Rotor gauge

[mateo]

Where do I find a gauge to measure the remaining thickness of my rotors. I'd like to be able to measure while on the car. If I actually need new rotors, I don't want the hassle of removing the rotors, taking them to a shop to be turned, only to be told they are too thin.

Is there such a device for the consumer?

Where is the best place to get rotors turned? What price should I expect to pay for the service and turn-around time?

Thanks,Mateo

[Hijacker]

yeah. it's called a micrometer and you can generally pick one up at a local auto parts store. Some mechanics do machining in house, so you just need to find them. Ask your local auto parts store worker while you're buying your brand new micrometer from your local auto parts store.

I don't know what the prices are for your rotors, but in some instances, it's actually cheaper to buy an all new rotor than to get an old one turned. Check up on the price while your buying the micrometer and then cross reference it with a quote on getting the rotors turned.

I gouged out the rotors on my old tempo once, and a new rotor cost me 14 bucks at advance auto and getting it turned would have been like 10, so I figured the extra 5 bucks wasn't poorly spent

[mateo]

Thanks. I just priced them on tire rack - $62 per rotor for a J30. Couldn't find the micrometer on autozone.com. Will try napa or kragen.

[Grant@tirerack]

If the rotors are worn badly it might make more sense to just replace them. Many times when you have them turned, they are more apt to warp because they remove even more mass from the rotor.

[mateo]

Thanks Grant. I've been thinking about that. I will probably do that for one of my cars. Your prices and service have been great. I'm happy you carry Brembo too.

[mateo]

I saw several micrometers on different websites that were pricey. But I also found this one for about $20. Will that give me a good reading? What is the correct method for measuring. I assume it is fairly straight forward.

[Grant@tirerack]

That should be good enough for what you are testing. Simply check the thickness of the rotor and compare it to the minimum. The minimum will be in your shop manual or typically stamped on the edge of the rotor itself.

[Nismo_Freak]

If you drive the car hard I'd advise getting new rotors, crossdrilled rotors help to lower the rotor temps which may or may not help prevent warpage, it really depends on your driving habits.

Also keep in mind that if you replace the rotors and not the pads you will have an unbedded pair and the brakes won't work as good as they used to because you replaced one worn part and not the corresponding one.

I'd just drive on what you got till you can afford to replace the pads and rotors on the front. In the long run it's the best option.

[VitaminT]

Note that if your rotors have a lip on the edge, i.e. they have been turned before, then that micrometer might not work. There is another type that looks more like a C-clamp that will work better. BTW, you may want to check pawn shops. I know many around where I live have them. Also Sears has many models of the type mentioned above.

[Nismo_Freak]

Rotors that have been turned shouldn't have a lip on them if they are turned correctly.

The first thing you do is chew that lip off if not the machine will bind and stop at the end.

[VitaminT]

Haha, ok.

[mateo]

I've borrowed a couple of micrometers for the weekend. They are both C clap shape - one big and one small. They aren't in metric though and I'm not sure how to read them. I'll search the internet for info. If any of you can give me some tips, that would be great.

BTW, I did by new brembo rotors and ceramic pads for one of my cars. I will be measuring the rotor thickiness on my J30 tomorrow.

[mateo]

Oh yeah. Grant, thanks for your help on the phone. One more question for you. The pads came with lube, does that go on the back of the pad on the shims?

[VitaminT]

If you need to convert inches or in this case thousands of an inch to milimeters just use the following.

0.001inch=0.0254mm

[Nismo_Freak]

Oh yeah. Grant, thanks for your help on the phone. One more question for you. The pads came with lube, does that go on the back of the pad on the shims?

Yes, it's a vibration dampening lube.

[mateo]

Okay, my math really sucks right now. Here is what I read on the micrometer. Does this read 1.05 inches? How do I do the math?

[mateo]

I figured out how to read the micrometer. These websites helped: http://feh.eng.ohio-state.edu/....html & http://www.formtechservices.co....htmlLuckily the specs I found for my J30 is in inches: The front rotors should be 1.1 in for new thickness and and have a minimum thickness of 1.024 inches. I will have to get new rotors - mine read .92-97 inches.

[Grant@tirerack]

The lube goes on the caliper slides/pins (the parts that slide in and out as the caliper compresses), not on the back of the pad or shim!

[Nismo_Freak]

The lube goes on the caliper slides/pins (the parts that slide in and out as the caliper compresses), not on the back of the pad or shim!

Depends... there are two kinds

[mateo]

Well I've finally finished brakes jobs on two cars. Everything seemed to go just fine Grant. I used the molly lube that came with the pads, on the back of the shims. I bought some disc caliper brake lube and used it on the slides/pins. No problem!

[vq35de]

quick micrometer lesson, the first picture above is a vernier micrometer. the kind you want to use with rotors is an outside micrometer. This is the kind that mateo used and is in his picture.

there are also inside micrometers, depth or hole micrometers.

when tightening down on a micrometer only go to the first "click" on the locking knurled nut.

outside micrometers can be calbrated with a feeler gage set to see if they are ballpark or not.

Just some'n to think about before you rebuild an engine as you need all shapes and sizes to do that work correctly

another instrument used for brake checking is a dial indicator. This is set in contact with the rotor then the rotor is spun in a circle and moved in and out. the dial indicator will measure the furthest deviance from the zero setting that you started with. the difference is "run out" or a measure of rotor warping. There is usually a spec for this in shop manuals as well. It is also used for measuring journal bearing taper/wear. This is if you pull the bearing all the way out. Some bearings have holes in the casing to perform this without removing the bearing with a depth micrometer.