Author Topic: rotors: when to machine vs. replace (Read 10191 times)

55inthe54 · « **on:** May 28, 2016, 06:46:13 pm »

Hey all,

About to bring my car in to get the rear pads replaced, and although I've Googled this to death, wanted some thoughts from the forum on when to machine vs. replace the rotors (or even leave them as is).

Here's what I've found:

1) leave them as is: ok as long as grooving is minimal, more than minimum thickness is still there, and no vibrations, pulsing, or noise from brakes. Then, make sure to properly bed new pads.

2) machine: ok as long as minimum thickness is still there after machining

3) replace: do this to ensure proper mating b/w pads and rotors

The rotors are expensive for my car at $250 for the pair so I want to ensure it's absolutely necessary at this point - see pics below. The rotors have never been replaced but this is the 2nd time the rear pads have been replaced. First time was at 30k km, car is now at 75k km.

Thank you!

EV Dan · « **Reply #1 on:** May 28, 2016, 07:54:15 pm »

Based on what I'm seeing in your second pic, at full resolution, I'd definitely replace the rotors first. Did you look at rockauto? $250 seems steep.

aquadorhj · « **Reply #2 on:** May 28, 2016, 09:04:58 pm »

That doesnt look too bad, and its vented discs so i would think the rotor would last longer than 70k or so.

Looks like pad surface area is small thats why the rear brakes wear so quickly, but if the unworn part of the rotor isnt too deep, it should be fine.

blur911 · « **Reply #3 on:** May 28, 2016, 09:57:51 pm »

They are cracked, maybe this is why they are wearing your pads so quickly.

What car?

wing · « **Reply #4 on:** May 28, 2016, 10:02:26 pm »

Rotors are so cheap now, just replace with white box

aquadorhj · « **Reply #5 on:** May 28, 2016, 10:22:27 pm »

Quote from: blur911 on May 28, 2016, 09:57:51 pm

They are cracked, maybe this is why they are wearing your pads so quickly.

What car?

Holy crap, you r right. That is a crack!. I though that was pad gunk left on rotor after it sits for a while....

I take back what i said. Replace.

safristi · « **Reply #6 on:** May 29, 2016, 03:16:09 pm »

why do they make crap ROTORS.....to save WAIT a minute???..no to replace them every brake change

Rupert · « **Reply #7 on:** May 29, 2016, 07:40:36 pm »

Does anyone machine these any more...probably cheaper to go new and quicker. The inner rotor surfaces fare the worst in my experience...especially on the rear brakes. Why, I don't know. It means getting down and dirty to check though and there is a plate in the way. Also service the slide pins with grease....very important.

ArticSteve · « **Reply #8 on:** May 29, 2016, 11:02:23 pm »

Does anyone machine these any more...probably cheaper to go new and quicker

Time to move on from the 20th Century Rupert.

Rotors are machined right on the vehicle these days.

http://www.procutusa.com/

Rupert · « **Reply #9 on:** May 30, 2016, 07:53:49 am »

It's not worth the trouble and can't imagine the set-up for that...maybe you could give a photo ref. Also can't imagine the benefit resulting from such an operation. Suppose you do that and find that the rust patches have not been machined out when at min. thickness. Now...machining drums on rear brakes is a different matter and... again in my experience...will carry you to trade-in. Often with the same shoes.

Firm · « **Reply #10 on:** May 30, 2016, 08:06:57 am »

90% of the time I replace. Why mess around? Plus, to get them machined I'd have to drive around, find a shop, wait for them to do it, etc. New rotors, just slap them on and go.
The other 10% of the time I would be reusing the current rotor, and that's normally because I am not happy with the pads and replace them long before they've worn out, or grooved the rotor.

safristi · « **Reply #11 on:** May 30, 2016, 08:31:12 am »

so u all agree today's Rotors are Rooters...and made of used tableware

..

I see Ramic

in my carbon future

55inthe54 · « **Reply #12 on:** May 30, 2016, 09:48:58 am »

Thanks for the replies, all. It's an Infiniti FX35.

