Forks juddering und...
 

Forks juddering under braking

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I have a carbon forked (and frame) GT Grade, I run it with GravelKing slicks. When I brake hard, especially on steep downhills round where I live, the forks judder like crazy. Any tips to stop this ? (Everything seems torqued up properly)


 
Posted : 22/08/2022 4:46 pm
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play in the headset. my gravel bike needs tightening up every once in a while


 
Posted : 22/08/2022 4:48 pm
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I've had this before. Some combination of weight, speed, fork length/stiffness, brake disc pattern and maybe pad compound sets up resonance.

That was my guess, I changed disc pattern and size, made the problem go away for me.


 
Posted : 22/08/2022 4:50 pm
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play in the headset. my gravel bike needs tightening up every once in a while

and/or that!


 
Posted : 22/08/2022 4:51 pm
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Definitely the forks? So many variables here, I sometimes get a judder with a different type of brake pad


 
Posted : 22/08/2022 4:53 pm
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hand around bottom of head tube, front brake on and rock bike back and forth, turn the handle bars while you do it to see if there's any play in the headset. Then slowly eliminate all the possibilities - brake mounts loose, warped disc/rims etc

my town bike has an annoying judder on the front brake, you can't see it but the rim is very slightly kinked  - with v brakes you get a pulsing judder when braking at speed


 
Posted : 22/08/2022 5:01 pm
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Definitely the forks.....they literally judder back and forth several mm. All bolts and headset checked. I may just tweak a little more before starting to swap pads/disc. Thanks people.


 
Posted : 22/08/2022 5:06 pm
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Loose disc rotor bolts? Don’t ask me how I know!


 
Posted : 22/08/2022 5:21 pm
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Not on a gravel bike, but I had similar on my Soul with 32mm QR Rebas (so fairly flexy), which was exacerbated a lot by the "wavy" rotor I had on it. I switched it out for a more uniform rotor and it was fine again.


 
Posted : 22/08/2022 5:23 pm
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Wavy rotors are a common cause, I try to avoid them but it's difficult. At least SRAM and Shimano rotors have a consistent surface area as they pass under the pads, some are so variable you wonder what the manufacturer was thinking. New rotors and pads often won't set up a judder but once they're worn in they may do. Matching pad and rotor brand and types helps so that the pad isn't too deep for the rotor.

Generally it's just fork flex and braking power varying slightly that causes it, it's fairly normal as well as annoying. The worst judder system is a canti brake on a steel fork with a stem or headset mounted hanger, that can be fun..


 
Posted : 22/08/2022 5:40 pm
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Generally it’s just fork flex and braking power varying slightly that causes it, it’s fairly normal as well as annoying.

The judder on mine is dangerous. It is the first time I cannot ride down various local hills on the hoods of a drop handled barred bike and have to do most of the braking with the rear brake rather than the front. (I've never had fork judder before)
I'll start eliminating potential causes...when the rain (yay) stops


 
Posted : 22/08/2022 6:11 pm
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My vitus road bike did this for a while when new (105 brakes and rotors) it was quite scary! I realigned the calipers and it stopped.


 
Posted : 22/08/2022 6:49 pm