alanfleisig

So, I have a new Trek 5.2 SL, stock Ultegra triple with Kysyrium Elites (Standard factory, does that make the hubs Mavics or Shimano?).

I love it, etc., etc. Normally smooth as silk, but...

I notice when in a sustained hard accceleration -- I'm estimating in the 300-350 watt range -- I can feel a vibration, almost electric-like (yes, kind of like that kind of C-battery vibration, and don't make me answer how I'd know), in the drivetrain.

I ride a lot in the middle ring of the triple, so this is happening typically when I'm riding like the 42-14 or 42-16 combination. (I'll shift to the large ring before riding any smaller cog.)

Any notions what might be causing this? Is it cross-threading? Something else?

Turbonium

idon't know about your vibrations. but you should get a compact double.

Cypress

A 350 watt vibrator? You're freaking hardcore.


(make sure your chain isn't rubbing on the FD)

Phantoj

Is that called "feeling the chain"?

I have an older bike that does what you describe. I figure it's worn cassette or chainrings. Replaced the chain and BB; still does it.

alanfleisig

Wheels and hubs have over 5000 miles on them, though I did just replace the bearings. Cassette and chainring are brand new (i.e., less than 1000 miles), so I don't think that's it.

Paul L.

Whatever you do don't turn it up to 400 watts until you have broken the engine in.

Tom Stormcrowe

Harmonic vibration in the frame?

alanfleisig

That would be my biggest fear. Is that possible?

samsation7

From my limited knowledge, I think that it's possible. It is commonly produced by the unbalance in rotating machinery. If this unbalance is consistent and sustained over time, you will achieve harmonic vibration. It may be that your rims, crankset or handlebar set up(e.g. not centered) is unbalanced in some way.

samsation7

Sorry, I didn't read all the threads. I don't think that the vibrations emanate from "inside" the frame. I think it's possible that some rotating part on your bike(external to the frame) is unbalanced and this is causing the vibrations. I worked in a biology lab at my university. We use many hi tech machines that employ centrifugal force to concentrate cell extracts. Usually, even a slight imbalance--placing odds numbers of test tubes in the slots or using even number of test tubes but each with different volumes--can produce harmonic vibrations.

Psimet2001 

Yes.
Likely?
No.

My first reaction to the title "Virbration at 300 watts" was to recommend checking the flux capacitor.

The combinations you mention make me think ac ouple fo things could be the cause. Those are combinations you probably ride most frequently - driven home by your statement that "you dial it up" in those combos - meaning you feel comfortable in them. That will produce more wear on those cogs than the rest of the casette.

the source of the vibration is most likely chain mesh. Chain mesh is the natural vibration produced by the chain meshing with the cassette at higher revs. Worn cassettes, new chains, old chains, heavy load conditions, derailler misadjustment, worn derail cable housings, etc. all factor into helping to set up the conditions that will intensify chain mesh.

If your casette is new, chain is new, chainring is new, then check the RD and put new cables on it. How is your shifter looking? This can cause the RD to be slightly off in a few gears used the most and correctly aligned in some of the ones not used as often.

Also consider the lube you are using on the chain. Did you change to a different brand or model of chain? etc...

FrankBattle 

I've heard of these power generators. Where can I get one?

hiromian

Captin, sheez brekin up. She just cant handle the power!!! said Scotty to Kirk.

slvoid

Why don't you try a different set of wheels?
Better yet, hook it up to a trainer at the LBS and have the guy see what exactly is doing that.
If it's doing that at a certain "wattage" it could mean a few things.

It might mean that when you put that much power into it, the chain slacks a little more on the bottom and it might be vibrating.
It might mean that you usually hit a certain speed at that power output and there's some imbalance in your wheels or drive train.
Could be the angle of the chain.

Eatadonut

My completely random guess is that your hubs need attention. sounds like they're skidding down the races instead of rolling. Do you have another set of wheels you could try?

Nachoman

No need for the gratuitous reference. We're all with you.

pelotonracer

Don't worry, the vibrations will be gone when you dial it up to 400 watts.

Unless you're racing.

Psimet2001 

Kind of like when they broke the sound barrier and the buffeting stopped, but at "like 19mph".

alanfleisig

Thanks everyone for your input.

The chain, cassette and crankset were all brand spanking new, and I replaced the bearings on the rear hub.

Did about 100 miles this weekend (January in New York!) and didn't experience the vibration. I'm guessing it may have been "chain mesh," which has now settled down as I put some more miles into the drivetrain.

urbanknight

Sounds like you're flexing the frame so the bottom bracket goes side to side, which causes the chainring to be slightly off and the chain to rub a little differently on the gears.

jamiewilson3

It may be the pavement that you ride on. In my area, there are roads that are a not smooth asphalt. When I hit specific ones at certain speeds, they will vibrate the frame at a resonant frequency. This isnt a problem, as every object on earth resonates somewhat. The annoying thing about it is that it vibrates the cables, which pass throught the BB on the way to the FD. The cable vibrates through the hole and makes a rattle. Very annoying, but I just have to put up with it when it happens.

Bockman

That could be the threshold where the Flux Capacitor engages-- sending you back in time to 1955. Plase be careful.

DocRay

Yes, don't ride at anywhere above 100,000 rpm.