Thanks for the responses guys – good stuff
Ok here goes . Fox RL 2010 f-series so they should be compatible with 180 mm rotors
Mount is the correct way around. It’s the bottom of the fork thats visibly vibrating. Like it’s gripping hard, then judders then fades.
Sanded the pad to remove any glaze, sanded rotors to give it something to grip onto (done this for years with no ill effects)
Headset tight, bolt from fork to adapter tight and brake to adapter tight
Is it a toothed rotor – it may be clipping the claiper.
Laid the rotor flat and is good, flat as any other rotor (this rotor is second hand btw) – what’s a toothed rotor Mike?
iolo – Member
Put the old disk on.
Problem solved.
– yup, your bang on and it may have to be put back on
Kayak – that’s what i thought, too clean. Gripping sooo tight the fork wobbles? but that can’t be right can it?
goodgugu – it’s almost flat but not totally flat, i think it’s more than acceptable but maybe i’m missing something?
globalti – Member
If none of that works you might just have to accept that you’ve accidentally engineered into your brake a problem that people have been trying to engineer out for years. A bigger rotor will be exerting a bigger twisting moment on the caliper, the mounts and the fork, changing all the forces in the setup.
Fork judder can be caused by so many things but my best guess is lack of rigidity in a vital component. The brake works and everything clamps up then something distorts and lets the brake off a little. The brake jumps then everything moves back to its original efficient position, grabs and distorts again, and so on setting up a cycle of vibration. lol – never a truer work spoken. That’s exactly what i’ve done and that’s exactly what is happening
Cheezpleez – i hope it’s the adapter cos i’ve added 2 components – an expensive 20 mm larger formula rotor and a cheap pm to pm superstar adapter. it’s gotta be one of those that is now causing the problem that Gobalti beautifully put
coatesy – not sure i understand, it’s deffinatly not overhanging? – when i get my head sorted i will post some pics on flickr – don’t have a head cam otherwise i’d film it but the vibrations are quite shocking
retro83 – Member
my guess is a manufacturing fault with the rotor, either a small thickness variation, or it is out of true vertically.
– again it’s one of the two new components added so yes that would make sense
nwgiles – if the formula adapters went silly money then i would have done the same thing. Everything is formula (even pads) other than the adapter
PolisherMan – Member
I had exactly the same problem with judder. New mazocchi forks and headset. I was using “wavy” aftermarket rotors and it made the bike unridable. I swapped it to “round” shimano rotor (using SLX brakes) and problem solved. I didn’t really notice it with the old forks ‘cos they were completely knackered!!
– now you may have something here – my 160 mm rotors are ’round’, the 180 mm is wavy. ahhh, ok we might be getting somewhere now
martinxyz – when i installed the new rotor i swapped the front and back pads round as the back are always near new – i haven’t swapped them back yet but like you say, worth a try
thanks guys – love you all