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If MacPherson strut rod bends, what about the strut tower... does it also bend?

531 views 9 replies 5 participants last post by  The BTR  
#1 ·
2009 SES Sedan w 171,000 miles. I'm curious. If one were to hit the curb with the left front wheel while making a right turn (which I did), and it resulted in the following:

  • LCA being bent slightly rearward
  • MacPherson strut being misaligned inward and rearward

then what is the chance that the strut tower (i.e., the "cup" where the MacPherson strut attaches to the frame) can be bent?

Looking at the "cup" in the engine bay, it doesn't look like the steel is very thick. Thus, I'm wondering how "strong" the cup actually is. I wonder... is the cup strong enough to not bend but allow the strut rod to bend? I know strut rods do bend, but I'm curious if the "cup" also bends.

Please advise. Many thanks.
 
#3 ·
Depends on how much defelction happened. Are you sure the strut rod is bent? The macpherson strut system is designed to absorb some flexing at the strut mount; due to how the angles change when you turn the wheel and the suspension travels up and down.
The strut rod is not directly connected to the unibody via a steel plate, but via the strut mount, which is a sort of rubber bushing that is designed to take some deflection.
 
#4 ·
@Merv - Thanks for replying. To clarify... the strut rod is not bent... the strut housing is not bent... the steering knuckle is not bent... the strut tower appears to not be bent, but due to the way it's shaped (rounded like a cup), it's hard to tell if there's actually a small amount of bend in it.
The LCA is bent back, which is making the steering knuckle and strut be too far back and too far in. My suspicion is... when I remove the bent LCA, the steering knuckle and strut will want to move back to their original positions (more forward and more out). The desire to move forward and out (toward their original positions) will be driven by the unbent strut tower. This is my theory. We'll see.
 
#5 ·
Follow up:

I can now answer the question I previously posed, i.e., "What's the chance that the strut tower (i.e., the "cup" where the MacPherson strut attaches to the frame) can be bent?"

My curb-collision bent the LCA back (toward the rear), which resulted in the strut being angled farther back than normal. None of the other components were bent. Thus, I wondered if the strut tower was bent. The tower looked like it wasn't bent, but it's hard to tell due to its "cup" shape. I also wondered how hard it would be to get the strut to move forward... back into its original position.

After removing the bent LCA, it became clear that the strut CAN be moved quite a bit forward and backward without bending the strut tower. Thus, it was easy to move the strut-knuckle assembly forward in order to align it with the new LCA. The collision, nor moving the strut forward into its original position, bent the strut tower. Thus, apparently, significant misalignment of the strut is required in order to bend the strut tower.
 
#7 ·
The strut rod coming out of strut often bends inside the strut outer casing and often can look dead straight. You have to take spring off and plunge the, rod in and out to see the damage. If LCA took a hit then almost impossible for rod to not be bent, the tire deflects in and back to do it while using the ball joint as a leverage point and the rod and outer tie take most of that hit so tie rod likely messed up too. As force increases the ball joint pivot point then begins to deform the LCA.

EVERYTHING there can bend given enough force but tie and strut rod almost always go first in a lower force accident, then LCA comes next. The upper strut tower will deform at some point but not at the top, usually the entire thing begins to move in to centerline and opens up space where it attaches at the lower front frame rail, you will see gaps begin to open up between the spot welds there. At that higher force the top of strut tower bent back toward back of car is indicated by fender moving back to catch front edge of door.

If you get the K member involved you are talking a pretty serious hit.
 
#9 ·
Possible but unlikely, look at the cars in the junkyards. If LCA DIRECTLY impacted itself as the first object struck, maybe. As in curb impact where car jumps up to let curb ht LCA directly. The strut can be bent inside at rod and looks perfect to only show up as an alignment issue, you needed to plunge the rod to check if it was still straight. Spring has to be off to do that.

I have personally struck another car at 35 mph and out of line so that only the outer 15 inches or so was in line to impact other car straight on and impact force just missed the inside front frame rail and the LCA was perfect and no alignment needed at all after changing strut and tie rod end. The driver side strut tower is now about 1/4"-1/2" further back than pass side bu car runs perfect and handles fine even in skid conditions. I did perform some tricks to get caster back even with other side like that and the fender to door, bumper cover, and hood fit was fun too but fine when I finished. Car used like that since '08.
 
#10 ·
Here's a picture of my bent-backwards driver-side LCA. Look closely at the curved part of the LCA that's circled in red. You'll see a slight "buckle" that signifies that the outside portion of the LCA bent backwards when I hit the curb.

Image