milktree

I basically exclusively work on my own stuff. I don't do oil changes in my car because it (essentially) requires a lift and it's a huge pain in the ass and no fun, but I do all my own work on motorcycles, and as much as I can on my cars.

I worked as a mechanic in two bicycle shops, but that was 30 years ago so I'm unfamiliar with the new tech. Hydraulic disk brakes are kind of space-age to me.

"Becoming great at working on my own stuff" is paramount here. I've got all the fundamentals, so nearly all the details I can learn from YouTube and forums. It's just the weird things like this that I'm stumped on. (although the "rotor:hub interface" is looking really promising)

Or said differently: I really dislike going to a bike shop unless it's to 1) buy something, or 2) have them do something I can't do at home because of special tools.

esasjl

I'm not adding anything but I'd suspect stiction somewhere in the rotor/hub interface as the pads deform the rotor. The spokes just resonate in response. Maybe remove rotors and adaptors from the hub, check for cracks then reassemble with lightly greased contact surfaces?

alexk_il

Wow, I just discovered exactly the same issue on my monster-cross project bike that finally got new shiny wheels and rotors and some old TRP Spyres brakes.

I get the same creaking with my rear brake on the stand. A strange thing, if I leave the bike alone for some time, the creaking disappears and only comes back if I "pump" the brakes a few times.

FBinNY 

Please pardon my ignorance of disc brake particulars. But it possible for the pads to move slightly within the brake?

I ask because it happens in the auto world, causing squeal or chirping, and wonder if this is simply a case of finding a meaningless anomaly.

alexk_il

My Asima rotors have more cutouts than real metal, it's quite likely that the pads are chirping when pressed hard against the hard edges of the cutouts. And then the whole frame resonates. Maybe, I'm out of my depth here.

Anyway, ​​after my initial curiosity was satisfied by playing for an hour with these creaks and tightening every single bolt in the system, I decided to simply wait and see if it gets worse and if it affects the braking. Luckily I can now wait and see the conclusions of this thread, whatever these would be.

​​​

cyccommute 

The camera on a tripod would help…just sayin’.

It looked like the spokes were aero, my mistake. It does (kinda) look like the spokes are moving when you are rocking the wheel back and forth. It’s hard to tell with the camera movement but towards the end of your video, it looks a little like they are moveing.

The issue, I think, is that the straight pull spokes aren’t interlacing and bracing like a J-bend spoke do. The J-bend spokes come from close to the same plane while straight pull don’t. One thing you might try is tying the spokes. Just so that it’s reversible, I’d not go with the soldering right now. You could solder them later if you like.

TiHabanero

i have encountered this before and it was the brake, not the spokes. I replaced the brake pads and scratched up the rotor on both sides and the problem was solved. I suggest removing the brake pads and sanding the surface, then take 60 grit paper and thoroughly sand the rotor on both sides moving across the rotor, not with it.

cxwrench

There is a black block right below the member's name that says "Thread Starter" when that person (the OP) posts in a thread he's started.

FBinNY 

Interesting.

I was very active on this forum some years back, and am only back after a 5 year hiatus. I don't remember ever noticing that feature, so I thank you for the info.

OTOH- These days I'm often posting from my cell phone while killing time, waiting on stuff. I'm lucky I can post a legible reply with my fat fingers while coping with auto-correct that thinks it knows what I'm thinking.

milktree

Yes, but that's not what's happening here as far as I can tell. I'll re-check to be extra sure, but it doesn't feel/look like it.

milktree

You're describing the "squeal' you get from glazed pads and/or rotors. That noise requires some movement between the two. This is happening when the rotors are *NOT* moving against the pads. (and the sound is very different)

Crankycrank

As kind of a hail Mary attempt, try putting a teeny drop of oil on the spoke heads at the hub so they can move freely with the spoke flex then go for a ride to let the oil penetrate and see if you can re-create the noise. Nothing to lose except a few minutes of time to apply the oil.

cyccommute 

I missed this post earlier. Looking at the picture above, I think the problem might be with the wheel build. The spokes should touch at the green arrow and would using a J-bend spoke. The spoke with the right should pass under the spoke on the left which would brace the spoke and make the whole structure stiffer. By not bracing the spokes that way, the wheel can flex and where the spokes do rub, they can make noise.

The sound is only partly related to the disc. The disc puts more stress on the hub which winds up the spokes more than a rim brake would. The short contact point on the spokes would make the spoke vibrate more allowing for sound. You could try tying those contact points so that they can’t move. I don’t know that it would work but it would be worth a shot. The real solution would be a wheel rebuild.

You have a very interesting musical instrument right now. It’s almost like plucking a guitar or violin string.

cxwrench

^Typical Mavic 'engineering'^

Iride01 

I use to true my own wheels when younger. However eventually I realized that I sometimes wound up with a perfectly true wheel and some spokes very loose and others very tight. Not wishing to get more tools I just found that letting the wheel guy at the bike shop handle wheels made sense for the few times I've ever really needed wheel work.

