ive got a set of fox float 140 rl’s with qr15 and the tapered headtube thingy. nice enough forks and all that but they do flutter a bit under heavy braking. ive checked all the other possibilities; brakes, hub, bushings, headset etc and i think it can only be the fork. would a set of revs with a 20mm axle be any stiffer or do i need to go back to a set of 36’s spaced down to 140mm?

I know, mtfu and all that, but when im boom-gnarring it up to the sick-rad its a bit off-putting…

I don’t think a 20mm axle would make that much difference over a 15mm personally, not as much as larger stanchions would make anyway.

Do you “need” burly forks? Depends how important this is to you. I used to get on fine with an old set of 2001 Marzocchi Z1’s at 130mm travel, really plush fork. But as soon as I rode a set of Fox’s (ironic in this context) with 32mm stanchions, I couldn’t go back as I then noticed how flexy the Marzocchi’s were all the time… This was a number of years ago by the way.

How heavy are you, and what brakes (and rotor size) are you running, as both could be a very contributing factor too…

What brake rotors do you use? IME, pretty much anything that isn’t properly circular can result in pretty catastrophic flutter.

clean the discs?

check it’s not warped?

a spot of oil, or a warped disc, can cause fluttery/juddery braking.

I’ve found that Fox 15mm forks are not as stiff as 20mm RS forks, although it never bothered me. I’d suggest trying (beg/borrow/steal) some with a 20mm axle and see what you think and failing that do what you say and go for reduced 36’s.

What brake rotors do you use? IME, pretty much anything that isn’t properly circular can result in pretty catastrophic flutter.

Actually, that’s a very good point. Had some A2Z sawtooth rotors a couple of years ago, they caused constant braking pulses almost as if you’d braked too heavily in a car (probably Audi) causing the ABS to kick in and pulse the pedal.

Clean and lube your brake pistons if you haven’t already. Mine were rubbish, lazy piston at fault.

Fox 32’s are the least stiff forks fore-aft ime, esp. the 140s, but not to an extent where it’s an issue, you just notice when swapping between them and rebas, revs or DT.

Sand down the disc – could have uneven deposits of pad material

I found that my Magura Julie brakes fluttered loads. I inquired about this to Magura UK and they said that the wavy disc could be the cause.

My Magura forks used to judder a fair bit under hard breaking.

Don’t get it on my RS forks.

It was evident riding rigid so I went down a rotor size.

Problem solved/hidden 🙂

The brakes are formula’s, I’ll try that though, ta