Are you sure they're cracked? I was also thinking it could be pad transfer cause of the blue/grey discoloration immediately beside what looks like the cracks.

Here are some higher res photos:
- http://i.imgur.com/MrANbJV.jpg
- http://i.imgur.com/cmsMwRG.jpg

Quote from: aquadorhj on May 28, 2016, 10:22:27 pm

Quote from: blur911 on May 28, 2016, 09:57:51 pm
They are cracked, maybe this is why they are wearing your pads so quickly.

What car?

Holy crap, you r right. That is a crack!. I though that was pad gunk left on rotor after it sits for a while....

I take back what i said. Replace.

Fobroader · « **Reply #13 on:** May 30, 2016, 10:38:58 am »

Thats cracked, time to upgrade

Sent from my SM-G900W8 using Tapatalk

ArticSteve · « **Reply #14 on:** May 30, 2016, 10:49:01 pm »

Quote from: Rupert on May 30, 2016, 07:53:49 am

It's not worth the trouble and can't imagine the set-up for that...maybe you could give a photo ref. Also can't imagine the benefit resulting from such an operation. Suppose you do that and find that the rust patches have not been machined out when at min. thickness. Now...machining drums on rear brakes is a different matter and... again in my experience...will carry you to trade-in. Often with the same shoes.

ProCut has been one of those grand slams that come along once in a blue moon to new car dealers. Customer call backs for vibration after brake pad replacement is virtually nil. Pay back is fantastic.

Rupert · « **Reply #15 on:** May 31, 2016, 06:24:00 am »

How does the equipment work? and why does it work.

jamie1 · « **Reply #16 on:** May 31, 2016, 08:53:17 pm »

Quote from: Rupert on May 31, 2016, 06:24:00 am

How does the equipment work? and why does it work.

The lathe is bolted right to hub. Runout in the hub and rotor are then taken into account and the rotor can be cut true as one rotating mass with hub. Works great and is a very quick way to machine the rotors. For some manufactures, an on-car brake lathe is required equipment.

rrocket · « **Reply #17 on:** May 31, 2016, 08:58:48 pm »

Quote from: jamie1 on May 31, 2016, 08:53:17 pm

Quote from: Rupert on May 31, 2016, 06:24:00 am
How does the equipment work? and why does it work.
The lathe is bolted right to hub. Runout in the hub and rotor are then taken into account and the rotor can be cut true as one rotating mass with hub. Works great and is a very quick way to machine the rotors. For some manufactures, an on-car brake lathe is required equipment.

Dare I even ask how much the charge is to have the rotors machined this way?

jamie1 · « **Reply #18 on:** May 31, 2016, 10:59:36 pm »

Quote from: rrocket on May 31, 2016, 08:58:48 pm

Quote from: jamie1 on May 31, 2016, 08:53:17 pm
Quote from: Rupert on May 31, 2016, 06:24:00 am
How does the equipment work? and why does it work.
The lathe is bolted right to hub. Runout in the hub and rotor are then taken into account and the rotor can be cut true as one rotating mass with hub. Works great and is a very quick way to machine the rotors. For some manufactures, an on-car brake lathe is required equipment.

Dare I even ask how much the charge is to have the rotors machined this way?

I can't say for others, but we charge the same as the off car machining.

rrocket · « **Reply #19 on:** May 31, 2016, 11:04:02 pm »

Quote from: jamie1 on May 31, 2016, 10:59:36 pm

Quote from: rrocket on May 31, 2016, 08:58:48 pm
Quote from: jamie1 on May 31, 2016, 08:53:17 pm
Quote from: Rupert on May 31, 2016, 06:24:00 am
How does the equipment work? and why does it work.
The lathe is bolted right to hub. Runout in the hub and rotor are then taken into account and the rotor can be cut true as one rotating mass with hub. Works great and is a very quick way to machine the rotors. For some manufactures, an on-car brake lathe is required equipment.

Dare I even ask how much the charge is to have the rotors machined this way?
I can't say for others, but we charge the same as the off car machining.

Which is how much?