Front rotor warpage

My 99 K1500 ext cab ( 98 body style ) is warping front rotors about every 20,000 mi. . The truck is stock, I have checked the rear brake and adjusted them, checked the calipers they are floating on the pins and release as they should. Recently I changed the master cylinder, this improved the feel of the brake pedal but the rotors need replacing again. I have not had this problem with any other vehicle so any help would be appreciated.

How much drag are setting on the rears? If the emergency brake pedal goes too far, the rears are not tight enough.

You should feel some drag when you turn the wheel or drum.

//2000CAYukon

was this truck ever in an accident? you might have a bent hub or loose wheel bearing.

Are you using factory pads? Some aftermarket pads have the wrong hardness and can cause rotors to heat excessively. Also you may want to check for Technical Service Bulletins from GM, I think there is one for 92-99 trucks. Check clearance between caliper and Spindle, if clearance is not correct may have to file some off spindle to make correct clearance. I think the TSB also mentioned something about replacing a valve (proportioning valve I think). Does the vehicle pull when braking?
I replaced my factory rotors with cross drilled and slotted ones from R1 concepts in California, cost was $99 plus $15 to ship to AZ, Suburban stops way better plus the rotors are supposed to stay about 250 degrees cooler which will prevent warping.

How much drag are setting on the rears? If the emergency brake pedal goes too far, the rears are not tight enough.

You should feel some drag when you turn the wheel or drum.

//2000CAYukon
The emergency brake pedal does not travel far at all and the rear brake are set so that they have a slight resistance when spun by hand.

Are you using factory pads? Some aftermarket pads have the wrong hardness and can cause rotors to heat excessively. Also you may want to check for Technical Service Bulletins from GM, I think there is one for 92-99 trucks. Check clearance between caliper and Spindle, if clearance is not correct may have to file some off spindle to make correct clearance. I think the TSB also mentioned something about replacing a valve (proportioning valve I think). Does the vehicle pull when braking?
I replaced my factory rotors with cross drilled and slotted ones from R1 concepts in California, cost was $99 plus $15 to ship to AZ, Suburban stops way better plus the rotors are supposed to stay about 250 degrees cooler which will prevent warping.
The pads are NAPA premium semi metallic, and the truck does not pull to one side or another. I will have to look into the service bulletins , thanks.

was this truck ever in an accident? you might have a bent hub or loose wheel bearing.
The truck was a dealer demo unit so I would doubt it was in an accident but it was probably not treated with tlc the first 20,000 mi. . I have checked the spindle or wheelbearing assembly and that checks out fine.

You said that the brake pedal is firmer now... could it be that you might be pressing too hard now?

You said that the brake pedal is firmer now... could it be that you might be pressing too hard now?
The problem started before the master cylinder was replaced

Are you using factory pads? Some aftermarket pads have the wrong hardness and can cause rotors to heat excessively. Also you may want to check for Technical Service Bulletins from GM, I think there is one for 92-99 trucks. Check clearance between caliper and Spindle, if clearance is not correct may have to file some off spindle to make correct clearance. I think the TSB also mentioned something about replacing a valve (proportioning valve I think). Does the vehicle pull when braking?
I replaced my factory rotors with cross drilled and slotted ones from R1 concepts in California, cost was $99 plus $15 to ship to AZ, Suburban stops way better plus the rotors are supposed to stay about 250 degrees cooler which will prevent warping.
I have been unable to locate any service bulletins from GM regarding this type of probem online. Is this something that only dealers have available?

I have a '97 K1500 and it does the same damn thing. Mine only warps the right side though. It's starting to shake again and the brakes were all done just over a year ago.

check and see if your calper is floating. the pins tend to rust and that will stop your calper from returning to center when the brake is let up.

also check the spendal for ware. if you see a spot ware its been rubed the bearings will not seat right.

clean the calper and lube it. when you replace the rotor change all the bearings. saves you headacks later.