Disc brake fork chatter / shudder?

Discuss light weight issues concerning road bikes & parts.
spud
Posts: 678
Joined: Sat Feb 07, 2009 5:52 am

by spud

generally, chatter in the front fork only happens when braking force varies during rotation of the wheel. In the case of cantilevers, if the cable is strung from the stem, the effective tension on the brake increases as the fork deflects back from braking force, causing the system to vibrate. Sticky spot on the rotor will cause the same thing. Just work through the checklist - headset bearings, proper tension on stem bolts, sand and clean the rotors and pads. It is highly unlikely that your fork simply developed this problem, though checking for cracks, especially at the mount, wouldn't be a bad idea.

Mr.Gib
Posts: 3230
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

Brake force variation which leads to fork shudder can also be caused by the design of some rotors. As Kaiser points our above, Rotors with large voids can exacerbate this problem when combined with a flexible fork. A rotor design where the rotor to pad contact is consistent can solve this problem. I found the Sram Centerline very good in this respect but the braking power seemed less then more aggressively carved rotors.

I had a real problem with my Trek Boone. The bike is great for cross but that fork is not up too hard braking on the road. Bringing the bike down from 50 km/h to a stop on a descent would result in a hard shudder starting at about 20 km/h down to a full stop. I ended up settling on Shimano IceTech with which ironically the OP is having issues. With the IceTech rotors the braking was acceptable and shuddering significantly reduced though not eliminated.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

by Weenie


MoPho
Posts: 461
Joined: Sun Jul 10, 2011 7:48 pm
Location: NorCal/SoCal

by MoPho

Mr.Gib wrote:Brake force variation which leads to fork shudder can also be caused by the design of some rotors. As Kaiser points our above, Rotors with large voids can exacerbate this problem when combined with a flexible fork. A rotor design where the rotor to pad contact is consistent can solve this problem. I found the Sram Centerline very good in this respect but the braking power seemed less then more aggressively carved rotors.

I had a real problem with my Trek Boone. The bike is great for cross but that fork is not up too hard braking on the road. Bringing the bike down from 50 km/h to a stop on a descent would result in a hard shudder starting at about 20 km/h down to a full stop. I ended up settling on Shimano IceTech with which ironically the OP is having issues. With the IceTech rotors the braking was acceptable and shuddering significantly reduced though not eliminated.



I had issues with the pads pulsing, noise and a bit of shudder with the ice tech rotors at speeds below 20mph, pads seemed to be clipping the cutouts on the parameter of the rotor, it was incredibly annoying. Using the Sram Centerline now and it has gone away. Only have a few hundred miles on them so far, but the Sram seem to not cool as well under sustained hard braking



.

Delorre
Posts: 966
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Mr.Gib wrote:Brake force variation which leads to fork shudder can also be caused by the design of some rotors. As Kaiser points our above, Rotors with large voids can exacerbate this problem when combined with a flexible fork. A rotor design where the rotor to pad contact is consistent can solve this problem. I found the Sram Centerline very good in this respect but the braking power seemed less then more aggressively carved rotors.

I had a real problem with my Trek Boone. The bike is great for cross but that fork is not up too hard braking on the road. Bringing the bike down from 50 km/h to a stop on a descent would result in a hard shudder starting at about 20 km/h down to a full stop. I ended up settling on Shimano IceTech with which ironically the OP is having issues. With the IceTech rotors the braking was acceptable and shuddering significantly reduced though not eliminated.


The latest DA rotors have less cut-outs at the outside edge then the 'old' ones, hopefully a good thing! I'm really curious about brake feel on the new bike!

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