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]

Two other parts had to go through the chemical process, namely the hub and the dust cover. When I took Betsy's wheel bearing out, there was no dust cover! I believe that everybody on this site that reads this will know of other examples, but I've come to expect stuff like this on Betsy, because of the very poor service that so-called 'mechanics' have provided for her over the years. They have taken numerous short cuts (trying to be kind), so why not expect to find a dust cover missing here or there? After all, me, the customer wouldn't find out, normally ever, but at least a long time after the service was performed. Oh well. . .

But I can't stay mad when there is work to be done. Luckily, the knuckle I found in the auto cemetery had its dust cover, only this one was much more rusty than my nonexistent one would have been had it been there.

So, these two parts have now been through their Phosphoric Acid bath, followed by a rinse with Denatured Alcohol. These are the parts on the left of the following picture, Betsy's original hub and the junked dust cover:



The parts on the right are the hub and ball joint that came off the junkyard steering knuckle, and they have been processed to the same extent as the primary parts (Betsy's hub and the dust cover). The next photo shows the same parts, but turned over so you can see the undersides. I note that for this side of the hub, the side with the studs sticking up, I previously spent a lot of time die grinding (with buffing compound) on its surface, as well as the surface of the hubs circular rim. My die grinding had produced a polished look similar to that of the spindle of the hub. Quite nice it was. . . Now look at it:

At least there is no rust.



I've been tossing in a few other miscellaneous junk parts that I haven't yet thrown away, as simple experiments, to see what this solution is capable of doing, for good or bad. One bad thing I now clearly see is that this acid eats polished metal surfaces down to a dull metal finish. Don't know yet how much die grinding with abraisive polishing compound it will take to restore surfaces, such as the spindle of the hub where it penetrates the bearing, to their original mirror finish, if ever (as it has yet to be attempted).

The advert claims that another good use of this acid is to 'etch concrete'. If I am not mistaken, it is also etching the surface of the metal that it removes rust from. There is no doubt that it likes to eat oxidized iron (rust).