Honda Rebel 250 & 450 Forum banner

Front brake sound (howling)

2K views 16 replies 5 participants last post by  Norbertas 
#1 · (Edited)
Hello,
i undestrand, that this wont be easy to identify, but maybe somebody can help me understanding the cause of howling front brakes. (Rebel 450 87')
It appeared after few rides after changing brake pads to new ones. Thought that it could be brakes or front axle or bearings.
Driving on the road it dissapears only if i press the brake handle slightly. After stoping it howls even on pushing the bike forward. Going backwards it gives no sound.
I suspect, that the new wider brake pads just don't release the brake disc enougth.
Tryed to reassebmle ant clean the brake calipers and cylinders. Found that the inside caliper metal plate small teeth, that keep the bottom of outer brake pad were bend. So the outer caliper could be a little loose and after braking just being stuck in slightly angled possition, for the sound to appear.
Bend them back, but the sound is still there.
Actually it was hard to mount the brake caliper back. It is made of two parts - one monting element at the fork, and the caliper itself. They are connected by two bolds with rubber spacers. Is it kind of caliper depth regulator? as on other models i see it is moving freely in that place.
Maybe because of it caliper stays a little bit angled to the brake disk, thats where the sound comes from? Can caliper be adjusted regarding brake pads wear, or it adjusts itself?
And also i was able to push cylinders back inside caliper only with lots of preasure on them. Should it be this way?
 
See less See more
#5 ·
Thanks, it seams that its the case.
I released the mounting bolts, but the caliper itself was holding on the brake disk, as it was clamped. It can be seen in video below:



Thats how the cylinders move



How easy should it be to push cylinders back to caliper after they are out?
I am not able to do it by hand. I have to put caliper down and then push each cyinder seperately with force.
Thats how it goes:



So those are my next questions:
Should the top bolt rubber be so squezed? I was affraid not to tear it moving the caliper.
Have read the service manual to see if i am not missing something.
After pushing back cylinders, some brake fluid was gushed out of fluid case (through inspection glass).
Is it possible, that cylinders don't go back easily because of too much brake fluid? Could not check it, as the screws on the top are screwed (was able to take out only one. other is stuch with messed out head).


And see how the bold with rubber on the caliper is stuck in one place. Only pushing it out brought it back to center possition.


Any leads or suggestions.
 

Attachments

#6 ·
that mounting bolt with rubber seal is contributing to your problem - may be the whole problem - the bushing inside should move freely with hand pressure on both of them - that allows the pads to center over the disk

you would not be able to push caliper back in with your hand

you may need to remove some brake fluid - it would be a great time to change the fluid too if it hasn't been done for a while
 
#11 ·
Nope, the diagram slightly differs from the manual. Seen that scheme. Thanks for it anyway.
Actually found that pin stuck on mounting bracket. It was so dirty that both became same colour.

Now i only have to figure a way to screw the brake fluid tank bold out. Metal became soft and the centre of it is all messed up. Thinking about using small dremel to cut its top across and use flat screwdriver to take it out.
Brought the caliper home, so next up is a good cleaning and lubricating.
 
#14 ·
Brakes are the most important thing on the bike. There are 2 ways they can kill you. They can fail to work altogether, or they can lock up. Brakes should NEVER be hard to put back together. If they are something is wrong. Because you bike id 33 years old, there could be a lot of deterioration in the brake system. Any of the rubber parts could be bad, the bores in the caliper could be corroded, as could the bore in the master cylinder. Those screws that hold the master cylinder cap on can be a nightmare on any bike. I have found that a #2 drywall bit seems to work best to remove them, but if yours are already messed up, that won't work. I would probably try to drill the heads off, remove the cover, and still have a little bit of the screw left to grab a hold of. If the screws brake off, they almost always break off flush with the top of the master cylinder. And they are so soft it doesn't take much to break them. If you have any doubts about the brakes, don't ride the bike.
 
#15 ·
I have a feeling the sound comes because of pad spring hooks being bent during earlier repairs. As after bending, the bottom of the stacionary padis pushed closer to caliper wall, that makes pads top part to lean into brake disk. So even releasing the brake, doesn't help as the hooks keep that pad quite fixed.
Tried bending those hooks to normal possition, but the spring metal is too hard, so they snaped off ar the bending point. Will be ordering the spare part.
 

Attachments

#16 ·
You HAVE to take the cover off the reservoir when you want to compress the pistons into the caliper. When the fluid goes backwards up the brake-line into the master's reservoir the air in the reservoir has to go somewhere, or else you are fighting to compress that air. The rubber diaphram #9 is designed to cup downward into the reservoir as the fluid level drops. the backing plate #8 and cover #6 allow a trace level trickle of air over days to compensate the pressure behind the diaphragm changing over time.
If brake fluid oozed out around the sight glass when you compressed the pistons in the caliper the seal around the sight glass might be bad.
 
#17 ·
Thanks to all. I have changed the sight glass with new watch glass. It's quite easy and looks clean.
The sound was from the brake cilinders. I didn't take out the cilinders when cleaning the caliper, so one of them was moving hard enougth to keep one side of brake pad pushed to brake disc. That made the metal sound.
So don't forget to take those cilinders out, clean them and if possible, change the rubber rings inside.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top