etan

i get a bad vibration when braking at high speeds. and it gets scary bad with coming down mountain passes as you would expect. I'm thinking i most likely have warped rotors, or excessive run out causing high and low points on the rotor. my pads are still meaty so i'm thinking i can get away with replacing rotors only. is this true?? i know that pads have to develop transfer film over time. To accomidate new rotors, will i need new pads? secondly, will i need to get the NEW rotors "turned"... which i'm guessing is the non directional wear using a lathe. my logical guess would be NO BECAUSE THEY'RE new... but you never know.

now for the technical...i've done the searches and have seen many posts in the past and got some writeups from 4x4wire....etc...

i assume that because i'm only changing the rotors i would need to just take off the caliper through the two bolts on the back... and PB blaster and BFH the rotor off?? for new rotor replace and reverse process...

do you guys measure run out or do anything to prep the rotor and make sure its all good?


THANKS IN ADVANCE

GSGALLANT

I always check the runout of my new rotors (but I'm anal that way). I like knowing how things were when I install them... it makes diagnosing things that go wrong later on easier.

Turning rotors is only done to correct runout (or as you mentioned in your post, to even out the rotor so there are no high and low spots). There is no need to turn new rotors. If you buy rotors from a decent company, they should be in spec for runout, if they are not, return them for a new set, or buy them somewhere else.

That being said, I got free rotors from an aftermarket company here that were borderline in spec for runout. When I brought my stock ones in to be turned and the company screwed them up on the lathe, they gave me new aftermarket ones). Even though the new ones were borderline acceptable, I did not get them turned to make them "perfect". I kept them because they were free (I didn't want to push my luck). So far, they haven't gotten any worse, and they've been on there for several months. If they get worse, I'll replace them with higher end rotors. I notice a very slight pulsing during heavy braking, but only because I know to look for it, I think (that's one disadvantage of checking the runout of new rotors). Keep in mind that everytime you get rotors turned, you'll typically lose at least 0.020" of total thickness, which equals a lot of brake applications lost.

You don't need new pads when you replace rotors, as long as your existing ones are still good and they have worn evenly. To prep your new rotors, clean them off well with brake cleaner (they will typically have a preservative oil all over them to keep them from rusting.

Mason Dixon

I would also take your back drum in to get turned too, surprisingly, alot of my vibration during braking came from the drums being slightly warped, remember to adjust your rear shoes after turning the rotors with the reverse e-brake trick

1eye

If your pad still have lots of material left you could reuse them. But, make sure that you "true" them before you reinstall them onto the new rotors. I just "lap" the pads flat on the lapping table [or emerycloth/sandpaper on a hard smooth flat surface]. You want to get rid of the "high/low" spots on them. They should "match" in thickness from end to end and from top to bottom before you put them back on. Be "nice" on using the braking the first dozen stop. It sometimes take a few/multiple stops to get them back working 100%. If you dont feel qualified to work on the brakes, get help from someone who is certified to work on them. [mistakes on brakes could cost you or someone else their life] Good luck. 1eye
PS. do NOT breath the dust, VERY bad for the lungs.

etan

thanks for the help... i was planning to go with brembo flats. i took my rotor off today to take a look, but i'm going to take off the hopefully tommorow if i have time.

91TPU

brakes are very simple and if i was you i would just replace my rotors and pads, better to do em all at once...

it goes as follows
pop hood, remove master cylinder cap
remove the wheel
unbolt you caliper
removing retaining screws with impact driver
remove pads from caliper along with shims
push pistons back into caliper
replace pads and shims and coat rear of pad with antisqueal
put rotor on, put screws in hand tight
put caliper back on, tight bolts to spec
wheel back on, lugs to spec, repeat on drivers side

breknraj

I feel that pads are cheap enough that I would want new on new or turned rotors, unless, for some reason, I had to change a rotor very shortly after changing pads.

For example, I had done a full brake job on my BMW. About 3 months later, I got a killer deal on new Bilstiens for it. When I removed one of the front strut assemblies, it slipped out of my hand, and I bounced the assembly, rotor first, on the driveway. That broke the rotor casting at the small positioning / retaining bolt for the rotor.

Obviously, that kind of screwed over my great deal on the struts, but I ordered another rotor, and just put it on, as is (I didn't even have to bleed the caliper).

DSAB

Don't Forget To Adjust The Rears