_zebra

alright, y'all're gonna have to forgive my dumb-dumbness, but i'm just trying to diagnose a brake problem & want to make sure i know what i'm doing. i don't work with brakes all that much.

i've been getting a distinct vibration when braking from about 45-50mph and higher, and i can hear/feel that it's coming from the right rear. the thing is that it only does it when the brakes are warm. if they're cold, i can do a few ABS stops in a row that are smooth and normal. after they've heated up, just a light application from cruising speeds will make a strong vibration.

do i sound like i'm on the right track? i plan on having the RR rotor checked and turned as necessary, but do i really need to take them all off?

RedZMonte

Tipically a warped rotor will vibrate in different ways. Make sure you are checking the correct ones. If they dont vibrate when cold then they are pretty true, if they shake when hot then they are warping slightly to cause vibrations.
Vibrations when braking in the steering wheel=Front
Vibrations when braking in the Seat/Floor=Rear

I wouldnt waste my time turning rotors. if they are warped then turning them will only make them warp sooner/worse. as cheap as rotors for the Vettes are i would just order new ones, and yes you will want to remove them to turn them if you want to do that. Check the Pads, if they are worn unevenly then replace them as well, the rears dont wear as fast as the fronts normally. Lots of options for replacments, if you are not looking to spend a lot some stock style Blanks from Rockauto are good.

S

_zebra

thanks for the advice. i know i have to take the rotors off to turn them; i've actually done a little brake work in the past - it's just been a long time. i was just checking to see if it sounded like i had the right one because i'd rather not get the car up on stands & tore down more than i have to in case this good weather suddenly turns back to the crap we've had the past 5 months. and i'm going to upsize to C6Z stuff (just ain't got the cash right now), so i'd rather just fix what i've got without putting too much into the stuff that's about to come off.

i also hear the NAPA rotors are a good inexpensive replacement

_zebra

and yeah, shaking in the floor/seat - not so much in the steering, with a thumping sound from the right side

corvettebob1

Rotor's don't warp they crack if you look closely you will find radial fine lines running from the rotor hat outward to the OD.
You really don't want to chance a chunk cast iron breaking out and getting stuck between the wheel and something else.
Replacement is your only option!

VGLNTE1

Warped rotors are a myth. They don't warp. It's either cracked, something stuck in it, or the pads are shot and they are grinding

Bill Curlee

I replaced my worn out cracked rotors on my 02 ZO6 with NAPA Premium rotors and couldn’t be happier.

I brake HARD and have never had an issue with them. NAPA gives a great military discount if you rate it!

Unless you autocross your car or do extended HPDE events,, you don’t need any fancy brake rotors. Its more BLING than useful over what you have already. The C6 ZO6 /Z51 drilled rotors are known to CRACK a lot easier than a standard rotor! If you want something better than stock, find a quality SLOTTED rotor and the correct pads for your intended purpose.

Save your cash and get what works. If you want bling, then go for bling!

REMEMBER.. Your brakes only work as good as the friction/traction that your tires can apply to the road. If you can activate the ANTILOCK SYSTEM,, your brakes are working fine.

Find a wider stickier tire that overloads your current braking system and then you will need a better brake system. If you are overheating your brake pads,, then you need an up-grade. How often do you over heat your brakes to the point of severe brake fade??????????

BC

VGLNTE1

Aaaaaand, napa gives a lifetime warranty. So when they take ancrap again later on, they can be replaced for free. Lot of road race guys do that trick.

_zebra

pads have plenty left. sun was going down, so i didn't quite see if they had any weird discoloration, cracking, etc.

i'll look the rotors over again, but i don't remember seeing cracks

i know about the structural issues with drilled & that's why i've been planning slotted only. i do HPDE the car along with mountain runs, hence the upsize for more heat dissipation & clamping force. for tires, my invos are a decent compromise, but i'm definitely going 200TW or less next time - thinking NT05s or R888s since i don't DD the car.

for braking frequency, i've just been conservative due to the limitations of what i have at the moment so as to not put myself in a worse situation - hot into a turn & the brakes fail. that said, i've only got them too hot a time or two

hmm... thanks for the tip

_zebra

and the ABS only kicks in right at the end of a hard stop

Bill Curlee

Well,,,,,,,,,,,, that explains your goals. There are dedicated track guys that can recommend a better combo for you. You may get by with premimum track pads pads and a better quality cyro rotor. Depends on how serious you drive.

