Disc Brake Rotors

[Cofe]

I have heard conflicting stories about people getting their disc brake rotors turned. I am just curious...... Do you have your rotors turned? Or buy new rotors?

 

[Silly Seville]

Re: Disc Brake Rotors

Really depends on the circumstances. A reputable machine shop will not turn down rotors if they are near to or out of factory recommended spec's. In that case, new ones are bought. But if I can save $40-50 a pair by machining them down and getting a few more miles out of them...why not?

 

[wtp]

Re: Disc Brake Rotors

I work at a car dealership and we have rotors turned all thime. Silly Seville is right. It does depend on the circumstances. You can bring them in and if the are below recommended specs they should tell you to get new ones if not they will turn them. Around here it costs us $9.00 a rotor to have them turned.

 

[Cofe]

Re: Disc Brake Rotors

Just wanted to mention......I have always replaced rotors when they warp. I was taught that once a rotor overheats and warps, that the metal grain structure has changed and will continue to warp, even though it was turned, and will warp again at a faster rate.

 

[ezmobee]

Re: Disc Brake Rotors

I have had them turned before and it worked well. However, that involves removing them, taking them somewhere, going back later to pick them up. I'd prefer to get the whole job done at once. I just priced rotors on RockAuto.com for my '09 Accord which needs front brakes soon and Raybestos Advanced Technology rotors (which I prefer) are $40 a piece. Cheaper ones are available.

I'll be replacing them.

 

[oldjeep]

Re: Disc Brake Rotors

I just replace them for most vehicles. The only ones that I would turn are the C30 rotors on my 1 ton streetrod - they are an integrated dually hub and rotor which cost a mint to replace, they've got plenty of thickness for a couple turns.

 

[TilliamWe]

Re: Disc Brake Rotors

I replace mine, only because the ones for my vehicles are about $22/ea and I can get them at the same time I get the brake pads. To have them turned, I have to drive 5 miles, drop them off, wait a couple of hours, drive back, and it costs me $30. Seems kinda silly at that point. Now if I had some fancy hi-po rotors, I'd turn them. But I don't. I can't have one of my vehicles sitting dead for a whole day, when I can do a complete one axle brake job in 1.5 hours, if I have all the parts right there.

 

[skargo]

Re: Disc Brake Rotors

My Dodge Ram 2500 has a TON of meat on the rotors and can be turned a lot. Plus they are expensive.
On my Cadillac and 4runner, they are much cheaper and have less meat to be cut, so I just replace those.

Depends on the vehicle in my case.

 

[QC]

Re: Disc Brake Rotors

If they are not warped, and you have not gone metal to metal, why do either?

 

[RogersJetboat454]

Re: Disc Brake Rotors

As others suggested, it depends on how much meat is left on the rotors and even the material the rotor is made out of.

If I recall I attempted to cut a set of later GM rotors, (can't remember what for, Buick or Cadillac maybe?) and the material the rotor was made out of just wasn't as happy with being cut like a standard iron rotor. That being said, I have probably cut thousands of rotor's while turning wrenches.

Best thing to do is find the service spec for the rotor, and use a set of calipers or Mic it before the cut. If it's acceptable. It usually takes a couple of passes with most lathes to completely clean up the rotor. Then measure the rotor after the cut to be sure you are still within spec's. The hub face, and tapered portion of the rotor that the center of the hub goes through must be 100% clean of rust/junk in order to get an accurate cut.

 

[RogersJetboat454]

Re: Disc Brake Rotors

If they are not warped, and you have not gone metal to metal, why do either?

Ahh... a good old pad slap...

Yeah it works, but takes longer for the pads to break in.
Cutting the rotors to remove the glaze, then putting a non-directional finish on them with a roll-lock "cookie" helps the pads break in quicker. New rotors aren't glazed, and most are now coming with a non-directional finish.

 

[QC]

Re: Disc Brake Rotors

I've heard conflicting info on this forever. When I was young and stupid and poor I even put new pads on a metal to metal rotor . . . Know what happened? They worked themselves together and the rotor ended up smooth, and the car stopped well. I am not suggesting this, but a question: Why do we assume the rotors are glazed if the pads were good until changing? If they are glazed, why did it stop well yesterday?

I'm no expert, I don't even qualify as a novice, seriously just askin' . . .

 

[badkins50]

Re: Disc Brake Rotors

my truck's tow rating is 7500lbs. my boat/trailer/gear is pushing around 5000lbs. my camper/gear weighs 6000lbs. that being said I'm going to go ahead and replace them even though both trailers has trailer brakes too. as for the other cars they are cheap enough to replace wither way.

