I have a 2004 ST3 which I acquired about 2 hears ago and finally got around to changing the rear pads on, which turned out were almost toast. As the rotor was close to minimum spec I also changed this along with a new rear caliper. While the wheel was off all bearings were changed by a workshop but the rest of the work was done by me. After installation, setup and a ride, I noticed that the rotor in parts had a slightly bluish tinge to it and was too hot to touch. The wheel seems to spin ok but with a light pad on metal sound. Another day I took he bike for a spin around the block and did not touch the rear brake. The rotor was mildly warm in this case. The pads are EBC HH as were the previous ones. The chain alignment was adjusted using a Motion Pro alignment tool so I believe the rotor is running true. Any ideas on why this may be happening?
Rear rotor getting very hot after pad change
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Pull the caliper and push the pistons all the way in. They should need a bit of force to move, but not so much that they feel bound up. Before you do that, make sure you have enough room in the reservoir to take the fluid or you'll have a mess! With the pads all the way in, test fit the caliper to the rotor and be sure there is some clearance. This checks for two possibilities, bound up pistons and too thick pads or rotor. If all good, reinstall everything and bleed the crap out of the system. When done bleeding the crap out of it, bleed it again. Use a fresh unopened bottle of fluid for this. The reservoir should not be overfilled. If anything default to the lower end of the marks. Last thing I can think of is make sure, as someone said already, the master cylinder and lever are set up correctly and move freely. Not a bad idea to pull the lever pivot pin and grease it from time to time.
It could be that the caliper pistons are not retracting all the way even if the master and pushrod are adjusted properly. After you’ve made sure both of those are adjusted as they should be, see if the pistons are sticking. Sometimes with new pads and rotor you push the pistons in past where they used to be and a little dirt on the pistons won’t allow free movement.
Apologies for not replying to the posts as I am currently travelling in Vietnam. I will update as soon as I return home and attend to the problem. I should mention that the rotor and caliper were new and Ducati OEM so thickness of the rotor and condition of piston and seals will be to spec. I will pull the caliper and check the thickness of the EBC HH pads which I installed, and compare with the thickness of the included Ducati pads which came with the caliper. A good idea to check the position of the master cylinder rod and also the height of brake fluid as I may have over filled the container preventing fluid to return. The caliper pad retaining pin was tough to fit in through the retaining spring even though lubricated with silicon pad grease. Are the pads supposed to move easily or with some resistance. Anyway, I will update the situation in about 3 weeks.
A follow up on the issue I was having with a rear rotor getting very hot after changing the rotor, caliper and new pads. I checked out all your suggestions. The caliper was brand new so the pistons should have operated ok. The new EBC HH pads seemed similar thickness to OEM. The rotor was OEM. Brake fluid height was correct and I adjusted the push rod for correct play and bled the brake again. I also considered my riding style which uses the engine braking alot, and I discovered maybe I use too much rear brake! If I don't use the rear at all for a section of road and check the heat, the rotor is slightly warm. I have modified how I brake and hope all will be well. Thanks for all the suggestions.
It's hard for me to imagine that the rear disk would get hot enough with even strenuous street use to turn the disk blue. I'd try to be more precise about what the base temperatures are by using an IR thermo gun. Ideally, one would start cold and then make a straight run at ~ 100 kph without using brakes. Failing that use the front only, then check the disk temperatures. The rear should read less than the front and be within a few degrees as the temperature of the rear wheel. If not, it's still dragging.
With use, a dragging brake will heat up enough that the fluid expands, causing it to drag more, which heats it up more and so on until bad things happen. Early in my ownership of my then 17 yo, 5000 mile ST2, crud and crap cause my rear brake to heat up so much that I had to pull over because the rear wheel wouldn't turn anymore!
Another possibility is that I find the brake pedal in an awkward place. With the connecting rod adjusted per manual it's in the way of my resting foot. If I'm not careful, my foot ends up resting on the pedal. (It reminds me I need to try again to adjust it to a "safer" angle). Perhaps this is also an issue for you too.
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EXACTLY ?
"If I don't use the rear at all for a section of road and check the heat, the rotor is slightly warm."
If the rotor still gets warm without you activating the brake then you still have a problem. So this is not an issue of riding technique. If checking the freeplay at the master cylinder doesn't resolve the issue, remove the caliper from the wheel; remove the brake fluid reservoir cap, force the pistons back as far as they go. Unless you remove the reservoir cap there will still be pressure in the system which will only force the pistons together again (this could be the cause of your original problem...). Check for free movement of the pistons as one, or both, could be binding - be careful for brake fluid spills at this point, and then put it all back together once any issues have been remedied.
If the rotor still gets warm without you activating the brake then you still have a problem. So this is not an issue of riding technique. If checking the freeplay at the master cylinder doesn't resolve the issue, remove the caliper from the wheel; remove the brake fluid reservoir cap, force the pistons back as far as they go. Unless you remove the reservoir cap there will still be pressure in the system which will only force the pistons together again (this could be the cause of your original problem...). Check for free movement of the pistons as one, or both, could be binding - be careful for brake fluid spills at this point, and then put it all back together once any issues have been remedied.
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Don't top off the fluid in the master cylinders! Everybody seems to do this. Somewhere in the middle is where you want to be.
Thanks for your comments. I am having issues with front brake setup on another thread and someone mentioned it might be a technique issue. The two are related. I will also pull the rear caliper again and follow your suggestions re possible pressure build up...and yes..I did top up the reservoir with fluid, so will reduce the amount also.
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