warped rotor?

**chuckstop00** · 06-07-2007, 09:29 AM

I got some Baer Decella rotors and Morse ceramic pads last summer at
Autozone. The other day I was driving to work and started getting a bad
vibration at about 70 mph on the right front. If I slow down it goes away. When I drove home, it did the same thing, but only after 5-7 miles. When I got home, I touched the rotors, and the rf was hot, but the lf front was only warm. Thinking this might be a hung up pad, as the inboard side of the rotor was hotter than the outboard. Going to break it down this weekend and look. The question I have, is there an easy way to tell if the rotor is warpped? I am hoping that because it doesn't vibrate right away, even at 70-75, that
the rotor might still be ok. Also, they should still be under warranty, 3yrs, so
I need a way to see if it is warpped.

**bigrondownhiller** · 06-07-2007, 11:26 AM

do you have a dial indicator? it only takes a little bit of runout to cause a vibration.

**chuckstop00** · 06-07-2007, 12:47 PM

no. eyeball only, may not be good enough. Another idea I had is a straight
edge, at least that would work for the inboard side.

**lightingrod** · 06-07-2007, 02:03 PM

more info needed.

does it pulsate when braking at 70? or is it shaking the car without braking like a out of balance tire at 70? stock rims/tires? is the car lowered? wheel bearings howling? alignment caster shake? u-joint? shocks?loose lugs? driving over the same uneven road surface streach of highway? ect. more imput needed.

also the the rotors are going to be hot and burn your fingers after you have driven it and applied the brakes a few times. the piston side of the rotor will allways be hotter. thats where the primary force is applied the the inner and transfured to the outer pads. is the either of the rotor surfaces turning blue?

a straightedge isn't going to tell you anything you need a dial indicator to measure runout properly.

**chuckstop00** · 06-08-2007, 07:06 AM

Pulsate at 70? No - however, a few weeks back I did notice that if I used
the brakes firmly, they would pulsate a little, then it would stop. It cleared
up by itself, so I thought it was just dust/dirt or something.

I drive about 20 miles on the highway to/from work. Had been fine until a
couple daze ago. I was about halfway to work and it started shaking on the
rf, actually thought I had a tire going down. On the way home, same thing,
was ok for half way then started shaking again. This was at 70. Slowing down
to 60 made it go away, but speeding up would make it come back. Didn't do
that for long. Now I go the back roads, 45 to 50 tops, no vibration, even
under firm braking.

I typically don't use the brakes a lot anyway, 6-spd and downshift with SLP
loudmouths more fun anyway!

As far as the tires/rims, tires have maybe 15K, but the rims are bone yard
stuff, had to take the peeling chrome stock rims off. Had these rims on for
about the same time as the new brakes ~ year.

As for the heat, one side is definetly warmer, rf vs lf.

Will be looking at it over the weekend and update. Will also check suspension
and stuff.

Appreciate all the feedback!

**lightingrod** · 06-08-2007, 08:04 AM

viberations are a funny thing and can be hard to diagnoss. they can transmit from one end of the car to the other, making it seem that the vib is coming from one area when its actually coming from another.

well from how you are explaining it, the brake rotors are not your problem. there only going to shake the car when you apply the pedel. lessin their pulsating so baddly that their shaking your teeth out.
for the amout of time they have been run, you would have felt an out of balance rotor from the get go. older rotor design had weighted plugs insreted into the cooling fins for balancing and, have been known to loosen and fall out. newer designs are now counter balanced by grinding away material. which is what design your's are. very hard to knock these designs out of balance. less you sledgehammered them to remove them from the flange.

bent rim? no wads of rust between the rim and flange? ....have your tires balanced on a properly caliberated machine. an out of balance tire will pound the road surface ,and the vibs will be absorbed by the shock till, the fliud becomes hot and thin then you'll begin to feel it through the car.
than again your shock could be ready to shit the bed and cause this vib. rightside suspension allways takes the most abuse from potholes and such.

tierod joint and upper ball joint tight? if there loose they can cause a vib.

u-joints on the way out can cause some funny viberations. they may not be loose to the touch, but the needle bearings can be dried up and just starting the send out the shake of death. take a peek at those. while your there look for the balance weights on the driveshaft itself. they can loosen over time and fall off, or be knocked off from road debris kicking up. steel shafts will have a small circular spot weld and aluminum shafts will have an epoxy patch where the weights are/were. they'll both usually have one on both ends.

have your alignment checked.

motor/trans mounts trashed?

one otherthing, brake pads are cheaper to replace than a flywheel, pressure plate and clutch disc.

**chuckstop00** · 06-08-2007, 01:42 PM

not if u shift right

Thanks for the tips, will be looking at stuff over the weekend. Need to do a
water pump (rattling and leaking) and power steering pump (leaks when real
cold) anyway, so I will have all the tools out.

**JEB** · 06-10-2007, 08:33 PM

Sounds as if you may have an out of balance wheel/tire.

**chuckstop00** · 06-11-2007, 08:10 AM

Well, things didn't go exactly as planned. The good news is that changing the
water pump got rid of the rattle from the old one. Bad news is the rebuilt
power steering pump I put on leaks worse than the old one. Looks like it's
coming out of the back of the unit. Bottom line is I didn't get much time to
diagnose the vibration. I did jack up the rf with the wheel on and pulled and
pushed on it in various directions. Doesn't seem to have any loose suspension
parts, tie rod end, ball joints. So I took the wheel off and spun the rotor by
hand, didn't seem to feel any uneven pressure. Pads looked pretty good. So
put the wheel back on, and now it shakes under braking at about 50 mph.
Gonna check where I bought the rotors and see if they have a way to check
them out. Aggh! While I was under the car, I noticed some surface rust under
the back seats!!!!!!!!!! The more you look the more you find . . . .

**chuckstop00** · 06-20-2007, 10:18 AM

Well, after getting the ps all set, missed an o-ring as stated in another thread
I tore apart the front brakes. I found that a slide pin on the passengers side
was sticking slightly, and one on the drivers side was frozen completely. Had
to get a new bracket. Now the vibration at speed is gone. But once in a while
I still get some shudder when I get on the brakes. But if I let off, then brake
again, even if I speed up, there is no shudder. The calipers/pistons didn't look
all that great, so I am thinking maybe one is sticky. If the rotor was warpped
the vibration would be constant under braking right? Would speed matter?

**SteveC** · 06-20-2007, 06:00 PM

Originally Posted by JEB

Sounds as if you may have an out of balance wheel/tire.

I agree 100%.

SteveC

**99'CajunFirehawk157** · 06-20-2007, 07:11 PM

I went to have a nail removed from my rf tire last week, seems the prev owner was a lil sloooooow and used at least one can of fix a flat or maybe two and LEFT IT IN THE TIRE, not ever getting it repaired, well just imagine adding a 16oz glass of water to the inside of your tire and driving that around for a while, @ 55-60mph the front danced like oprah on crack, tire fixxed the correct way, no vibration.

PS-My brakes do pulsate a lil upon braking but I think that a stock gm thing...new rotors coming soon.

**02z28ls1** · 06-20-2007, 07:29 PM

Fix a flat is really a bad idea-not just because of the balance thing. It deteriorates the rubber. I would replace this tire if you drive or corner hard-wouldn't trust it.
Generally speaking, as a rule, tire balance issues will surface around 30-35 mph. Other vibrations will be under different circumstances.