Brakes hot

[jimbo409]

I have a 1988 560 sl with the original alloy wheels.
My question is when I drive the are for 15 minutes or so the wheels a so hot to the touch.is this normal because of the ally wheels.the front are much hotter than the rear rims.thanks jimbo

[oldsinner111]

either your brake lines are old,or you need to rebuild brake calipers.

[97 SL320]

Brakes turn kinetic energy into heat energy so having them get hot is normal. The front brakes do more of the work so they will be hotter.

If you haven't touched the brakes in those 15 min and coasted to a stop, something may dragging and needs attention.

If you drive an automatic transmission car with two feet, make sure you are not dragging the brakes while on the gas.

[fonzi]

I've got a 1992 500sl with big chrome open AMG 5-spoke r129 wheels and I'm experiencing the same thing. I tested one of the very hot front wheels (so hot at the wheel lip that I can't hold my hand on the wheel for more than a second without burning). The wheel spins freely when in the air. So calipers aren't locked. I wonder if it's the rusty old rotors that are slotted and have dots them.

I also noticed some sponginess in the brakes and wonder if maybe there is mild dragging from expanding water vapor or air in the brake lines. As the car and brakes heat up with driving, I wonder if the expanding fluid is very mildly pressing the pads up against the rotors. The drag could per imperceptible, but just enough to add the extra heat.

We both probably need to bleed out our brake system as brake fluid takes on water over time.

[Graham]

It's normal for brakes to get quite hot. I know that I can't touch the hub area on my alloy wheels on my cars after even driving around town. At one time I measured temperatures with an IR gun - Forget numbers, but in the 150F range. The pads are always almost in contact so even when not applied, there is some heat generated.

My concern, was that it could be the wheel bearings that were getting hot. Had this happen on trailers, and there the IR gun was useful. But not on cars because of the brake heat.

Search found this:

"The typical generic "normal driving" temperature range for well balanced vehicle brakes is 100 to 200 degrees. A controlled mountain grade descent can produce brake temperatures between 200 and 400 degrees." from this site: Brake Failure Analysis

Over 500F and you will apparently smell the brakes and perhaps see smoke.

[meltedpanda]

if you are pulling left or right youmay have a sticking caliper , or collapsed hose when you get home , jack her up when they are hot and see if the wheel spins freely or feels like it is stuck. Are both sides the same?

[jimbo409]

The wheels spin freely on both fronts,I am going to bleed the fluid just in case.i am hoping this is normal,neither wheel pulls to the side

[meltedpanda]

thats all good, is the pedal spongy? sounds normal at this point , if wheel bearings are the cause , you might be hearing a slight roar??