nillevang

Hello,

New bikeforums user here! I've got a ca. 95 Dawes Super Galaxy I recently bought relatively cheap. It's in good nick, but the front wheel has a very distinct pull to the right; it actually drives off the road within a couple of meters if uncorrected. I've checked the frame for alignment using Sheldons string method, and it seems like the rear triangle is off by app. 2-3 millimeters when measured to the seat tube. Is this a lot or a little, and will it cause the above reaction?

I also pulled off the front fork and placed it on a mirror with the cantilever braze-ons pointing upwards, and it seems the fork blades are skewed 5-6 millimeters off each other - this actually seems like a lot! Is that the case, and will this cause the above reaction?

I hope my writing is somewhat understandable; being resident in Denmark english is not my native language.

Best regards Niels Lillevang Hansen

Murray Missile 

Sounds to me like that bike has been in an accident or has had some rough handling. Each item by itself may not cause an issue but the two combined might and what else may be tweaked that you don't know about? I'm just throwing out possibilities though, I'm no bicycle alignment expert, or even amateur. I know it doesn't take much of a misalignment to turn an automobile into an ill handling beast though.

By the way, welcome to the forum. Your English is fine, in fact it is better than some for whom it IS a native language.

cny-bikeman

It takes relatively little misalignment on a fork to cause problems, and the rear triangle being off certainly can't help. At this point you already have the answer as to whether either is off "enough." The question is what to do about it. Sheldon discusses straightening the rear triangle, but it's best to align the dropouts as well, which takes a little more prep, best done with proper tools. Straightening a fork properly is extremely difficult, due to the necessity of having the blades correct both laterally and fore-aft, best done with a dedicated tool and experienced hands - also including dropout alignment. Here is one place I found with a Google search: https://bolsjefabrikken.com/wp/?page_id=254. I would think they could directly assist or point you to a good shop.

Please excuse my Danish - it is nonexistent!

dabac

Well, it's not doing you any good, but I don't think that's the biggest villain in this case.
I've ridden bikes that have been off by about the double without any dramatical handlig consequences.
One I spotted during cold setting. Another remained undetected until a wheel swap revealed that the original wheel had a custom dish to compensate for the rear triangles being off.
But then I don't do much hands-off riding at the best of times.
I'm not certain I understand the geometry here. Fork blades generally point away from each other a bit. They're closer together at the crown than by the dropouts. That itself doesn't tell you anything.
Let's say you put the fork on a table, with the crown resting at the the table and the blades hanging over the edge; both fork blades need to be at the same distance from a line drawn through the steerer tube, both when looking at the fork from above and from the side.
And while doing that, the distance between the dropouts should be a good match to the width or O.L.D. measurement of the hub.
So blades can be off both sideways and front or rear. It can affect either one blade, or both. It's a bit tricker to measure than a frame.
And it can certainly do funny things to the handling of the bike.

davidad

https://www.sheldonbrown.com/brandt/pull-side.html
https://www.sheldonbrown.com/brandt/align-fork.html

Andrew R Stewart 

I posted about a low cost drop out aligning check tool a few days ago and mentioned that I used the same trick of looking through a small diameter tube in my, also, low cost method of checking fork alignment. Some have asked that I describe this fork checking process in greater detail. So here's what I do.

But before I continue a few comments about frames, bikes, people and their relationships. "Show me a perfect body and I'll build a perfect bike". This was said by Albert Eisentraut during a framebuilding class I attended 34 years ago. His point was that we are not perfectly symmetrical beings, favoring one side over the other with limbs of different lengths and curvatures where we might be straight. Additionally our bikes are not a perfect mirrored device. Wheels are usually off dish, stems/bars not perfectly square, horizontal, straight or symmetrically curved. Seats are off to one side WRT the rails that also might not be quite parallel. Then there's the "Q" factor and that many of our on topic cranks are not off set from the frame's center line equally side to side. So this pursuit of a well aligned frame/fork is tempered by the reality of the imperfection that we and our bikes are.

Fork alignment has three aspects/axis that we need to be concerned with.
- Steerer axis being parallel with the wheel's plane
- Axle being parallel with the fork crown
- Drop outs centered WRT the steerer's axis

I will establish one aspect then the next then the last during my process. As changing each aspect does effect the others I'll go around this process a few times, with each cycle getting each aspect closer to "good enough". At some point I find I am chasing very minor amounts of "offness" and will call the fork aligned. (More on this point later).

First I start by getting the drop outs parallel to the crown. Photo #0356 shows a pair of Campy "H" tools placed in the drop outs although any straight edge that fits fully into the drop outs would suffice. (The "H" tools double as drop out aligning devices saving a step). There is another straight edge placed on the blades front surface up near the crown. These two straight edges need to be parallel to each other. I will bend one blade forward or the other backward as needed to get the two straight edges parallel. Note that with the "H" tools being attached to separate pieces (drop outs) that as a blade is displaced the tool will no longer align with it's sister. So after each blade bending the "H" tools need to be realigned to each other to recreate a straight edge running through the drop outs. (A simple solid straight edge would not need this step for axle/crown aligning but the drop outs would need a realigning to each other after. The "H" tools just let you do this without changing the tools in the drop outs. The previously posted drop out aligning tool made from an axle cut in half would be the tool for getting the drop outs parallel to each other.)

