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[rayivers]

It's taken a while as I wanted to be absolutely sure this time, but my front brake is finally silent.  I've done two extended pad/rotor break-in rides on the street and four 45 min. dirt/street rides, all without a sound.  Brake operation is also much more consistent than before.

In a nutshell, the brake was a mess. The hub rotor flanges were angled every which way and two of the threaded holes were crooked, the rotor was warped from being tightened to them, the FastAce fork mounts held the caliper at a slight angle, and who knows what else.  Rather than blueprint this rigid old-school design and hope for the best, I chose to add a little 'give' here and there to even out the misalignments, like most modern front brakes.

The plan was to thin / true the rotor to add flex & minimize pad chatter at the source, then reduce mechanical coupling between the rotor and hub to eliminate warpage & keep any remaining vibration out of the spokes and fork.

Here's the rotor (modified left, OEM right) - the swept area has been thinned .030" per side and trued L/R to within .0005", and bolt holes countersunk at 100°:



Diagram for above:



The rotor has small copper shim washers (Grainger 5ZLU0) between it and the hub, and is held on with stainless M8x20 flathead screws (90° head angle) along with lockwashers / jam nuts on the spoke side of the flanges.  These bolts were tightened to 1 (one) ft/lb, and the locknuts tightened.  This setup has not loosened at all.



It might be possible to use the FX rear rotor (same mounting circle, holes already counterbored) on the front with the flathead screws / copper washers / etc., but I haven't tried it and don't know if it would eliminate the noise.

The next challenge will be to get some acceptable braking power happening (neither of my Zeros can lock the front wheel on dirt, let alone pavement).  The big-piston master cylinder should be replaced with something more correct for this small single-rotor system.  Check out this thread on front master cylinder replacement.

Ray

[nigezero]

Great work Ray: I have the same squeal and have tried loads of things but not this.

[rayivers]

Thanks! One thing I forgot to mention is that you could test the rotor-isolation part of this fix easily, just by loosening your rotor bolts and then tightening them a bit more than finger tight.  This should be fine for a short test ride, and if the squeal's gone, then you could decide what alternate method of rotor mounting you're comfortable with (my fix isn't the only way to do it).  There's not a lot of clearance on the LH side of the rotor, and one of the spokes passes quite close to one of the hub flanges, so options are a little limited as far as rotor bolts / locking setups go (there's always Loc-Tite, of course).

Ray

[BenS]

I know the Zero discs have a strange 4 bolt pattern, but a good thing to have would be a 260mm front disc and a different mounting bracket for the caliper to be re-positioned. My KTM and GG came stock with 260mm front discs, but I bought a 260mm EBC kit for my YZ. You wouldn't think it'd make much difference going from 240mm to 260mm, but it really does. I'm wondering how much it'd cost me to have a 4 bolt 260mm disc machined up. I'm thinking that a caliper mounting bracket already available for other brands should probably fit the Zero.

[rayivers]

I looked into putting a bigger disc on mine, but the caliper mount is cast into the LH fork leg so I figured it would be more trouble than it was worth -  it looks like the '15 FX Showa fork is similar.  The disc specs for the '14 FX are 240mm O.D., 105mm I.D., 4.90" / 125mm M8 4-bolt circle, 4.5mm thick.

I also looked around for a 240mm floating-rotor setup, but could only find a 220mm (Brake Tech BTD220R).

I really like the KTM 85 mounting method, which allows bigger rotors to be used just by changing caliper spacers.

My YZ's 250mm disc is incredible, I'm very happy with it.

Ray

[BenS]

I looked into putting a bigger disc on mine, but the caliper mount is cast into the LH fork leg so I figured it would be more trouble than it was worth -  it looks like the '15 FX Showa fork is similar.

Yeah, that's how it works; the adapter bracket bolts onto the original attachment points, and then provides new points for the caliper to mount to.

[rayivers]

This place seems to have a number of the adapters you mentioned, but i haven't contacted them about it:

http://www.moto-masterusa.com/photos/mx/rallye/supermoto-oversize-adapter-brackets

Perhaps they can supply one based on bolt-pattern and offset measurements, but it sure would be nice to have an OEM model that used the Zero caliper, or a Nissin part number, to give them as well.

