Pulsating brakes after replacing pads and rotors.

[Yamaha_Fan]

So about a week ago I did some work to my 97 vmax.

Rebuilt the forks (new seals, bushings, fluid, Progressive springs).
New wheel bearings.
New front brake pads and rotors. I had a problem getting 3 of the rotor bolts out, and ended up welding a nut to the bolt to get them out. I'm planning on flushing the fluid and installing SS brake lines but haven't done it yet.

I'm now having a problem with a pulsation as I brake. It's most noticeable as I'm coming to a stop. I cleaned the rotors and took it around the block, and it helped but the next day with some more riding it got just as bad. Tried cleaning the rotors again and hit the pads with a little 400grit sandpaper, again same thing, helped at first then the pulsating came back.

I checked the runout on the rotors, got 0.006" on one, and 0.0055" on the other one. The manual I have says the max is 0.006"

I also checked runout on the wheel, got 0.013" axial, and 0.004" radial. The manual has a max of 0.008". I didn't do it with the tire off on a truing stand, I had the bike on a centerstand and the front supported on a front stand, so I'm not sure how accurate my numbers are, or if they are bad enough to cause my problem.

Is there anything I could have screwed up with the forks or wheel bearings that could cause this? In my mind if it were in the forks or bearings, it would do it all the time, not just under braking, but I could be wrong.

Could it be something grabbing in the master cylinder or calipers?

 

[blaxmax]

Which pads? HH?

 

[Yamaha_Fan]

These are the pads I bought:

http://www.ebay.com/itm/300557414710?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[one2dmax]

Did you clean and lube the rotor buttons?

 

[Yamaha_Fan]

Did you clean and lube the rotor buttons?

I did not, I'll try that.

 

[Yamaha_Fan]

The other thing I noticed while checking runout was a slight clicking noise every revolution. Is that coming from the odometer cable counting the rotation of the front tire?

 

[MaxMidnight]

You also need to check the thickness variation of the rotors as this is more critical than run-out in causing the pulsing you describe.

Whilst max run-out is 0.15mm (to '92) and 0.3mm ('93 on) thickness variation should be no more than 0.03mm (source Bendix).

With run-out as the pistons on one side of the calipers are pushed out by the rotor the others move in thus little fluid is displaced.

Conversely a small thickness variation will push the pistons out on both sides which will displace fluid and result in the pulsing you are feeling.

You would need to take ten or so reading with a micrometer around the circumference of the disc(s).

 

[sdt354]

I'd check the rotor seating on the hub, then check the rotor itself. Make sure everything is clean. Tighten your rotor bolts in the correct pattern. Torque to spec. Sometimes you do get new parts that are bad. And that sucks, when it happens. I've learned to assume nothing when working on anything.
Steve-o

 

[D-Max2012]

I had a problem getting 3 of the rotor bolts out

Hopefully, you did not take any material off the bolt mount, when taking off the stubborn bolts, or leave any foreign matter on the mount. If so, when tightening down the new rotor bolts, it could leave a slight hill or valley on the rotor's surface, resulting in a pulse when brakes are applied. A magnetic dial indicator placed on the rotor could rule this out. just something to think about..

 

[HyperPete]

You said new rotors, right? I don't suppose they are wave rotors, are they?

 

[Yamaha_Fan]

You said new rotors, right? I don't suppose they are wave rotors, are they?

They are.

Hopefully, you did not take any material off the bolt mount, when taking off the stubborn bolts, or leave any foreign matter on the mount. If so, when tightening down the new rotor bolts, it could leave a slight hill or valley on the rotor's surface, resulting in a pulse when brakes are applied. A magnetic dial indicator placed on the rotor could rule this out. just something to think about..

I checked runout with a dial indicator, got 0.006" and 0.0055", right on the edge of max spec per the manual I have.

I attempted to clean the rotor buttons today. I could not get them to turn. I used the method of running a bolt with washers through it, and tightening down to turn the button. I stripped the threads off several #10 machine screws (the biggest that would fit), and the button still did not turn. I tried on 3 or 4 different buttons. Would squirting some penetrating oil down there and letting it soak be a good idea?

 

[Traumahawk]

Look at post #13 in this thread. It might help.

http://www.vmaxforum.net/showthread.php?t=17926&highlight=rotor+button

 

[HyperPete]

Re: Wave Rotors

They are.

Did you "stagger" them, so the high and low parts on each side are in different locations? I've heard, (on a different forum for a different bike), that this can cause a pulsation.

 

[D-Max2012]

I checked runout with a dial indicator, got 0.006" and 0.0055", right on the edge of max spec per the manual I have.

If you're getting 0.001 difference on both rotors (Front Tire), that's almost perfect.. You should not feel a pulse because of any warping.

 

[MaxMidnight]

As the run-out is within spec anything relating to the filling of the discs can be ruled out.
I have wave discs on my bike and have not had any issues due to the cut-outs being 'in phase' nor can I think of any reason why that would cause a pulsing.

The OE discs and to the best of my knowledge Galfer and Braking Wave wavy discs are semi-floating. This is where the friction surface is riveted to the mounting carrier via buttons which do not allow any side to side movement. I wouldn't expect you to feel any movement between the two parts and adding lubricant wouldn't perform any useful function but will collect the brake dust and potentially contaminate the pads.
Fully floating discs have the same make-up but the buttons allow side to side movement which you will feel and probably hear.

On the basis of the above that only leaves thickness variation which (IMHO and experience) is the most likely case of a pulsing brake lever.

Has this been checked yet?

 

[Yamaha_Fan]

As the run-out is within spec anything relating to the filling of the discs can be ruled out.
I have wave discs on my bike and have not had any issues due to the cut-outs being 'in phase' nor can I think of any reason why that would cause a pulsing.

The OE discs and to the best of my knowledge Galfer and Braking Wave wavy discs are semi-floating. This is where the friction surface is riveted to the mounting carrier via buttons which do not allow any side to side movement. I wouldn't expect you to feel any movement between the two parts and adding lubricant wouldn't perform any useful function but will collect the brake dust and potentially contaminate the pads.
Fully floating discs have the same make-up but the buttons allow side to side movement which you will feel and probably hear.

On the basis of the above that only leaves thickness variation which (IMHO and experience) is the most likely case of a pulsing brake lever.

Has this been checked yet?

Not yet. I need to get a micrometer and I'll check it.