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

[Langing]

Picked up a 'new' steering knuckle at the local junkyard, pulled the wheel bearings, races and ball joints out of Betsy's old SN and the 'new' one and cleaned up the 'new SN so I could get a 'side-by-side' comparison of the parts.

Will share photos of the two steering knuckles. The darker one is Betsy's:



and from a different angle:



and still a different angle:



The BENT ear isn't obvious, is it?

So far I have only measured distances from the ears to a flat 'surface plate' (all I could find for that was the steel flat of my table saw). I was able to determine a difference in two measures, one from the closest point of each of the lower ears to the surface plate, and the other from the farthest point of each of the top ears to the surface plate. I have not yet attempted to measure the differences in angles of the mating surface planes. Here are the differences in the measures:

Lower ears:

0.0122047 inches or 12.2 thousandths of an inch difference in the lowest excursion of the bottom flat side of the lower ear and

Higher ears:

0.0551181102 inches or 55.1 thousandths of an inch difference in the highest excursion of the bottom flat side of the higher ear.

The differences are in opposite directions, meaning that the measured point on Betsy's lower ear is farther away from the surface plate, while it is the measured point on the upper ear on the 'new' knuckle that is farther away.

Ordered and have received most of the parts necessary to complete the job on both front wheels. New wheel bearings and seals, new ball joints, new tie-rod ends, new axle nuts, etc. Just when I was feeling like the light. . . the Tacoma, in a fit of jealous rage, coughed up a "Check Engine" MIL, code P0402 "Excess flow in EGR." That's a whole nother story.

QUESTION: I used a braided steel wire wheel in my angle grinder, which did a pretty good job of removing the rust, oil, dirt, and other crap from the 'new' steering knuckle in reasonable time. The photos show that I am getting close to bare metal on the new sn. While I am busy fixing the emissions system on the Tacoma, I would like to know how to remove the rest of the rust, and then what material I should use to coat the part with to preserve it from immediately rusting after putting Betsy back on the road.