Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 09-15-09, 02:53 PM   #1
daintonj
Senior Member
Thread Starter
 
daintonj's Avatar
 
Join Date: Apr 2008
Bikes:
Posts: 372
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Brake Judder Issue - The Return

Over the last 12 months I've had varied problems with brake judder on a carbon forked cyclocross bike, much time has been spent reading posts and at times the problem has completely gone away. It has now returned with a vengence and I'm at a loss as what to do.

Steps taken to rectify issue

1) Replaced headset mounted hanger with fork crown hanger - slight improvement
2) Replaced brakes with Tektro CR520 - massive improvement
3) Returned to headset hanger - no change
4) Changed from canti blocks to the pad style used in CR720 - no change but fork judder not present in dry conditions, minor in wet.

All well and good for six months until the pads started wearing

5) Replaced pads with similar looking dual compound - Fine for a day, then the judder really started
6) Tried usual fiddling with toe-in etc with no luck
7) Fitted a brakebooster to see if flex was the issue - problem fixed for all of three days

The only thing I can think of now is to replace the brake pads with something cheaper and harder.


Items to note

1) Wheel has an ever so slight deviation from true latterally but I haven't got a truing stand and it's too small to do using tie wraps.

2) Wheel has been cleaned with wire wool and degreaser to see if that would help

All pictures can be found here





Does anyone have any ideas of what else I could do to resolve this? My last idea is that the headset is wearing a bit but does not feel loose.
daintonj is offline   Reply With Quote
Old 09-15-09, 03:30 PM   #2
Cynikal
Team Beer
 
Cynikal's Avatar
 
Join Date: Apr 2004
Location: Sacramento CA
Bikes: Too Many
Posts: 5,927
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
You can try raising your straddle cable to reduce effectiveness. I would also take the brakes off the posts and regrease.
Cynikal is offline   Reply With Quote
Old 09-15-09, 04:47 PM   #3
daintonj
Senior Member
Thread Starter
 
daintonj's Avatar
 
Join Date: Apr 2008
Bikes:
Posts: 372
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Brakes were only removed and re-greased 10 days ago when I fitted the brake booster.

The straddle wire is something I'd thought of but I was thinking the other direction, but your suggestion makes more sense. I'd have less modulation as it would be over a shorter distance but there would be less time where only part of the pad is touching the rim where the rest could vibrate.
daintonj is offline   Reply With Quote
Old 09-15-09, 04:55 PM   #4
neil0502
My bike's better than me!
 
neil0502's Avatar
 
Join Date: Feb 2005
Location: Northern Colorado
Bikes: (2) Moots Vamoots, (1) Cannondale T2000 tourer, (1) Diamondback Response Comp mtb
Posts: 2,041
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Unrelated thoughts:

Have you tried a different rim?? Just curious if something about the braking surface on yours is causing excessive 'grippiness.'

The fact that the brake booster helped -- if only temporarily -- should indicate that fork flex was, at least, a part of your problem. Looks like yours is CF. Hate to ask, but ... have you tried a different fork -- perhaps aluminum or steel?

Generally speaking, it sounds like you need less stopping power, so ... a harder pad could help, adjusting for less mechanical advantage, ....
neil0502 is offline   Reply With Quote
Old 09-15-09, 08:47 PM   #5
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Bikes: 1984 Trek 660, 2003 Specialized Hardrock, 2004 LOOK KG386i (RIP), 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2014 Islabikes CNOC 14 (son's)
Posts: 10,189
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 189 Post(s)
Have you made sure that your headset adjustment is too loose?
joejack951 is offline   Reply With Quote
Old 09-15-09, 10:32 PM   #6
operator
cab horn
 
Join Date: Jun 2004
Location: Toronto
Bikes: 1987 Bianchi Campione
Posts: 28,306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by joejack951 View Post
Have you made sure that your headset adjustment is too loose?
Uh what.
operator is offline   Reply With Quote
Old 09-16-09, 06:18 AM   #7
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Bikes: 1984 Trek 660, 2003 Specialized Hardrock, 2004 LOOK KG386i (RIP), 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2014 Islabikes CNOC 14 (son's)
Posts: 10,189
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 189 Post(s)
Quote:
Originally Posted by operator View Post
Uh what.
Seriously, WTH was I trying to say there?

Oh I know...Have you checked that your headset preload adjustment is NOT too loose?
joejack951 is offline   Reply With Quote
Old 09-17-09, 02:12 AM   #8
cs1
Senior Member
 
cs1's Avatar
 
Join Date: Feb 2004
Location: Clev Oh
Bikes: Specialized, Schwinn
Posts: 6,682
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Why does seem to only happen with CF forks?
cs1 is offline   Reply With Quote
Old 09-17-09, 04:29 AM   #9
MilitantPotato
Subjectively Insane
 
MilitantPotato's Avatar
 
Join Date: Jul 2008
Location: Saint Louis, Missouri
Bikes: '09 Rodriguez Adventurer Custom, '08 Trek 7.3Fx
Posts: 802
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Also, have your brakes developed any play at the mount?

Any chance the rim walls are bulging out very slightly instead of being out of true?

Check your fork for cracks?

I'd think judder is from something flexing too much. Maybe swap the spacers around, reduce the leverage the rim puts on the brakes (since they look set up properly this may reduce braking power.)
MilitantPotato is offline   Reply With Quote
Old 09-17-09, 11:04 AM   #10
daintonj
Senior Member
Thread Starter
 
daintonj's Avatar
 
Join Date: Apr 2008
Bikes:
Posts: 372
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Miniscule play at the mount but I've only had them a year so I'm not replacing them and it's about the same amount of play as the rears which have barely been used.

Bike shop checked headset pre-tension and it's correct.

The rim walls don't appear to be bulging out but I'll take a closer look.

Forks appear uncracked.


What has helped is today I went and bought the cheapest brake pads I could find and fitted them with a small amount of toe in (match stick between rim and pad 4 mm from back of pad). Judder is minimal when breaking from the hoods and non-existent when breaking from the drops.

The bike shop opinion was split. The owner pointed out that most people with cf forks and canti brakes like him have no problem (lots of cyclocross in our area). Agreed that the brake booster could help but thought it was probably the pads and sold me some for 3. The other guy suggested going for disc brake solution for around 200 which included labour, but agreed that the pads could solve 90% of it.

I'm still tempted by a front disc brake (cable) as it's an all weather commuter and touring bike and being able to stop faster on steep hills in the rain would be nice.
daintonj is offline   Reply With Quote
Old 09-17-09, 07:32 PM   #11
operator
cab horn
 
Join Date: Jun 2004
Location: Toronto
Bikes: 1987 Bianchi Campione
Posts: 28,306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by cs1 View Post
Why does seem to only happen with CF forks?
Cheap ones aren't stiff enough. Although i'm not convinced a more expensive one will help either.
operator is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 03:02 PM.