Can the ball joints be replaced in these?
I know you can in the steel arms, just curious as I have the chance to buy a set for a very good price (considering they are $350 a pop new).
He has assured me that the ball joints are in great condition with no play, but I was thinking if you are going to have all that stuff apart might as well put as new stuff in as possible.
I was under the impression the whole arm should be replaced every few years due to the aluminum possibly getting metal fatique?
I think in a racing environment, I wouldn't think that would be necessary on a street car that will only see the occasional Auto-X/HPDE.
I just got all excited about getting 8 lbs of unsprung weight out the suspension since I'm running 17 x 8s.
Anyone?
The failure isn't from fatigue of the aluminum and is present on the steel arms as well. When running at higher stress levels (over-torqued installation, under torqued causing play, lowered car, stiffer springs, additional load caused by slicks etc...) the shaft of the inner balljoint shears off - usually causing a bit of damage and the browning of shorts sometimes accompanied by a huge crash.
The E30M3 aluminium arms and the steel beefier E36 M3 arms have non-replaceable ball-joints. If you have a milling machine and an AC TIG I'm sure you could do it... but then you could also make really sexy arms with rod-ends that sit in double-shear and never worry about it again.
I'm going to just start emailing you with my E30 questions since you seem to have all the answers!
What is this double shear you speak of? Obviously I don't have the skills to fabricate something like, but it sounds interesting nonetheless, I'd like to understand the concept.
Although I do have an uncontrollable desire to have carbon fiber control arms, but no skills to make them.
The current ball joints are in single shear... which is a fancy way of saying that they have a single point where failure can happen - the point where the sub-frame places 100% of its sheer load on the shaft. If that load were to be in double sheer... say the sub-frame had a box and instead of a ball-joint it used a rod-end that was inserted in the box... and a bolt passed thru the box, the rod end, then the other side of the box. The sheer load would be spread over the bolt effectively increasing the load it would take to "sheer" the bolt
I'm not sure if that is very clear... Caroll Smith's Tune to Win has a pretty good treatment of loads in sheer and tension (as well as a great deal of engineering explainations for the non-engineer).
Interesting. Thanks for the info!
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