 

[RogersJetboat454]

Re: Disc Brake Rotors

I've heard conflicting info on this forever. When I was young and stupid and poor I even put new pads on a metal to metal rotor . . . Know what happened? They worked themselves together and the rotor ended up smooth, and the car stopped well. I am not suggesting this, but a question: Why do we assume the rotors are glazed if the pads were good until changing? If they are glazed, why did it stop well yesterday?

I'm no expert, I don't even qualify as a novice, seriously just askin' . . .

With out a doubt, all rotors that have been used for anything more then a couple of stops are glazed . The shiny metal is telling. The old set of pads worked, because they were broken in. This would be a similar situation to pulling an engine apart and replacing the rings with out deglazing the cylinders. The new rings may seat eventually, but it will take longer.

If I remember correctly, the average break in period for a set of conventional pads is somewhere in the neighborhood of 500-700 miles. Ceramic pads taking a little longer.

I've done pad slaps to insisting customers vehicles ("I don't want to pay for that, just put the pads on!") and you can feel a difference between a brake job done with machined/new rotors VS just replacing the pads. Yep, eventually it works out in the mix, but that uneasy feeling when you hit the brakes, and the car doesn't slow down as quick as you expect it to, leaves something to be desired.

 

[BuzzStPoint]

Re: Disc Brake Rotors

Have them spec'd out. If they are within factory specs. Turn the rotors down.

I'm not sure where this whole "Replace" deal got started. Years ago we used to fix al ot of things on cars.
Starters. Used to rebuild them. Alternator/Generators. Used to rebuild them. Rotors, Used to turn them down.
Hell I remember a time when we used to clean and file spark plugs.

My alternator on my Chev truck was squealing. Took it to the shop, (Curious, on price) was going to cost around 300 to fix. Putting on a new alternator. I asked the shop if they can fix it instead or replacing, and he looked at me like I came from Jupiter. Next day I tore the alternator apart and replaced the front and rear bearing. Total cost. 8 Bucks.

I've always been in the "lets fix it, instead of replacing" if you can. Not only will you get the job done, it will save you money.

 

[QC]

Re: Disc Brake Rotors

I'm not sure where this whole "Replace" deal got started.

Cost went down on new and rebuilt components and with that the warranty risk to the shop went down . . . Kind of a good thing.

 

[RogersJetboat454]

Re: Disc Brake Rotors

Cost went down on new and rebuilt components and with that the warranty risk to the shop went down . . . Kind of a good thing.

Not to mention the big factor.... Time.

I like fixing/rebuilding stuff on my own vehicles if I can. But how long will it take for me to yank a dead starter out, send it to a rebuilder, wait for the builder to finish it, pick it up, then re-install it, all the while having a dead vehicle on my hands?

The other problem is the resources available for a shop if they wanted to rebuild stuff like starters/alternators on their own. You would be hard pressed to find a part's readily available for the literally thousands of different types of starters, alternators, etc.

 

[ufm82]

Re: Disc Brake Rotors

After hundreds of brake jobs and having done them every way imaginable, I have found a couple things.
1)New pads- used/unturned rotors. May work OK and stop ok but have a HIGH chance of being squeaky/squealy. That drives me NUTS!
2) New pads- turned rotors. Usually OK but depends on the tech doing the machining. If someone gets in a hurry and cuts too fast the rotors wind up "threaded" resulting in a thump,thump,thump on stops. I always hit them with the roloc cookie before installation.
3) New pads- new rotors. CLEAN the rotors thoroughly. That grease will melt and cause issues if not completely removed.
4) New pads- grooved rotors. They'll work but will eat the pads and not last 1/4 of their expected life. Not a good idea unless you just don't care.

One more thing- with the hubless rotors used on all FWD vehicles it is critical to torque them to the proper torque in the proper sequence. With a lot less metal than a hubbed rotor to act as a heat sink you'll warp the rotors very quickly. Uneven pressure generated by improper torque sequence will also warp them. Most FWD cars like 90-95 ft/lbs.

On the main topic- I replace mine due to convenience. Hate waiting a day to get them back from the machine shop and I'm no longer a dealeship mech so I don't have access to a shop.

 

[marcoalza]

Re: Disc Brake Rotors

When I was young and stupid and poor I even put new pads on a metal to metal rotor . . . . .

I'll second that! I used to do exactly the same and never had a problem.
Best way to tell the pads needed changing was when you heard the grind!

When I was a boy, I had a car that had discs all round and new rear linings were about 20% of the thickness of new front linings....guess what.....when the fronts were wearing down, I'd slip them in the rear and put new on the front!!

 

[guy74]

Re: Disc Brake Rotors

I guess the best advice I have is: If you warped them with heavy braking, replace them as they will warp easier the next time since they will have less mass to dissapate the heat. If they were warped from over torquing, or grooved by bad pads you can turn them and probably get along fine for a long time. The choice is yours to decide, but that is how I base my decision whether to resurface or replace.