Ducati Monster Forum

Moto Board => Tech => Topic started by: slash on September 01, 2008, 09:36:39 AM

Title: bad front end shudder on hard low speed brake
Post by: slash on September 01, 2008, 09:36:39 AM
I have an 06 s2r1000 with 20k miles on it.  It just had the 18k service done 10 days ago at really good ducati dealer.  Yesterday I had to break hard suddenly at low speed (about 25 mph; used front break only) and the front end shuddered/vibrated severely.  I immediately let up on the break and the shudder ceased.  I've also had the front end wobble a little at a high speed (100 mph) lane change recently. 

I had my rear tire changed early in the summer because of wear (6000 mile), but left the front because the wear bars were not even close to being exposed (both are pilot powers).  The front has 9k miles now and has some significant cupping/profiling.  I was advised to run high pressures in the tires to prevent cupping (37 front/35 rear).

Do you guys think that the cupping would cause a severe shudder on a sudden low speed braking?

What else should I check...rotor warp, steering head bearings, wheel balance... anything else?  I think they checked steering head bearings for play at the service 2 weeks ago.

I probably will just change the front tire... but I want to make sure everything else is ok.  If I had really needed to stop I would have been make the beast with two backsed.

Thanks for the input...
Title: Re: bad front end shudder on hard low speed brake
Post by: Howie on September 01, 2008, 09:55:03 AM
Sounds like you have the drill down.  In addition, make sure the rotor buttons are free, clean the rotors with a Scoth Brite, and you may be due for new brake pads.  If so, renew, otherwise, sand the glaze off the old ones.
Title: Re: bad front end shudder on hard low speed brake
Post by: EEL on September 01, 2008, 12:19:32 PM
+ 1 on rotors or pads being the culprit. I have the same issue with my bike. I tend to ride hard sometimes and make use of my brakes. My ultra soft ductile iron axis rotors are grooved from the use. If you've got 20k miles on your rotors, you might be in the same boat.

Take a picture of your rotors and post it..
Title: Re: bad front end shudder on hard low speed brake
Post by: slash on September 01, 2008, 03:05:13 PM
Sounds to me like you guys think it is the brakes and not the front tire, hmm.  I have plenty of pad.  I'm not sure how to check to see if the rotors are warped except a visual inspection to see if there is a really obvious warp.  Any suggestions...if there is a warp will I be able to spot it by spinning the wheel and looking for a warp relative to the pads?
Title: Re: bad front end shudder on hard low speed brake
Post by: Howie on September 01, 2008, 03:37:04 PM
Start cleaning buttons and rotors, Slash.  Run out on a semi floater can be from a bent carrier, the blade (disc) itself or dirty buttons.  Your shudder can also be caused by uneven transfer of brake pad material to the rotors. 
Title: Re: bad front end shudder on hard low speed brake
Post by: Ddan on September 01, 2008, 03:51:31 PM
You have most likely got an uneven deposit of friction material on the rotors.  Clean it off with some 220 grit w/d paper and brake cleaner, then remove any left-over crud with some alcohol.  Sand down your pads until you get a clean surface and re-bed them by doing 10 or so hard stops from 60 to almost stopped, but don't stop.  You may start to smell the brakes.  Do another 6 hard stops from 80 or so, but again don't come to a complete stop.  Ride normally untill everything is cool and you should be set.

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
Title: Re: bad front end shudder on hard low speed brake
Post by: Spidey on September 01, 2008, 04:26:19 PM
Dan, I've been told not to clean rotors with sandpaper because of potential silica deposits.  Anything to that?
Title: Re: bad front end shudder on hard low speed brake
Post by: Popeye the Sailor on September 01, 2008, 05:22:45 PM
Quote from: Spidey on September 01, 2008, 04:26:19 PM
Dan, I've been told not to clean rotors with sandpaper because of potential silica deposits.  Anything to that?

I've never heard anything of the sort.
Title: Re: bad front end shudder on hard low speed brake
Post by: Ddan on September 01, 2008, 05:28:48 PM
Quote from: Spidey on September 01, 2008, 04:26:19 PM
Dan, I've been told not to clean rotors with sandpaper because of potential silica deposits.  Anything to that?
I've never heard it either.  I wonder what brake hones are made of?
Title: Re: bad front end shudder on hard low speed brake
Post by: Howie on September 01, 2008, 09:05:46 PM
I use a Sotch Brite on the rotors and sand paper on the pads.  Sand paper or emery cloth is fine too, but a little more aggressive on the rotor.  Whatever you use, it is good to clean the grit off all parts before reassembly. 
Title: Re: bad front end shudder on hard low speed brake
Post by: Ddan on September 02, 2008, 03:59:24 AM
I did a bit of googeling and brake hones are made with aluminum oxide silicone carbide among other things, and a recommended treatment for rotors is bead-blasting so I don't thing silicon is a problem. Regardless, +1 to what Howie said, clean everything well before reassembly.