New front rotors

[czarcaustic]

So I finally got around to taking my front wheels off today ... with the intent of putting new calipers on. I was greeted with absolutely zero braking surface on the old pads and about a 1/8" deep gouge down the center of the rotors from the old pad's backing plates. So new rotors it is.

EVERYONE I talked to down at autozone said that bearing grease is bearing grease is bearing grease and that the Coastal All-purpose is all I needed to pack my inboard and outboard bearings on my new rotors. One of the old fellas even opened up the package and showed me how to pack the bearing with it. Everything seemed A-OK. When I got home and read the package it states that it is good for everything BUT disc brake wheel bearings.

So - IS any old bearing grease OK, despite the packaging? Or do I need some SPECIAL bearing grease for these rotors? Help.

[GASoline71]

There is "high temp" bearing grease. Which is designed for bearings in brake rotors. Since the rotor heats up as the pads are applied, the bearings are subjuct to a little more heat than on drum systems. Drums are their own entity and have no contact with bearings and dissipate their heat differently. So standard bearing grease works just fine with drums.

Gary

[Hardesty454]

Follow instructions. Most people at parts stores do not know what they are talking about. I worked for autozone a few years back and was constantly correcting other employees and management about these types of things.


In this situation, there is a reason is says to not use it in disc brakes. May be a breakdown process or viscosity issue... Who knows. Just follow instructions.
Posted via Mobile Device

[Lee H]

WOW, grease is so cheap it's hard to believe there is so much discussion. Get the right stuff and have piece of mind or use what the auto zone geek sold you and worry.
Posted via Mobile Device

[Rufton]

I'd use hi temp grease but std grease would likely be ok except for street racers.
Probably a legal CYA disclaimer.

[czarcaustic]

I will probably go get some high temp bearing grease in the morning ... how do I get the all-purpose grease out of the bearing that the nice fella packed for me?

[Rufton]

Just pack the hi temp grease in till most of std grease is extruded out.

[czarcaustic]

Thx

[czarcaustic]

Originally Posted by Lee H

WOW, grease is so cheap it's hard to believe there is so much discussion.

Ha! Well, it doesn't surprise me. I have never been a truck guy, and I am learning every little piece as I go.

I have only recently started this hobby. My dad wasn't around growing up and I never learned ANYTHING about cars or trucks. About 4 years ago while studying for the bar exam I bought my first '72 short/fleet for $900 as a way to 'relax' and get a hobby outside. I did a little work here and there, but I wasn't in love with the truck because I was super stressed with the bar exam looming and the previous owner had done some stuff to it that I wasn't crazy about, so it just sat for a few years taking up space ... barely driven. Fast forward 3.5 years - I recently lucked into finding my current '71 longbed for sale (in much better 'stock' condition) AND someone wanting to buy my '72.

To make a long story a bit longer ... Now I have a longbed that I actually get excited about working on. The small amount of around the neighborhood driving I have done (due to the brakes being in such bad shape) has been great. I want to make sure that I do EVERYTHING as correctly as possible, not only for my own education, but so that my truck lasts at least another 40+ years. From this board, and the pdf versions of the 1971 C10-30 chassis Service and Overhaul manuals I got my hands on I have learned a bunch already. Unfortunately, tonight, standing in Autozone I didn't have this board or my service manual handy - only a bunch of guys telling me something wrong, and I didn't have any way to check them. Woe is me.

[TBONE1964]

"I was greeted with absolutely zero braking surface on the old pads and about a 1/8" deep gouge down the center of the rotors from the old pad's backing plates. So new rotors it is"

Are you sure this was from the pads? Right in the center? Most of the 69 - 72 1/2 ton 2WD's had a groove there from the factory. Can you post a picture.

Find out what the 1999 Chevy Tahoe police editions use. That should solve any issues with thermal breakdown.

[czarcaustic]

Originally Posted by TBONE1964

Are you sure this was from the pads? Right in the center? Most of the 69 - 72 1/2 ton 2WD's had a groove there from the factory. Can you post a picture.

I am NOT sure it is from the pads. I was just shocked to see such a deep gouge in the rotor, which in my mind should be flat and blemish free. This is possibly stock?

I can get a better picture in the morning. Until then ...

[TBONE1964]

Originally Posted by czarcaustic

I am NOT sure it is from the pads. I was just shocked to see such a deep gouge in the rotor, which in my mind should be flat and blemish free. This is possibly stock?

I can get a better picture in the morning. Until then ...

Yes, that is a factory intended groove and I am not sure why it is there. I am sure others will chime in and confirm this also.

[czarcaustic]

The amount of knowledge on this board constantly amazes me. I really should just post pictures and a question before EVERY task I am doing before I spend money or get myself elbow deep into something that could have been avoided. lol

[GASoline71]

LOL... I didn't even think of the factory groove. The rotors on my '72 GMC look just like that. Heck the rotors on the '71 ElCamino I had were the same.

