Minimum Thickness Rotors?

[LibertyTC]

Does anyone have the minimum rotor spec for Rear and Front of KJ?
I know it should be stamped on rotor somewhere, just hoping someone might Know specs.
Thanks in Advance!

 

[ridenby]

They are not designed to be turned.

 

[LibertyTC]

Thanks!
Found Rotor specs (looked in wrong section) of FSM section 5 page 6- 2004 FSM=
Rear Solid Minimum is 11.0mm or 0.4331 inches
Front Ventilated Min 26mm 0r 1.0236 inches

 

[Ry' N Jen]

They are not designed to be turned.

This information was copied directly from the Full Service Manual
BRAKES - BASE Section 5 - Page 17

ROTORS
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - DISC BRAKE
ROTOR
The rotor braking surfaces should not be refinished
unless necessary.
Light surface rust and scale can be removed with a
lathe equipped with dual sanding discs. The rotor
surfaces can be restored by machining in a disc brake
lathe if surface scoring and wear are light.
Replace the rotor under the following conditions:
² severely scored
² tapered
² hard spots
² cracked
² below minimum thickness
ROTOR MINIMUM THICKNESS
Measure rotor thickness at the center of the brake
shoe contact surface. Replace the rotor if worn below
minimum thickness, or if machining would reduce
thickness below the allowable minimum.
Rotor minimum thickness is usually specified on
the rotor hub. The specification is either stamped or
cast into the hub surface.

Where does it say "They are not designed to be turned."?:shrug:

 

[ridenby]

Well turn them then,I did,they didn't stay true. New rotor can be had for $33,two year warranty.

 

[LibertyTC]

With only 12 mm left on current stock rotors time to replace the rear rotors at 37 k miles.
Going Napa & new pads are in order at 20-25 % or less only left.
http://i779.photobucket.com/albums/yy75/LibertyTC/KJDiscThickness.jpg[/IMG]"]

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[tjkj2002]

With only 12 mm left on current stock rotors time to replace the rear rotors at 37 k miles.
Going Napa & new pads are in order at 20-25 % or less only left.
http://i779.photobucket.com/albums/yy75/LibertyTC/KJDiscThickness.jpg[/IMG]"]

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That is the inccorrect way to measure a rotor.That micrometer is mearuring the rotor in a area where the pad does not contact the rotor so it will be thicker.You need a brake mic(in pic below) to properly measure the rotor where the pad actually hits the rotor face.

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[HoosierJeeper]

Want to say 3 MM is the rule of the thumb. If you get new pads before the old ones scrape, you won't have to touch the rotors. That's what I did.

 

[Ry' N Jen]

Tim couldn't get my micrometer on the business end of his rotor because of the brake back plate/dust shield was in the way.(I've got dial indicators, vernier calipers, and an assortment of micrometers... Just not brake mic yet!)
I didn't think he was going to post that picture as we both knew that that was not the correct way to measure a rotors thickness.

 

[tjkj2002]

Want to say 3 MM is the rule of the thumb. If you get new pads before the old ones scrape, you won't have to touch the rotors. That's what I did.

You must always "Turn" the rotors or replace the rotors to start with a flat surface for the new pads.The new pads with old rotors that have not been "turned" will have sub-par perforance due to the rotors not being true(flat surface).Alot of new vehicles are coming out with "one time use" rotors,meaning when you need brakes you must replace the rotors also.This is to reduce weight for mpg's,same thing when they went to synthetic gear oils,just a way to improve mpg's but more costly for the owners to up-keep.

 

[Ry' N Jen]

You must always "Turn" the rotors or replace the rotors to start with a flat surface for the new pads.The new pads with old rotors that have not been "turned" will have sub-par perforance due to the rotors not being true(flat surface).Alot of new vehicles are coming out with "one time use" rotors,meaning when you need brakes you must replace the rotors also.This is to reduce weight for mpg's,same thing when they went to synthetic gear oils,just a way to improve mpg's but more costly for the owners to up-keep.

What else is new!

 

[LibertyTC]

Tim couldn't get my micrometer on the business end of his rotor because of the brake back plate/dust shield was in the way.(I've got dial indicators, vernier calipers, and an assortment of micrometers... Just not brake mic yet!)
I didn't think he was going to post that picture as we both knew that that was not the correct way to measure a rotors thickness.

Ya Ryan with the backing cover, we knew it was not correct, and larger size, but often you got to use what you got.
The whole process yesterday of removing the rear tires was to estimate rotor thickness and approximative condition of pads and left over percentage. We also got to test on lifted KJ, both stock and other scissor jack!
Since our (larger) measurement was just over 12mm, and the actual rotor thickness will be less, if the minimum stamped thickness is 11mm, it is time for new rotors and pads etc.
We were able to determine rotors do need replacement and that is what counts!
Also got mud off many areas!
39589[/ATTACH]"]

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[LibertyTC]

So besides my steering rack bushing woes..at 36 k miles on my KJ....
My Rear Brake Parts Arrived today!
39697[/ATTACH]"]

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Everything including E-brake goodies. I can return them if not needed.
"JEEP" = Just Empty Every Pocket!!

 

[BjBnet]

did mine 2 weeks ago. Easy job and make sure you do one side at a time so you don't forget how the springs go.
Rotors are so cheap these days I always replace them with the pads. No screwing around with taking them somewhere to have them turned and get charged for it. Many places won't even do it anymore.

 

[LibertyTC]

Rear Brakes All New Again!

Done in Shop, Good thing I had new E-Brake shoes & Hardware kit!
39790[/ATTACH]"]

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The New Shoes and Kit work great after adjusting before and after test drive.
39792[/ATTACH]"]

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Oh ya I guess the new rotor and pads shot too..
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Feels much better also McGard Lugs finally.
39796[/ATTACH]"]

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[LibertyFever]

Wow guys, this post has been real educational. I've learned whether or not disc rotors should be turned or replaced, advice on brake shoes and that LibertyTC is OCD about cleaning his Jeep! :happy175:

Today I plan to rotate my tires. I'll be inspecting the brakes to see how worn they are.

FYI: If you happen to check the brake fluid in the master cylinder and notice it's low you should check your brake pads first before topping up the fluid. Likely the pads are worn down and the missing fluid is in the caliber pistons.

 

[LibertyTC]

Randy,
The brake fluid level is considered a gauge as to notify ya of pad wear or system leak. Never top up to full line unless you have new brakes all the way around on.
Before the rear brake job was done, removed DOT4 (non abs) from reservoir to ensure it would not overflow when compressing piston/lube sliders.
Refilled to full line after new rear brakes were completed, as fronts are also 95 % new.
One note on calipers: My rig only has 38 k miles (63km) and still has original calipers. It is best to consider also replacing the calipers if pads are not wearing evenly or you are approaching higher mileage, like in the 100k mile zone.
A brake fluid flush should also be done every couple of years anyways.
Regarding my front brakes, The dealer completed the brake service before I bought the kJ and noted on the bill that they "turned" the rotors. This really is not the best choice. I will now prepare myself soon for new rotors and pads up front again, as I bet the rotors will soon be approaching close to, if not minimum thickness. Will get the rotors measured, just forgot to do it yesterday.
The best course of action is: If your pads are worn out, get new rotors. If you are doing the rears, have e-brake pads and hardware kit ready, you will probably need them too!
and PS I am not OCD about clean. Can I borrow some paint though, the clevis needs painting and clear coat! (LOL)