My buddy muled some new XYX Calipers and rotors and raved about them. I will see if he still have connections.

http://forums.corvetteforum.com/c5-g...t-in-here.html

BC

_zebra

not looking for that much awesome! ever since i got stuck up north, the closest track is 8hrs away & i can't really drive the car for half the year, so i'm pretty sure a set of used C6Z calipers with some decent slotted rotors & pads should do me just fine for 1/2 what them probably cost

k24556

So if you ardoing hpde the pads are an important selection. You porably have glazed spots on you rotors. If your car is an auto, then holding the car at stop when they are hot from a run will transfer pad material. The rotors are either cl 60 or 70. Either one will crack instead of "warping". Now the hub is a different matter, they are plain carbon steel. That part can bend but it would take one heck of a direct hit, and if bent from a hit, something else had to bust, too.

The spec allows several thousandths runout for the rotor like .005". So with the wheel off spin the rotor. Your should be able to see .005 wobble.

If your rotors are not badly glazed,, then putting fresh metallics on an doing a proper bedding, followed by some street driving after a cool down might scrub off the glazed spots.

Drilled rotors tend to crack sooner, but, hey, the abuse of track use will crack them all

k24556

Oh almost forgot, check your guide pins for proper lube and free movement. Then you may be boiling the brake fluid. Flush before every event. Either of these will cause the abs to go bonkers. Boil a front and suddenly your abs lights up to prevent rear lockup.

I suggest waiting on a caliper upgrade. Until you are smoking the dust boots on your caliper pistons, you have a maintenance problem not a hardware problem.

LoneStarFRC

Or there is material from the pads that has transferred onto the rotor surface causing a "pulsating" sensation most noticeable when rolling to a stop, and which is often wrongly diagnosed as a "warped rotor".

_zebra

people really road race automatics?
(obviously aside from the cars that are auto-only)

Dave68

Most racing teams use "J-hook" rotors, which have many J-shaped slots in them. I believe the C7 has them as well. Uneven pad deposits were a problem for me until I bought slotted rotors. Hawk has what they call a "Quiet Slot" rotor that is similar to J-hook, except the slots are not hooked. They are patterned like chicken feet but perform in a similar manner to the J-hook principle. The pads stay parallel to the rotor's friction surfaces and glazing will never happen, due to infrequent use.

k24556

The C6R's were and the C7R's are auto as well. In HPDE there are a lot of Corvette drivers with autos. Maybe not so much if you move up to club racing, but only the pros can afford a race-ready slush-box. However that's off topic.

I think what several of us are saying is you probably need to do some more toubleshooting of your hardware. You might save some dough and keep yourself safe and others too!. Good brakes are more important than anything else. Like parachutes, and concealed handguns, if you need and don't have, there is no substitute.

I suggest you do a thorough dusting and cleaning, pull everything apart. You may not need much, but here is a list:


New rotors if inspection says warranted

The correct pads for what you are doing. Based on what you are writing Hawk HP+'s should serve you well, but watch the dust, it pits the paint on the wheels if it gets wet. If you buy too much brake pad, they won't get hot enough to work right on the street.

Braided steel flex brake hoses

NEW dot 4 brake fluid, (you will need 2 liters for a good flush) I use ATE TYP200 or Super Blue (which from what everyone is saying Super Blue is going to be unavailable. Linda at Apex Performance says she still has some or did a few days ago)

Brake Caliper Hardware kit Dorman HW5634 (F) and HW 5633 (R) These kits include the dust boots for the caliper pins

Caliper seal kits if leaking Dorman D351-810 (F) and D670013 (R) If leaks are seen

you can get the Dorman stuff at a local auto store or Summit.

New Caliper pins if you see any signs of wear. Best ones are dealer items. They are Cad plated steel, so if you see shiny silver instead of the dull gold swap them. A whole set is $30 or so.

Now the service manual says replace the caliper pin bolts and the caliper bracket bolts. These are dealer items and about $70 worth of bolts retail, so your choice. Nonetheless, a shot of blue threadlocker might be warranted if you decide to re-use

A can of high temp caliper pin lubricant. Now I only lube the pins. I find if I put it on the moving surfaces of the contact points on the caliper, it catches fire and burns to ash, so I put my calipers in with no other lube besides the pins.

put everything together clean and dust-free. Then bed your pads in according to the manufacutrer's procedure. Then, after the pads cool go out again and get into your brakes enough to run the ABS for a couple seconds. Bleed your brakes again, maybe 50 ml from each caliper. Then cycle the abs again. Some say you can do it on a lift, but I've never tried. After a couple cycles you should have new fluid in the ABS, where you want it.

generacer

This is a very good discussion and I think I have bad rear rotors