Why is my bike leaning over?
 

So I don't exactly know when this started, but the other day I sat up straight to ride no-hands for the first time in a while, and almost fell over. The bike wanted to lean to the left, hard. I tried again and managed to get upright, and I can go along, but I have to lean my body way to the right to balance the bike going the other way.

This is a 60cm crosscheck, which I've been commuting with all year. Near the beginning of the year, when I had some pinched nerve issues, I had to do a lot of hands-free riding so I could stretch, and I never had this problem. But that was with a whole different drivetrain and wheels. Since I rebuilt, I can't remember whether I've had occasion to ride hands-free, seems like I must have, because it's been at least a month of daily commuting and some longer rides.

I first noticed it with my rack & small bags on (although my typical load is quite small: a polo shirt, socks and underwear, and maybe lunch). This morning with the rack&bags off, I tried again, still leaning. I don't think it can be a weight distribution issue because if anything, bikes are heavier on the right side, what with all the drivetrain over there, and I don't have an asymmetric skeleton (I know all people are asymmetric to some extent, but I'm "normal" as far as I can tell)

I checked the wheels, they seem quite well centered in the fork and stays.

Before this happened, I never noticed the bike pulling to the left (even when I ride hands-free, even though balance is akimbo, the bike runs straight), now that I'm thinking about it, maybe I can feel a little more pressure in my right hand on the bar to keep the bike up, but it may well be my mind playing tricks on me.

Any ideas what can be causing this, and how to resolve it, or other tests I can try and report back?

UPDATE: Problem solved, overtightened headset with detent, thx to bent-not-broken (&all others), see my ONE THOUSANDTH POST below

How old are the wheels? If they are new give them some wear and it might fix it.

They are new, been riding them for I guess about a month. Can't remember if I've tried hands-free in that time.

Why would new wheels cause this problem, or what would wear so that it goes away?

Could it be that when I put tires on these wheels (same tires as I was using before*), my Mr Tuffy's slid way to the left, and that little bit of imbalanced spinning weight is causing a gyroscopic effect?

(Actually before I had Conti CountryRide 700x37 on the back, and Conti something 700x32 on the front; now I have the 37 CountryRides both front and back, so the front tire is different than before, since I put the new wheels on)

the problem has nothing to do with new or old tires
this is ridiculous

it is a problem of alignment

either
the one or both wheels are out of dish
or the fork
or frame is misaligned
or one or both wheels is not seated in properly

huh ???
Making up silly answers is more suited to the road forum.

Wilfred's suggestions are most likely.

Could be biomechanical in a few cases .... someone with back problems who leans to the left or right, but it's not apparent when holding the bars.... maybe ?

Well I certainly hope the frame/fork are OK, it's a sturdy steel CrossCheck, only about 9mo old, and I've never crashed it.

I will loosen the QR, jiggle and re-place the wheels, and tighten the QR, and report back.

also could be bent saddle rails

I think it is likely an alignment issue also because my bike was doing the exact same thing - leaning and pulling hard to the left. I noticed that sighting straight down at the front wheel, I was seeing the left side of the entire wheel. I looked at the way I was seated but that was not it. I finally turned the bike over and stretched a string from the front to back wheel. and found an offset of 3-4 mm. I also leveled the bike with shims under the bar, using a 16" (43mm) carpenters level and found the wheels were not plumb. After considerable pondering over many weeks, and with some hesitancy, I filed the front front dropout a bit, and then rode the bike for a while. Stability seemed improved some so I filed a bit more. This went on for several months, evaluating stability after each session of surgery.

The bike now can be ridden no hands but even better, holding a line in a corner is a pleasure as is diving into fast switchback turns. The improved stability feels good on fast descents.

I've since calculated that an error of 1/2 mm in placing a dropout produces an error at the rim of 3-4 mm. I hope this helps you track down the problem.

It's fairly common for mass-produced frames to be out of alignment. Try the "string test" for a quick check:

http://sheldonbrown.com/frame-spacing.html

I think it's the lube...

Is the headset free and properly adjusted? I have had several older bikes which pulled to one side due to binding in the headset.

Thx for the SB link, I will read it -- but this same frame/fork was behaving fine for months earlier this year, and has not suffered trauma.

Short answer, you have an alignment issue.

Generally it's a wheel tracking problem, but the causes can be complex, including poor wheel dish, wheels not on a common plane, wheels not vertical in frame, or some combination of the above. It could also be that your center of gravity isn't on the bikes central plane, so you have to lean to get the yourself over the wheel track.

Before you go crazy, test the bike in a parking lot. Most roads are crowned, and bike geometry is such that they turn uphill if riding across a slope, so there's a slight pull to the left on crowned roads. It's slight, and you probably aren't posting about that, but should rule it out before starting in on the complex alignment checks.

