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Alignment

Old 01-19-21, 08:40 PM
  #1  
byrd48
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Alignment

Hi there,

Got a new bike, built the wheels myself, and have started breaking it in and noticed that it seems to dart right then left after taking hands off the bars, so I flipped it upside down and put a 6 ft level against the wheels. With the level contacting the front tire at two places, it contacts the rear wheel in the front, but has about 3/16 to 1/4 " gap in the rear. This is from the non drive side.

If I hold the level to contact two points on the rear wheel, it won't touch the front wheel at all.

I have flipped the wheel around backwards and have tried a wheel from another bike with the same results.

The dropouts are vertical, so no real adjustment in the plane that would need to be adjusted.

When I use my engineers ruler and measure the distance from the rim to the chain stay, one side is 1/16" closer to the stay than the other. That works out to about 1.5mm, which would be 0.75mm out of center. These numbers sound small, but when you look at the level across the wheels and see the gap in the rear, it seems more significant and makes me think the bike will dog track and never feel stable hands off.

Would the rear dropouts be adjustable with a frame tool? I tried uploading a photo but it goes to 50% then shows an empty alert window and stops.
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Old 01-19-21, 08:41 PM
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Old 01-19-21, 09:04 PM
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Before you start to make non reversible changes I would learn a bit more about alignment and how to separate the various aspects of alignment from the others. What you show can be the result of more then one misalignment. There are a number of threads here and in the Framebuilder's sub forum about this stuff. Andy
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Old 01-19-21, 09:46 PM
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Maybe I am missing something...But your "method" doesn't seem very solid: how do you know that the front end (wheel) is in the dead-center position? If it is even a degree or two off-axis, your level won't hit the rear wheel properly.

Or your rear wheel might not be dished properly, in which case the rim won't be in the same axis as the front rim.

Maybe you are just not very good at riding "no hands." When you take your hands off the bars, you are likely releasing one hand first, then the other, and/or shifting your weight slightly (even imperceptibly). That would cause the "darting" you describe.

The last thing I would suspect is frame misalignment.

As is often the case, the best advice is probably to just ride your bike and stop fretting.

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Old 01-19-21, 09:58 PM
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^^^^
...in general, frames and forks are aligned so that the fork ends and dropouts are equidistant from a center plane, and parallel.
The wheels are constructed to be straight (and properly dished in the rear), so that when mounted in the already aligned frame, the tyres, (your contact point with the road,) run in that center plane.

You can't use the wheels to figure out whether your frame is properly aligned.

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Old 01-19-21, 09:59 PM
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I know on my 2 bikes, if I let the axle slide all the way into the NDS DO, the NDS front side of the tire is firmly against the stay.
How did you bike handle before you noticed? How about after?
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Old 01-19-21, 10:06 PM
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Originally Posted by Koyote View Post
Maybe I am missing something...But your "method" doesn't seem very solid: how do you know that the front end (wheel) is in the dead-center position? If it is even a degree or two off-axis, your level won't hit the rear wheel properly.

Or your rear wheel might not be dished properly, in which case the rim won't be in the same axis as the front rim.

Maybe you are just not very good at riding "no hands." When you take your hands off the bars, you are likely releasing one hand first, then the other, and/or shifting your weight slightly (even imperceptibly). That would cause the "darting" you describe.

The last thing I would suspect is frame misalignment.

As is often the case, the best advice is probably to just ride your bike and stop fretting.
I tried two different wheels and flipped the original wheel around and got the same result. The reason I suspect it's the rear wheel was the measurements taken from rim to chain stay were slightly different. If it were just dishing, I would still expect the rear and front wheels to be parallel, just not in the same plane.
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Old 01-19-21, 10:06 PM
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It's a new build, so I don't have a before story to compare to.
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Old 01-19-21, 10:13 PM
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Originally Posted by 3alarmer View Post
^^^^
...in general, frames and forks are aligned so that the fork ends and dropouts are equidistant from a center plane, and parallel.
The wheels are constructed to be straight (and properly dished in the rear), so that when mounted in the already aligned frame, the tyres, (your contact point with the road,) run in that center plane.

You can't use the wheels to figure out whether your frame is properly aligned.
The straight edge indicates that the wheels are not parallel. Maybe it's the frame, maybe not, I flipped the wheel and tried another wheel with the same result.
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Old 01-19-21, 10:31 PM
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I would not trust the tire to be a good "foundation" for the straight edge.
Deflate the tire and use the rim.
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Old 01-19-21, 10:32 PM
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Originally Posted by byrd48 View Post
The straight edge indicates that the wheels are not parallel. Maybe it's the frame, maybe not, I flipped the wheel and tried another wheel with the same result.
...read what Andy said. Then take a minute to think about it. The front wheel, situated as it is in a fork that rotates in the head tube, relative to the rear wheel, will never give you a good idea about frame alignment. There are too many variables. The frame drops need to be in alignment relative tot he frame. The fork ends need to be in alignment relative to the fork crown.

When those conditions are satisfied, mounting a set of straight wheels in those should give you a straight bike. More or less.

You are measuring something that won't give you a good result in diagnosing a problem.
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Old 01-20-21, 06:54 AM
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Another possibility is the front end geometry of the bike.

I have no idea what you have built, but my 1970s Carlton Continental had its front axle noticeably in front of the centre line through the steering stem, and could be steered by a mere lean through many a tight entryway*. My current Romet Jubilat folding shoppers have their axle line only just in front of the steering stem centre line and can be vicious ridden hands free.

