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Old 09-06-2006, 06:27 AM
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Default HOT ROTORS - - 98 LT

Hi All!

This weekend I replaced the right front wheel hub on our 98 Blazer LT.

While replacing the hub, I noticed the disc pads were getting close to the wear indicator making its wonderful screeching sound, so I replaced both front disk brakes. This was the first pair of replacement pads since we bought the SUV in 99 and today it has a bit over 83K miles.

Having never replaced the pads, I never noticed or took the time to check how the rotors felt after a drive. Today, I checked the fronts after normal driving and average braking. When I got home, I felt the wheels, they were quite warm, and after wetting my fingertip I checked the rotors and they were both quite hot - just like water hitting a hot pan - had I not wet my finger, the rotor(s) may have burned the tip.

I jacked up the front end, gave both left and right wheels a spin and they spin freely.

I hear no brake sound while driving at low, medium or high speeds.

What I don't know is just how hot these rotors are expected to get with normal driving. The rear calipers are notably less hot than the fronts. Today's local temp was around 80 so I doubt the sunshine had any significant effect.

I suppose I could rebuild the calipers, or maybe just pull the rubber boot out from the pistons (if this is possible without damaging the assembly) and blow a little air pressure around the perimeters.

I tried to Google, "HOT ROTORS" and "BLAZER" but had little success finding valued hits.

We also have a 94 Audi 100S and at 3600 lbs, four wheel disc brakes, the front rotors are no where near as HOT as the Blazer.

Perhaps Blazer rotors typically run HOT and I shouldn't worry? Then again, I do not want to take this condition lightly.

Any thoughts or recommendations are sincerely appreciated.

Many thanks,

Old 09-06-2006, 09:40 AM
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Default RE: HOT ROTORS - - 98 LT

Well... Unless you know how 'hot' is hot... If they aren't warping and/or you aren't experiencing brake fade, then you're fine.

Rotors do get hot. Most of the time well in excess of 500*F. The larger the vehicle, the more heat is generated during braking. The faster the speeds, the more heat is generated.

My research shows an Audi 100 Quattro at ~3200lbs curb weight (3000lbs for the base no AWD). A '98 4dr 4wd Blazer weights in at ~3700lbs. The Audi probably has the same size rotors (if not a bit larger) so it will be cooler. Plus, depending on the cooling of the brakes themselves and the condition of the rotors (rust inside the vents), every rotor will cool differently. The Audi's brakes probably cool faster than your blazers as well. So unless you tested the temps with an infrared thermometer IMMEDIATELY after stopping from the same speed in the same distance, you really can't tell if one was cooler or not.

And that's not even getting into the heat dissipation through the rest of the metal in the rotors, wheels, etc. All of the metals in contact will transmit heat through them. The size of the rotor also has an impact on the heat dissipation.
Old 09-06-2006, 03:04 PM
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Default RE: HOT ROTORS - - 98 LT

Can't compare apples to oranges, GM vs Audi is not a fare comparison to Audi. A lot of the heat generated is due to the rotor/pad material construction. Consider a Ferrari with full composite rotors and pads, they have to reach a specific temperature before they even work well, which equals aggressive braking and driving until the brakes are fully functional...i.e. more speeding tickets for Ferrari drivers especially an F-40 or newer. Whereas a GM and now even the Audi brakes would fade in those conditions.

GM factory brakes are not designed to withstand lots of high speed aggressive maneuvers so they get hotter and wheel design has a lot to do with how fast the rotors get cooled. Audi and most European auto manufacturers support and race their cars. GM, Ford and Chrysler only support the most popular form of racing and that is in left hand circles so feedback from racing teams is limited and technology advances not as with only two major designs racing Corvette and Viper it is hard to transform that to a Neon and Malibu...
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