Shrevvy 

I purchased a used bike at the local bike store for my son this weekend. It is his first road bike. He test road the bike at the store, but I did not. I did ride it after we got home. The bike is obviously too small for me. So, I don't if that would contribute to what I experienced.

From the start even at low speeds, the front wheel does not feel entirely stable. It feels like wheel will pull from its rotation (like a gyroscope?), but it does not pull to just one side. It may pull left then right. I have trouble riding no hands on the bike as well. Again, it doesn't pull to just one side but may start pulling one way and then over correct to the other way. The pull is light, but it is there. It does not seem to go away as speed increases. My son doesn't feel anything, but I don't know that he would given that it is his first road bike and he is more focused on learning the shifters and riding on drop bars. The bike is an older (probably early 1980s) steel bike. I plan to take the bike back to the shop to have them look it over, but wanted to see if anyone had any ideas on what could be causing the problem.

55murray

Some very loose spokes is my vote.

SquidPuppet

Are you familiar with bike geometry? It sounds like the bike may have a lot of "Trail". Too much trail will induce a symptom called "Wheel Flop." To me it sounds like you are describing wheel flop because it is not specific to one side and it occurs (exaggerated) at low speed.

You can read about it here https://rolobikes.com/pdf/rolo-wheel-flop.pdf

Shrevvy 

I read the wheel flop link, but most of that goes over my head. Is too much trail fixable if that is the cause?

corrado33

I think you shouldn't worry about it. If the bike is far too small for you much of your weight will be more forward than normal, making the steering act weird.

I rode a small recumbent bike the other day that acted the same way. I eventually figured out it was because the front wheel was directly UNDER my legs (legs horizontal) meaning much of my weight was in front of the wheel, which made slow speed steering... creepy. Extremely floppy.

Trail isn't fixable... easily. (You'd have to change the fork.)

If the kid is fine on it, let him have fun. Besides, you don't go slow on a road bike.

cny-bikeman

The headset could be binding from poor adjustment or even having bearing cages mounted backward. But certainly riding one much too small may be a factor as well. As you are already planning to have a shop look at it I think they are better equipped to determine if there is a problem in-person.

Shrevvy 

I was thinking it could be my weight and size vs his causing the problem. I just want to make sure I have a safe bike for him. I've ridden smaller bikes before (maybe not this small) that didn't feel much different other than size. Also, it doesn't go away with increased speed. When I searched on the issue, I found a lot of links to "death wobble", but that all seemed to occur once a given speed was hit (usually 25-30 mph). This occurs basically from a dead stop all the way up to a brisk short decent (all that I have tried).

As kid, I had a whirl wheel toy where you moved a spinning wheel up and over a wire frame. Once the wheel got spinning, if you tried to move left or right there was some resistance. That is what the front wheel feel likes when I ride it.

Chief

bent fork?

corrado33

Actually, I fix "floppyness" by tightening the headset a tiny bit. A couple of my bikes were somewhat hard to ride with no hands (frames were perfectly straight) and a tiny twist of the headset cone fixed it right up.

I think mounting the bearing cages backward would cause the opposite problem (headset too hard to turn when properly adjusted.)

SquidPuppet

Wheel flop can be reduced by replacing the fork with one that has more offset (rake), moving the axle forward, which will reduce the trail number.

Usually though, bikes with a high trail number will become more stable as speeds increase. Typically a bike with high trail geometry is easy to ride hands free once you get going at a really good clip. Oddly, it's the same combination of angles that cause the bike to be very stable at high speed, that cause it to feel like it wants to tip over into turns at low speed.

Do have the shop take a look at it though, because there could be other things going on.

FBinNY 

I suspect, but fall short of claiming, that it may simply be that you're not used to that bikes handling, and your own steering inputs are the issue.

"Balancing" a bike is a matter of alternately falling to either side, ancdcatching yourself by steering into the fall to bring the bike back under you. This is similar to standing on one foot, or balancing something like a broom in your hand. When things are dialed in, you're sensitive to the what's happening, and correct with very small inputs done early.

However, if the handling properties, or even the handlebar width are different, you either or under correct because your "autopilot" doesn't know the precise corrections needed.

So ask yourself, how different is this bike from your own bike? Wider bars, more race oriented geometry, are you sitting farther forward or back, etc.?

If the bike is different from your own, either ride it a bit more and see if you start dialing it in, or ask a friend who rides a bike more similar to it to do a test for you.

tyrion

Long shot, but: are the wheels/tires the same size? A smaller front tire (700c front, 27 inch back) could make the handling weird.

cny-bikeman

In my experience I have not found that front instability is often caused by a loose headset. The dynamics of the fork and wheel are enough to keep the bike stable unless something interferes. As the OP had instability in both directions that eliminates frame or wheel problems as well. The reason I suggested headset tightness or binding is that if the headset hit a binding spot that was slightly off center in either direction it would tend to pull the bike in that direction. Incorrect cages can cause unpredictable behavior as well.

Shrevvy 

Thanks for all the help. I just got home and looked the bike over again. The wheel/tires are the same size. We looked at the forks when buying it and I looked again tonight. They don't look bent. Since the headset was mentioned, I picked the bike up by the top tube. When I do that, the front wheel does not flop to either side. It stays fixed in a straight position. So, that means the headset it too tight or is binding? That may be the source of the problem?

FBinNY 

Yes a tight headset can make a bike unrideable. As you make the tiny steering corrections to stay upright, you're fighting the sticktion and tend to over compensate, then need to come back, and end up riding like a drunk.

So, start there, and give it another shot.