# "Mechanic says new rotors" question...



## ArloS (Feb 10, 2009)

What would happen if I just put new pads on slightly scored rotors that can't be machined? Would the world explode? I'm not a brake expert by any means, but I'm EXTREMELY practical. Any advice from the forum?

Thanks.


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## bruiser (Jul 30, 2005)

If the rotors are to thin, they could crack and cause brake failure.


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## Tumbleweed36 (May 14, 2005)

Check with another mechanic to make sure. Some shops will say you need new rotors when they are not needed, it is called "money." If they are only slightly scored, then (and they have not been already turned), then you should be able to get them turned.


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## ArloS (Feb 10, 2009)

Thanks for the replys, but my question remains unanswered.

My plan is to put new pads on these rotors as is (slightly scored). 

I've replaced pads on this vehicle a couple of times and pads/shoes on other vehicles many times. I know what I'm doing but don't understand what difference it makes if the rotors are a little rough. 

Just put new pads on the thing and drive it. What would be the problem with that?

Edit: I will be doing the pad swap myself, incase that wasn't clear.


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## Tumbleweed36 (May 14, 2005)

That was certainly not clear to me, but maybe I just missed it while reading. If you do this, it may (not will, but may) do several things, depending upon how much they are scored: 

With major scoring your braking would likely be very rough and grabbing at times and where there is more scoring on the rotors, it would likely pull to one side somewhat. Second, it will cause your new pads to wear out very quickly and due to the uneven stopping, might also wear on tires rapidly. 

With minor scoring, you might not notice much difference, except it would certainly wear your new pads out much quicker and might not provide you the same stopping power if they were not scored.

Have you considered taking those rotors after you take them off and getting them turned by an auto store, they will do that pretty reasonably priced. That can save a bundle if you take them in instead of having someone else do them. 

Unless they have been turned multiple times, normally they can be turned or at least that is the experience I have had.


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## ArloS (Feb 10, 2009)

I got the car back tonight and can't figure it out. Pads are close, maybe 80-90% but no scoring. I had originally taken the car in for another problem that was fixed. I put new pads on and called it good. Thanks guys.


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## Tumbleweed36 (May 14, 2005)

Some mechanic has $ in his eyes and that was why I asked you originally to take it to another source to make sure. That happens quite often and glad you dodged that bullet.


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## 2088bob (Feb 10, 2009)

No the world is not going to end. If the rotors have never been turned and as you say are only slightly scored 

Here is a trick i have been using for along time Go your local parts store and buy the hardest pad available for your car don't tell the zit faced kid behind the counter why, just tell him you want the hardest or premium pad for your car 

Now depending on how bad your rotors are scored you may experience a small amount of pulsation in the pedal and may even wiggle a small amount 


Some rotors on cars nowadays are very soft there is a very good chance the hard pads will clean the rotors up 

I have a 2003 f150 ford with 150000 kms on rotors using this trick and it stops quite well 

take some fairly coarse sandpaper and break the glaze on the rotor before you install the pads


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## vnestohr (Feb 27, 2009)

ArloS said:


> What would happen if I just put new pads on slightly scored rotors that can't be machined? Would the world explode? I'm not a brake expert by any means, but I'm EXTREMELY practical. Any advice from the forum?
> 
> Thanks.


As some other posts highlighted, there are a couple of other considerations.

But, the big question is: why can't they be machined? Are they too thin, or are they too warped (or combination)?

Setting aside those concerns, the scoring is a combination of raised and lowered 'rings' in your rotor (that matched your break pads). New break pads would be flat - so you would (initally) have less contact between rotor and break pad, therefore less braking power (at the same depression point on the pedal). You would need to push a bit harder on the pedal to get the same braking effect. How much, I can't say - depends on the amount & depth of the scoring - it may not even be noticable.

The effect of this is to concentrate the forces of the braking - same braking demand on less surface area.. The good point is that both the pad and rotor will wear at the contact points and this will tend to smooth things out, so you have less / smoother scoring. The bad point is that this will also concentrate the heat that is generated during the braking. This cause bad things - warping, 'burning' the pads on those groves, etc. to happen. Of course, these are extreme cases, and I'm mentioning them only to scare you. 

What you may notice is a bit less stopping power, 'throbbing' in the break pedal, uneven stopping, pulling to one side, and squealing. These may occur only under certain conditions - like when you are stopped and ease up off the brakes just enough to inch forward, lightly brake in a turn, etc. 

I like to do a lot of the more simpler maintenance jobs on my vehicles. Replacing brake pads falls into this category, so I've done exactly what you are thinking of on a number of ocasions. My 'road test' consisted of finding a 'safe' place - getting up to a decent speed, and slamming on the brakes as hard as I could. I'm not going to recommend this of course... It did tell me what my maximum braking power was, though. 

At any rate, I found that it was pretty close costwise between having the rotor turned, and just plain buying a new rotor from an autoparts store and installing it myself.


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## 2088bob (Feb 10, 2009)

Given the cheap cost of rotors today I would not even bother thinking about turning rotors anymore eg. 2002 sunfire new rotors $24 turning rotors$16 its pretty much a no -brainer


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