steel_on_wheels

So I was going down a short little hill today. And I felt my bike shaking...like outta control shaking...Since the ground was paved pretty nicely, I'm starting to suspect the wheels. BUT, being a newbie, I have no idea if what I just said is right! My bike is steel, pretty new, and the wheels have never been trued since I got them. My bike only has 33 miles on it. Can anybody let me know what I should do??? Or, is it just that all bikes do that??? thanks!

Namenda

Nope, not all bikes do that. If your wheels are true, and the QR's are properly set, the next place I would check is the headset.

mriley

There may be nothing wrong with the bike. Shimmy can happen under varied circumstances, but expecially down hill. Read this article:
https://www.sheldonbrown.com/brandt/shimmy.html

mriley

steel_on_wheels

What are QRs and what should I be looking for on the headset? Also, is there a way I can know that my wheels are true just by checking it out, or do I have to go to the lbs to find out?

EDIT: mriley, thanks for that link. It helped me understand that there's prolly nothing wrong, whew! And I now know how to dampen the shimmey!

the beef

Wheels "in true" refers to the state of spinning straight. An easy way to check is to give your wheel a spin and see if part of the rim catches on to the brake or wobbles closer to the pad. If it does, it's out of true. If the distance between the brake pad and the rim is the same all around as it spins, then it's in true.

edit: oh yeah, "QR" refers to quick release. If your quick release skewers aren't tight enough it can cause problems.

azwhelan

Your headset is probably loose and it's really easy to fix. Lift your front wheel off the ground and grab the fork and see if there is any play. If there is that is your problem. Look for information on adjusting your headset. I'm sure what ever you find will be less confusing than me trying to explain how to do it. All you need generally is hex wrenches and 10 minutes of your time.

DannoXYZ 

Hmm... wobbles at 20mph would be something very, very loose to cause that low of a vibrational frequency... Yeah, I guess headset too, or very, very loose wheel-bearings. Certainly not due to flex in the wheels, fork or frame...

TYB069

Just out of curiosity, what kind of bike do you have? Brand wise? Was it new when you bought it or used?

rufvelo

Once you check for true wheels by spinning them and also headset for smooth movement, it could simply be bike geometry - too tall a bike with a very short wheelbase and steep fork will shimmy.

johnny99

I disagree. Shimmys are 50mph may be unavoidable with some bikes, but there must be something loose or broken or poorly aligned to shimmy at just 20mph.

steel_on_wheels

I have a 2005 mercier corvus. It was new when I bought it. Hmmm, headset being loose...I just had a tuneup the day before from a reputable lbs. should they have checked it? I'll check though.