Front Rotor Freeplay Concern

[Gregger]

I have a problem with a pulse in the front brake lever while braking. You can also feel the bikes speed pulse as you come to a stop at slower speeds. There is no pulse while braking at higher speeds. Problem is strictly with the front brake.

My concern is with the amount of freeplay the rotor should have on the floating buttons. From what I know, the front rotor on our Rockets is made up of 3 sections, the inner piece (bolts to the wheel), floating rotor buttons and the outer friction disc held in place to the inner portion with said floating buttons. Mine are seized. The friction disc can't move on the buttons. I cannot spin the buttons by hand either. I'm guessing the rotor cannot float on the buttons which is causing this condition. Checking Youtube, some guys spin the buttons to free them up using either brake cleaner or some penetrating oil and others say don't do anything. What have you guys done to solve this.... or has it been an issue?

Unfortunately I can't do anything till the temps get higher since the Rocket is sleeping for the winder in the cold, cold, cold, shed. (hate winter when I can't go south).

 

[1K9]

I replaced my originals with these EBC. There is some OK free play in the OEM. How much? Can't tell. If they are sized, loosen them. Put a bolt through the button and clamp it down with nuts on both sides. The spin the button loose. If they won't budge try rubbing alcohol to break the corrosion. Clean with brake cleaner and soapy water. Decontaminate the disc well. This is best done with the rim off the bike and the disc off the rim. The hex heads strip easy. Buy a titanium set. Blue locktite is recommended. If you use is do so sparingly. Careful with the torque. I check the brake caliper and rotor bolts periodically.

 

[TURBO200R4]

I would spray with wd40 or similar let set a day then try to wiggle a little if that does not work use the bolt & nut like 1k9 says
i think they they can have a lot of play.

 

[John Miller]

Ok let me chime in. I actually had the very same front brake pulse and shudder when I would apply the front brake lever. The faster the road speed when brake was applied the front end would vibrate harshly like a warped disk, you could feel it through the brake lever s well. I then cleaned out all the disk buttons and spun them whilst flushing with brakleen to get rid of the dust and grit that had built up over the years which was causing the disk to run out and wabble, this action corrected about 90% of the problem. I then threw away the old brake pads that were about half worn and deglazed the disk with 600 wet and dry sand paper fitted new pads and went for a ride to bed in the pads and see if the fault was still apparent. The shudder and vibration was totally gone. The issue is the buttons when full of grit and dust they wont allow the disk to float thus causing the run out or wabble of the disk which in turn causes irregular glazing across the surface of the disk. Correcting the run out buy cleaning the buttons is only one part of the fix, you need to deglaze the both disks and the entire brake swept surface area on both faces. It worked for me 40,000km on still no problems.

By the way the buttons should be firm and you should never be able to rotate them with your fingers, but you should be able to push the disk with the the palm of your hand to feel some movement under tension when pushing the disk sideways. The disk is meant to float laterally not radially.

 

[Gregger]

Perfect @John Miller, exactly what I was looking for. Low cost repair that makes everyone smarter and safer. Much appreciated.

 

[John Miller]

To explain a little further the disks on the Rocket are semi-floating, there is a wave washer behind the inner head of each rotor button (quite a stiff one actually).

This will allow the disk to flex laterally to take up minor errors in lateral alignment - a somewhat self centering action.

If the buttons are gummed up then you have the problem we discussed above.

I am guessing most of the spanner guys are aware of this arrangement.

 

[cootertwo]

I've got the rotors off my 05 at the moment, to clean the "bobbins/buttons/whatever. Not a vibration problem so much, but one side seems to run hotter than the other. I changed calipers, same problem. Wheel bearings good/new.

 

[Tripps]

Never mind, it thought it said foreplay
( Jim isn't around, someone has to take up the slack)

 

[John Miller]

I've got the rotors off my 05 at the moment, to clean the "bobbins/buttons/whatever. Not a vibration problem so much, but one side seems to run hotter than the other. I changed calipers, same problem. Wheel bearings good/new.

My thoughts are that it can be normal to have some differential temps between disks 10% would not be out of the question more if you have fitted new pads while they are in the final stages of bedding in or if pads are badly glazed. Deglazing the brake swept area of the disks and also more importantly the old pad surfaces if you are reusing them should improve temp imbalance. One thing to remember is that the pads will cause a temp imbalance while they are bedding and after when using older worn disks which will have slightly different surface areas due to the variable amount of micro grooves across the faces of each disk face (more grooves means more surface area which in turn generates more temperature).
Glazed pads can cause extreme temperatures in brake systems, a lot of the guys in track racing will pull their pads after each race to deglaze them in an effort to improve brake performance and reduce braking temperatures.
Hope that helps a little to diagnose your problem.

 

[cootertwo]

Thanks for the tips. I agree, a little difference in heat, ain't bad, but when one side almost boils spit, while you can hold onto the other side, is TOO much. I'll post any differences after I do the cleaning, and put her back together. I own 3 Rockets, so not in a big hurry. Just got back from a 70 mile ride on my 2013. She rides like a magic carpet.