Jump to content
Sign in to follow this  
gazzr11r

Break lever pulsing

Recommended Posts

gazzr11r

Hi my 1999 r11r ive just acquired has a front brake issue. Whilst braking at lower speeds, say 20mph to a stop, the brake lever pulsates slowly and as you come to a stop the nose dives and rises at the same rate as the lever pulsing. I've checked the discs, which are recent ebc replacements, and they are not warped as expected. The general feel of the front brake at higher speeds is not good, a little vague, brake fluid was also replaced recently. I have new pads and brake cleaner for the discs on order. Any ideas ?

Share this post


Link to post
Hosstage

How's the tire? Any cupping? I would also double-check for rotor warpage again. How was it checked the first time?

Did you use old pads with new rotors?

Share this post


Link to post
Hosstage

.

Share this post


Link to post
dirtrider
3 hours ago, gazzr11r said:

Hi my 1999 r11r ive just acquired has a front brake issue. Whilst braking at lower speeds, say 20mph to a stop, the brake lever pulsates slowly and as you come to a stop the nose dives and rises at the same rate as the lever pulsing. I've checked the discs, which are recent ebc replacements, and they are not warped as expected. The general feel of the front brake at higher speeds is not good, a little vague, brake fluid was also replaced recently. I have new pads and brake cleaner for the discs on order. Any ideas ?

Afternoon gazzr11r

 

With floating rotors & 4 piston calipers the rotors would probably have to be visibly warped to cause brake lever pulsation or movement.

 

The biggest cause of brake lever pulsation is rotor thickness variation as that can cause a fluid displacement in the calipers that feeds back into the master cylinder. (so mike all around the brake rotor looking for  thickness variation) 

 

The other usual cause is brake rotor staining or oxidation areas that increase braking friction as the that stained rotor area passes the brake pads. This is usually caused by  washing a motorcycle then parking it for a longer period as the trapped moisture between the brake pads & brake rotor surface cause the staining or oxidation areas (metallic brake pads make this worse).

 

If it's light the staining or light oxidation then it can sometimes be removed with fine sand paper, scotch pads, etc. If the staining is heavy or deep then it will take turning the rotor surface on a brake lathe (usually not possible on already thin motorcycle brake rotors). OR, I have had some luck at removing staining on motorcycle rotors by masking off the rotor center section then doing a light  blasting in my sand blast cabinet using very very fine well worn out glass bead media at low air pressure. 

 

If you can see the shadow of a brake pad outline on either side of the brake rotors then suspect staining or oxidation)

Share this post


Link to post
gazzr11r

The EDC discs were fitted prior to me acquiring the bike and were fitted last year, although the pads are near to minimum wear so unbelievably I suspect new pads were not fitted. I've elevated the front wheel and spun it up while holding a scribe  against both discs and there appears to be no visible warpage. A visible warpage would be expected due to the large displacement experienced on the brake lever during low speed braking and the dipping of the front end whilst coming to a stop. There is no evidence of any sign of brake pad binding during storage, indeed the bike has done a steady 10k yearly for previous years. I have new organic edc  pads and brake cleaner to clean the discs, I'll also remove the front wheel and take it to my motorcycle shop to spin up on the wheel balancer to check the disc and mic them. I'm sure the abs would not cause such a fluctuation on the lever at low speed ?

Share this post


Link to post
dirtrider
2 hours ago, gazzr11r said:

The EDC discs were fitted prior to me acquiring the bike and were fitted last year, although the pads are near to minimum wear so unbelievably I suspect new pads were not fitted. I've elevated the front wheel and spun it up while holding a scribe  against both discs and there appears to be no visible warpage. A visible warpage would be expected due to the large displacement experienced on the brake lever during low speed braking and the dipping of the front end whilst coming to a stop. There is no evidence of any sign of brake pad binding during storage, indeed the bike has done a steady 10k yearly for previous years. I have new organic edc  pads and brake cleaner to clean the discs, I'll also remove the front wheel and take it to my motorcycle shop to spin up on the wheel balancer to check the disc and mic them. I'm sure the abs would not cause such a fluctuation on the lever at low speed ?

Evening  gazzr11r

 

With floating rotors & 4 piston calipers I just don't think you will find brake rotor warpage would cause that lever pulsation & definitely not cause the brake pulsation & front end dip. 

 

Rotor thickness variation will REALLY cause the above brake disturbance. (this needs to be checked for). It doesn't take much. 

 

If rotor thickness variation is not found then that pretty well leaves a brake pad to rotor friction variation in different places on the brake rotors. It takes very little friction variation (some not even visible) to cause what you are feeling in the brakes. It is also difficult to get rid of on thin motorcycle brake rotors.   

 

Brake cleaner won't do anything for a friction variation problem. 

 

 

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...