The point is that there are many factors, and I would put a 1.5 mm misalignment fairly low on the potential cause list.

*until I ran it into a kerb hard enough to bend the forks back, then it was vicious too.
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Old 01-25-21, 08:28 PM
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After removing the tires from the rims, I was able to turn the fork 180 and the level is just a hair from the making contact at all 4 points, literally almost a negligible gap. So it seems that the two wheels are parallel and coplanar with the fork backwards but out of alignment when pointed forward.
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Old 01-25-21, 09:08 PM
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Originally Posted by byrd48 View Post
After removing the tires from the rims, I was able to turn the fork 180 and the level is just a hair from the making contact at all 4 points, literally almost a negligible gap. So it seems that the two wheels are parallel and coplanar with the fork backwards but out of alignment when pointed forward.
With no more then what's written I Am thinking there's at least two alignment issues going of. Not exactly uncommon though. Since I can't do more here without the frame in hand and without better data I am done. Andy
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Old 01-25-21, 09:15 PM
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What data would help, I'm not sure what else I can measure.
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Old 01-27-21, 08:55 AM
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Originally Posted by byrd48 View Post
What data would help, I'm not sure what else I can measure.
You've made my point about understanding what and how frame alignment works. Here are two of the many threads I contributed dealing with alignment. If you search "alignment" and my name you'll pull up a large number of threads, mostly started by others and with other's thoughts besides mine. Some of my posts show fancy tools, others use self made tools. Andy

Alignment thoughts - Bike Forums

Front wheel turns hard right. - Bike Forums
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Old 01-27-21, 10:12 AM
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byrd48 I've many times taken a long strait edge and laid it across the sidewalls of a tire and looked to see how it matched up with the front. And eyeballed it to the rest of the frame. I rest it on the rear tire though and just turn the front to see if it matches or can be made parallel.

It's helped somewhat on a few occasions to help me note when things are wonky. But some questions I've ask several times in various places have never been answered.
  1. Will or should the front and back wheels always be in the same plane?
  2. If they are in parallel planes, then how much separation is okay?
  3. What effect is produced as the planes get further apart?
Realize that what you are showing in the picture with the straight edge being fixed to the front wheel doesn't tell you if the rear wheel might be in a plane parallel to the front. If you fix in to the edge of the rear wheel, then you might find it is in a parallel plain and only out by perhaps the amount of dish and axle spacers that may or may not be correctly set on your rear wheel.

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Old 01-27-21, 07:54 PM
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Originally Posted by Iride01 View Post
byrd48 I've many times taken a long strait edge and laid it across the sidewalls of a tire and looked to see how it matched up with the front. And eyeballed it to the rest of the frame. I rest it on the rear tire though and just turn the front to see if it matches or can be made parallel.

It's helped somewhat on a few occasions to help me note when things are wonky. But some questions I've ask several times in various places have never been answered.
  1. Will or should the front and back wheels always be in the same plane?
  2. If they are in parallel planes, then how much separation is okay?
  3. What effect is produced as the planes get further apart?
Realize that what you are showing in the picture with the straight edge being fixed to the front wheel doesn't tell you if the rear wheel might be in a plane parallel to the front. If you fix in to the edge of the rear wheel, then you might find it is in a parallel plain and only out by perhaps the amount of dish and axle spacers that may or may not be correctly set on your rear wheel.
It I fixed the level to the rear wheel, I could possibly turn the front wheel until it looked parallel to the rear, however due to the headtube being angled, the front wheel can only be coplanar to the rear when it is pointed straight ahead.
I think I have an issue with my fork. Turning it around backwards made it line up nicely, however I would have thought it would still be off, but on the other side.
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Old 01-28-21, 04:29 AM
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String method in post 5 is very accurate.
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Old 01-28-21, 09:21 AM
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Originally Posted by dmark View Post
String method in post 5 is very accurate.
Agreed... for the aspects the string test can show. Much of this thread has been about what is wrong and how to measure that. Having the main triangle and the rear triangle centers in plane is but one aspect of alignment. Because it's relatively easy to measure it gets talked about frequently. Far more talk then the other aspects of alignment. If I had a hammer I'd hammer and look at the world for nails. But there's screws, bolts, rivets, bonding, welding and other assemble methods a hammer won't be the answer for. My goal is to open the eyes to those other aspects, have the OP and readers better understand the other alignment relationships and do this before the bending bars/files, (or hammers) come out.

Much like our social politics there's so much more to a topic that what many are willing to discuss or accept. Andy
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Old 01-28-21, 06:18 PM
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First instinct to put a straightedge on the wheels was absolutely correct. First time I saw that done the guy holding the straightedge was Oscar Wastyn Sr., for a number of years the only working framebuilder in US. Absolutely standard technique. Your bike failed the test.

Now continue and get the frame aligned. The links already given are a good start. Finding a good mechanic who can guide you would help too.

When the frame is straight and the wheels are straight the universe is divided into left of the bike’s centerline and right of centerline. You can feel that. When your bike does that you are done.
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Old 01-31-21, 07:07 PM
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Andy, I did read your articles, including the low cost methods for checking the fork. Yes the rear triangle is easier to measure and I believe based on what I have done thus far that the frame, or at least the rear triangle is ok, the issue seems to be up front. I have no intention of filing the drops or doing anything without knowing where the real issue is. So I am not looking at every issue as a nail, I'm acknowledging that I have not identified the cause of the misalignment. The approach you took to analyze the fork seems easy enough.
Thanks for the help!
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