# Doing brakes, opinion on rotors



## de-nagorg (Feb 23, 2014)

Change the pads, everything else will be fine until the next time. 

DO NOT touch the rotors with a grinder, or you will be needing more than new rotors, When that cast iron shatters by grinding on it, you will need a few stitches, and maybe some reconstruction of your body. 


ED


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## 47_47 (Sep 11, 2007)

As long as you don't have a pulsation, I'm with ED, just change the pads. Make sure you clean and lube the sliders well seeing as this car sits.


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## pbr (Feb 6, 2014)

*No to new rotors*

Replace rotors just like main bearings, when there is a problem(warpage/vibration) or when they are worn-out
(below min specs.). If rotors have a very polished look 
to them you could have a problem seating new pads (if
they are very hard pad material), in which case you 
should burnish them in at 50 mph or so first.This will
usually do the trick.
Both of the answers you got were 100% and 1 even came 
with a safety warning label ! LOL The other had very 
important details also.

pbr


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## ukrkoz (Dec 31, 2010)

Loan or borrow elliptical grinder. One where pad moves in spirals. Looked at mine, it's called "dual Action Sander. Oh, got the word. ORBITAL.
Use *rough* sand paper. Take rotors off and get them into vise, solid into jaws. Place sand pad flat, as in - FLAT - onto rotor surface and in circular motion, without applying much downward force, clean rotor surfaces on both sides.
Orbital sanding is also known as Blanchard grinding, it's just Blanchard grinding is done by large machines and grinding stones. But the point is - in both cases grinding is done in circular - elliptic motion and parallel to the surface.
Blanchard grinding is the best way to turn a rotor true. Your goal is to remove any pad material build up. So simply get it to shiny METAL. You'll know, when to stop. I did when I do mine.
Don't really worry about the ridge.
FIRST THING you do next after done installing it all back, do proper pad bedding procedure. !!!!!!!!'
Then your rotors will be good for next who knows how long.
*PLEASE WEAR DUST MASK.* That dust sucks.


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## pbr (Feb 6, 2014)

ukrkoz, that's not going to work very well unless done on the car with stones which requires a very expensive machine.You'll never sand a rotor flat /true with it clamped in a vise using sandpaper. You can scuff it up where ever it makes contact , but the ridge will have to be ground at the same time as the rest of the surface and it takes a machine to remove variable parallelism and rotor run-out.
But it's serious over-kill in a normal brake job and not necessary. I have used on car grinders using stones (Honda factory tool), on-car brake lathes and many conventional brake lathes.I also apply non-directional finish to rotor surfaces after machining, however it is rarely necessary .
Just use good pads,apply *anti-seize to sliding surfaces* and back of pads and spend time and money on things are needed(recommend brake fluid flush every 2-3 years).
pbr


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## rusty baker (Feb 13, 2009)

I never change rotors unless they show signs of damage. Been doing it that way for 30 years with no problems.


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## Mort (Nov 26, 2008)

I usually swap them out rather than turn them because it's more convenient (especially if it's your only vehicle, only one trip to the parts house), and it used to be cheaper. 

Plus, around here, rotors get badly corroded from deicer so they can't be turned anyway.


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## r0ckstarr (Jan 8, 2013)

Would you believe that after 324k miles, im still on my original factory installed rear drums?


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## Mort (Nov 26, 2008)

I believe that. Most of your braking force is on the front anyway, and if your shoes are adjusted properly they don't ride on the drum like a disc brake pad does. 

Hybrids are even better, you can look at brakes on a 100K mile Prius and the rear brakes look like brand new.


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## taylorjm (Apr 11, 2013)

I know that's not true with the Chevy Tahoe. They wear out the back faster than the front. Gm has it proportioned that way so the front doesn't dip and make the ride less comfortable. If you slam the brakes hard they will hit the fronts more but for everyday driving the rear does most of the work. 


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## WillK (Aug 29, 2010)

Weight transfer to the front wheels happens regardless of how the brakes are proportioned, and no manufacturer would ever bias braking to the rear because that would create oversteer which is instability and highly undesirable for the passenger vehicle driver operated vehicles.

Anti-dive is achieved through suspension geometry.

Also, although I don't in general disagree with a warning about DIY machining, cast iron is not going to shatter during grinding.


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## ratherbefishin' (Jun 16, 2007)

+1, no pulsation=no significant runout....replace the pads and don't worry about it. If it was a hard working daily driver truck, I wouldn't say you'd necessarily get good life out of the new pads, but a passenger car, no problem. I've done that a few times successfully, but when I'm in a situation where I can get a 1 hour turnaround at $10 a rotor, I have those suckers turned....but, then, I don't use the cheap pads, so I like to get the best life and performance out of them.


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## taylorjm (Apr 11, 2013)

WillK said:


> Weight transfer to the front wheels happens regardless of how the brakes are proportioned, and no manufacturer would ever bias braking to the rear because that would create oversteer which is instability and highly undesirable for the passenger vehicle driver operated vehicles.
> 
> Anti-dive is achieved through suspension geometry.
> 
> Also, although I don't in general disagree with a warning about DIY machining, cast iron is not going to shatter during grinding.



Well I think millions of Tahoe, suburban and truck owners would disagree. I belong to a couple of boards and they all say the rear brakes wear out first. And mine does the same. I'm not saying it's the right way, but gm has proven itself to do things against what logic and common sense dictates several times before. 


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## Oso954 (Jun 23, 2012)

> I belong to a couple of boards and they all say the rear brakes wear out first.


Yes, and most of the the posters live in the rust belt. It is rare for someone from a sunshine state to complain about it. Best explanation I have heard is corrosion on the sliding parts keeping extra pressure on the pads. With more drag on the pads, they would wear out first.

Water spray (and salt) from the front wheels corrode the sliding parts of the rear calipers worse than the front.

This may be the reason that GM has re-introduced drum brakes on some of their trucks.


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## WillK (Aug 29, 2010)

As a side note on the particular vehicle I was working on, earlier this afternoon I did a drive check to see if the original grinding noise was resolved and it was still there, so I checked the rear brakes.

Left rear, the pads were consistent with the front, just under 3/16" of material on both pads. Discs measured 0.040" over the discard limit. On the right rear, the outer pad was worn to the rivets. Disc worn below the limit. So both rear rotors and a set of pads will be replaced, plus I have to make sure the RH caliper will float good.


As far as GM... I didn't say there wasn't an issue of undersized rear rotors, which would cause what you're describing, but if there was a reliance upon the rear brakes to provide substantially more brake system torque than the ideal balance, it would lead to more stopping distance and a greater risk of initiating a spin and loss of control in a slide. That would be a problem of the level of the Ford Explorer rollover concern.


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## taylorjm (Apr 11, 2013)

The gm truck brakes were set so that in light braking, and casual stops, the rear does more of the work. In an emergency type stop, the fronts bear the load to shorten the stopping distance as in most vehicles. Especially in the 00-06 models. I think the consensuses was they were set that way to increase stopping capacity when towing. I believe it was in 07 they re engineered everything, including the vehicle geometry, and increased the front rotor size, and set the to be more proportional with the front and rear. Until that time, it was common for people to get over 100k with the original front brakes. Many went 150k until finally just changing them for the sake of maintenance, even though they didn't need it, but the rears were needing to be changed at least every 30-50k.


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