Originally Posted by bkspeedo
Anyone have an idea why this is done?
If you're going to play with arm sweep, remember that the sweep of the arm also changes the wheelbase and the toe. You should correct both of them to see the function of arm sweep without confusing yourself with excess toe out or a shorter wheelbase.
Quoted from a post by Nexxus Racing.
Ah yes, the mystery adjustment...
It's a very common adjustment on rubber, but lately it has been surfacing in some foam setups. The most plain way I like to view it is to say that sweeping the arms "out" will you more steering into a corner, and (the more uncommon) "in" will give you more steering out of a corner. Just like with everything else, that statement isn't set in stone.
Lots of things come into play when you change arm sweep. When you sweep the arms out...
- the wheelbase gets shortened (moving the front axle back), and the wheelbase will change slightly as the suspension is compressed
- more ackerman results because of the wheelbase change
- the angles of the universals change. On most cars, sweeping the front arms out will make the car less susceptible to "chatter" because at any input of steering throw, the universals will assume less of an angle. This is because the universal joint is moved towards the rear of the car while the front spool/diff stays where it is, and the steering block will be toe-in some from its original position to get the proper overall toe
- the arms will bind less against the hinge pins during hard cornering, which is considered a big deal to some pro drivers
- weight transfer...it seems like less weight is transfered to the front suspension overall, however a higher % of the weight that is transferred goes straight to the tires (resulting in more turn-in) because the slightly changing wheelbase is causing the front suspension to resist compressing.
- hmm...what did I miss?
When I sweep my arms out on my rubber tire setups, I like to adjust the front end for more ackerman to give the car a nice steering feel at both low and high speeds.