Ducati Monster Forum

I was wondering if I just had common Monster brake vibration, but I've noticed that it's my entire front wheel that rapidly judders up-and-down when I'm braking.  It doesn't happen all the time, usually only in a medium-slow stop.  It also happens much more often on bumpy pavement, which makes me think that the whole process gets started by a pavement bump and is then amplified somehow by braking forces.  I don't have the problem unless I'm using the front brake.

Thoughts? Thanks again, you're a great crowd!

Okay, I've been researching this topic a bit on the old site...has ANYONE found a definitive answer yet?  It seems to be Monster Voodoo...

Year and model of your Monster, and how many miles on it?

How long ago were the forks/brakes/steering head serviced?

'04 S4R / 4600miles / probably never (I'm the 2nd owner) 

Guess I should get this info listed on my profile...

Short answer - No you should not be experiencing this.

Pretty new bike, low miles - wear *shouldn't* be an issue yet... has the bike even been down? 

Do you feel any pulsing the the lever - like it's pressing back against you fingers a little?

I've been having the same problem on my 01 900 Sie since I bought it when it had 2100 miles, 6500 now.  The problem occurs at speeds below 10mph under heavy braking.  I have tightened the head bearings and adjusted the damping settings in the forks, I cleaned the brakes and rebedded the pads.  Nothing has worked so far.  I have narrowed the problem down to the brakes, this weekend I'm going to "hammer" the rotor, aka make them full floating rather than semi.

Measure the thickness of the rotor all the way around in the braking area. If the thickness varies by .001" then the rotors need replacing.

You'll need to do this measuring with a micrometer, as opposed to calipers.  You need to get the thickness where the pad contacts the rotor, not the outside edge of the rotor, as calipers would measure.

My 2000 900ie did that when I got it at 19,000 km.

I gave the contact areas on the rotors a big going over with wet and dry emery paper and scraped the pads on a rough concrete slab until all glazing was gone.

Since then have done over 16,000 km without a problem.

My S4 does the same exact thing...I had a thread regarding this exact problem on TOB, and never really came to a conclusion...

-Speeddog was saying it could likely be the steering head bearing loose or worn, which is apparently a common problem on the S4... I never did get to pull off the front end to check... :-\

-Could also be the forks compressing to their limit...Have you noticed if they do??

-I figured it might be the pads grabbing-and-letting-go, or "pulsing" against the rotor, but wouldn't you see evidence of this on the rotor itself??  ???


-I may do the same...Sounds like a good weekend project!!  [thumbsup]

  I've just been living with it, as it doesn't do it under normal braking conditions...Only heavy braking at ~20-to-zero mph...

Nope.  Unless they are badly warped and have created really bad hot spots on the rotor.  You'd need a micrometer to find a difference in thickness that you can feel in the lever.

WTSDS's suggestion is cheap and not very time consuming, and that's great.
Give it a go, worst case is that you've eliminated a suspect.
Best case, it solves the issue.

Gotcha... I luckily have one here at work, so I'll bring it home tonight and check it out.. So it's thousandths of an inch (.001) we're talking about here?? Plus-or-minus a thousandth can cause that much chatter, huh??? Wow...

You should check with the manufacturer for the +/- tolerances - I can't speak to those numbers.  But the micrometer is more because you can get a measurement of the surface of the rotor where the pads actually contact.  Calipers would just get the widest point which will probably be the outside edge - which the pads probably aren't touching.  So if you used calipers, you wouldn't get the real info you're looking for,

He has the experience to know the actual number that will give you issues.

Keep in mind Ducati changes tolerances to suit advertised maintenance costs. ;)

In my experience this problem will never fully go away.

Obviously check the breakes, but you should also check the stearing head bearing again. Mine gets loose all the time.

This could be caused by the really skinny rotors that Ducati spec's from Brembo. And also the aggressive sintered brake pads.

A few Ducatis suffer from a temporary heat induced warpage. Is common at the first part of a ride when the rotors are cool. Different sections of the rotor heat up unevenly and they warp. Usually, when the rotors come up to temp, the warp goes away.

I'm special, though. The warp stayed for me ... :P I put the bike on stands and stuck a dial indicator on mag base against the stand with the dial gauge pointed at the edge of the rotor near the perimeter. They both had .030" of deflection. Yes, thirty thousandths.

That was what helped me get brake techs...
(http://pics.livejournal.com/ca_cycleworks/pic/0001aqgg)
(photo gallery (http://pics.livejournal.com/ca_cycleworks/gallery/0000gg7t))

Yep, I've warped a few sets of Ducati rotors - first being a 2003 620 Monster Dark (I think everyone who has owned that bike warped the rotors!). The symptoms in the original post definitely sound much like that.

Worst I have done was my track bike running a single rotor and dp racing pads .
ambient temp was about 60 degrees F.
I ran it hard in one session (20 min) and pulled into the pits to grab a student. After sitting for about 10 minutes chatting with another instructor I I decided to go looking for the student. As I pulled on the brake lever it went straight to the bar :o
I rode it back to my pit and thought I would be bleeding the brake but discovered that I had just turned my rotor into a large cone washer. You could flip the cone from side to side pushing the pads back into the calipers each time. [thumbsup]

I've got a rear disc off of a Monster that's coned about 1/4".

It won't flip.  [laugh]