Weird harmonic rumble

Drif10

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Two days ago, I picked up a weird rumble on my 14ES.

It's right at 99 kmh/61 mph. If I'm at steady cruise, you really feel it through your butt, not through the bars. Go faster or slower, it's sympathetic to that speed.

At first I thought rear wheel balance, but if I drop it to fifth, resume cruise, it's gone. That means everything that's turning wheel speed is eliminated: wheel, final drive, drive shaft, and output shaft of the transmission.

I figured out what is f creating the condition, but be damned if I can figure out why. Earlier in the afternoon I had put the suspension setting on hard, from standard.

Preload stayed on two up with luggage, my normal setting. I'm 240 plus gear, so that along with a Lusk rear +20mm raising link works for me.

Every time I'm rolling with the hard setting, the harmonic rumble happens at speed. Like going over 6 rumble strips with the rear, same length of time no rumble, then rumble again.

I'm at a loss to understand why it's happening. It's not a critical thing, just confusing. I wonder if it's a precursor warning of excess wear on a part, but that's a weak guess at best.

Anyone got any ideas?
 

holligl

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What tires and mileage on them? I've noticed more noise in curves on my aging Mitas 07s. Granted at the same speed in different gears, you would expect simlar results, but it it could be harmonic with the powertrain rpms.

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Drif10

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3k kms on a set of trailmax missions, which replaced a 15k set of the same. Not the same worn 50/50 vibration you're talking about.

The rumble does occur both straight up and while moderately leaned.
 

Squibb

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Probably just the tyres starting to cup. Mine have been 'singing' for a while now, but seem to grip fine.

Fresh rubber should cure it, but not really necessary if they grip OK.
 

BaldKnob

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993CA784-D3B6-4B42-A0C5-8C1716175469.jpeg

I had a similar rumble with these tires. Zoom in and see those stepped side knobs… as they wear down, I believe are the primary cause of this vibration.
 

Drif10

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On my second set of these. Yes, they do vibrate, especially when you put some lean in. Get louder too. This set has 2 weeks and about 4k kms on them, and they're behaving the same as my first set.

All of which to say that this does not appear to be related to these symptoms. Straight up or around a corner, if the ES is set to hard, that rumble phasing in and out. Set to standard or soft, doesn't occur.

Checked again yesterday, still does it.
 

~TABASCO~

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Probably tires. Check pressure & rebalance them. See if this makes a difference before moving on.

(general) most people think you get your tires balanced once when they are new and that’s it. If you have any type of 50/50 tire and you want the best performance this is NOT true. It’s totally OK to pull them off after a few thousand and re balance them. Smoother / better / can make the tire last longer. The knobs wear, the weight balance changes, the ‘balancing’ will need to change. It’s NOT a “1 & done”. :)
 

Drif10

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Rebalanced them myself, but they were still good. And it still happens.

I'm not prone to running in the hard setting, it was a very warm day on rough roads, so the suspension fluid was really warm. The switch to hard did a i wanted, and cut down the pogoing i was getting. Forgetting that setting change when i went to cruise home is when i found the rumble.
 

Don in Lodi

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So the rumble stopped when you took if off the hard setting?
 

Drif10

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Yes. I can select soft or standard and it goes away. Been meaning to try standard at +3 to see if it happens on that too, haven't remembered when I've been riding this week to do it.
 
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