Second step is to check the steerer and wheel's being centered WRT each other. This is where the sighting tool I have mentioned comes into play. You'll need a good wheel, dished on center and true with a Presta valve hole if possible. The sighting tube is any piece of tubing (I've used plumbing stuff and 4130 stuff before) with a length a bit more then the steerer's and an ID maybe about 3/16". Then tape (masking in this case) is wound around this tube in a couple (or more) places along it's length. This tape will build up the effective OD of the tube so that the tube can slip inside of the steerer and snug up with no play. One winding of the tape is slightly smaller in diameter so that it can butt up inside the steerer's butted section (like a cone would center on a tube end) and the other snugs into the full ID of the steerer. The windings are placed along the length so that a little bit of the sighting tube will stick out just past the bottom of the crown or steerer's bottom end and just above the rim. Photo #0350 shows a sighting tool made and ready to install into the steerer. The wheel is installed in the fork and lightly clamped in place so that the rim is centered between the blades up near the crown. The rim is rotated around so that the valve hole is lined up with the sighting tube's line of sight. I hole the rim in place with a rubber band to free up my hands. Photo #0351 has the sighting tube installed with the rim held so the valve hole is in line. Then by looking down through the sighting tube you can see across the wheel's diameter and to the rim on the other side. If the fork is centered the view will be centered on the rim. A mark on the rim helps this judgment. Photo #0354 is an attempt to show the spotting through the tube to the rim's far side. Now if the drop outs were too wide or narrow apart you would have to bend a blade in or out to get the axle to just slide into the fork's drop outs with out any blade movement when the axle securing is tightened. Also if the axle (and then the rim as seen through the sighting tube) was off center one or the other blade would need to be bent over to correct this. This drop out width and wheel centering correction is done simultaneously, back and forth with rechecking the axle's fit within the drop out width and rechecking the wheel/rim's centering as seen through the tube. When done the axle fits within the drop out width with very little slop and the wheel is centered WRT the steerer/sighting tube.

Last is the blade length. Note how with step 2 I was centering the rim near the crown by hand and then clamping it there, without regard to how deep into the drop out slots the axle seated. Now we check for whether the wheel sits within the drop out slots evenly. Loosen the axle securing and fully seat the axle up into the drop outs. I like to use both hands at each axle end to pinch it up fully before I resecure the QR or nuts. If you pull the rim up toward the crown it's easy to think you've seated the axle fully but I've been wrong doing this before. (Of course if the bike were upright gravity would seat the axle fully but that is not what the arrangement is for this process). Photo #0355 shows a wheel installed as though a blade was longer then the other (actual the fork used as the sample has already been fully aligned so I had to miss center it to show this). At this point there is a threshold to consider. Up to now all bending/aligning can be undone, no forks were injured in the making of this process. But this next step changes that. If one blade/drop out is longer from the crown then the other the wheel will sit crooked WRT the steerer's axis. So a blade has to be shortened. We do this by filing the slot of the long side's drop out deeper. This allows the axle to seat up further and the rim to, bit by bit, sit centered between the blades. Remember the levers at play. The axle is about 100mm wide, the rim is about 300+ in radius. So a 1mm deepening (by filing) of the drop out slot will equal a 3mm shift over of the rim between the blades near the crown. And the filing needs to be in line with the blade, NOT the angle of the slot. While I do this very often on new bike builds at work (it's surprising how off even cast suspension forks are) I feel that (unlike the TV commercials say) less is better. Only a few file strokes will produce a lot of rim centering movement. The file used should be sharp and of the same diameter as the slot's width (or the axle's diameter). I hold the blade at it's drop out and have the rat tail file run through both drop outs but only apply pressure on the drop out needing filing. This keeps the filing square and give one a bit of a guide. Again this is a point of no return. If you're uncomfortable with the possible consequences then STOP. Have a pro take it from here.

If you've done all these steps right and with care, then run through them a second and third time you'll see a fork that was off becomes more and more on center. The cost (besides the gumption to bend or file away at your classic fork) is very low. A good wheel (that we all should have anyways), a length of small diameter tubing, some masking tape, an axle to make a drop out aligning tool from with some extra nuts and the effort to have the fork bare of frame, caliper or fender.

Now back to something I mentioned but passed by. I said that alignment is not a perfect thing. I have had for a number of years a precision flat surface which is hand scraped to a VERY flat spec. I also have a fork steerer block clamp that bolts to this surface plate. With these I can use my dial indicators and "measure" the fork's center height off the surface, then the drop out's heights, place a dummy axle in the drop outs and indicate off it's vertical surface (or use a square) and check the axle's perpendicularity WRT the steerer and also the axle/crown parallelness. But just because I can see a single thousandth of an inch does not make it important or repeatable. I can refit the fork in the clamp and get different readings. I do check my forks with these "precision" devices but do my actual aligning and the running checks during the aligning with the low cost process described above.

