patch for this same side (this line is sometimes called the "force line"). once you have created the force line for both sides, you will find the roll center is where the force lines intersect.

the location is expressed as the distance from ground level (and the horizontal distance from the cars centerline if off center).

sorry if that was hard to follow .... I'd buy a book.

c21

powerglides
Dirt Full Roller

Total posts: 69
posted January 21, 2003 10:41 AM
Update on roll center. I was measuring my upper a-arm inner pivot point WRONG :-(). With only the addition of 1985 chevy pickup lower ball joints my roll center is now at 2.780 I'm happy with that. I use 1985 camaro center link left tie rods,right inner tie rod. righ outer tie rod is 1980 monza. it improves bump steer.

DMS CEO
Dirt Freak

Total posts: 212
posted January 21, 2003 12:50 PM
I thought I was the only one, Powerglides. I dont guess I need to patent that do I...lol.

fast_crew
Dirt Roller

Total posts: 25
posted January 21, 2003 07:01 PM
powerglide what kind of chassis do you have, and what control arms and spindles are you using. also what kind of mods are needed to use those ball joints.

Thanks alot Josh K.

powerglides
Dirt Full Roller

Total posts: 69
posted January 22, 2003 06:33 AM
I run a 1984 Monte Carlo Chassis. Stock spindles and A-arms. In order to use the chevy pickup lowers (that is what the tall afcos are). the lower ball joint hole needs to be reamed out. I have found that the hand tapered reamer that K-D tool makes works great on the lowers @ 2" taper per foot. The KD# is 2044 mechanics reamer. I welded the lowers into the A-arms last season but this year I'm going to try the sleeves AFCO makes.

[This message has been edited by powerglides (edited January 22, 2003).]

c21
Dirt Freak

Total posts: 346
posted January 22, 2003 10:47 AM
I've bought those sleeves from a couple of sources ..... never seemed to work out. I think they may be intended as a spacer to aid in better welding, because all the ones I got were a slip fit, not a press fit.

A few years back, I ended up cutting the balljoint area (hole and 1/2" around) off of some 70 1/2ton lowers and welding them into Camaro lowers.

Later.....I machined up some weld in rings (had a shoulder and looked like the internally threaded weld-in rings made for the K727 scroo-in BJ's .... except, was machined to 1.970" I.D.) that worked out great ...... allowing changes at the track with one of those balljoint (c-clamp lookin) tools.


c21

If you really want to try some of those Afco rings .... private message me your address and I will send you a couple (no charge) still in the package.

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