Ray

[BenS]

Yeah, if the mounting point measurements are the same for j.juan as they are for nissin, then I think the spare adapter I have for my YZ should fit the FX.

[BenS]

Hi Ray, I meant to post ages ago re the mounting points. I see what you mean, the spacing between the two mounting holes is much closer than on my YZ. I still need to look into trying to fit a bigger rotor and caliper mount adapter, 'cause my front brake still howls, it's the noisiest part on the bike! I noticed a while ago, while doing some research, that some Suzuki rotors use a four bolt pattern, but that was as far as I got.

[rayivers]

Ben,

Did you ever try loosening your rotor bolts to finger-tight for testing?  I think decoupling my rotor from the hub using the copper washers was what finally got rid of my brake noise for good, although the Honda pads and rotor machining helped too.

Ray

[Lipo423]

Great job…I can tell you knew what you were doing 

If I may suggest something (although it is unlikely you will face any issues with M8 bolts) get them replaced for DIN/SAE CL 8.8 or 10.9 grade bolts (12.9 might be too much/rigid). They will rust, which is not nice, but the level of safety will be boom proof...

[rayivers]

Thanks very much - I think I may have just gotten lucky.  

The screws on there now are supposedly DIN7991, which is a 10.9-equivalent spec. I thought they were just generic A2 stainless (8.8 at most) and have been waiting for them to loosen up and need tightening, but not yet.  I think the copper may have compressed a bit, as when I tap the rotor now it sounds quite dead and no longer rings like the OEM rotor did.  I can't move the rotor by hand at all, though.

I'm going to try this same machining/mounting scheme on my J Juan rear brake next.  It's not noisy, but it's weak and inconsistent like the front was and hopefully I'll get a similar improvement.

Ray

[BenS]

Ben,

Did you ever try loosening your rotor bolts to finger-tight for testing?  I think decoupling my rotor from the hub using the copper washers was what finally got rid of my brake noise for good, although the Honda pads and rotor machining helped too.

Ray

I tried them a bit loose, but not as loose as finger tight, I didn't really dedicate time to test properly. I'll give the copper washer trick a go. I was thinking, last night, and although it sounds ridiculous and will add weight, about deadening the spokes by running a strip of thin rubber through them so that the wheel doesn't resonate, just to see if that works. Pro Desert racers here cable-tie their spokes in pairs so that if one breaks, it at least stays in place, so I was wondering if that would be enough to deaden the sound too.

I think I'll give up on trying to fit a bigger disc, I still haven't found anything that'll fit. Getting a custom disc machined up is fairly common, but the tricky part would be to get an adapter machined up(if only I was a machinist, I'd make one!). Maybe a simple stepped, steel plate machined up could be used as an extender. Even a simple steel plate bolted to the outside of the fork attachment points, then bolts with  spacers to hold the caliper would work, but might be slightly flimsy and dangerous, and obviously not ideal.

Hopefully ZERO will add a bigger disc with a caliper adapter to the FX in the future, so then I can just buy one!

[Lipo423]

Thanks very much - I think I may have just gotten lucky.  

The screws on there now are supposedly DIN7991, which is a 10.9-equivalent spec. I thought they were just generic A2 stainless (8.8 at most) and have been waiting for them to loosen up and need tightening, but not yet.  I think the copper may have compressed a bit, as when I tap the rotor now it sounds quite dead and no longer rings like the OEM rotor did.  I can't move the rotor by hand at all, though.

Mmm…DIN 79991 stainless flat head countersunk are not designed/intend for hard tightening applications…I would definitely replace them…If you had more than 4 bolts, you could be fine, but with 4, if I were you I would not take any risk...

[rayivers]

I've never tried the spoke thing, but I've heard of it before and it sounds like a good idea. When my front spoke broke, it very nearly snagged on the caliper.

A master cylinder from an '08 YZ250F dropped right in and made a huge difference - now it's a 2-finger brake.  I think the extra pressure helped with the squealing too.  It looks like Zero still uses the same MC as my '14 OEM unit with the ABS setup, so it should work with your bike too, I think.

Ray