Front wheel suspension resonance

[dannydibbert]

Interestingly, after you all helped me discover that the strange grinding noise on my ebike was from the reflectors attached to my front spokes (removed and resonance noise eliminated), I now have a "new" annoying resonance noise (not brake clearance nor bearing after close inspection) coming from the front wheel which seem to be driven from the front suspension and/or spokes. My 4 inch fat tire 750 watt rear Bafang hub is carrying my 260 lb self.

When I lock out the front suspension the noise is less but still there. We all know that front spokes (OEM cheapo) touch each other and I think there may be some kind of dampening needed. Also, I assume there is some find of fluid in the front suspension which may require maintenance.

Looking for ideas. Thanks.

 

[AHicks]

I'm 300 here, and would suggest you look into your spoke tension right away - prior to spoke breakage. Guys our size are asking nearly 100% from our spokes (especially the back ones), and they need to be set up near perfectly to do that. Done correctly there will never be an issue. Let it slide, and I can pretty much guarantee noisey/broken spoke issues.

If you're handy/willing to learn, get a spoke tension gauge and some tools to allow you to adjust your own. If that's beyond you, make arrangements to have a shop take care of it for you.

 

[Chalo]

All normal bicycle wheels these days have spokes that touch each other (unless they're radially laced). They don't make any noise if the spokes are adequately tight. I believe AHicks has correctly diagnosed your problem.

Most cheap e-bikes use spokes that are too thick, both to pander to uninformed buyers and to allow the use of cheaper, lower quality spokes without suffering instant breakage. But in fact, the more load you put on a given rim, the thinner the spokes need to be, to allow the rim to flex more deeply without making the spokes slacken. Wheels with too-thick spokes paradoxically are only suitable for lower riding loads than wheels with normal 14ga or thinner spokes.

The best you can do with whatever spokes you have is to take your wheels to a pro and have them tightened up to at least 100 kgf on the tighter side of each wheel. That may or may not do the trick in the long run, but it should help substantially. It is possible to overtighten spokes and damage normal bicycle rims, which may in turn make the wheel impossible to keep true. So go to someone who has a spoke tensiometer and plenty of wheel building experience. Even if you want to learn to maintain your own wheels, which I recommend, you should start from the point of having wheels that are in proper condition first.

 

[MadRhino]

It is still possible that it comes from suspension internals. Tuning the wheel is good anyway, and should be done periodically. Here I would swap the wheel first. Takes a minute, and if it is the wheel I would like it off the bike for tuning.

 

[Chalo]

It is still possible that it comes from suspension internals.

I've not encountered that. Would it be caused by dry bushings, valve flutter, or something else?

 

[MadRhino]

It is still possible that it comes from suspension internals.

I've not encountered that. Would it be caused by dry bushings, valve flutter, or something else?

If it is from the suspension, resonance would require that something is loose or broken apart, and it would have to be above the oil level. There are so many forks today, that it is very difficult to point the possible cause before opening, especially for a fork that we know nothing about, yet. One occurrence that I have seen (heard), was the plastic tube that isolate the spring from the stanchion. The fork was making noise because the top of the tube was worn out and the spring was touching the stanchion, making some vibration resonance. I fixed it by turning the plastic separator upside down, in order to move this contact below the oil level.