Gary

[slikside]

That appears to be the factory groove on an original rotor. The reason it is there, that I have deduced on my own (haven't read it anywhere), is that the bottom of the groove coincides with the minimum thickness or width of the rotor that is allowed. The minimum is stamped right into the rotor, near the hub somewhere. If you measure that bottom groove to bottom groove (front side to back) it will correspond to that minimum required thickness.

So, you could run that rotor until there is no groove left, and then you must discard it. It would be worn to the minimum thickness.

Does that sound right? Anyone know otherwise?

[SS Tim]

Might measure a rotor if you have one handy. There is no mention of the grooves in the service manual but they are shown in pictures. Min. rotor refinish is 1.230 and discard thickness is 1.215".

[slikside]

Originally Posted by SS Tim

Might measure a rotor if you have one handy. There is no mention of the grooves in the service manual but they are shown in pictures. Min. rotor refinish is 1.230 and discard thickness is 1.215".

I guess I neglected to mention, that is what I did, or rather the parts guy did...to my rotor prior to turning it, when I did a total overhaul on my brakes about a year ago. He measured it, and it corresponded to the 1.215 thickness, bottom groove to bottom groove that is. That's when I put what I thought was 2 and 2 together. As you say, they don't say anything about it in the manual.

Thanks for the specific measurements, Tim. You're always right on that from what I've noticed. You must have that manual right there at your computer, or the electronic version?? Mine is in the garage, and I'm usually just too lazy to go get it!

[TBONE1964]

The grooves being a wear indicator is a good theory that I have never been able to confirm. It does make some sense to have that and it would be a great way to gauge wear. I am not sure if the groove is on the inboard side from my memory but it is possible.

I hope you did not throw these away because the Chinese ones you replaced them with will unfortunately not last nearly as long.

[TBONE1964]

Originally Posted by slikside

I guess I neglected to mention, that is what I did, or rather the parts guy did...to my rotor prior to turning it, when I did a total overhaul on my brakes about a year ago. He measured it, and it corresponded to the 1.215 thickness, bottom groove to bottom groove that is. That's when I put what I thought was 2 and 2 together. As you say, they don't say anything about it in the manual.

Thanks for the specific measurements, Tim. You're always right on that from what I've noticed. You must have that manual right there at your computer, or the electronic version?? Mine is in the garage, and I'm usually just too lazy to go get it!

Yes Tim is the **** on this board. Never dought his word Are you talking about the groove also being on the inboard edge? I can not recall from memory if it is or not.

Everyone gets educated on here.

[slikside]

Originally Posted by TBONE1964

Yes Tim is the **** on this board. Never dought his word Are you talking about the groove also being on the inboard edge? I can not recall from memory if it is or not.

Everyone gets educated on here.

I know what you mean. Don't get in a tangle with him....he ALWAYS has the numbers to prove it!

Yep, the groove is on the inside edge as well.

[SS Tim]

Lots of stuff at hand electronic and paper. Boxes more if I really need to dig something up. Always want more and right now some parts manuals are highest on my list.

[czarcaustic]

Originally Posted by TBONE1964

The grooves being a wear indicator is a good theory that I have never been able to confirm. It does make some sense to have that and it would be a great way to gauge wear. I am not sure if the groove is on the inboard side from my memory but it is possible.

I hope you did not throw these away because the Chinese ones you replaced them with will unfortunately not last nearly as long.

I haven't replaced them yet; That was going to be my job tomorrow.

After this thread, I may take my 42 year old rotors and have them turned, replace the wheel bearings, races, seals, and calipers .... then return the non-grooved chinese rotors and call my brake system overhauled.

[slikside]

Originally Posted by czarcaustic

I haven't replaced them yet; That was going to be my job tomorrow.

After this thread, I may take my 42 year old rotors and have them turned, replace the wheel bearings, races, seals, and calipers .... then return the non-grooved chinese rotors and call my brake system overhauled.

If you can have them turned and still have 1.230 as Tim has posted above, there is no reason to replace them now. Save yourself the $$, and have real GM for a while longer.

I agonized about that GM thing for a while, and I finally decided that I could not turn in all my GM parts for cheap China stuff. So I had the booster, M/C and calipers overhauled by a brake shop. The prop valve was shot, so I got a new brass valve. The brakes work so much better now.

Good luck, and let us know how it all works out.

[slikside]

Originally Posted by SS Tim

Lots of stuff at hand electronic and paper. Boxes more if I really need to dig something up. Always want more and right now some parts manuals are highest on my list.

Boxes......I guess that's where your original brochures come from. Always amazed by what you find. You're a great resource here....thanks for that.

[cdowns]

i like to use synthetic grease when i pack wheel bearings// the synthetic is slicker and more temp resistant as well as more resistant to water