are there set tolerances that after the rotors get down to a certain degree that they must be replaced? The reason I ask, I have a friend that needed new pads and the brake shop said that his rotors needed replace (120k) said that the rotors are 1.5 mm (?) new and at 1.015 they have to be replaced. I have never heard this before. I am sure there are some guidelines, but have no idea.

what is the typical life of normal rotor with light towing on a 3/4 ton trk?

120k seems far too early, can't they just be spun? If they warp can they still be spun?

I searched thru several pages, but couldn't find anything.

Thanks

 

Chances are they are testing your friend to see if he will buy new rotors. There are limits at which they need to get replaced, based on the original thickness of the rotor when new, usually in inches though, not mm. A lot of brake shops like to turn the rotors if they have a little lip at the end or slight gouges from worn pads, but this is totally your friend's option, I have changed pads on my truck with both of these issues, and they seat just fine. If they have deep gouges from running the pads down to bare metal or if they are warped they usually need to be replaced, but just like the pads, it is not that hard to do yourself. Have the brake shop show you the thickness measured with a micronometer, and have your friend make his own decision.

 

Most reputable shops do measure the rotors. There are specs printed right on the rotor ( if you can get thru the rust! ) Also, most reputable shops will not do any brake repairs if everything is not within specs. I have seen trucks due for their second brake job in need of new rotors. I'm sure I will catch a lot of grief for saying that, but the rotors wear! Not as much as the brake pads mind you, but they do wear. Also if they were turned at the first brake job, thats all it takes. Most rotors only have enough extra surface to machine once, even the aftermarket ones like NAPA and such. I have seen a few vehicles that need new rotors at the first brake job too. On my own vehicles, I only machine ( turn ) them if they are warped or grooved. As for the MM measurement vs. the inch measurement, the factory rotor's specs are printed on the rotor in MM's. This is my opinion !

 

Jezz hunting.... One thing to consider is turning a warped rotor is actually inviting a warped rotor when you apply the heat. If the rotor is warped, and you turn it, the metal will no longer be at the same thickness throughout it's circumference. Metal expands and contracts differently depending on it's thickness, and thin spots will bow/warp sooner. (I have my flame suit on.)
This may not become apparent depending on how much warp there is to begin with, how much metal is removed, and if the driver ever gets them hot.
IMHO, just replace the rotors, they are not that expensive and after all they are only thing keeping you from plowing into the back of the semi.
What I have found most important in doing any brake job is the caliper condition and the freeness of the sliding side of the caliper. Seal kits are cheap, it allows you to remove any debris from the piston cavity, and if the sliders are free and lubricated it will stop your shoes from dragging creating hard spots and brake pedal pulsing.
Good tires and good brakes= cheapest insurance you can buy!

 

Great Advice Mr Bee. I couldn't agree more. My post was long enough without getting into all of that as well, but they are very good points!

 

i agree, time for rotors and pads, 120k i believe is a loooong life for a set of rotors... even more so for a truck that big that towed... i just replaced a set of rotors and pads on a car today under warranty because they were below the minimum specs at 48k miles... the company i work for is a firm believer in not turning rotors due to the fact that your removing heat absorbing mass... which will cause them go even quicker

i also suggest a brake fluid flush for your friend also if it hasn't been done in the last 2 years