Spinning rear wheel causes entire bike to vibrate/pulse...wheel balancing?

Triathlon Forum
1

Ok…so here’s the story…

I was adjusting the rear derailleur of one of my bikes. Don’t have a stand, so I just had the bike flipped upside in my kitchen. I was fairly satisfied so I’m just going through the gears. I get the bike in to the big ring/small cog combo…and just crank it with my had as fast as I can. When I let go, and the wheel is freewheeling, the entire bike pulses or vibrates. I’m like, “WTF?”

I get the wheel in the truing stand. Doesn’t seem out of round or out of true much at all. “WTF?”

So now I have to know if my other bikes do this. I get my other two bikes and do the same thing. I encounter the same phenomenon. I check to make sure those wheels are true and round as well. They are.

What causes is that? Is this normal? Or does something have to be done about my wheels/tires?

I noticed the WORST were my two factory built tubulars (Reynolds MV32T UL, Zipp 404, and Zipp 900 disc). The factory clinchers I have (DT Swiss Mon Chasseral) were similar to the two handbuilt clinchers (Velocity A23 and Stan’s ZTR Alpha 340).

The only thing I can think of is wheel balancing. And it makes sense to me that a tubular with glue is just not going to be super well balanced. The Reynolds in particular was RIDICULOUS!

However…I have never noticed discomfort or pulsing when riding.

Anyone have any insight or thoughts?

2

Normal.

3

Normal.

Is it the wheel balance that causes that pulsing? If so…why does it matter for cars but not for bikes? Just curious! I’m glad I don’t have to buy or fix anything though! Thanks!

4

normal - applying force “tangential” and not uniform and causing the “pulsing”
.

5

Third- normal.

Even the tiniest asymmetries present in all wheels, visible or not, will cause that pulsing. You obviously won’t see it pulse like that in the truing stand- you can’t spin it fast enough and the wheel is fixed at the axle, whereas when it’s on the bike it is able to resonate.

6

Normal, but can cause speed wobbles during fast descents on some bikes (depending on the severity and the bike’s resonant frequency). You can balance it out with some epoxy putty if need be.