handlebar vibrating when hard braking

[nudgedoink]

hi guys i've recently got into an accident in which my front rotors were bent. I had the bike fixed up - replaced new rotors, new pads, new brake pump and had the front forks pressed. However I am getting vibrations in the handlebar when i brake hard. when i brake lightly to a complete stop i can feel a slight pulsing of the brake (not smooth deceleration). I asked my mech about it and he told me to give it a few weeks for the pads and rotors to sit in. It has been 2 months now and the vibration and pulsing still persist. any ideas what could be the problem?

 

[KingY]

you need new head race bearings or head stock bearings its called one or the other, i had the same thing on both of my Fazers from doing to many wheelies so i think the little bumb you was in caused shock to the bearings and now they need replaced

 

[Motogiro]

I agree to first check the head bearings.

There are also other things that can cause vibration. Even though your rotors and pads are new. if any oil or contaminant has ever gotten on the rotor surfaces it can cause the rotor surface to have different areas that have different grip characteristics that will cause vibration. If this is the case and the rotors are new, it should be easy to clean (acetone) and scuff the rotors and pads. I've heard that the wrong compound pad can also cause shutter/ vibration.
Check the wheels bearings.

 

[TownsendsFJR1300]

+1 on both the above. Two months to break in, is BS.

There is a short break in period for the pads to set to the rotors but even that, they shouldn't shudder, period...


To confirm the head bearings, get the bike on the centerstand and a sizzor jack under the header to get the front wheel off the ground.

Gently grab the front forks at the bottom and pull forward and push back (a helper sitting on the seat wouldn't hurt so you don't pull the bike off the CS). There should be no play.

*Also, when you mentioned you had the forks "pressed", were they bent and someone straightened them?


BTW, should you have to replace the head bearings, "All balls" tappered bearings are superior to the stock, regular, round bearings, (more contact area) and the price is not bad at all.... There's numerous posts re the install. I had them on my old Goldwing (which had a de-cel head shake-normal for this heavyweight bike). All Balls bearings solved the problem (the dealership actually recommended them, as did the guys on the wing forums)

 

[nudgedoink]

oh ok. I'll definitely have a look at the bearings or get my mech to take a look at them. But shouldn't worn bearings create vibrations throughout the ride and not just when braking? just a question.

My mechanic told me my forks had to be pressed and so I let him do what needed to be done. I'm not very savvy mechanically so I'm not too sure what was needed or not needed. just had to trust the mech. but apparently after he "pressed" them he told me the bike was good.

 

[outasight20]

The wheel bearings are under a LOT more load when braking hard. So an imperfection could show itself under hard braking only. Same applies to all front end components.

 

[nudgedoink]

also, just to be clear, when u say to pull forward and push back the front forks, do you mean when u are facing the bike from the front direction? when the surface of the tire is in front of you? not from the side of the bike yea?

 

[Motogiro]

I'm not understanding the terminology, "Pressed"

Is that like truing when something is bent?
If it is I would not expect proper performance from the forks.

Also bleed the brakes starting with the left caliper (farthest from the master cylinder) first.

 

[TownsendsFJR1300]

also, just to be clear, when u say to pull forward and push back the front forks, do you mean when u are facing the bike from the front direction? when the surface of the tire is in front of you? not from the side of the bike yea?

Exactly!

Your looking at the front of the bike, standing/sitting on a stool right in front of it. The forks/wheel is hanging down in the air. If the bearings are loose/worn, damaged, etc, you'll be able to pull the front wheel up, it'll have some slack (not good), likely not alot, but if you feel ANY CLUNKING / PLAY somethings wrong.

Its more pronounced when riding as at normal speed, the triple clamp/steering head are tilted back (if you would). When you apply the front brakes, that slack in the bearings now literally shifts the front end up and they tilt forward. The front is teetering back and forth depending on conditions.

I'm also curious if he straightened the fork tubes as well. They pretty much need to be dead nuts straight..

 

[nudgedoink]

thanks for all the useful info. I just checked them the way townsends instructed and they do have some freeplay.

 

[TownsendsFJR1300]

thanks for all the useful info. I just checked them the way townsends instructed and they do have some freeplay.

When the bike was wrecked, it could have damaged those bearings. In either case, that play shouldn't be there. IMO, being you have to tear it apart to check, tighten, replace them, go for the All Balls kit. Should be cheaper than the stockers and will definitly outperform them...

Glad you found something, too bad the mechanic didn't.

IMO, if your not doing the job yourself, find someone else to do it and who's done it before. If the last mechanic missed that, he wouldn't be wrenching on my bike...

Good luck and please post the outcome....

 

[nudgedoink]

hey guys. got my bike fixed up. apparently what happened was that the steering cone bearing was loose.. all my mech did was tighten it. he checked the wheel bearings and told me they were fine. on the ride back home the brakes did seem to be much better and i didnt feel any vibrations. however i may have to ride more to further evaluate them. thanks loads for the the input, it really helped