Right front steering knuckle caliper mounting bracket tabs bent Options

[Langing]

ADDED NOTE: I am not a trained auto mechanic; I try to DIY whatever I can to keep my 300,000 mile Celica happily running. Thanks to a wise comment below, I now see that making the statement 'my steering knuckle is bent' is oxymoronic on its face. The steering knuckle is made of cast iron and it is well known that cast iron does not bend (though exceptions exist). Cast iron acts more like a brick which cracks when a transverse force is placed between its two ends. Nonetheless, there exists a situation with my right front caliper mounting bracket, in conjunction with the disc, that causes it to seem very much like the mounting tabs on the steering knuckle are bent. I am seeking the true explanation for this (at least apparent) bending of a cast iron part. It would be great if some expert in front suspensions would stop by and explain my observations set out below, and pinpoint my problem. Until then, I dare not change the title of this topic; what cannot be is.

2nd ADDED NOTE: After much on-line research, I have been convinced that bending of the tabs (or ears) on steering knuckles is more common than most people believe, despite the fact that "cast iron doesn't bend." Not sure what that has to say about steering knuckle castings, or what exact metal they are made of, but evidently it does happen. See my posting near the end of this thread.

94 Celica ST Coup 1.8L Manual:

Installed a new rotor (measures 0.986"; manual specifies 0.984" maximum). Rotor run-out minimized; much less than maximum. The caliper mounting bracket bolt tabs/ears on my right front steering knuckle are slightly bent toward the rotor (worst is the lower tab; 3/32 inch; shown in following photo). This causes the caliper mounting bracket to be misaligned so much that it interferes with my new rotor.




It has severely scratched the last ¾ inch of the rotor (to the outer rim), during short test drives (less than 1000 feet). Of course it made a lot of noise, but it was the first time I had ever done a job like this and just wasn't aware of the severity of the problem.



What is the best way to fix this problem?

Should I attempt to bend the steering knuckle tabs? Is the steering knuckle a cast iron part? Should I die grind the proper alignment into the caliper mounting bracket surfaces where they meet the steering knuckle tabs? Should I buy and install a new steering knuckle; they cost around $200 and require a lot of work to install?

This post has been edited by Langing: Jun 1, 2014 - 4:44 PM

[njccmd2002]

If the rotor was bad, then it would wobble. I bet the braket or the ears are bad.

[Langing]

If the rotor was bad, then it would wobble. I bet the braket or the ears are bad.

Agree!

Bracket or ears is normally where I would expect to find the source of this problem. Trouble is. . . cast iron doesn't bend, and. . . I have worked on the bracket mating surfaces long enough to build up confidence that my cleaning/polishing them could be, but isn't the problem. It was when I tried to polish the worst mating surface to an angle that would bring the bracket install back into alignment that I realized that I was getting no where fast, and began to ask what else might be wrong? My first thought was that the ears were bent (then I proved that to myself by measuring from each ear to the rotor, and compared those measures with the left side). "Yep," I said to myself, "clearly, the dang ears are bent".

All of this is so confusing. It defies understanding (well. . . it defies mine).

My latest plan (when I have a working dial indicator) is to first start with the most basic and prove to myself that there is no run-out, or bearing back-lash at the hub/rotor, to establish a point of reference. But, even if perfectly aligned, I imagine that the hub/rotor could possibly be rotating (perfectly) in a plane that isn't correct with respect to the bracket, so that's next.

Tell me how to determine that the hub/rotor, when there is no run-out, is spinning in the exactly correct plane with respect to the bracket?

Is it possible that the wheel bearing was installed at some angle? And, if so, wouldn't that cause the tire to wear badly? Those tires have been on the vehicle for almost three years and the treads still aren't showing bad wear. Is there anything else in the suspension that might put the steering knuckle a bit off such that it causes an illusion that the steering knuckle ears were bent?

Finally, it is possible that the dial indicator I used when determining there was little to no run-out was giving flaky results (yesterday I sure thought it was erratic) so perhaps I really didn't have the run-out set properly from the get-go. But if that was the case, why did the rotor show absolutely no wobble when I rotated it many times while watching that spot where the inner edge of the rotor was almost touching the bracket after I had managed to set the mating surface of the bracket such that it was no longer interfering with the rotor?