Rotor wear advice

[cperez]

What BikePilot says. Also fwiw, I've done pad only replacements without changing rotors (on many different cars). Some with a lip on the rotor, some with not. I think squealing is probably more of a pad compound factor and lack of a good bed in.

Good to know that you've had success with pad-only replacement. I have wondered a lot about how thorough the bedding process is when I have this done at a shop. One time I got the vehicle back with barely any extra mileage on the odometer from when I brought it in. Made me wonder how the bedding was accomplished, but the brakes performed well and were silent so I didn't dwell on it.

 

[cperez]

My approach is to use up every last bit on a pad/rotor combination right up to the pad scarring the rotor at end of life when the rotor is nearing where it would have to be turned anyway. Then I have no hesitation on replacing with new and I'm good for another 50k or more.

This is in effect the approach I'm using right now. I would probably let them go another couple of weeks but there are a few group trail rides coming up and a road trip at the end of the month so I'm going to get them done this week.

You also gave me something to think about re rotor mass on our hulking vehicles. I had not considered that but it makes sense.

That said, I am going to keep the old rotors and look into having them turned for future use as some have suggested (assuming they'll still be in spec after being machined).

 

[cperez]

There's less metal as a base when the rotor is turned. Even if it's in tolerance the rotor will heat faster, wear faster, warp faster. Believe it or not they may be actually trying to save you labor dollars by replacing them.

I get the logic of that. This thread could rival any oil or tire thread when it comes to producing conclusive findings.

I appreciate everyone's input.

 

[Robin Parsons]

No JLR dealer will turn rotors any more. I have been to 5. My LR4 is prone to warp rotors, and I have heard the same from other owners. Especially if one tows a lot.

I turned the original rotors 3 times, and then replaced with EBC premium heavy duty drilled and slotted rotors. I took them to Orilieys and had turned before installing. (Its hard to believe, I kniw, but many rotirs are stored vertically for years befire sold, and are slightly warpped, brand new. Enough to feel in steering).

The rotirs, pads, hardwear and pad sensors, were all total less than $500, all 4 corners. About 3 hours of work to change out. I now have 30,000 miles on them, and still smooth as silk, and yow 3 to 4000 lbs regularly.

 

[Quijote]

Good to know that you've had success with pad-only replacement. I have wondered a lot about how thorough the bedding process is when I have this done at a shop. One time I got the vehicle back with barely any extra mileage on the odometer from when I brought it in. Made me wonder how the bedding was accomplished, but the brakes performed well and were silent so I didn't dwell on it.

I had never before done pad-only replacements. I always changed rotors and pads together. The LR4 is the first vehicle where I just threw in new (OEM) pads. Did that for the rears 2 years ago, and this past fall for the fronts. No issues whatsoever. Rear pads fixed a squeal I had. It also worked well despite some slight grooving - which has since gone away.

I also am not a fan of turning the rotors.

 

[BikePilot]

FWIW turning a rotor that's in spec takes off only a tiny bit of metal. In terms of heat capacity, running around with half-worn pads will reduce capacity by much more than a few thousands of an inch off the rotor (and that's really just the high spots, done right you barely graze the low spots). Usually a rotor that's been heat cycled several times is pretty stable and tends not to warp. I definitely agree that all else equal more mass will handle more heat than less, but we are talking about fractions of a %, and all else probably isn't equal (e.g., the new rotor probably hasn't been heat cycled and if aftermarket may be lower quality metal). If the rotor is near min thickness than replace for sure, but if it has plenty of room to turn it, then I'd certainly turn it.

 

[BeemerNut]

My rear rotors have an almost imperceptible lip on them but otherwise have plenty of meat left.

I then asked why not try new pads only and if they squeaked, THEN replace rotors? I was told that if I wanted to resolve squeaks in that situation, I would have to get new rotors AND another set of new pads.

These guys have been good to me over the years so I'm not inclined to totally disregard their advice. But does it sound right to you guys?[/QUOTE

"imperceptible lip" that a good sign of rotors having a lot more life remaining.

"If I wanted to resolve squeaks" "new rotors AND another set of new pads".
Even new rotors depending on new new or different pad material you can develop a squeak.

Dealerships CYA besides making them more money selling you a full blown brake job.

