Can you reuse your old rotors when replacing brake pads? Why do you need new or machined rotors when replacing brake pads? Dealer says it's standard practice.

 

If they are worn down below acceptable thickness, or if they are warped, you need to replace. It is not standard practice to replace rotors and pads at the same interval.

 

There are good reasons for machining rotors when changing pads. It ensures a flat surface thus eliminating squeaks or brake pedal pulsations.

 

You should check the dealer's cost for new rotors vs the cost and labor of machining the old ones. My Lexus dealer in north NJ matched Sewell's price for new rotors which turned out to be about the same as machining the old ones. So it was a no-brainer to just replace with new ones. I am sure that most will agree that machined rotors, now a bit thinner, become warped faster than new ones.

 

Machining, not replacing.

Either way, don't go to the dealer for a brake job. It is a very simple procedure. You will be over charged.

 

Thanks for the info. What is the typical life of the original brakes under normal driving conditions on the RX? I have 74k miles on them and dealer says I have only 4mm left on the pads. What is the thickness of a new pad?

 

That is not good! If you have only 4mm on your brake pads you need to replace them ASAP.

 

Don't panic! My favorite quote from a dealer is "Your brake pads are wearing out." That statement's true. They're wearing out from the first time you use your brakes. Duh. Your pads started out at about 11mm thickness. The wear limit is 1mm. At 4mm you have 27% brake pad life remaining allowing for a 1mm final thickness. I like to have my rotors scuffed to assist with new pad break-in. Any deep grooves that you can catch a fingernail in should be machined away. If your rotors are pulsing your brake pedal then I'd replace them instead of machining them true. I've seen too many warped rotors trued and the warping returns after it goes through several thermal cycles.

The one most important thing to watch is torquing the lug nuts. Most shops over tighten them using their torque-sticks and this leads to rotor warping. I keep a torque wrench with a lug nut socket on it to re-torque my lug nuts whenever I have the tires touched. No matter where I go (except Costco as they hand torque) they're over torqued. I always request hand torquing but "trust but verify" is always best. An overtightened lug nut will howl with a loud CRACK when loosened. Not good. Standard Toyota/Lexus flat-seat lug nuts only require about 80 ft-lbs torque. This seems ridiculously low but it is sufficient and won't warp your rotors. AND it's easy to change a tire if you have a flat AND you won't break your locking lug nuts if you have them. If you have a flat and you break one of those you're pretty much screwed. I simply don't use them. End of rant!

 

I just did the front and rear pads on our '07 RX350 that has 122K miles. I noticed the OEM Akebono pads all have center slits in them that tell you when to replace the pads. When the slit disappears at about 1mm pad depth left, replace the pads. Rotors were still in great shape even at this mileage, so I just scuffed them up a bit and moved on. Brakes feel better than new!

 

Agree 100% with what Bon wrote - the key to long rotor life is to torque the lug bolts properly. I do it on the side of the next clear side street after a tire change. Costco, however, has been very good - the guy even adjusted his clicker wrench for the Lexus correct setting.

 

I never knew that you could warp the rotors that way. Is that 80 ft/b for all the Lexus models? How about for the GS 3rd gen, is it also 80 ft/lb?

 

Manual specs are 76 ft/lbs...but many round up to 80 ft/lbs which is not too excessive.

I beg to differ about rotor warp from excessive torquing. These RX's will never exceed braking temperatures to warp cast iron rotors unless someone is doing some road racing on a closed track.

It is uneven torquing and not using the proper torque sequence that leads to rotor runout issues which is often mistaken as warpage. Uneven caliper piston pressure from a dragging or stuck brake piston can also cause runout that results in brake shudder.

 

+1 on this. Machining the rotors at some places costs higher than buying OEM rotors online. For cars like our age and if you haven't replaced the rotors, you may want to consider getting a new one rather than machining it since you'll need to replace within near future.

 

From a Stop-Tech article on the "myth" of warped brake rotors:

"With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s; one of the most intense brake development program in history - I have never seen a warped brake disc."

So warped rotors are a myth but the fact that improper torque (amount and order/technique) can cause a shudder while braking is plausible. The term of warpage has several meanings for sure: plastic and elastic. High temperatures reached as in racing may cause plastic warpage while improper installation can cause elastic warpage.

 

This past winter I had to apply brakes on a slippery decline. The abs went crazy, and it was very cold out. I am pretty sure that this caused one of my rotors to warp.