Pulsing when coasting fast downhill

[fritzschantz]

I usually ride on flat trails, so I never really get going very fast. This abnormally awesome weekend here in MD, I went out for a road cruise, and got the Super 32 up to a good clip going down a hill. I noticed that the back wheel seemed to be pulsing a little. I suspect that the brass valve stem and extra rubber where it attaches to the tube might be throwing the wheel a little off balance? I'm going to try attaching a lead fishing sinker to a spoke on the opposite side of the wheel from the stem and see if that fixes it. As far as I can tell the rim is true and the spokes all produce the same tone when struck with a screw driver.

 

[ifitsfreeitsforme]

Is the coaster brake catching a little maybe?

 

[mikeeebikey]

Is the coaster brake catching a little maybe?

I Also have the same question!

 

[fritzschantz]

Is the coaster brake catching a little maybe?

I moved the pedals back and forth a little when it was happening - no change.

 

[fritzschantz]

Could also have been that the valve stems on front and back happened to be lined up in rotation. If one was opposite the other, it would cancel out the effect...

 

[mikeeebikey]

only time I've ever seen tires affected by N Out of balance condition, they were filled with fix a flat.

 

[fritzschantz]

I weighted the spoke, no change. With the bike upside down, both wheels pulse when spinning fast.

 

[user 135]

Deflate flat the tube.
Slowly inflate 10psi at a time. Then run your thumbs to make sure the bead is fully seated.
Repeat till full.

 

[heartlandcruisers]

Deflate flat the tube.
Slowly inflate 10psi at a time. Then run your thumbs to make sure the bead is fully seated.
Repeat till full.

from experience of a similar problem id say cman hit it on the head.
the bead may be out of whack.
that does happen..
if it was just the coaster id suggest greasing the inners on the wheel.
also possibly adjust the bearings if you had serviced them lately they may be a bit off.
that's the most obvious reason i can think of judging by you're symptoms
or maybe they just need to be repacked?
try those first and see what happens
Sean

 

[ozzmonaut]

I'd bet it's the bead. I had one giving me grief the other day. I thought that a slight wobble in the wheel was the culprit. But I trued it with no change. That's when I saw the sidewall of the wheel jumping out a bit. I let a few pounds out and pushed it back in and reinflated. All is well now.