Frame/headset alignment problem - ghost steering
04-02-09, 12:13 PM
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Frame/headset alignment problem - ghost steering
I have a funny problem.. This bike is a very entry level Huffy, and it looks like it's pretty much NEVER been ridden. Definitely has not been in an accident.
But this bike desperately wants to turn right. So much so that it's noticeable even with a firm grip on the handlebars.
What's even more odd is that it tends to steer right even when it's not moving.
If I hold the top tube and lift the front tire just off the ground, the bars will flop to either side equally easily. But as soon as I put weight on the front wheel, the wheel wants to go to the right. It's as if something is misaligned to the point that the entire front of the bike lowers considerably when the wheel is turned right, so gravity is forcing the bars to turn.
Any ideas about what part of the geometry could be out of whack to cause this? This is for a casual rider, no sense in making her buy a new bike - but I actually suspect manufacturing defect in this case. Everything looks straight by eye, but of course that is nowhere near scientific.
It does have a very cheap front suspension but again, everything is centred - bars to forks, wheels to frame... What I was thinking was maybe the head tube was not welded plumb...?
Or it's literally haunted.
Any ideas?
But this bike desperately wants to turn right. So much so that it's noticeable even with a firm grip on the handlebars.
What's even more odd is that it tends to steer right even when it's not moving.
If I hold the top tube and lift the front tire just off the ground, the bars will flop to either side equally easily. But as soon as I put weight on the front wheel, the wheel wants to go to the right. It's as if something is misaligned to the point that the entire front of the bike lowers considerably when the wheel is turned right, so gravity is forcing the bars to turn.
Any ideas about what part of the geometry could be out of whack to cause this? This is for a casual rider, no sense in making her buy a new bike - but I actually suspect manufacturing defect in this case. Everything looks straight by eye, but of course that is nowhere near scientific.
It does have a very cheap front suspension but again, everything is centred - bars to forks, wheels to frame... What I was thinking was maybe the head tube was not welded plumb...?
Or it's literally haunted.
Any ideas?
04-02-09, 12:26 PM
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It could be many things. bent fork, bent frame, wheels improperly seated in the drop outs. Improper dish in the wheels, bent axle, etc. Pics?
04-02-09, 01:20 PM
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I flipped the wheel and got the same result so I don't think it's dishing. I shifted the wheel to the extremes of crookedness in the dropout and no matter what it always turned right. Front to rear frame alignment should not affect it since even if I hover the rear wheel and push down on the front, it goes to the right - hard.
I suspect fork or misaligned head tube - but swapping the fork on a bike this cheap is a little extreme. Any ideas about anything I can measure before digging too deeply?
Here are some pictures, not sure if they will help at all...
I suspect fork or misaligned head tube - but swapping the fork on a bike this cheap is a little extreme. Any ideas about anything I can measure before digging too deeply?
Here are some pictures, not sure if they will help at all...
04-02-09, 01:37 PM
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Maybe something with the shock absorbers in the fork?
Or try unbolting the locknut and the cups of the fork to see if there's something wrong with the headset I guess.
Or try unbolting the locknut and the cups of the fork to see if there's something wrong with the headset I guess.
04-02-09, 02:34 PM
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How smooth is the headset? Headset that's too tight with indexed-steering will cause pulling problems. Loose headsets can wander as well.
Find the "string alignment" test on Shedon's site somewhere. With careful set-up, it can be pretty good at spotting misalignments in the frame. To check fork-alignment, I made my own tool from a broomstick. Milled it down to 22.2mm to fit exactly inside the steerer-tube from below. Then measure distance from fork-tips to centre of broomstick and they should match.
Find the "string alignment" test on Shedon's site somewhere. With careful set-up, it can be pretty good at spotting misalignments in the frame. To check fork-alignment, I made my own tool from a broomstick. Milled it down to 22.2mm to fit exactly inside the steerer-tube from below. Then measure distance from fork-tips to centre of broomstick and they should match.
