Trying to diagnose if I need to replace my rotors.
both fronts have soft but not rigid grooves in the inside and outside face of the rotors, the rotors measure 1.3 thick. Pads are very low but not past the wear grooves yet. I have no issues with breaking, car drives and stops normally

 

you need to have them cut down before putting new pads on them. What has happen NOT enough pad to the braking you have been doing & to much heat has done that to them..Robert

 

Thanks Robert
So you think the thinness of the pad was the cause, are these rotors grind-able? I know the Levine auto shop near me does offer that service still.

 

Yes I do my BMW did the same thing a shop will look at the thickness of them & go from what the factory says they can be cut down too. Then if that is within what is safe they will cut them down from the looks of no worse than they look in the pic & if they not been cut down before you should be good.

Just think about it once the pads get down so much the pad is glue to the back of a piece of metal that will hold heat more with less pad. Then that is what I was told that small uneven groves come in at before it gets down to metal to metal.

Plus you don't want to just to new pads on the car with those uneven groves in the rotor if you do the pads will wear out faster & you will not get a good pull down due to the groves. Robert

 

All three grooves are for that style of slotted rotor. Notice they line up with the trailing edge of the slots. Debris builds up in the slots and is swept toward the rear of the slot where it will cause a slight groove. Measure rotor thickness in the grooves using a rotor thickness gauge that will reach into the deepest groove and let you put the jaws in the groove on each side of the rotor.

Check the thickness of your pads with a gauge. The slot in the pad may or may not represent the true wear. If the pads are above 2/32 thick you have more life in them. I wouldn't bother turning the rotor.

Bill

 

OP Bill know these rotors here you can go by what he is saying on these rotors.

 

Thanks for your note Bill
i am not following, are you saying the wear pattern is normal? The rears are smooth with no grooves. The pads are at .17” thick which is about 1/32 shy of 3/16”

 

I have not seen 1 shop capable of cutting rotors. Spend the $600 on new.

 

Last I checked that’s the price per corner.
It’s not chump change for me as much as I would like to think it is.

 

You should see what happens to rotors on track. In comparison yours look brand new... thus I wouldn't lose a wink of sleep over those rotors and keep driving.

 

There still are shops around that turn rotors, you just need to call around. They are usually in smaller towns and cities that haven't adopted the throw away mentality. One thing that may be a problem is if you do find someone to do it they may not take them due to the slots (I found they had problems with drilled type). I have found some bigger NAPA stores do it and if they don't will know if someone is close.

 

Rotors are about 400 a corner.

https://www.rockauto.com/en/catalog/...hub,rotor,1896

 

As Bill said that is totally normal. I wouldn't bother turning the rotors and when you need a new set of pads they will wear in to any minor imperfection like that.

Replace the rotors if the grooves start to disappear or you get a crack that goes to the edge.

 

If still within specs, put on new pads and try them. It isn't like they are instantly going to quit working. All the best.

 

thanks guys
i am going to keep them and put new pads on.
the rotors have plenty of thickness left. I am putting on new carbotech pads for the track and street. Hope all goes well.

 

Yes, it is normal and it isn't limited to GM rotors. AP Racing Brake rotors and other brands can have the same grooves. I used the explanation that AP uses for why the grooves occur.

Here is a link to an article that describes issues and concerns related to AP Racing Brake Rotors. The groove is mentioned near the bottom of the article: https://www.essexparts.com/news-blog...-my-iron-discs

This is a copy of that section:

GROOVE IN THE CENTER OF AP RACING J HOOK DISCS

It's not at all uncommon for AP Racing J Hook discs to develop a groove or ridge in the center of the disc where the J Hook slots converge (see pic below). That groove is a result of the J Hook slot design. We see it all the time across all applications, and it doesn't in any way impact performance.


Here's why it happens: If you notice where that ridge forms on the disc face, it's at the termination of the J Hook slots. The pad material that gets scraped off the pad with each rotation disc rotation fills up the slots. If you think about the direction the disc is spinning, the 'back' of the J hook (the arced part) is leading into the pad. That pad material then exits at the tapered ends of the slots (see the red arrows in the image below). In the spot where that groove is, you're getting pad material exiting from both ends of adjacent J Hook slots. In other words, at that spot in the center of the disc face, you have pad material exiting the 'top' of the J from the slot closest to the hub, and the 'bottom' of the J on the adjacent slot closest to the OD of the disc. As that pad material exits the slots, it rides along under the pad squeezing the disc, and digs a little groove into the disc face.

There are many thousands of J Hook discs in circulation at all level of motorsport, and we've never had a premature failure or performance problem in any way related to this type of groove forming on a disc. That includes winning the NASCAR Sprint Cup championship 8 out of the past 9 years, winning Le Mans 8 times since the year 2000 on the factory Corvettes, and a host of other championships. The groove looks a little funky, but that's about it...nothing at all to worry about.

Despite a lot of shop mechanics with no experience of what happens in the racing world getting heart palpitations over the grooves, there isn't an issue.

Bill

 

Bill
Thank you very much for that detailed explanation. I feel much better knowing this is common, I am surprised it’s not common knowledge but feel comfortable using them.