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There is visible twang/flutter movement back and forth under braking on my Fox Float 32 140's.
Can't remember seeing it before but then I haven't been out on the mtb for a while.
I'm running a 200mm wavey rotor which probably doesn't help but is this normal?
Would RS Revelations suffer in the same way?
It's partly the brake for not providing constant force (non-wavy rotors may help)
It's partly the fork for being so noodly - you may not have noticed it before.
Revs would most likely be better but it would still happen to some degree.
Yes. I had 32s on my Ti456 using a 180 hope rotor. 100-150 talas. There was alot of flutter under braking. Also extreme flex with or without lockout when riding out of the saddle.
Revs have thicker/wider stantions iirc so there will be less flutter.
140mm really is the most travel you want on the 32s, I noticed more flex on mine when I had the travel spacer removed (130mm up to 140mm). Now on 34s @ 150mm on a different frame and there's way less flex. I only ran a 180mm rotor on mine, 200mm will cause more flex than I saw again. So I'd say its normal as you're at the limit of the 32 really.
Combination of flex,worn bushes,pads !,& don't forget it could just be you pushing the performance envelope to its max !!!
it could just be you pushing the performance envelope to its max !!!
I like that!? Yep, I was riding down a tarmac'd lane with nothing more to amuse me than listening and watching for any problems with my bike. Super hardcore 😉
I have been looking at X-Fusion Slant forks but the axle to crown length on bigger stanchion/longer (160mm) travel forks seems to be proportionally longer for the amount of travel (i.e. another 20mm a-c when comparing 150mm Revs to 160mm Slamts).
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Thanks Dave, so like for like the Slant is 535 for 150mm travel Vs 528 for a Revelation
As others have already said the forks are on the limit of being stiff enough for their travel and use...
But a closer look at the pads and rotors will probably get rid of the worst of it for you. I have had the same thing in the past with other forks and smaller rotors. The pads had just gotten very worn and the rotors were a bit old and out of true. Basically everything got very juddery all of a sudden and was cured by new pads and rotors.
Its the rotor I promise you
I had exactly the same problem on some revelations - It was obvious as I had just fitted a 200mm wavy rotor - removed the rotor and the vibrations disappeared.
Weird - it cant be on all forks or no one would buy wavy rotors. Mine weren't fox but they were 140mm so perhaps its a certain length of fork that sets up the resonance??
Absolutely normal, 32 is an XC fork that's been stretched too long. It's why they invented the 34- having established their weakspot they turned it into a selling point, that's what Fox do 😉
But if it didn't bother you before, why worry?
There is a difference between a fork being a bit flexy (like fox 32s) and the vibrations the OP is talking about (which I had with a set of revelations - so bad I thought the forks would snap in half). Swap to a none wavy 200mm rotor and the problem will go away.
happens on my 140mm Revs, and I don't have a wavy rotor.
happens on my 140mm Revs, and I don't have a wavy rotor.
Likewise. I just thought that was what forks did under braking.
It's almost certainly NOT the forks, it'll most likely be a combination of pad and rotor where the pad overlaps on the inside of the rotor and interferes with the rotor legs every 6th of a rotation (or however many legs your rotor has) and it won't make any difference what forks you fit it'll still happen.
Fixing it at least in my case was just a simple matter of removing the pads and filing off the tiny lump that was appearing on the inside of the pad and taking a bit more off in the form of a chamfer to delay the onset of it next time.
Mine was a Saint brake (M800 vintage) ans 203mm Aztec rotor combination if it helps any.
Bottom line is have a look at your pads/ rotor before you replace anything. If your situation is similar there will be some wear on the very end of rotor legs.
HTH
Gaz
Mine was also an Aztec rotor and Deore brake. Standard Shimano rotor worked fine.
I'll disagree with you on that Speeder, has happened from new everything on mine and I certainly don't get any lumps forming on my pads, it is also irrespective of speed so the 6 rotor thing isn't valid in my case.
It certainly isn't as bad as it was on my 28mm Judy's back in the day, the flutter was so bad on them with discs on steep stuff I'm pretty sure it caused me at least one off.
I am a bit over 13 stone though, punier beings might not cause as much fork flex 😉
I'm on Ashima rotors, which are like the Aztec ones. I like the Aztec rotors cos they're light but can't have it all ways probably.
I was never really looking before, but this time I was.
A new fork was part of the plan to beef up my Zesty for going to Spain later this year, and avoid buying a full new bike.
So you chaps are just not helping me to justify that by agreeing a change of rotor will fix it 😉
Again check pads. Mine fluttered impressively but was down to pretty knackered pads.
Its the rotor. Magura wave and storm rotors created huge pulsing in the fork, only really a noticeable issue on tarmac or buff bridlepath. Nothing wrong with the fork.