One of my most recent changes was to lower my stem, which did involve re-tightening the headset stem cap, maybe I cranked it down too far. Another thing I have noticed recently (but not thought of it much), when I walk my bike to/from my cube at work, I sense steering squirreliness, but I put that down to rubber tires on industrial carpet. Only noticed it recently however.

I bet this will be the winning suggestion. I will loosen the stem and put it back less tight, see if the carpet-squirm and the leaning goes away.

I sure hope it doesn't come down to filing for me! I don't think this is it, because as far as I can see with eyeball, the wheels are well centered and in the same plane as the frame

Oh this is almost certainly the problem. I just peeked at SB, and on his advice:
I have a definite detent in the headset, must be holding the front wheel slightly left of straight. When I lift the front wheel with the bike nearly upright, the detent will hold the wheel. If I lean the bike, the front wheel flops fairly easily, so it's subtle, doesn't manifest while steering, only when riding hands-free and letting the wheel go where it will.

I will cut back on the headset preload and hopefully it will go away for now, meanwhile I will start shopping for a new headset. Any recommendations would be welcome (but remember, I'm a real cheapskate, so I'm not going to drop $500 on a custom Chris King with unobtanium bearings hand-lubed with Llama spit.)

It sounded to me like an alignment problem too, but since it didn't behave like that new and there was no trauma (Are you sure you didn't do anything that could have shifted the fork blades?), I can't see this as the likely culprit. Since it now shows up with the new wheels, I am going to throw out that the new front wheel is dished to one side a bit and you are compensating for this by aligning the axle in the fork so the rim looks like it has proper alignment. Making sure the axle is seated in the DOs is the first thing you should do. Second, be aware that crowning of roads may cause similar behavior so you may want to look for a level parking lot to try a test.

Also see this article by Jobst Brandt: http://sheldonbrown.com/brandt/pull-side.html

I was going to suggest he still has winter air in his tires and needs to switch to summer air...

Next guess would be alignment, then lube.

DO NOT file the dropouts just because that worked for someone else. Besides, that's an illogical solution for you, considering that the bike previously rode no-hands.

You should first check dish, and certainly nothing wrong with checking headset adjustment, though I don't know what about it would cause deflection in only one direction.

If your eyes are good it is not that difficult to mostly determine where the problem lies with no tools at all. Either use a stand that allows you to rotate the bike to an inverted position or get a friend to help you. As you say the wheels are already centered in the fork and rear triangle, first sight along the wheels from front to back, turning the front wheel as needed to align it. First look across the top of both wheels to see if one is canted off vertical in relationship to the other. Then site along the sides of the front wheel toward the rear, observing to what extent you can see the back end of the rear wheel. Then do the same along both sides of the front wheel while looking toward the down and top tubes. Add the string test and you should be able to determine whether the problem is front or rear.

Being a Cross Check, make sure you have the rear wheel even in the dropouts. It is easy to have the wheel off center a little bit in horizontal dropouts. Even with dropout adjusters, if the adjusters are not quite even or if one is bent, then the wheel won't be straight and you will be riding a little bit sideways.

bent-not-broken FTW (and BF FTW)! I loosened the stem and tightened it back down just snug this time, and all is right with the world. Front wheel flops freely when lifted. Walking the bike by the saddle exhibits no "carpet-squirreliness". A quick spin up and down the aisle of the parking lot yields perfectly upright hands-free riding (and a few seconds of getting used to a floppy front wheel again!!)

The reason it was so tight was that a friend of mine at work (who is a racer and mechanic from way back) noticed that my headset was loose. He said that happens after an install sometimes, riding awhile will cause the press-fit to set a little better and things get loose. So I torqued that mofo down HARD! I guess too hard.

Any suggestions on proper preload torque would be welcomed, but (a) I don't own a torque wrench and (b) "just snug" seems to be working great.

Thank you thank you everyone for all of your suggestions, even wheel-based ones which did not turn out to be the problem this time. The extra knowledge is added to my mental bag of tricks, and will surely come in handy some day!

One more edit: This is my ONE THOUSANDTH POST here at BF. I am so pleased that this momentous occasion marks all that I love about this community -- so many experts, so willing to share and help. Thank you all 1000 times!

Streets are crowned in the center.. its higher so rain drains off.

you may be straight up on a sloped surface..

stop posting right now!

the correct torque is the torque that eliminates play or rattling
when the bike is dropped or rocked with the f brake squeezed
but the bars still turn freely

This reminds me of a story. When I met my, now, wife she had an 8 year old Specialized road bike. So to help win her over I offered to service her bike (and to insure i didn't have to play "on the road" mechanic). I did a complete clean and grease of the mostly 105 equipped bike. When she roads it for the first time she could barely keep from falling off. The bike was very unstable. She complained that if felt like the bike was drunk! What had happened was that her headset had been so overtightened that it acted as a steering damper. Now that damping was gone and she had to get use to the freely moving nature of a properly adjusted headset. Andy.

Great story! If you had gotten here sooner, you probably would have been able to solve my problem first!