It's come to my attention, as the day gets closer for my new KW's to be installed, that there is a potential issue with lowering the suspension, especially the front, that can cause issues with the ball joint on the A-arm being stressed too much and failing. Has anyone done anything about this such as substituting the standard A-arm to a 'Charlie Arm' or the like?Apparently there is a kit which allows you to change just the ball and pin part to a substantially beefier version while retaining the original A-arm? Any opinions? Fen, Rick, Big Dave et al.........................
Lowering suspension...any side effects?
- Thread starter 333pg333
- Start date
Dont go too extreme and you should be Ok, a pair of charley arms or similar is on my wishlist but I have been running lower (tech art springs then leda adjusted to similar height) without issue (70K+ miles on original (180k now) arms), Somewhere on rennlist there is a reccomended minimum height on standard arms but the post is at least 3 years old.
Tony
Tony
As I said on 968UK I intend to go Charlie Arms myself, but as with Tony I have had a lowered car for (in my case) 25,000 miles on the original arms and no problems so far.
I don't know of any kit that lets you mess with the standard arms aside those that are intended as a cheaper way to repair a worn joint. Personally I don't like the sound of them and I'd rather an unmolested standard arm than one that has had the joint replaced.
I don't know of any kit that lets you mess with the standard arms aside those that are intended as a cheaper way to repair a worn joint. Personally I don't like the sound of them and I'd rather an unmolested standard arm than one that has had the joint replaced.
There is a kit that has longer ball joints.
This has the effect of keeping the arms at the same height even though you have lowered the car.
if i remember right, its www.rennbay.com
under ball joint kits, 944, and its the geometry correction kit.
This has the effect of keeping the arms at the same height even though you have lowered the car.
if i remember right, its www.rennbay.com
under ball joint kits, 944, and its the geometry correction kit.
The main issues with lowering suspension beyond manufacturers tolerances is that it changes the roll centre which can induce bump steer and strange geometry changes under compression and when loaded in corners.
If you are stiffening the suspension at the same time you may not get into the regions of strange geometry.
If you are stiffening the suspension at the same time you may not get into the regions of strange geometry.
The other thing though is that if you go low enough the pin from the ball joint runs out of travel and binds on the edge of the socket on the arm itself bending the pin and/or fracturing the arm around the ball causing failure. The idea that my ball joint could very suddenly come apart is what drives me to want Charlie Arms or similar.
Here is some info Karl from Racers Edge has sent me. I would probably go these even though they may not look as good as the original 'Charlies' they are out of site:
"My A-arms are in stock and are made of tubular steel which I had to have custom extruded. The arms were computer designed and analyzed and then samples were mechanically tested to confirm the computer predictions. Where the factory arms will break with about 4800 lbs load, mine just start to yield at about 10000 lbs of load. The most important issue that my arms solve better than any other arms out there is the one of pin failure. The factory and all other aftermarket arms, including Charlie, just use a "pin", like a finger, that comes up out of the ball joint and goes into the bottom of the spindle. This "pin" is subjected to high loading and is otherwise unsupported, only the internal strength of the pin has to resist all the loading it is subjected to. My pin is different in that it is a stressed member. The way we accomplish this is that like the Charlie arm we drill the bottom of the spindle to 19 mm (as our pin is 19mm) but we also then tap the bottom of the spindle so the pin can be threaded into it. Then over the bottom of the pin we slip a separate spacer. The spacer is then located between the bottom of the spindle and the top of the spherical bearing. Then you slip the A-arm with bearing over the pin and then put a jetnut on the bottom of the pin. When you torque the bottom nut you are putting the pin in about 30000 lbs of tension. So this in essence is now a bolted joint with enough preload (stored energy) that no outside induced force from the wheel can overcome, so the pin is not subjected to bending loads like the factory and Charlie design. Another issue that we paid close attention to is geometry. Our arm replicates the factory arm geometry 100%. The Charlie product and maybe others took short cuts and made the arm in one plane in order to be easier to manufacture. I went to great lengths to make the pickup points be exactly in the same spot as the factory pickup points in 3-D space, something Charlie did not do.. So those are the positives,... the negative is that my arm is about 1 pound heavier each than the Charlie arm."
"My A-arms are in stock and are made of tubular steel which I had to have custom extruded. The arms were computer designed and analyzed and then samples were mechanically tested to confirm the computer predictions. Where the factory arms will break with about 4800 lbs load, mine just start to yield at about 10000 lbs of load. The most important issue that my arms solve better than any other arms out there is the one of pin failure. The factory and all other aftermarket arms, including Charlie, just use a "pin", like a finger, that comes up out of the ball joint and goes into the bottom of the spindle. This "pin" is subjected to high loading and is otherwise unsupported, only the internal strength of the pin has to resist all the loading it is subjected to. My pin is different in that it is a stressed member. The way we accomplish this is that like the Charlie arm we drill the bottom of the spindle to 19 mm (as our pin is 19mm) but we also then tap the bottom of the spindle so the pin can be threaded into it. Then over the bottom of the pin we slip a separate spacer. The spacer is then located between the bottom of the spindle and the top of the spherical bearing. Then you slip the A-arm with bearing over the pin and then put a jetnut on the bottom of the pin. When you torque the bottom nut you are putting the pin in about 30000 lbs of tension. So this in essence is now a bolted joint with enough preload (stored energy) that no outside induced force from the wheel can overcome, so the pin is not subjected to bending loads like the factory and Charlie design. Another issue that we paid close attention to is geometry. Our arm replicates the factory arm geometry 100%. The Charlie product and maybe others took short cuts and made the arm in one plane in order to be easier to manufacture. I went to great lengths to make the pickup points be exactly in the same spot as the factory pickup points in 3-D space, something Charlie did not do.. So those are the positives,... the negative is that my arm is about 1 pound heavier each than the Charlie arm."
Well the Charlie arms are much nicer looking but I've had a bit of advice from Karl at Racers Edge on a few things, all of it so far free of cost. So I am inclined so far to choose his model. He sells the Charlie arm as well so he's obviously gone to a bit of trouble to sort out what he feels is an inherent deficiency in the others. I will also post some of his advice to me on calculating spring rates on our cars with torsion bars. It's much more complex than you think.
Peter Empson
PCGB Member
I think I was told that the M030 wishbones were designed to be safer than standard parts when run at lower ride heights (although undoubtedly not as low as some of the aftermarket ones on offer). Can anyone confirm or deny this?
Best regards,
Peter
Best regards,
Peter
I think what you are say Thom is what I was going to post; the part number for the 968 and 944 arms are only the same because nowadays Porsche will only sell the 968 part as it fits the 944.
The 968 part now supercedes the 944 part which was different in detail as Thom describes.
The 968 part now supercedes the 944 part which was different in detail as Thom describes.
And as far as I new they weren't rebuildable?
So I've now put in my order for the RacersEdge A-arms with the 19mm ball joints and the spherical bushings along with a pair of billet hubs, plus adjustable drop links and solid rear sway bar mounts and rear banana solid bushings all to go with new KW's.
Oh, by the way if anyone is having trouble burning up some money, let me know as I am quite the expert!
So I've now put in my order for the RacersEdge A-arms with the 19mm ball joints and the spherical bushings along with a pair of billet hubs, plus adjustable drop links and solid rear sway bar mounts and rear banana solid bushings all to go with new KW's.
Oh, by the way if anyone is having trouble burning up some money, let me know as I am quite the expert!
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