Brakes vibrating?

[vinpub]

My front brakes seem to hesitate/vibrate/shake when I first start applying the brakes. When I pull them enough, they seem to get a little smoother and work fine and teh vibration/shudder is gone.
The initial hesitation is a little unnerving. I can feel the front wheel kind of shudder and feel te vibration all the way back into the fork/handlebars.
These are not new, and the bike has ~12K miles. The brake pads seem to have enough left in them.
What shoudl I check - is it the brakes or may be front forks?

 

[mustnt grumble]

Is it a juddery feeling? If so it's most likely a warped disc. I have the same problem and I'm trying to work out whether to try and get a replacement myself or pay an arm and leg to my local dealer.

 

[coursonap]

check your caliper bolts and make shure they are tight, then i would see if the pads might have pieces missing, or tire going bad, or you just might have a warped rotor. First thing i would do i check all bolts.:spank:

 

[aussiejules]

definately check all the bolt tensions, some guys here have had caliper bolts fall out.

 

[Oscar54]

You can check for rotor warp by putting the bike on the centerstand and raising the front wheel off the ground so you can spin it freely. then take a straight edge and mount it on something like a block of wood and place it like a 1/16 of an inch from the front side edge of the rotor and spin the wheel and observe if there is significant warp. If so replace the rotors.

All used rotors have a little warp to them but the caliper can absorb some of the feed back because it is on slides to allow for pad wear. However if the slides are getting dry the caliper may not float easily and that is why you feel the vibration momentarily until you put more pressure enough to over come the resistance of the lack of lubrication on the slide pins. Severly warped rotors will cause pulsing regardless of how much pressure is applied.

So if I'm guessing you probablly need to pull the calipers, clean out the dust, lube the pins and shims and check your pads. If the pad as worn unevenly, that is one pad is thicker than the other, and/or the wear is ****ed, (this indicates sticking due to poor lubrication), then replace the pads. Permatex has a good synthetic brake grease that you can use for the slides, shims to elimiate sqeele, and even the caliper piston, I would recommend using it. It comes in a white bottle with a green lable at the auto store.

And since you are at it, check the color of your fluid and if it is turning brown, do a fluid change. There is a thread somewhere on bleeding using the Mighty Vac. I used it and it works like a charm.

HTH

Lewis

 

[vinpub]

All used rotors have a little warp to them but the caliper can absorb some of the feed back because it is on slides to allow for pad wear. However if the slides are getting dry the caliper may not float easily and that is why you feel the vibration momentarily until you put more pressure enough to over come the resistance of the lack of lubrication on the slide pins. Severly warped rotors will cause pulsing regardless of how much pressure is applied.

So if I'm guessing you probablly need to pull the calipers, clean out the dust, lube the pins and shims and check your pads. If the pad as worn unevenly, that is one pad is thicker than the other, and/or the wear is ****ed, (this indicates sticking due to poor lubrication), then replace the pads. Permatex has a good synthetic brake grease that you can use for the slides, shims to elimiate sqeele, and even the caliper piston, I would recommend using it. It comes in a white bottle with a green lable at the auto store.

And since you are at it, check the color of your fluid and if it is turning brown, do a fluid change. There is a thread somewhere on bleeding using the Mighty Vac. I used it and it works like a charm.

HTH

Lewis

Thank you. Will check it. Is there a how-to for calipers? i hope i dont have to drain the brake fluid.

 

[vinpub]

Just got done with the front calipers and disc floats.
I hope I did the floats right - I tried to get some white lithium in the gap between the disc and the black bracket, was very careful not to get it on the disc surface.
Opened up the calipers and cleaned the cylinders and springs, Tried to sqeeze some white lithoum on cylinders too. And then squirted some on the mounting pins.
Will take it out tomorrow and see the results. Thank you all for help.
Q: does anyone use blue threadlock on the caliper bolts? I have seen some threads warning about the bolts coming loose and even falling off.

 

[Oscar54]

Vinpub:

Did you actually break open the system? I mean break the oil nuts and pop out the pistons for the calipers? I'm not sure since you did'nt mention bleeding.

I was not suggesting going that far, but if you did it's not bad, I'm just confused when you say you tried to squeeze the grease between the Disk and black Bracket?

If you dismantled the entire caliper you should have been able to lube anywhere needed. The free service manual you can download from the site will walk you through the entire brake rebuild if you are not sure of something. The thing that concerns me in your post is the use of white lithium grease? Is this is specifically for disk brakes? The grease you use must be a High Temp grease for brake systems so it doesn't melt. Also the grease you use to lube the pistons needs to be compatible with brake fluid, which the synthetic grease I mentioned is.

Let us know what you found and if you eliminated the vibration.

Lewis

 

[vinpub]

Lewis:
I didn't dismantle the whole system. I took the caliper off, took the pads off. Cleaned the springs, cleaned as much of the piston as was showing out with WD40 (didnt take them off, didn't bleed the fluid). Tried to get some grease around the pistons and pushed them in for mounting. Also squirted some grease into the holes where the caliper mounting pins go.

The black bracket I was talking about was the inner plate onto which the brake disc (outer silver plate) is mounted. I wasn't quite sure how to grease those. I attached the thin tube on the squirt can and tried to get some grease in the gaps between the silver disc and the black bracket. Had to be very careful in squirting just a touch to avoid getting it on the disc surface.
Here is a post that shows a similar issue related to this:

http://www.600riders.com/forum/fz6-general-discussion/4467-shudder-low-speed-turn-front-brake.html

I am not sure which one of the two really helped or was it just a loose caliper.... but when I took it out this morning the brakes were fine. No shudder and they were biting hard!
Thanks a bunch for your help. I feel a lot better with those brakes now.

 

[Oscar54]

I'm glad to hear that it took care of your problem.

It makes you feel good when you fix something yourself, doesn't it?

Good Job!

Lewis

 

[reiobard]

http://www.600riders.com/forum/fz6-general-discussion/4467-shudder-low-speed-turn-front-brake.html


in addition to checking the caliper bolts i would add this process to your oil change check list.

 

[Oscar54]

http://www.600riders.com/forum/fz6-general-discussion/4467-shudder-low-speed-turn-front-brake.html


in addition to checking the caliper bolts i would add this process to your oil change check list.

Excellent Point. Safety checks on a motorcycle is much more important than in a car. So doing a walk around before each ride and doing a PM on your brakes every oil change, and checking air pressure at least once a week go along way to eliminating surprises at speed.

Lewis