[sketterman]

Hello All Again!

As the title suggests, I'm looking for any and all owners to chime in here. My rear brake drag seems to be worse than I believe it should be, as my rear wheel is filthy after every ride. I'm looking to see how badly your guys' rear brakes drag and how much dusting you get on your rim.

As a reference example - I washed my bike, rims were spotless. I removed my rear brake pads and scrubbed them with a brillo pad, then cleaned them with brake cleaner. I also used the brake cleaner and rags on the rear rotor, spraying and wiping until the rag was completely clean after a wipe. Did this on both sides of the rotor.

Put everything back together, went on a ride that was less than SIX miles, and did not touch the rear brake once.

Photos below: I did not wipe the entire rim, maybe a quarter of the surface area on each towel, just to get a sample. First photo is from the chain side, 2nd is from the caliper side. These are the OEM pads.

Again this amount of dusting, in just a few miles, is without even using the rear brakes. All of the dust is from the drag. Am I crazy...? This can't be normal?

As for the front...this bike is the complete opposite of all bikes I've ever owned to this day, as the front wheel has ZERO brake drag. The front wheel spins freely, no sound of rubbing whatsoever.

Shaun

 

[noveske556]

Try pulling the chain off and putting the rear on a stand to see if the pads drag enough to limit wheel rotation. A little bit of drag is normal with disc brakes but if it's enough to significantly restrict the wheel from rotating, then you will want to check the caliper piston and slide pins to ensure they can move freely.

The rear wheels on all of my bikes have always been perpetually dirty. It's a combination of brake dust, lube, and all of the road grime and dust that gets kicked up from the front.

 

[09_Blade]

Is the rear rotor hot after a short ride? If it's really making that much dust should be quite hot to touch.

 

[sketterman]

…but if it's enough to significantly restrict the wheel from rotating…

It doesn’t impede movement any more than any bike I’ve had before, it just dusts a lot more haha. Thanks for the reply!

Shaun

 

[sketterman]

Is the rear rotor hot after a short ride? If it's really making that much dust should be quite hot to touch.

Hey Blade, I’ve never considered this. In the spirit of approximation, how warm/hot should the rotor reasonably be under normal conditions? Safe for bare skin? Just wondering how to gauge it.

Shaun

 

[sketterman]

Is the rear rotor hot after a short ride? If it's really making that much dust should be quite hot to touch.

So after a ride that was ~ 12 miles, but mostly at freeway speed, when I parked the bike I felt the rear rotor. I could touch it very quickly which didnt 'hurt' per se, but I could tell it was very hot. If I were to leave bare skin on it for even 1 full second it would surely cause a burn.

Shaun

 

[09_Blade]

If you don't touch the rear brake lever, it's not normal for the rear rotor to be heating up like that, highway speed or not.

As others have mentioned, check that the caliper can move freely on the sliding pins. Make sure the brake line isn't torquing the body of the caliper and thereby contributing to brake drag. Check that the rear rotor is true with a runout gauge.

 

[sketterman]

If you don't touch the rear brake lever, it's not normal for the rear rotor to be heating up like that, highway speed or not.

As others have mentioned, check that the caliper can move freely on the sliding pins. Make sure the brake line isn't torquing the body of the caliper and thereby contributing to brake drag. Check that the rear rotor is true with a runout gauge.

May have had a successful test just now.

I pulled the rear pads and pushed the piston most of the way in. Then I tested the movement of the sliding pins. They 'seemed' to have been stuck in a sense. It took a bit of force to get them to move initially. But I moved the caliper back and forth as far as it would go a few times, ultimately leaving it all the way 'in' toward the wheel.

Then I put the pads back in and pumped the brake. Pins slid with ease as the piston came out and everything realigned. Went for a really short ride...maybe 2 total miles...didnt touch the rear brake. When I got back to the garage, I felt all the rotors. Fronts were hot to the touch from use, rear was kinda hot, but I could easily keep my bare skin on it with no issue. The rear wheel also appears to rotate with less resistance now, although that could admittedly be an induced placebo effect since the rotor isnt too hot.

In any case, I'm taking the CBR to work tomorrow, which is just over 80 miles one-way. I'll (try to) not touch the rear brake again and see how hot it is when I get to work. Thanks for all the info so far!

Shaun

 

[09_Blade]

Does not hurt to pop the rear caliper off to clean and lubricate the sliding pins. Use a high temperature caliper grease and make sure there is no galling on the pins when you inspect.

Avoid moly-based greases for this application. From my experience, it tends to bind the pins over time.

The grease is not applied very evenly at the factory. Apply a layer inside the bore and on the pin itself.