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Lower Control Arm NORMAL movement is what?
Posted 25 April 2008 - 06:30 AM
I was looking for some assistance. I have noticed that the lower control arm on my SVX moves FORWARD and BACKWARD when I pry on it with a crow bar. It doesn't move side to side or up and down just forward and backward. It moves less backward and more forward. Both side do the same movement.
So then I checked the lower arm on the Impreza and it does basically the same thing. It moves forwards and backwards.
On both cars it does not take much force to move the lower arm so I am thinking it was designed to move this way. I think it must have something to do with a smoother ride.
So now I am concerned about wheel alignment during heavy braking and heavy acceleration. During heavy braking and acceleration the lower control arms will move backwards andforwards.
I check the alignment with the lower moved backward as when the car brakes and there isn't much of a change but when the lower arm is moved forward it makes a very big change in the toe. This would be the case for heavy acceleration. More of an issue on the SVX then the Impreza or any higher horsepower Subaru if the arms are all made this way.
So I just wanted to know if anybody else know if this is normal motion for the lower control arms.
Take care of that Subaru,
Posted 25 April 2008 - 08:53 AM
Posted 25 April 2008 - 12:08 PM
Posted 25 April 2008 - 02:25 PM
I wasn't trying to say the forces precisely counteract because they don't and of course they change with speed and conditions. I'm just trying to say there's a certain amount of offset there. These kinds of things affect toe as well, and are why at least for a long time rwd cars ran a little toe-in and fwd cars ran a little toe-out. It's not necessarily that way any more.
Posted 09 May 2008 - 11:57 AM
I have been interested in this lower control movement to see how it affects the tire wear.
I have measured the toe when I rolled the front wheels onto a block of wood. I used a 2x4. I rolled backward so the 2x4 displaced the lower control arm forward. Then I measured the toe. I am surprised at how much the toe changed. I got 1/4 of inch diference from the front to the back of the rim.
So I am thinking that if I am always on the throttle the tires will be running with toe way over the limit.
I want to put a shim in between the control arm and frame to keep it from moving.
Would the STI have this same problem since it is horse power related?
Any comments are welcomed.
Posted 09 May 2008 - 03:04 PM
I replaced my rear control arm bushing with a whiteline alk. It's a stiffer urethane bushing that also alters the suspension geometry slightly for better front end grip while turning and accelerating.
I really noticed a difference in braking responsiveness and stability due to the added stiffness. It is a bit harsher when you hit expansion joints and whatnot.
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