Brake pulsating at lever

[salty_monk]

What are the other causes apart from warped rotors?
I believe the wheel bearings are fine too.

Could caliper problem cause it?

These are Kawasaki with the plastic inserts inside the piston that push against the pad... Maybe if they're worn at an angle or something? First time I have come across it like this.

The rotors are brand new EBC so I know they're straight!

 

[posplayr]

did you bed in new pads with the new rotors?

 

[salty_monk]

did you bed in new pads with the new rotors?

EBC HH pads FA 129's from memory. Brand new. No especially break in reqd that I know of. The pulse has got a bit more pronounced with use....

 

[Nessism]

Dan,
Is that your old G?

Any spacer behind the disc? Sounds like something is not sittting down flush like it should.

 

[tkent02]

Try getting them hot, by dragging them lightly for 1/2 mile or so, then braking HARD,. Do not come to a stop, just go from around 60 down to 20mph or so. Speed back up and do it again,
several times.

http://www.zeckhausen.com/bedding_in_brakes.htm

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Sorry, these are car sites, but the science is the same.

 

[kirkn]

Well, a pulse in the lever has to come from runout somewhere...

Either a warped rotor, or something that rotates that's not seated. I don't see how anything stationary (ie, all caliper components) could pulse since it's stationary.

Hmmm.....

 

[tkent02]

Well, a pulse in the lever has to come from runout somewhere...

Either a warped rotor, or something that rotates that's not seated. I don't see how anything stationary (ie, all caliper components) could pulse since it's stationary.

Hmmm.....

No, it doesn't.
Read the stuff I put up.
Here's another, there are many more.
http://www.powerbrake.co.za/downloads/tech_01_judder.pdf

 

[TheCafeKid]

No, it doesn't.
Read the stuff I put up.

I did, and it makes a truck load of sense. To be honest, I cant say as I have ever followed these instructions, but I will certainly now.

It also makes me wonder if the guys at Car & Driver, or Road & Track follow these precautions when they test these new supercars and then bitch about their braking. I just read a piece they did not too long ago where they ran a hot lap around Virginia (Is it Infinion raceway?) and managed to total a BRAND NEW high performance package 370Z into the walls because of "horrible brake fade"

 

[tkent02]

I did, and it makes a truck load of sense. To be honest, I cant say as I have ever followed these instructions, but I will certainly now.

It also makes me wonder if the guys at Car & Driver, or Road & Track follow these precautions when they test these new supercars and then bitch about their braking. I just read a piece they did not too long ago where they ran a hot lap around Virginia (Is it Infinion raceway?) and managed to total a BRAND NEW high performance package 370Z into the walls because of "horrible brake fade"

Could be, dunno. Maybe the car had sh:tty brakes, but a real driver would learn this before crashing.
Anyway I have been able to fix shaky brakes on a lot of cars and bikes by doing this proper bedding procedure, from my Mom's Jeep that went through about six sets of rotors, several high mileage BMWs I bought, couple Volvos, my Ford truck, several other cars and a lot of bikes too.

I don't understand why most brake pad manufacturers don't include pad specific bedding in instructions with every set of pads, probably the same fear of liability that makes them recommend riding a new bike slowly instead of breaking it in correctly.

 

[rustybronco]

You can always eliminate runout as the source of the problem with a dial indicator.

 

[kirkn]

No, it doesn't.
Read the stuff I put up.
Here's another, there are many more.
http://www.powerbrake.co.za/downloads/tech_01_judder.pdf

Now that's very interesting. I've heard of it, but never the statements about 0.0004" being detectable to the driver, and 0.001" being annoying.

And, in fact, I follow that bedding-in procedure every time I replace pads, car or bike, but I never knew all that reasoning behind it.


But, I still think I was on the right track - the pulsing is being caused by some component that's rotating (in this case, uneven deposits on the rotor) rather than any stationary component - pads or inserts, etc.

Kirk

 

[tkent02]

But, I still think I was on the right track - the pulsing is being caused by some component that's rotating (in this case, uneven deposits on the rotor) rather than any stationary component - pads or inserts, etc.

Kirk

Yes, absolutely correct.

 

[GS ace]

Pulsing

Pulsing

The pulsing can be attributed one or two rotors being untrue. I ran into this on my 1100E a few years ago and took the wheel to a friend's machine shop, where he straight-edged them to be sure.

A friend of mine has a ZZR1200 that had the same problem. I don't know if it's proper, but he used a series of polishing paper (not really paper) between the pads and rotors. He bled off some hydraulic pressure, placed the sticky-backed paper, lightly tapped the lever, and rode the bike up and down his street without applying the front brake. It worked.

 

[Road_Clam]

Had the same exact pulsation on my 1100. It's warped rotor(s) plain and simple. I do machining by trade, made a spacial arbor stub to hold the GS rotors, and skim cut until I got the rotors to within the spec runout (I beleive it was .012" ) ? Mine were warped pretty bad, got them right at the spec limit, and pulsation was gone.

 

[tkent02]

Had the same exact pulsation on my 1100. It's warped rotor(s) plain and simple. I do machining by trade, made a spacial arbor stub to hold the GS rotors, and skim cut until I got the rotors to within the spec runout (I beleive it was .012" ) ? Mine were warped pretty bad, got them right at the spec limit, and pulsation was gone.

This does not explain how hard brake applications can fix so many pulsating brakes.
Just the other day I noticed my 750 starting to pulsate a little, went out an cooked them by braking hard a few times, now it is smooth as silk again.

 

[posplayr]

Had the same exact pulsation on my 1100. It's warped rotor(s) plain and simple. I do machining by trade, made a spacial arbor stub to hold the GS rotors, and skim cut until I got the rotors to within the spec runout (I beleive it was .012" ) ? Mine were warped pretty bad, got them right at the spec limit, and pulsation was gone.

He also is running new EBC rotors which are floating so run out is not as much of an issue.

 

[crapwacker]

This does not explain how hard brake applications can fix so many pulsating brakes.
Just the other day I noticed my 750 starting to pulsate a little, went out an cooked them by braking hard a few times, now it is smooth as silk again.

If you have gotten contaminates on the rotors, they can pulse when applied lightly, but hard breaking can 'burn' off some containments.

 

[tkent02]

If you have gotten contaminates on the rotors, they can pulse when applied lightly, but hard breaking can 'burn' off some containments.

OK, believe what you want to.
I'll believe the experts this time.
All I know is it works.

 

[gearhead13]

Well, those links were interesting. But, with my calipers removed and by rotating the wheel I can see with my naked eye the rotor moving side to side in an irregular pattern.
These are the rotors I bought from a forum member (pousseux or something) here that wouldnt refund what I paid for them. deadbeat.

 

[tkent02]

But, with my calipers removed and by rotating the wheel I can see with my naked eye the rotor moving side to side in an irregular pattern.
These are the rotors I bought from a forum member (pousseux or something) here that wouldnt refund what I paid for them. deadbeat.

Well, yeah, those are probably not going to straighten out too easy.
So he's a deadbeat, huh?
I had not heard that.