Appearance of rear disc brake rotors

[Stephen Tashiro]

The rear disk brake rotors of a friend's 2001 Tiburon have the usual surface of a used rotor, but it is not bright and shiny like the rotors on the front brakes. Do the surfaces of front and rear disc brakes normally have a similar brightness? Or is it normal for the front ones to be shiny and the rear ones to be dull. The font and rear are different designs of rotor, but i'd think that they'd be made of the same steel.

[Kevin W Johnson]

The appearance is likely to differ due to the brake bias between front and back. Brake bias refers to the amount of brake caliper pressure applied front and rear when the brake pedal is depressed. More pressure is applied to the front brakes. If you've ever jammed hard on the brakes, the nose of the car dives, this is done for a couple reasons. One to keep weight on the tires, increasing traction, therefore reducing stopping distance, but also keeps traction for the steering tires to allow better control.

Its also possible that their braking style plays a small role in the difference. There are a lot of people that will ease on the brakes slightly to adjust their speed based on the person in front of them, when simply just letting off the gas would accomplish the same goal. This would cause more front rotor wear because of the bias.

In short, if the vehicle brakes properly, doesnt nose severely, or pull to one side under hard braking, then its nothing to worry about.

[Bryan Morgan]

Are you looking at them after the cars been sitting for awhile or after you just got out? If you jam on the brakes a lot the metal discolors a little bit from the heat. Are the pads the same material on the front and back? I use "racing" pads on my car and after a bit of, uh, "spirited" driving the discs darken a little until they cool off.

[Callan Campbell]

Most likely caused by the front bias towards the front brakes. With a load put in the rear of the vehicle like something heavy weighing a 100 pounds or more, you'd probably then see a different wear pattern on the rear rotors since they'd now be working harder than before. Look under the vehicle to see if there's a fairly large rear weight portioning valve connected to the rear brake lines. Once enough weight is loaded on the rear axle/suspension, these valves change the way the rear brakes are working to help with the increased load at the back. It's so rare that I load my Montero up enough to engage my valve thats mounted next to my rear axle, BUT, when I do, you really notice the difference in the braking of my truck.

[Jason Roehl]

The appearance is likely to differ due to the brake bias between front and back. Brake bias refers to the amount of brake caliper pressure applied front and rear when the brake pedal is depressed. More pressure is applied to the front brakes. If you've ever jammed hard on the brakes, the nose of the car dives, this is done for a couple reasons. One to keep weight on the tires, increasing traction, therefore reducing stopping distance, but also keeps traction for the steering tires to allow better control.



"Nose-diving" is entire due to the center of gravity of the suspended portion of the vehicle being above the plane of the axles. If the CoG of the suspended part of the vehicle were below the plane of the axles (tough to do), it would actually appear to lean backward during braking. It's not really a design issue, it's a physics issue. Stiffer suspension reduces nose-dive.

Braking will always cause more ground pressure on the front wheels, so more braking pressure can always be applied there since the higher normal force between the tire and the ground will allow it to keep rolling under higher that braking pressure. On most vehicles, up to about 70% of the braking is done by the front.

[Stephen Tashiro]

Are you looking at them after the cars been sitting for awhile or after you just got out? If you jam on the brakes a lot the metal discolors a little bit from the heat. Are the pads the same material on the front and back? I use "racing" pads on my car and after a bit of, uh, "spirited" driving the discs darken a little until they cool off.

I'm looking at the rotors after the car has been sitting for several hours. I don't think it gets any "spirited" driving.

The brakes act normally except the emergency brake isn't working correctly. It engages the drivers rear brake but not the passengers rear brake. As I read the info from AllData, it should engage both.

[Jeff Monson]

Its not uncommon for rear rotors to appear as you describe, however if you are having ebrake problems on top of rusted rotors I'd suggest a thorough rear brake inspection. Its pretty common for rear cables to stick or the ebrake portion of the caliper may be rusted up. Sounds like its time for a couple loaded calipers and rotors.

[Bryan Morgan]

I'm looking at the rotors after the car has been sitting for several hours. I don't think it gets any "spirited" driving.

The brakes act normally except the emergency brake isn't working correctly. It engages the drivers rear brake but not the passengers rear brake. As I read the info from AllData, it should engage both.

Is the parking brake drums inside the disc rotor or does it engage the caliper piston? Could just be out of adjustment. My cars have always been "self adjusting" but you have to drive in reverse and pull on the parking brake handle to set them.

[Stephen Tashiro]

Is the parking brake drums inside the disc rotor or does it engage the caliper piston? Could just be out of adjustment. My cars have always been "self adjusting" but you have to drive in reverse and pull on the parking brake handle to set them.

There is no drum. The cable from the parking brake goes to the caliper. I agree that the passenger's side cable could be out of adjustment.

The Tiburon is a problematic car to work on! There is no Chilton or Haynes for the 2001 and the ALLDATAdiy info isn't extensive.

[Russ Filtz]

The parking brake cables themselves can rust up as well as the caliper. Time for a thorough check of the entire rear brake system I guess just to be sure.

[George Lesniak]

There is no drum. The cable from the parking brake goes to the caliper. I agree that the passenger's side cable could be out of adjustment.

The Tiburon is a problematic car to work on! There is no Chilton or Haynes for the 2001 and the ALLDATAdiy info isn't extensive.

Stephen,

Go to http://www.hmaservice.com/ and create an account. Hyundai OE service information is free. All technical service information available to the dealership is on this website.

George

[Stephen Tashiro]

I got an account on that site, but I can't find anything on it that is equivalent to a service manual. I purchased an ALLDATAdiy account and the information on there is rudimentary, less than you find in a Haynes or Chilton book.

[George Lesniak]

I got an account on that site, but I can't find anything on it that is equivalent to a service manual. I purchased an ALLDATAdiy account and the information on there is rudimentary, less than you find in a Haynes or Chilton book.

Stephan,

Log in and click on "shop" which stands for shop manual. ID the vehicle as a Tiburon (RC). The entire dealership service manual is there. ETM is wiring diagrams, DTC is fault caode diagnostics, TSB is technical service bulletins, ECU Upgrade contains information on flash updates and what they correct, OBD-II contains additional non-code related diagnostics and OM is for owner's manual.

George

[Stephen Tashiro]

George,

Thank you very much for those directions. They work just as you said.