04-02-09, 04:00 PM
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I flipped the wheel and got the same result so I don't think it's dishing. I shifted the wheel to the extremes of crookedness in the dropout and no matter what it always turned right. Front to rear frame alignment should not affect it since even if I hover the rear wheel and push down on the front, it goes to the right - hard.
I suspect fork or misaligned head tube - but swapping the fork on a bike this cheap is a little extreme. Any ideas about anything I can measure before digging too deeply?
Here are some pictures, not sure if they will help at all...
I suspect fork or misaligned head tube - but swapping the fork on a bike this cheap is a little extreme. Any ideas about anything I can measure before digging too deeply?
Here are some pictures, not sure if they will help at all...
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04-02-09, 04:44 PM
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The headset it smooth, it flops easily in either direction when front is lifted, there are no detents. The rear wheel is straight, but like I said it steers right even when not moving, simply by gravity. The steering is actively pulling you - it's not just more difficult to steer left than right, when there is weight on the handlebars it actively steers to the right.
Here is a video of me just pushing straight down on the top tube and you can see how the wheel swings right. Even if I steer it slightly left, then push down on the to ptube, the wheel won't go left - and with a small nudge to the right it swings super fast to the right.
https://www.youtube.com/watch?v=up4wNfy3Kog
So gravity alone is causing this. It must be fork legs or head tube misalignment. I will try the broomstick method if I have the time. In the meantime I'm not going to recommend riding this bike for safety reasons!
Here is a video of me just pushing straight down on the top tube and you can see how the wheel swings right. Even if I steer it slightly left, then push down on the to ptube, the wheel won't go left - and with a small nudge to the right it swings super fast to the right.
https://www.youtube.com/watch?v=up4wNfy3Kog
So gravity alone is causing this. It must be fork legs or head tube misalignment. I will try the broomstick method if I have the time. In the meantime I'm not going to recommend riding this bike for safety reasons!
04-02-09, 05:06 PM
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First try setting the wheels in the dropout as close to straight as you can get them. Usually on the front this means all the way in to the dropout... if you can sit the weight of the bicycle on the axle and push down slightly on the bars as you tighten. Check to see that the tire looks centred between the forks.
Check that the rear wheel is either all the way into it's dropouts, if they are vertical dropouts, or at least the the tire is centred between the seat-stays and chain-stays.
If you do both of those and it still tries to swivel then the front and rear wheels are possibly 'twisted' out of plane, either because of a bent fork or frame.
Check that the rear wheel is either all the way into it's dropouts, if they are vertical dropouts, or at least the the tire is centred between the seat-stays and chain-stays.
If you do both of those and it still tries to swivel then the front and rear wheels are possibly 'twisted' out of plane, either because of a bent fork or frame.
04-03-09, 09:11 AM
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How smooth is the headset? Headset that's too tight with indexed-steering will cause pulling problems. Loose headsets can wander as well.
Find the "string alignment" test on Shedon's site somewhere. With careful set-up, it can be pretty good at spotting misalignments in the frame. To check fork-alignment, I made my own tool from a broomstick. Milled it down to 22.2mm to fit exactly inside the steerer-tube from below. Then measure distance from fork-tips to centre of broomstick and they should match.
Find the "string alignment" test on Shedon's site somewhere. With careful set-up, it can be pretty good at spotting misalignments in the frame. To check fork-alignment, I made my own tool from a broomstick. Milled it down to 22.2mm to fit exactly inside the steerer-tube from below. Then measure distance from fork-tips to centre of broomstick and they should match.
04-03-09, 09:21 AM
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First try setting the wheels in the dropout as close to straight as you can get them. Usually on the front this means all the way in to the dropout... if you can sit the weight of the bicycle on the axle and push down slightly on the bars as you tighten. Check to see that the tire looks centred between the forks.
Check that the rear wheel is either all the way into it's dropouts, if they are vertical dropouts, or at least the the tire is centred between the seat-stays and chain-stays.
