Alright, so my buddy has an 89 Toyota 4runner with an 84 solid axle swap up front and dual transfer case setup with 4.7 upgraded gears. He had been at an offroading event, and on his way home [highway driving, 60mph] his RF wheel hub caught on fire. I was wondering what would cause this to happen?? -- if you take a look at the pictures, the caliper is missing a good chunk of metal.

Master cylinder was recently replaced and front calipers weren't bled.......**against my advice**

 

Looks like plain old wheel bearing failure may have cascaded into other issues. The brake pads don't seem to be excessively burnt.

You don't show the hub and rotor. It's my guess from what you have shown that the brakes were not the issue that got the ball rolling.

 

Any suggestions on how to avoid this sort of failure in the future?

Thanks for the quick response @millball

 

Stuff happens

Clean bearings, packed with hi-temp wheel bearing grease, then correctly adjusted. The other side may need attention too.

Can't believe that there wasn't warning noise or steering/braking abnormalities before total meltdown.

From the looks of your pics, that spindle may be scrap. Still like to see an image or two of the hub and rotor too.

 

 

Bearing just needs some grease right? Lol

 

stay out of water, do proper maintenance
I bet it was wobbly and loud prior to grenading
I agree about the spindle being recycle material

 

The caliper, rotor, and hub don't look like they got super hot, so I stick with 'not a brake problem'.

The spindle and axle stub sure don't look good.

 

Take a closer look at the caliper picture.. It's missing a good chunk of metal

 

Sure, the rotor ground it up after everything got sloppy. It's ruined, but it's probably not what started the problem.