Singlespeed & Fixed Gear - "Throbbing" in drive train

Hi Folks

I just today got my first single speed. While bearing down (pedaling hard) I'm sensing a "throbbing" somewhere in the drive train. It's a bit hard to describe, but think of it as a low frequency vibration that is felt on the down stroke while pedaling. It also could be described as the feeling one would get while riding over a light, tight "washboard" pattern in pavement, but it happens while I'm riding on smooth, newly paved asphalt. I'm wondering if it might be the chain vibrating.

This "throbbing", or vibration is very noticeable, mainly because everything else about riding the bike is so smooth. I'm putting a bit of torque on the drive train, as I'm geared with a 46 chainring and a 16 cog. Again, it's only when I'm pedaling hard and at a higher speed.

Any help or suggestions would be appreciated. Thanks..

Your chain is probably too tight and the tight spot in the chainring just makes it worse. there's nothing wrong with a little chain slack

Your chain is probably too tight and the tight spot in the chainring

I don't disagree, and I'll loosen the chain a bit. It's where it was "adjusted" when the bike arrived. I'm wondering what you mean by "tight spot in the chainring" (?)

your chain ring isn't a perfect circle, so the chain tension will vary as you pedal.

Sounds hot.

I don't disagree, and I'll loosen the chain a bit. It's where it was "adjusted" when the bike arrived. I'm wondering what you mean by "tight spot in the chainring" (?)

What brand / model bike is it? If it's a BD bike, then it's definitely not "adjusted" from the factory. Both of mine arrived with the chain set waaaay too tight.

What brand / model bike is it?

IRO Phoenix, ordered from IRO factory. Based on what I've read here and other places, I expected something a little different than what I got, as far as how the bike was "built". Not really complaining. I'm an amateur, but I think fairly good, mechanic, and I'm a do-it-your-self-er.

Btw, I went and loosened the chain, and also systematically tightened the bolts on the chainring. Everything (pedals, chainstay bolts, etc.) seems to be tight. Took it for a ride and the "throbbing" is there, tho not as intense and seemingly at a somewhat higher frequency...really have to dig now to get it to happen. But sometimes I like to really dig...

Thanks for all the replies.

Perhaps this might be a cadence issue.

Perhaps this might be a cadence issue.

Nah. Shouldn't happen at any cadence. Never happened on my *much cheaper* 21 sp. hybrid during very similar type of riding, or at any time really.

im telling you, it's chain tension. I had this same thing going when I used to run my chain way too tight

I bet it's just the components of your new drivetrain getting to know each other. after replacing the chain on my geared bikes I can feel that sort of thing too. It'll wear itself smooth in a few hundred miles.

the components of your new drivetrain getting to know each other

This makes the most sense to me. I even thought of something similar to this, but was not able to articulate it in such a way. Thank you.

hey dude ur chain is too lose u gotta move dat wheel back and then have zen.

Chainwheel alignment.

Sheldon says:
http://www.sheldonbrown.com/fixed.html#tension

I've had this problem, but luckily it hasn't progressed past the workstand. It's actually a pretty simple procedure to line that sucka' up.

Chainwheel alignment.

Sheldon says:
http://www.sheldonbrown.com/fixed.html#tension

I've had this problem, but luckily it hasn't progressed past the workstand. It's actually a pretty simple procedure to line that sucka' up.

The link you provided addressed the issue for a fixed setup. I'm on a single speed.

There have been suggestions in this thread that my chain is too tight, or too loose. I'm guessing that a fixed configuration requires a tighter chain than a SS. After a suggestion, I loosened the chain a bit and I think I've now got the chain tension set correctly.

However, I feel that the chainring tightening procedure described could benefit me. I will try it and see. If it works and solves the issue, it makes me wonder why this wasn't addressed when the bike was "built".

you're right on. I had the same issue on my SS and did the chainring bolt tighten game, then played with the chain tension (looser than FG) and got it perfect. Now she's so quiet even ninjas can't hear me comin'

Well...

I did the chainring bolt tightening thing, and there's no change. I could have not done it correctly, but I think I generally got the idea of how to do it. I didn't rush through. I did what seemed to be right.

I guess now I'm waiting for the drive train components to "break in" and mesh more smoothly. I only have about 30 miles on the bike, so I'll let you all know when I have ~200 miles on her.

Thanks for all the replies.

OTP

This may be completely a completely non needed suggestion, but could you be running an even/even number of teeth on your chainring and freewheel. My drive train had what seemed like an undulation, a section of the chain that would slacken up, in it and the guy at my LBS asked what my tooth count was on my bike. "46/16" was my answer and he said that it helps to run an even/odd or odd/even to help the chain ride more smoothly. I'm running a 46/15 now and there's no sectional slacking in my chain that I was seeing/feeling with the even/even set up. That may be the answer your looking for unless you are already running an even/odd set up.

This may be completely a completely non needed suggestion, but could you be running an even/even number of teeth on your chainring and freewheel. My drive train had what seemed like an undulation, a section of the chain that would slacken up, in it and the guy at my LBS asked what my tooth count was on my bike. "46/16" was my answer and he said that it helps to run an even/odd or odd/even to help the chain ride more smoothly. I'm running a 46/15 now and there's no sectional slacking in my chain that I was seeing/feeling with the even/even set up. That may be the answer your looking for unless you are already running an even/odd set up.

I'm running 46/16. I still don't know what the problem is - waiting for "break in" to determine if that's all it is. I don't necessarily disagree with you about the even/odd chainring/cog, but Sheldon Brown does:

"One can make a case that it is better to use even numbers of teeth for straight chain drives, and keep the chain always set the same way on them. "

See: http://sheldonbrown.com/chain-life.html