I hope this has been informative to those who care about having a well aligned bike and like to understand processes. Andy.

Andrew R Stewart
Rochester, NY
[HR][/HR]

Andrew R Stewart 

Niels and all- I recently posted the above on Classic Rendezvous. I had replied to a post about aligning drop outs and suggested a simple home made tool using a hollow axle cut in two and then sighting through the hollows of each half (when secured into the drop outs) to check the parallelness of the drop outs. I also mentioned that aligned drop outs is not the same as aligning a fork and that i use the sighting through a small diameter tube in a home made fork aligning method. Some one asked me to describe this fork aligning method. So I did. The above was copied from CR.

I'll be happy to fill in more detail or answer any questions if you have some. Andy.

nillevang

Wow, thanks for the replies so far!! I'm quite amazed!

I've snapped a few pics hopefully showing the problem(s) and their scale.

Br Niels

nillevang

If you look at picture #1 the left dropout (the right side when you're riding the bike) is couple of milimeters lower than the other side.

FBinNY 

Sadly this doesn't tell you anything specific. The misalignment can be caused by the dropouts being in different places, bot just as likely by their faces not being parallel. When one uses dropout alignment tools (made for the job) the process requires that the ends not only meet in the middle, but that the gap between the cups be uniform all the way around (parallelism). With threaded rods, you can't know what you're looking at.

Frame/fork alignment is a complex thing involving many factors that can combine in various ways. The key is that both wheels be in the same plane and that the center of gravity of the rider is also in the same plane. Both conditions being met ensure that a bicycle will track, but interestingly the bicycle can still track if neither are met, as long as the various errors cancel.

In fork alignment the key is that the steering axis lies within the front wheels plane. This can be met even with a badly twisted fork, and may not be met with a fork where the wheel aligns perfectly between the blades.

The fact that your bike pulls is best evidence of misalignment, but without a series of measuements we can't rule out things like a twisted (off plane) head tube, bent steerer, off position front wheel, and so on...

I wish I could make this as simple as start here, go there, but it's just not that way.

If there's a framebuilder, or good shop in your area, let them do a thorough analysis of the frame and fork's alignment and straighten it properly.

nillevang

I'm afraid not to many of those framebuilders around here - I only know of two in Denmark, and I've got a sneaking suspicion a visit to those will set me back a whole lot more than a new fork ;-) But I'll definetely give them a call tomorrow.

Either way, thanks for the fast and highly qualified replies so far!

Andrew R Stewart 

I just got a $375 quote (unpainted) for a replacement fork from Waterford. (I'm brokering a repaint for a friend and we thought we had found that the headset stack height was 30mm, after we had sent the frame and fork off to them. Since I don't build for others we had considered Waterford building a new fork. Turns out the stack is 35mm and replacement HS options have opened up a lot).

If I were to align a fork already out of the frame i'd expect no more then $50 labor.

Shops that have experience and motivation might be able to do the aligning too, but far more claim such then actually have the skill. Good luck. Andy.

FBinNY 

Here's some things you do for yourself to get a sense of where the problem may be. You'll need a 1.5 meter length of pipe,or any reliable (not perfect straight edge). If you're willing to work in the cold, the edges of well made wide steps, such as you might see at a museum or church will do. You'll also need a 3/4 meter (or so) carpenters level with a crosswise bubble for finding verticals. And a friend or assistant.

Step one. Use straight edge or the edge of a step to try to establish 4 point contact between both wheels. If the front is offset to either side, you'll get 3 points, but not the fourth.

Step two. if you can establish the 4 point contact, slowly raise the bike to vertical while keeping the 4 point contact. This is easier with steps, than with the pipe. Use the level against the side of the seat tube to determine vertical, then move to the rear wheel (on a secant) to confirm. Now, keeping the bike vertical check if the front wheel is also vertical. You can do this with 2 levels for simultaneous comparison, or trust your friend to hold the bike steady as you check back and forth a few times. I prefer to do the whole job indoors, where I can brace the bike against a wall while a friend and I go through the process.

BTW- All this requires that both wheels are properly dished to center. If the bicycle has horizontal dropouts, the 4-point test can be made to work by angling the rear wheel slightly between the chainstays, but this is only possible if everything is already very close.

If both wheel cannot be vertical at the same time, either the frame is twisted (head tube twisted with axis of rear wheel), or the fork is bent. You can check the head tube, by comparing it to the plane of the seat tube, and/or the rear wheel, but only if the headset cup diameter is the same top and bottom (or remove the headset).

This is just for starters, but it'll give you a decent idea of where the problem lies, and you'll learn something about the principles of frame/fork alignment in the process. If you have friends who own the necessary levels and straightedge (or steps) this should cost you a few beers and maybe a pizza.