Disk brake basics -- removal
 

'89 Cherokee. The mission is to replace rotors and pads. Calipers themselves are fine.

Shop manual says use a big C-clamp to "bottom the piston in the cylinder bore." Neither this statement nor the accompanying photograph tell me what I'm actually doing here. I mimicked the photograph and tightened it but saw no rise in fluid or any other change. Then, none of my Allen wrenches exactly fit the caliper mounting pins. My best guess is I need 6.5mm since 6mm and 1/4" both tend to slip when torqued.

Of course, the Youtube videos are for newer models that are made differently.

My questions: What year did the brake caliper design change, so that I have a better chance of finding information that fits my '89? What size Allen wrench fits the caliper mounting pins? Is there a better description somewhere than in the Haynes manual, which I find confusing and inaccurate? Thank you.

Disk brake basics -- removal
 

You are just trying to push the piston back in enough to get the new pads over the rotor.

This suggests it has nothing to do with removal.

Check and make sure they aren't torx bolts. Some folks on jeep forum mentioned it could be t50 torx or even 8mm or 10mm hex head. Another poster mentioned having to buy a 3/8 Allen socket to do the work.

Once those are out the caliper should slide right off. The pads are held on by a type of tension clip. One goes down into the piston and the other onto the caliper "c". If the rotor isn't free a few bfh whacks should motivate it. :hammer: If still no joy use some penetration oils/PB blaster and try again.

If the whole combo won't fit back on because the piston is too compressed, open up the bleeder valve and use that c clamp to give some pressure. The excess fluid will exit via the valve. But I would think your initial clamping moved it all anyway.

Correct. The pads/caliper will pull right off after those bolts are out.

It ain't your fault. That's normal procedure for a Haynes manual. Waste of money.

Not to mention it doesn't give ideas on how to fix the 20 years of grime and rust. We have to get inventive to do work anymore. I've found much better information and solutions here than in that book. Good for specs though.

Disk brake basics -- removal
 

It's easier to just remove the cal on the resevoir. You don't have to bleed that way.