What`s the Deal with A arms?

February 21, 2014 — SCandC
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We get a LOT of calls asking about various different A arms and which one is “best”. We also get a LOT of calls from people who bought A arms without doing their homework and now have some alignment, travel and/ or fitment issues. So how do you know which A arms are “best” for your application? Read on.

For starters let`s get one thing straight, the A arms are the cart, not the horse. A arms don`t define the suspension geometry, they only connect the pickup points that do. That means no big geometry improvements or performance gains are possible by simply changing the stock arms out for aftermarket ones. There`s a lot of misleading advertising to the contrary but that doesn`t make it so. That is not to say that A arms aren`t important. Just try and drive the car without them. ;) I just want to make their purpose clear,for our applications they are a potential alignment aid but they are also part of the puzzle to fix geometry issues. Let me explain, if we do things to modify or correct the geometry on our cars it changes the locations of the critical pickup points of the suspension. As I mentioned before those points are connected to the chassis by the A arms. So if we make any meaningful changes in the geometry we must also change the A arms to match. This means changing the overall length, the offset fore/aft and the mounting angle of the ball joint plates to suit the new geometry, arcs of motion and travel. So without changing the A arms to new designs we really can`t correct the geometry.

Now it should be pretty easy to see that all A arms are NOT created equally and they are not at all interchangeable! I get a lot of calls from guys who bought a product or products to change the geometry and then bought “some tubular A arms” to use with them. Then they realize they can`t align the car, or the upper ball joints are almost out of travel already at ride height etc. etc. Bummer. Just because the arms look racy doesn`t mean they were designed to work with the new geometry that has been created. No matter what brand they are or how good the quality may be, if they weren`t designed with that geometry in mind they won`t fit or work properly. It`s like trying to run a flat tappet cam from a 1st Gen small block in an LS3. It`s a cam, it may even be a good high performance cam but it isn`t made to work with roller lifters or an LS block. There`s nothing wrong with the cam or the motor they just don`t work together.

Things get even more interesting with some of the super low cost “just as good as” A arms found in discount catalogs, auction sites and probably some bicycle flea makets.
Cue PT Barnum voice: Step right up ladies and gents, what we have here is a set of upper and lower tubular A arms for less than the normal cost of uppers alone. Hand crafted somewhere they won`t admit by “skilled craftsman” sitting in the dirt they`re just the thing to make your car handle like a dream and make your hair grow at the same time. Buy today and get a free bottle of Wonder Tonic!

You get the picture. C`mon, we`re all grown ups here right? We know there `s no such thing as a free lunch. If you pay for crap you will receive what you paid for. Most of the time these arms don`t fit properly, they are very poor quality, and cause frequent alignment issues. On top of that we have folks trying to use them with tall spindles or tall ball joints and thinking they`ll work just because they look “tooby”. Yeah, good luck with that. Now the guy has a big pile of cool looking parts that don`t work together and a car he can`t drive. Don`t be that guy.

To recap, A arms are necessary but they are not and cannot be a “magic bullet”. They compliment (or not) the suspension geometry of the car they do not define it. When doing suspension modifications it is very important to buy a cohesive package with geometry correction components and matching A arms together. Note that not all “packages” are matched components even when sold together. Hint: If a manufacturer is using the same A arms for geometry corrected packages and non geometry corrected packages, then one of them (usually the corrected one) is wrong. The same arms simply do not work well for both. If you`re putting your own “package” together do your suspension geometry mods first and then make sure you use A arms intended to be run with that particular modified geometry. Failure to do so will cause a lot of grief and likely cost much more money in the long run. Get parts that are all designed to work together and it`s a thing of beauty.