Ultegra 6800 cranks or Praxis adapter buzzing sound....

[loimpact]

So this one's weird & I figure I'll find it when I pull the cranks but wonderingif anybody knows what this might be right off..........

EVO with a Praxis PF30 adapter & Ultegra 6800 cranks

When out of the saddle, the downstroke on the drive side seems to create a "zizzing" noise. (best way to describe it). It almost sounds like 2 pieces of nylon fabric being rubbed together.

Sit down and it doesn't matter how hard I push, no noise. I definitely have to rock the bike to make it happen. Non-DS downstroke makes no noise. I'd guess crank to Praxis rubber cover, or rubber cover to bearing cover or bearings themselves, or ??

TIA if anybody knows this one.

[stien]

The fact that you have to stand makes me think it's something else. How close is the tire clearance? Brake pad clearance? Carbon wheels zing if pads rub.

[Tandem Rider]

Internal motor???

:eek:;):D

[adamhell]

could it be the crank arm plucking the cable end? this has happened to me so many times...

[tv_vt]

front or rear wheel flexing and rubbing against brake pad or frame possibly. are your wheels in straight and skewers tightened down?

since it's driveside only, could also be crank/rings rubbing against FD, but sound would be different.

how's your DS pedal spin? could it be pedal bearings wearing out, or shoe rubbing against crank?

[superbowlpats]

Internal motor???

:eek:;):D

That's brilliant!!:hello:

[loimpact]

Good answers here, though I'm still not sure. Had crit practice tonight so got to *hear* it but didn't get to troubleshoot.

Gonna swap my wide Altamonts with some skinny Aksiums to eliminate wheel/brake related noises.

Oh how many times I wish I had an electric motor! ;)

If not what stated here, gonna pull cranks & inspect cranks to BB, bearings, general lubing of such, etc.

I definitely have to rock the bike sideways pretty good to get the sound going so I know wheels sounds like a winner but not looking like it.

[rustychisel]

Not the 'zizzing' of a worn chain????

[loimpact]

Wow....can't believe I didn't think of this earlier but here goes I'm gonna give hints & see if somebody hits it.........

I swapped my wide Altamonts with Skinny Aksiums......noise gone! :eek:

Attention turned from cranks/BB now.

Loosen rear brake cable & open up calipers a bit more.

Swap back to Altamonts.......still there!

Back to Aksiums.....still gone!

What's going on here?

Back to Altamonts.......sound is the same whether caliper closed or open so now I'm reeeeeeally confused......then all of a sudden it hits me........

:crap:

[velotrack]

Wow....can't believe I didn't think of this earlier but here goes I'm gonna give hints & see if somebody hits it.........

I swapped my wide Altamonts with Skinny Aksiums......noise gone! :eek:

Attention turned from cranks/BB now.

Loosen rear brake cable & open up calipers a bit more.

Swap back to Altamonts.......still there!

Back to Aksiums.....still gone!

What's going on here?

Back to Altamonts.......sound is the same whether caliper closed or open so now I'm reeeeeeally confused......then all of a sudden it hits me........

:crap:

Wheel is flexy? Tire rubbing on chainstay?

[loimpact]

Wheel is flexy? Tire rubbing on chainstay?

Ding ding ding ding!!!

Right on the money!!

I put a piece of masking tape on the DS chainstay where I saw the mark and road around seated without rocking the bike back & forth.

Came back & tape was still clean.

Went back out & did some hard sprints rocking the bike back & forth. (and thus forcing the sounds again)

Masking tape was marked & diagnosis confirmed!!

And of course, this came right after going from 23mm Michelin Pro 4's on those Boyds to Conti Hardshell 25mm's. Whadda ya know.

Funny thing is that I have 2 EVO's. The 60cm EVO doesn't do it, but the 58cm does. Obviously a little more roomy in the back on the 60cm.

Things that make you go hmmmmmm! :rolleyes::cool::mad:

[foo_fighter]

How much clearance do you have?

[velotrack]

Ding ding ding ding!!!

Right on the money!!

I put a piece of masking tape on the DS chainstay where I saw the mark and road around seated without rocking the bike back & forth.

Came back & tape was still clean.

Went back out & did some hard sprints rocking the bike back & forth. (and thus forcing the sounds again)

Masking tape was marked & diagnosis confirmed!!

And of course, this came right after going from 23mm Michelin Pro 4's on those Boyds to Conti Hardshell 25mm's. Whadda ya know.

Funny thing is that I have 2 EVO's. The 60cm EVO doesn't do it, but the 58cm does. Obviously a little more roomy in the back on the 60cm.

Things that make you go hmmmmmm! :rolleyes::cool::mad:

25's don't clear on the EVO?
Actually, I take that back. Probably because of the wider rim.

[loimpact]

25's don't clear on the EVO?
Actually, I take that back. Probably because of the wider rim.

Correct. My Aksiums are 2014 (pre wide version of 2016) so they're only about 19mm external width.

My Altamonts are 23mm external and probably a smidge wider than that.

Add to that, the rear Boyd is slightly wider than the front while EVOs are a smidge narrower in the rear than than the front + hub/hoop/dropouts mfging tolerances = triple trouble.:no:

With 25mm Hardshells mounted I get these measurements:

Front tire width = 1.060" (26.92mm)

Rear tire width = 1.075" (27.30mm)

Now, I did some tire swapping & here's what I've got on the 58cm EVO:

Front Hutchinson Equinox 25mm mounted to Aksium = .990" (25.14mm)

Rear Mich Pro4 23mm mounted to Altamont = .995" (25.27mm)

I'm going on a climb tomorrow so will be out of the saddle lots. We'll see what the results look like. :cool: