Front Fork Judder/Chatter under braking - My Solution
09-13-11, 09:13 PM
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Front Fork Judder/Chatter under braking - My Solution
A started a thread a week ago mentioning my fork juddering under braking. Here's the story so far.
My cross build started with a Blus CXC frame with TRP cantilevers. Standard cable hangar from the top of the headset. First test ride, the front fork immediatly juddered. I set the brakes with about 1mm toe in. I changed the used pads for a new set and the juddering seemed to go away. Wrong! That only last for a very short time.
Upon further investigation, I noticed that there was play in my head set. This play was not coming from the inside diameter (ID) but from the bearing outside diameter (OD) and the bearing pocket in the headset. This is where the top and bottom bearings of the headset sit in the bike frame's head tube. Upon dis-assembly, I noticed both top and bottom bearing pockets had play. To fix this, I took a center punch and hammer and punched the aluminum inner diameter of the bearing pocket. I made punch marks all the way around the bearing pocket, about 3mm apart. These pock marks, when made with a center punch pushes metal "out" and makes the bearing pocket diameter slightly smaller. I then re-installed the upper and lower bearings with red loctite and re-assembled the fork.
The fork felt tighter on the stand already. My next move was too change my "toe in" to "toe out" on the canti's. I did a google search and responses were all over the map on whether to "toe in" or "toe out". Since I started with 1mm of "toe in", I decided to try "toe out".
Went for a ride and to my disappointment I still had judder. It was getting late, so I had to leave it for the night, but I was all prepared to go to mini v brakes of even a new fork.
Next day, for fun and as a last resort, I rest the brakes to about 2mm of "toe in". To my surprise - NO JUDDER. Not only that, the brakes work exceptionally well. I've tried everything to get them to judder and they're smooth as silk. Go figure.
"Toe in" BTW is with the front of the pads closest to the rim. "Toe Out", the rear of the pad is closest to the rim.
I think my original problem was a combination of loose bearing pockets compounded with not enought "toe in".
Looking forward to my first race.
Canflyboy
My cross build started with a Blus CXC frame with TRP cantilevers. Standard cable hangar from the top of the headset. First test ride, the front fork immediatly juddered. I set the brakes with about 1mm toe in. I changed the used pads for a new set and the juddering seemed to go away. Wrong! That only last for a very short time.
Upon further investigation, I noticed that there was play in my head set. This play was not coming from the inside diameter (ID) but from the bearing outside diameter (OD) and the bearing pocket in the headset. This is where the top and bottom bearings of the headset sit in the bike frame's head tube. Upon dis-assembly, I noticed both top and bottom bearing pockets had play. To fix this, I took a center punch and hammer and punched the aluminum inner diameter of the bearing pocket. I made punch marks all the way around the bearing pocket, about 3mm apart. These pock marks, when made with a center punch pushes metal "out" and makes the bearing pocket diameter slightly smaller. I then re-installed the upper and lower bearings with red loctite and re-assembled the fork.
The fork felt tighter on the stand already. My next move was too change my "toe in" to "toe out" on the canti's. I did a google search and responses were all over the map on whether to "toe in" or "toe out". Since I started with 1mm of "toe in", I decided to try "toe out".
Went for a ride and to my disappointment I still had judder. It was getting late, so I had to leave it for the night, but I was all prepared to go to mini v brakes of even a new fork.
Next day, for fun and as a last resort, I rest the brakes to about 2mm of "toe in". To my surprise - NO JUDDER. Not only that, the brakes work exceptionally well. I've tried everything to get them to judder and they're smooth as silk. Go figure.
"Toe in" BTW is with the front of the pads closest to the rim. "Toe Out", the rear of the pad is closest to the rim.
I think my original problem was a combination of loose bearing pockets compounded with not enought "toe in".
Looking forward to my first race.
Canflyboy