I have witnessed a neighbor's vehicle where the lady had normal smooth braking with worn pads i'd bet having another 10K miles of pad life left as well smooth rotors with barely a ridge the dealership cut her front rotors on the vehicle. First cut a massive amount of material removed with a light finish cut afterwards. Talking almost new rotors to now within 0.026" of minimum thickness. This fronts only hack cost her $328 fronts only. Within 150 miles now shuttering can't stand it with rumbling braking action, they destroyed perfectly good rotors. Same dealership then quoted her needing new rotors and pads replacements. They scared the hell out of the lady not knowing anything mechanically. I replaced with new rotors with now 175 mile new pads costing her only for the rotors.
An elderly family friend was told they needed new brake shoes, "they are getting rather thin". They ordered "Wagner's Premium" shoes by my recommendation. I removed the drums and saw the brake lining having thicker linings than the new replacement shoes. Scare tactics strikes again.
Fellow 94 D1 owner I help out with advice having solid rotors (same as my 95 D1) with a slight amount of ridge both sides of the rotors. Vehicle up on stands all four corners, in low range with slush box in low engine idling. Used a 60 grit flap wheel on a 4 1/2 inch grinder removing those ridges as well light resurface on the rotor faces. Rather hard rotors by the color of the sparks leaving a very nice smooth rotor finish.
New pads still braking smoothly and silently going past 27K miles.

The above remark Rover rotors too hard damaging the lathe cutters is total BS as rotors are not harder than carbide cutter bits......~~=o&o>......

 

[BBLR3]

Good to know that you've had success with pad-only replacement. I have wondered a lot about how thorough the bedding process is when I have this done at a shop. One time I got the vehicle back with barely any extra mileage on the odometer from when I brought it in. Made me wonder how the bedding was accomplished, but the brakes performed well and were silent so I didn't dwell on it.

I was in the automotive industry way back and I've never seen real bedding in done. Time is money. Do brakes, quick drive and feel the petal. If its nice and firm after a couple of stops, its good to go. Get back, do another quick visual and get to the next job. So my guess is most shops arent doing it with a complete brake job (resurface or new rotors).

 

[Keith Hollis]

Thanks guys. I did ask about turning my rotors. They said that given the hardness of modern rotors, machining them would eat through the machinery. At that point I had heard enough to know that they had had this conversation many times before. In fact, I mentioned that half-jokingly and they said that virtually everyone complains after slapping new pads in w/o a fresh rotor change.

That's odd. If the rotors were THAT hard, why would the brake pads cause the rotors to wear at all? Something wore, creating that telltale "lip" at the edge of the rotor!

Good rotors don't have to be crazy expensive. Yes, a shop can fool around trying to turn the rotors, but at what expense? If it comes back making noise, guess who wants it redone for free?

It's much more efficient to just replace the pads, rotors, and wear sensor and be done with it. If it makes noise then, tough. Get over it. Moving parts and different materials in contact with one another, not to mention the introduction of brake dust, humidity, temperature variations, etc.

Put quality parts on it (quality does not have to = expensive), and roll.

These vehicles are highly engineered, and command a high price to own one. Why does everyone want to be a cheapskate and pinch pennies on maintenance and wear items?

People don't seem to think that way when considering pretty wheels, luggage racks, fancy off-road lights, or bumpers...they love throwing money away at those things. But to service differentials and transfer cases, or even to pay for fuel induction cleaning, people balk at spending the money. Most people wopn't even spend what it takes to change the oil every 5K miles because the dealer says to do it at 10K, or even 15K. Like that's never going to cause any problems??

Rant over.

 

[gsxr]

I keep reading about a "lip" on the rotors. This lip is NORMAL if the rotors are not brand new. It doesn't automatically mean the rotors are worn out. A very pronounced lip may indicate the rotor thickness is below spec, but you have to measure to find out.

There is a factory thickness specification for a reason. Use a micrometer or vernier caliper to measure the exact thickness of the rotor to determine if it requires replacement. This assumes there are no issues with vibration or pulsation which may indicate deposits on the rotor friction surface, or a warped rotor. For the 2010 LR4, front min thickness is 27mm; rear min thickness is 17mm.

Back to the OP who stated: "One of my shops said that any amount of lip will almost definitely cause squeaking if I only replace the pads... [and] I would hear the new pads for as long as I had them." <-- Bullcrap. If the rotors are in spec and there are no existing issues besides worn pads, just replace the pads. I did exactly that on the front of my LR4 a year ago (OEM Ferodo pads) and there has not been the slightest hint of squeaking or noise; and my rotors are ~50% worn.

Random photos from Google (non-LR):