If you are going to work on your own spoke adjustment, then learn all the stuff you should know about building your own wheels so you'll be decent at assessing the condition of your wheels and whether they seem properly constructed for your use of them. I looked into building my own wheels briefly, but the few needed tools and the cost of parts... rims, hubs and spokes just made it return too little benefit compared to the deals I was finding on already built wheelsets. Even if they were suspected to be the worst machine built wheels possible, as long as the parts were decent brands I could just take them to a wheel person at a shop and get them reworked for cheap.

milktree

So... these wheels are 100% stock as came from Cannondale.

I find it hard to believe that Cannondale would use the wrong kind of spokes and lace them wrong. They're a huge company with good quality control.

The hubs are designed for straight spokes, using J-spokes seems contraindicated.

milktree

I've done basically that, with no change.

alcjphil

The OP has a centre lock hub but is using a 6 bolt adapter. This introduces an extra layer of possible slippage when brakes are applied. Would it be possible to simply install a proper centre lock rotor to eliminate one possible thing that could cause this problem?
I am a simple guy. I like simple solutions

GamblerGORD53

Maybe pry the spokes apart where the red arrow is.
The biggest noise will happen when the brake bracket rubs the disc. Just move the bracket and see what happens.

milktree

Possible? Sure. But I'm generally reluctant to doing the parts shotgun to debug things. That usually leads to a ton of used, but perfectly fine, parts sitting around the garage. (and added expense)


It came from the factory that way, so if this was a problem it would have shown up on all of them.

and... if this was a problem, either nobody would sell them anymore, or at least this design would be replaced with something else. But DT and Shimano still sell that design.

So, maybe I'll go that route eventually, but I'm inclined to not start there.

milktree

It's absolutely not the brake bracket or the pads rubbing the disk. When the brake is released, there's no rubbing at all. When the brake is tight, there's no rubbing (because the brakes are clamped on the rotor. Contact, but not rubbing.)

cyccommute 

They aren’t a Cannondale product. The catalog says that the OEM wheels are Mavic Aksiums. I don’t use Aksiums nor straight pull spokes but cxwrench already weighed in on the Aksiums.

I’m not saying to use J-bend spokes. I’m saying that the wheels may need to be rebuilt with the proper crossing to get rid of the sound. Or, again, you might try tying the spokes at the green arrow. If you don’t solder, you can reverse the tying.

milktree

Yes, they're Mavic Aksium wheels.

Cannondale didn't make the deraileurs, either, or the saddle, or the tires, and I'd bet real money they didn't make the headset, just rebranded it. But they're still a big company who has to do quality control even on the parts they didn't manufacture themselves. Just like Honda takes responsibility for all the parts that come from Denso that go into their cars, Cannondale has to take responsibility for the wheels they put on their bikes. If Honda has a recurring problem with a Denso module, they beat up Denso until the quality control meets their standards. I can't imagine Cannondale doesn't do the same thing.


I don't understand how tying the spokes where they don't touch would make any difference.

cyccommute 

Just as with a car manufacturer, Cannondale trusts the quality control of the supplier and doesn’t check the item themselves. There are several instances of the downside of that approach…see the Takata debacle for example. I’m sure that Cannondale never tested the wheels nor did anything other than unpacking them. I’m also sure that Cannondale doesn’t have the pull to tell Mavic what to do. Your wheels could be just a random problem due to some variances in manufacturing and/or use.

Because those spokes should be touching. Without the touching, the spoke can move and rub against each other further down resulting in the vibration that makes the sound you hear. Without rebuilding the wheel, tying the spokes together should result in a reduction of that vibration which would make the noise go away. It’s worth an experiment since the sound is so awful.

You can easily remove the wire ties if it doesn’t work. If you don’t want to go to the trouble of doing a wire tire, zip ties might do the same thing as tying with wire. You want the spokes to touch so that they can’t vibrate. I wouldn’t make the zip ties a permanent solution but as a test of concept, they would be easier to do than wire.

milktree

Well, with car manufacturers, you're absolutely wrong. They do check, and any problems that show up get reported upstream, and remedies are put in place.

Bikes are not cars, so their upstream QA isn't as robust, but every builder (if that's what we're calling Cannondale in this case) is going to have words with their suppliers if they run into problems.

Cannondale's market share is hurt by multiple reviews saying stuff like, "the wheels always creak under braking". Likewise Mavic's


Upon assembly of the bikes for sale, you might be right. But when they made their build of materials when developing the model they surely did. They had to have picked that wheel somehow. It's not like they just took the first hit on Amazon. And even in the for-sale production bikes they surely pulled an occasional bike out of of the line to inspect it. Any decent manufacturer would.

Perhaps, but you'd be surprised what a customer can get from a vendor. They can decide to use a different vendor though.

That's what I'm assuming.


Wait.. are you saying that there's enough friction between laced spokes to prevent them from moving longitudinally? The physics nerd in me says that doesn't make any sense. The only pressure between the spokes, the normal force, is pretty small compared to any changes in tension forces under braking or riding.

zip ties are a cheap and easy test, so I'll give it a try. I could use safety wire, but it's pretty sharp and I don't want to damage the spokes.

Is the intent to put enough friction between the spokes so they don't slide against each other, or to damp vibration?
The former seems.... really hard.