I have read some threads here about rear brake drag due to a failing secondary master cylinder. It has been suggested that if, with the bike on the center stand, the rear wheel won't spin freely, the rear brake is dragging.
My question is what exactly is meant by "spin freely." I understand that it's fairly common to hear some metal-to-metal-sounding grinding as the rear wheel spins and that is the case with mine. My wheel spins, but there is definitely _some_ resistance. If I give it a pretty good spin, it'll go a full rotation or maybe a little more, but that's it. I looked at the pads and they are not quite down to the wear marks. There is also basically no gap whatsoever between the rotor and the pads.
I have not noticed the bike being difficult to push around in the garage (other than its inherent weight) and I've not noticed that the bike slows down particularly quickly when I get off the gas. I also haven't noticed any significant drop-off in fuel mileage or increase in rear pad wear.
What caused me to wonder about all this in the first place is that I've noticed the rear disc gets much hotter than the front discs after a typical ride. Maybe this is normal - I just don't know. For example, today, I did a short test ride up the interstate to the next exit and back. The total round-trip was about 7 or 8 miles and the outdoor temperature was about 75. The only braking was done at the couple of stop signs between my house and the interstate and at the turn around point at the next exit. When I got back into my garage, I immediately attached a digital thermometer to the rear disc and it climbed to about 156 degrees before gradually cooling down. The front discs were simply warm (not hot) to the touch. Obviously, 150 something degrees isn't dangerously hot, but I was only gone about 10 or 12 minutes. My assumption is that if there is some drag, the temperatures would just continue to climb with each mile.
If I had access to a number of other bikes up on their center stands, I could just spin their rear wheels and see how mine compares, but since I can't do that, I figured I'd draw on the vast experience of this forum. Does this sound normal?
Thanks.
My question is what exactly is meant by "spin freely." I understand that it's fairly common to hear some metal-to-metal-sounding grinding as the rear wheel spins and that is the case with mine. My wheel spins, but there is definitely _some_ resistance. If I give it a pretty good spin, it'll go a full rotation or maybe a little more, but that's it. I looked at the pads and they are not quite down to the wear marks. There is also basically no gap whatsoever between the rotor and the pads.
I have not noticed the bike being difficult to push around in the garage (other than its inherent weight) and I've not noticed that the bike slows down particularly quickly when I get off the gas. I also haven't noticed any significant drop-off in fuel mileage or increase in rear pad wear.
What caused me to wonder about all this in the first place is that I've noticed the rear disc gets much hotter than the front discs after a typical ride. Maybe this is normal - I just don't know. For example, today, I did a short test ride up the interstate to the next exit and back. The total round-trip was about 7 or 8 miles and the outdoor temperature was about 75. The only braking was done at the couple of stop signs between my house and the interstate and at the turn around point at the next exit. When I got back into my garage, I immediately attached a digital thermometer to the rear disc and it climbed to about 156 degrees before gradually cooling down. The front discs were simply warm (not hot) to the touch. Obviously, 150 something degrees isn't dangerously hot, but I was only gone about 10 or 12 minutes. My assumption is that if there is some drag, the temperatures would just continue to climb with each mile.
If I had access to a number of other bikes up on their center stands, I could just spin their rear wheels and see how mine compares, but since I can't do that, I figured I'd draw on the vast experience of this forum. Does this sound normal?
Thanks.
If you're a Seinfeld fan, its like when George Costanza went to the doctor with an ailment and was hoping for a "get outta here" answer. Thanks for the "get outta here" answers.