If you do both of those and it still tries to swivel then the front and rear wheels are possibly 'twisted' out of plane, either because of a bent fork or frame.
Check that the rear wheel is either all the way into it's dropouts, if they are vertical dropouts, or at least the the tire is centred between the seat-stays and chain-stays.
If you do both of those and it still tries to swivel then the front and rear wheels are possibly 'twisted' out of plane, either because of a bent fork or frame.
What happens when you ride it? There's a whole different group of additional forces at play in motion, which become dominant. Does it pull? Can it be no-handed? Does it steer into and out of corners symmetrically?
Can you check the wheel dish with a dishing guage? I think you can see dishing errors that are really very small with one of these.
Frame twist is possible and might be hard to see. I once was present with Doug Fattic when he investigated the alignment of a frame. Nothing visible, but he found a warped seat tube and the head tube twisted out of the bike center plane. With the shortness of the head tube, I'm not sure the string test can detect it.
Last edited by Road Fan; 04-03-09 at 09:24 AM.
04-03-09, 02:03 PM
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This is what I believe the problem is. Or misaligned fork, which is equally likely based on the quality of construction of all the parts on this bike. As I said, the bars swing right even when it's not moving, even when the rear tire is lifted off the ground - the problem appears to be isolated somewhere between front tire contact patch and headset. I have completely replaced the wheel with the same results, so it's either the fork or the headset/head tube.
Here is something found wandering the internet today, might be helpful for future searches (emphasis added by me):
For less than million dollar bikes this is easy to fix, whether it corrects the cause or not. If a bike veers to one side when ridden no-hands, it can be corrected by bending the forks to the same side as you must lean to ride straight. This is done by bending the fork blades one at a time, about 3 mm. If more correction is needed, repeat the exercise.
The problem is usually in the forks although it is possible for frame misalignment to cause this effect. The kind of frame alignment error that causes this is a head and seat tube not in the same plane. This is not easily measured other than by sighting or on a plane table. The trouble with forks is that they are more difficult to measure even though shops will not admit it. It takes good fixturing to align a fork because a short fork blade can escape detection by most measurement methods. Meanwhile lateral and in-line corrections may seem to produce a straight fork that still pulls to one side. However, the crude guy who uses the method I outlined above will make the bike ride straight without measurement. The only problem with this is that the bike may pull to one side when braking because the fork really isn't straight but is compensated for lateral balance.
This problem has mystified more bike shops because they did not recognize the problem. Sequentially brazing or welding fork blades often causes unequal length blades and bike shops usually don't question this dimension. However, in your case I assume the bike once rode straight so something is crooked
The problem is usually in the forks although it is possible for frame misalignment to cause this effect. The kind of frame alignment error that causes this is a head and seat tube not in the same plane. This is not easily measured other than by sighting or on a plane table. The trouble with forks is that they are more difficult to measure even though shops will not admit it. It takes good fixturing to align a fork because a short fork blade can escape detection by most measurement methods. Meanwhile lateral and in-line corrections may seem to produce a straight fork that still pulls to one side. However, the crude guy who uses the method I outlined above will make the bike ride straight without measurement. The only problem with this is that the bike may pull to one side when braking because the fork really isn't straight but is compensated for lateral balance.
This problem has mystified more bike shops because they did not recognize the problem. Sequentially brazing or welding fork blades often causes unequal length blades and bike shops usually don't question this dimension. However, in your case I assume the bike once rode straight so something is crooked
04-03-09, 05:20 PM
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Here is the real problem...
Redundancy of the quote aside, the fork looks too tall, frame is probably crooked and original geometry poor.
This bike is a very entry level Huffy...
04-03-09, 05:26 PM
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I was going to suggest that the head and seat tubes are not in the same plane. This can often be checked visually, looking at the bike from the front. The eye is very good at detecting parallel lines and even a slight divergence is often visible.
You can also check using something like angle iron or some other piece of flat metal that is both wide enough and long enough.
You can also check using something like angle iron or some other piece of flat metal that is both wide enough and long enough.
