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I'm having to replace the front rotors on my 2013 EGlide for the second time. They are HD "floating" rotors. and have about 30000 miles on them. One is barely in spec and the other has .010" runout. So out they go. I was replacing the brake pads today and noticed that on both calipers the pistons were not moving freely and smoothly. So I extended them as far as I dared and cleaned them thoroughly. They seem to be moving a lot better now. So my question is could the stuck pistons contribute to the discs warping? What else could cause it?
I'm having to replace the front rotors on my 2013 EGlide for the second time. They are HD "floating" rotors. and have about 30000 miles on them. One is barely in spec and the other has .010" runout. So out they go. I was replacing the brake pads today and noticed that on both calipers the pistons were not moving freely and smoothly. So I extended them as far as I dared and cleaned them thoroughly. They seem to be moving a lot better now. So my question is could the stuck pistons contribute to the discs warping? What else could cause it?
Yes.....
Heat can cause warpage of the rotors.
If a caliper piston is sticking, and causing a pad to excessively rub on the rotor, that will create more heat which can lead to warping the rotor....
As a quick/easy/free check, you may want to make sure that you didn't get a tiny piece of sand or something back in-between the inboard surface of the rotor and the wheel boss where the rotor bolt attaches the rotor to the wheel. I found that recently on my 14 SGS just before a long road trip and thought I was going to have to replace my rotors. It caused one of the rotors to show about 0.020" warpage until I removed the sand or dirt. It want back to normal after that.
But I would think that if your calpers aren't retracting properly, that if one of the brake pads may have rubbed on the rotor hard enough and long enough, it could cause excess heat on the rotor, but not sure if it would get hot enough to warp it. MAYBE if it was pre-heated like that then followed by a long session of downhill twisties with heavy braking?
The pics below show how much space can open up to allow junk between the rotor and the wheel..........
That can most definitely can cause uneven wear on rotors and pads. If you do the work yourself. Take everything apart, clean, and lube it going back together.
I'm having to replace the front rotors on my 2013 EGlide for the second time. They are HD "floating" rotors. and have about 30000 miles on them. One is barely in spec and the other has .010" runout. So out they go. I was replacing the brake pads today and noticed that on both calipers the pistons were not moving freely and smoothly. So I extended them as far as I dared and cleaned them thoroughly. They seem to be moving a lot better now. So my question is could the stuck pistons contribute to the discs warping? What else could cause it?
Pads that arent retracting enough could cause excessive heat. Ride the bike and before you park make sure you apply the brakes, raise the front wheel and spin it. If theres enough drag that wheel will hardly rotate. I had to replace my rotors because they were warped at 10K. The replacement aftermarket ones have been on there for 13K and no issues. Possible the factory ones just suck.
I read about this problem in Cycle World magazine a few years. ago. A letter writer asked what caused his front brake to
lock up and prevent his front wheel from turning.
They claimed the problem was caused because the return hole, which allows brake fluid to return to the master cylinder after
using a brake, was partially plugged.
They also warned that if enough heat bult up it would cause more pressure against the rotor, which would create more heat,
more pressure, etc. until the brake would eventually lock up. Cooling down between rides or not using the brake would prevent
the heat buildup.
They recommended cleaning, perhaps even replacing the caliper. It may sound extreme but so does having a front brake lock up
at speed.
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Front disc warp
