97 TJ Disk Brakes

[TJSUPE]

Anyone know at what rotor thinkness you need to change out brake rotors??

I am changing my pads tonight and totally spaced on rotor maintenance. I am at 40,000 now, do you guys think I could just change out the pads without tending to the rotors. I know its hard to say without seeing them.

How often do you guys change rotors/ turn rotors?

[nagal]

Last time I changed my rotors was when I did the WJ Knuckle swap

I can lookup in the FSM when I get home to see what it says but I have always just eyed them. If they have any big/rough gouges or seemed warped I would just replace them. New rotors aren't that much more than having them turned.

I would think at 40k they should be fine.

[TJSUPE]

Thanks!!

They looked pretty good last time I checked, I just didnt have a measuring tool to really check.

[Dukes69]

On the rotor should be a cast number. that number is the thickness. The place that turns them should check to make sure they are within spec.

[Jerry Bransford]

Yep, look on the edge for the minimum allowable thickness.

[Chris_L]

As long as the rotors are still in good shape with no grooves they will be fine. You should NEVER turn rotors. If there bad, get new ones. Braking is bad enough on a jeep with larger tires, so you dont want to end up using thinner rotors.

[goodtimes]

Brake rotors should be turned EVERY time you put a new set of pads on them. The pads will not bed in properly if you don't turn them. The result is increased brake dust, loss of co-efficient of friction, reduced pad life, and increased pad vibration. But, you should NEVER run a rotor that is under the minimum thickness...as already mentioned, it is either cast into the rotor, or has been marked by a pinstamp of lazer etching machine. If it is rusted over and you cannot read it (it happens), anyone who turns them will have a book listing minimum thicknesses.

[mrblaine]

Brake rotors should be turned EVERY time you put a new set of pads on them. The pads will not bed in properly if you don't turn them. The result is increased brake dust, loss of co-efficient of friction, reduced pad life, and increased pad vibration. But, you should NEVER run a rotor that is under the minimum thickness...as already mentioned, it is either cast into the rotor, or has been marked by a pinstamp of lazer etching machine. If it is rusted over and you cannot read it (it happens), anyone who turns them will have a book listing minimum thicknesses.

When we sent out techs to the seminars put on by the brake suppliers, they came back stating that unless there were grooves, you should apply a non directional finish to the rotor surface and then bed the pads.

My job was to bed the pads. I've swapped out many sets of pads adhering to that wisdom on various vehicles and never had an issue with excessive anything except better braking.

From personal experience and knowing machinery, I'd likely not trust the average brake lathe full of chips and a less than experienced operator running it whose only function in the shop is to get parts out the door.

Given the average cost of premium rotors, my intense liking of a vehicle with good brakes, I'd consider replacing rotors each time I swapped pads if the old ones need turning.

I also know that the rotors on my Stupid Duty at less than 20,000 on them need replacing. The dealer would turn them under warranty, but could guarantee that that won't fix the problem. From that I'd gather that turning is a bandaid that will only solve a minority of issues.

[Jerry Bransford]

Few shops are equipped properly to turn composite rotors like came on your '97 TJ, and fewer techs are competent enough to turn composite rotors properly either. I'd swap them for better quality all-cast rotors which are more easily turned properly by just about any competent brake man who knows how to run his lathe properly.

[goodtimes]

When we sent out techs to the seminars put on by the brake suppliers, they came back stating that unless there were grooves, you should apply a non directional finish to the rotor surface and then bed the pads.

My job was to bed the pads. I've swapped out many sets of pads adhering to that wisdom on various vehicles and never had an issue with excessive anything except better braking.

From personal experience and knowing machinery, I'd likely not trust the average brake lathe full of chips and a less than experienced operator running it whose only function in the shop is to get parts out the door.

Given the average cost of premium rotors, my intense liking of a vehicle with good brakes, I'd consider replacing rotors each time I swapped pads if the old ones need turning.

I also know that the rotors on my Stupid Duty at less than 20,000 on them need replacing. The dealer would turn them under warranty, but could guarantee that that won't fix the problem. From that I'd gather that turning is a bandaid that will only solve a minority of issues.

I spent 5 years working for a leading supplier of braking system components for OEM's, with a small slice of the aftermarket pie as well. I picked up a thing or two along the way. As with everything else jeep, everyone has their own opinion. Here is the reason for my earlier statement. It might be right, it might be wrong....but here it is anyway.

When you do not turn the rotors, and simply replace the pads, or apply a "non-directional finish"...you are not doing anything to address the parallelism of the friction surfaces, or the lateral run out. Both of which should be addressed. Sure, you can live without doing it, but for the cost of turning a rotor (~$5 each), IMO, it is a no brainer. If you "apply a non-directional finish", at least you are breaking down the work hardened surface of the rotor...but still not addressing the parallelism or runout. Most brake lathes out there do leave alot to be desired...as can those piles of chips that the arbors are laying in. A quick walk through the shop will tell you if you want to go somewhere else. I have no problem running rotors that have been turned, as long as it was done properly, and you are still above the minimum thickness as required by DOT.

You are right on the money about premium rotors....they are the only way to go. I just wouldn't go there every time I replaced my brake pads. In my experience, castings from North America are the best you will find. We tried for years to get decent castings off shore....they just plain sucked. Another nice feature of premium rotors is the balancing. There is much more control of the balance when you mill balance compared to using the spring steel clips that the cheaper rotors have (they tend to clog up the vents, and you can only add weight in certain increments, making it inherently inaccurate). One last thing that I really like about the premium rotors...they are generally straddle cut, or double disk ground. DDG provides a superior surface finish, but straddle cutting eliminates the problem of having a large undercut up against the hat section of the rotor to keep the friction surfaces parallel. FWIW, most of the OEM's specifiy straddle cutting.

As for your stupid duty...yikes. The dealer actually admitted that their "fix" was actually just a band aid for a bigger problem...but yet (or couldn't?) tell you what that bigger problem was, let alone fix it? That just isn't right.......