I've run a flexy exotic carbon fork on my surly ogre with 29 x 3.00 up front for many years now . I have enjoyed the comfort but recently begun experiencing an unnerving juddering when slowing going downhill on easy off road tracks with uneven surfaces. Chris king headset seems fine and play free so I'm wondering what's the cause . I have actually begun running the front tyre somewhat harder than before so wondering if that is the likely culprit (must do some tests I know ) and that as the tyre gains and losses traction on the varying surface ..the fork twangs back and forth and gives the unpleasant juddering ? If not the tyre pressure then I'm presuming it may be brake related but it doesn't happen at all on tarmac descents with even surfaces. Any other suggestions ? Excuse the laziness and thanks in advance . Bill
First thing I’d be checking is the brake disc
Specifically, is it absolutely spotless, and I don’t mean visually.
Brake cleaner, some heat and a light going over with some sandpaper would be a start.
If that doesn’t cure it, next thing would be a thorough visual inspection of the fork itself.
Disks and/or pads.
Mine did that from new. New pads, cleaned and sanded disks, and a fluid bleed sorted it out.
Check everything as above but I had an exotic carbon fork in the past and it did exactly the same. Swapped it out for a Travers Prong, which seems more substantial and the problem went away. I'm reasonabley big so perhaps the Exotic was a bit delicate for me.
I had the same issue and it was entirely down to the fork flexing. Went through everything including over tightening the headset before I saw what was going on. Look at the fork as you’re braking hard to stop. I could see mine tucking under as I did so. Swapped fork to a less noodly alloy one and sorted. I am 92kg though….
I think it's just the fork construction, maybe the higher tyre pressures are removing some damping, hence you're noticing it more. FWIW I had some very, very light Pace carbon forks and you could see those flexing 😁
Cable discs? Go through the front brake from lever to disc, but I think that the fork flex is maybe affecting the pulled cable tension on the pads. Does depend on the inner/outer cable arrangement tho
Likely to be the rotor type or if it's a recent issue, an unevenly worn rotor. Almost all disc brake forks flex under braking but judder from fairly normal braking (rather than real slammed-on anchors) comes from a variance in the braking power that matches the flex in the fork blades. Rotors that present an uneven surface area at the pad as it rotates ie odd wavy pattern etc are the worst for this. I've had forks that suffered from it that were fine with a new disc rotor and pads.
eXotic carbon monocoque fork with 700x50 CX-style tyre here, Shimano RT66 180mm rotor with SLX caliper. Only time I ever experienced significant judder was when rotor was worn - replaced with new rotor and no issues. I do see a bit of flex in the fork in general (I'm 88kg or so) but it doesn't feel like judder.
thanks all ..good suggestions ..much appreciated.
I had similar symptoms on a fox 32, it turned out the pads didn’t meet the disc properly so a lip had formed on the pad which touched the outside edge of the disc if that makes sense.
And I was going to suggest the opposite to jsync, check to see if the pads are running off the inside edge and catching on the spokes of the brake disc