New rotors with old pads ?

[HTSS_TR]

My Lexus LS400 needs 2 new rear rotors because it's below minimum thickness, the pads are more than 1/2 remaining. I'm debating about replacing rotors only, because the braking on the rear is not as importance as the front. On the other hand, new pads on new rotors will perform better and last longer.

Did anyone ever replace the rotors only without replacing the pads ?

 

[mechanicx]

I've done it before and it's worked OK but sometimes not and the rotor wears uneven. It's tempting to not get the pads but it really doesn't save you much if anything in the long run.

 

[The Critic]

The pads should slowly seat unless they were worn at an angle before.

 

[tdi-rick]

All the time and it's not an issue.

In an ideal world you bed new pads with old discs and vice versa.

New discs are 'green' iron and need seasoning and new pads need the resins (binders) burnt out of them (unless already pre-bedded) which can load a new, green disc with [censored] and impair braking.

As I said, this is from an ideal (racing) perspective, but when you buy a new car it has all new everything anyway, so for the average user it probably doesn't matter a jot, but yes, you can run old pads with new discs.

 

[SteveSRT8]

^^^Love the sig! As an old Rover owner you have my sympathies.

But I do agree that you could run this way, But you already have the caliper off to get to the rotor. Pads are cheap.

I have run old pads too, but I would sand them down perfectly flat first to create a 'new' surface to bed into the new rotor.

 

[Jarlaxle]

It's a Lexus LS400...pads might NOT be cheap!

If they are, I'd replace them. If not...I'd run them. But then, I am cheap.

 

[barlowc]

Looking at RockAuto, rear pads are cheap. They have OE pads on closeout for $10.51 or you could get something like Wagner ThermoQuiets for $24.79 and there's a $10 rebate. So I'd go ahead and replace them while you have everything apart like SteveSRT8 suggested.

 

[JHZR2]

How much is a set of pads?
At least that is what I would do...

 

[bepperb]

Originally Posted By: JHZR2
How much is a set of pads?
At least that is what I would do...


I'd agree, unless you have some amazing pads I'd just replace them while you're there. ThermoQuiets with a rebate should be less than 50 bucks, maybe a lot less.

 

[cchase]

I'd say it depends on the cost of pads. Some rear pads can run $70+ and I'm not sure I see the cost savings there when rotors might not be that much.

 

[HTSS_TR]

I have Wagner ThermoQuiets on other car and like it, I'm thinking about the same pad for the rear of the LS400. After $10 rebate the price at Rockauto or Amazon is cheap, the question in my mind is the current pad has 1/2 life left, discard it is kind of waste and I hate wasting anything.

On the other hand, new rotor with new pad will lasted much longer than old pad with 1/2 life left, so that I don't have to touch it for much longer time, and as posted above why not change the pad while the caliper is out.

For convenience and time saving, I will get new rear pad too. For about $20 and I don't need to do rear brake for an extra 2-3 years is worth it.

Thanks for your opinions/advices.

 

[mechtech2]

For the projected life of the whole set up [years], I'd get new pads unless you really have to count pennies.

Sure, re installing can work,and probably be OK, but may take a long while to seat in - maybe cause problems.
Maybe skip a few lunches for the new pads.

 

[HTSS_TR]

All previous brake pad/rotor replacement, if the rotor was in good shape and above minimum thickness I just changed the pads and keep the old rotor, with/without resurface. Whenever I needed new rotors, usually the pads were near minimum so changed the pads at the same time were obvious.

This time the pads were a little above 1/2 life so the question was is it prudent to keep it. But as many had posted above, new rotors should go with new pads. Especially, the cost of new pads is only $20-30 a set for 3-4 years is not much to keep the old.

 

[wkcars]

can still save the used pads and use that as replacements the next time the pads need replacing?

 

[SteveSRT8]

I have a set of Stoptech pads that have many track days on them.

One of the nice things about the Brembo brakes on my car is you can replace pads WITHOUT removing the caliper! I take them out and sand them down to create new mating surface and put them in a box to re-use.

if you can sand them very flat and true they will bed in just like new pads with the advantage of many heat cycles so no resins/binders to be burnt off.

The only caveat is increased potential for squeal and noises. That's why I suggested that while it's apart, why not change to new pads.

 

[stephen9666]

To the OP-

Why even replace the rear rotors before the next brake job is due? I doubt having them below the minimum thickness will matter at all. Most of the time, people only consider the thickness when deciding if they should turn the rotors or replace them during a brake job.

 

[HTSS_TR]

I was thinking about replacing rear rotors on the next brake job too.

According to Firestone measurements, I took the car there for free brake inspection, both rear rotors are below minimum, I had a quick look and they looked very thin. But I didn't feel any difference in braking performance, no shaking and no vibration while making some rapid stops to test it.

The nominal thickness of the front rotor is 1.26" and minimum is 1.18", currently they are 1.21" and 1.22". For the rear, minimum thickness is 0.59" and could not find nominal thickness, currently they are 0.56" and 0.57". I think 0.03" below minimum is not that critical for now, but it's needed to be changed no later than the next brake job, which can be around a year or so.

 

[HTSS_TR]

Found the nominal thickness for the rear rotor, it's 0.63" only 0.04" more than 0.59" minimum.

With these numbers, I think I will delay replacing rear rotors until next brake job, at that time I will replace both front and rear pads and rotors.

 

[CharBaby]

Jumping in late here but, I have done both...New rotors with the existing pads and visa-versa!

It may not be the optimal brake job but, it gets the job done!

 

[HTSS_TR]

Bought Wagner ThermoQuiet PD613 pad and 2 ATE CW16701 rotors from Amazon yesterday. The price of the Wagner pad was $30.xx for few days but dropped to $24.xx yesterday and back to $31.xx today, when I saw the price drops by $6 I could not resist. The cost of the pad is only $14.xx after rebate, too cheap for not replace it.

Total for 2 rotors and pad was $68 before $10 rebate from Wagner. I will do the rear brake in a few months on a nice summer weekend.

Also bought an impact driver with 4 bits, had been borrowing from brother in-law several times, now is the time to own one.