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I recently bought a 2016 Cannondale Synapse Carbon Disc road bike, which is working great -- however I notice that occasionally when my front wheel hits a bump (e.g. a small pothole or the lip of a driveway), the front fork (or something beneath it) goes into some sort of vibration mode and makes a noise that sounds a lot like the "twang" of a door-stopper for about a quarter-second.

It's a little surprising when this happens (both due to the unexpected sound and the vibration I feel through the handlebars), but I don't observe any obvious problems other than that.

My question is, is this sort of behavior normal/expected with this type of bike, or is it an indicator that something needs adjustment? (The quick-release lever seems to engaged tightly AFAICT, and there is no reflector mounted on the front spokes)

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    The thing that needs adjustment is the riding style. Pot-holes, manhole covers and sharp steps in the tarmac are best avoided, either by navigating around or by lifting the wheel (slight bunny hop) to get over. The noise you hear is from the stress that's imposed on the wheel. – Carel Aug 12 '18 at 18:55
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    Well, yes, that is usually what I do, but as a human being I'm not 100% successful at it. – Jeremy Friesner Aug 12 '18 at 19:28
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    It may be spoke noise -- two spokes rubbing together when they stretch slightly. – Daniel R Hicks Aug 13 '18 at 2:51
  • Did your rear wheel make similar noises when you first rode on it? Mass-produced wheels are often very poorly stress-relieved and can make noises when they initially get stressed. Rear wheels get stressed a lot more than front wheels, so will rapidly stop making noises. Front wheels don't get stressed much, so might still make noises when hitting bumps for some time. – Andrew Henle Aug 13 '18 at 15:46
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    @JeremyFriesner I was thinking you might have bought the bike new, maybe as old stock at a bike shop. If it's used, the wheels not being stress-relieved isn't a likely cause, but loose/undertensionsed spokes might be. Also check your rim for cracks around the spoke holes. A cracked rim won't be noticeable at first, but can make all kinds of noises - and might fail rapidly, especially with disk brakes, which put a lot of stress on the spokes compared to rim brakes. – Andrew Henle Aug 13 '18 at 16:00
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I have a GT Grade Carbon which is designed and produced by the same corporation as your Cannondale. I have the described effect on high speed braking only which is quite common problem and it's easy to find information about it over the internet. Moreover, this effect was one of the reasons manufacturers switched to through-axles on road bikes too, and I believe it makes sense because this vibration makes quick-release loose with time. Make sure to check it more often while you have this effect unresolved.

I wouldn't say that I'm confident on why it happens to you during the normal operation, but some basic sense suggests that it could be something loose, online forums suggest that it could be the headset and I believe it can make sense because that's the only thing keeping your fork steady. I would suggest to you to run through the checks in this video, it's not as complicated as you may think:

Please let us know if tightening the headset helps!

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    I'd be mentioning "torque wrench" and "don't exceed the stated values" in the answer. – Criggie Aug 13 '18 at 9:30
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    Tightening the headset (as shown in your video) appears to have done the trick! Thanks :) – Jeremy Friesner Aug 14 '18 at 2:23
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I would guess these are the spokes. When hitting a bump, you wheel gets compressed. The harder you hit it the more.

When you wheel is getting compressed some (Upper and lower) spokes obviously loose their tension. The wheel then will pop back in it's original shape due the rest of the spokes which are streched. This will bring back the tension to the compressed spokes which usually is noticeable with the "twang" noise.

It may be a hint that you need to tighten your spokes. The looser your spokes are, the more compressed the wheel can get, which again can loosen your spokes even more. This can create a downwards spiral until the spokes start breaking. Simply check your spokes an tighten them if necessary.

Look I drew a nice picture :)

enter image description here

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    It may be a hint that you need to tighten your spokes. Or check for individual spokes that are undertensioned or even loose. – Andrew Henle Aug 13 '18 at 15:48
  • @AndrewHenle Anyway, if it's the spokes, something needs to be done about it. Preferably thorough re-tensioning and truing. Because the danger of breaking spokes due to temporary unloading is very real. And just adjusting some spokes just won't cut it. – cmaster Aug 13 '18 at 20:14
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Pretty much any bike’s gonna ‘ring’ a bit if you hit a sharp bump hard. It should not be making that noise though.

I’d just go over the whole bike looking for anything loose. Don’t forget cables, housings, spokes etc, You can try dropping the bike onto its wheels from six inches or so to see if you can replicate and locate the general area the noise is coming from.

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