Framebuilders:Tandem rear triangle alignment

[pinkshogun]

The rear wheel does not sit correctly up near the brake bridge, chainstay area is fine. the dish is fine, dropouts aligned, string test is spot on on both seat tubes

the wheel needs to move about 3-4mm to the right. would filing the top of the left dropout help this situation

[weisan]

I bet you couldn't tell the difference when you ride it.

[stien]

Try a different wheel yet?

[Tandem Rider]

Are the wheels in the same plane?

[pinkshogun]

I can't tell when riding but it's a problem that needs to be fixed if possible. I did try another wheel to no avail

[pinkshogun]

How do I determine if the wheels are in the same plane?

[cmbicycles]

Is the rear wheel off to the left at the seat/mid/and chainstay or just at the top?

Are the wheels dished properly? If you put the rear wheel in backwards is it off the same amount on the other side, or the same side?

Are the dropouts aligned? Most bike shops should have the dropout alignment tools, as well as a frame alignment tool (or know how to do it without one).

[pinkshogun]

Is the rear wheel off to the left at the seat/mid/and chainstay or just at the top? JUST AT THE TOP

Are the wheels dished properly? YES

If you put the rear wheel in backwards is it off the same amount on the other side, or the same side? HAVENT TRIED THAT BUT ANOTHER REAR WHEEL YIELED THE SAME PROBLEM

Are the dropouts aligned? YES

Most bike shops should have the dropout alignment tools, as well as a frame alignment tool (or know how to do it without one). STRING TEST SHOWED THE FRAME WAS ALIGNED AT BOTH SEAT TUBES

[Kontact]

This is one of those things that can be over-thought. If everything else checks out, then the problem likely is going to be that the dropouts are not in the same spot. I'd be okay with breaking out the file.

It isn't going to take much, so work slow and check often with the QR fully closed.

[pbarry]

I wouldn't file on that until you figure out if the wheels are in the same plane or not. Without putting it on a big surface plate, I can't think of an easy way to check if the wheels are parallel. Seat stay alignment is often a little out of perfect on mass produced bikes. A good sign that it passed the string test. :) If it doesn't pull one way or the other with only the captain aboard, no hands, just enjoy it.

[Kontact]

I wouldn't file on that until you figure out if the wheels are in the same plane or not. Without putting it on a big surface plate, I can't think of an easy way to check if the wheels are parallel. Seat stay alignment is often a little out of perfect on mass produced bikes. A good sign that it passed the string test. :) If it doesn't pull one way or the other with only the captain aboard, no hands, just enjoy it.

Why not just "fix" it? If the half millimeter filed out of one dropout produces any detectable riding oddness, it is easy to remove by taking the same out of the other dropout.

[pbarry]

Why not just "fix" it? If the half millimeter filed out of one dropout produces any detectable riding oddness, it is easy to remove by taking the same out of the other dropout.

What are you fixing?

[Kontact]

What are you fixing?

A frame that doesn't center its rear wheel.

If the OP wants to confirm that the frame isn't the problem he can do the string check to the brake bridge. If the brake bridge is centered and the wheel is dished, there's nothing else that can really be happening and the wheel not be tilted out of plane.

[marciero]

If you have to move it 3-4 mm to get it even, that means there is about 6-8mm more space on one side than the other. Is that correct? That sounds too much to "call it good". But it sounds like you've checked everything, approximate nature of string test notwithstanding.

One possibility is that the wheel and dropouts are in fact aligned properly but it is the frame tubes themselves that are asymmetric. If one of the seat stays was cut a little shorter and had slightly different curve to it that would do it. I would guess that is not so uncommon on a factory made frame. In that case you dont want to be using the seat stays as an alignment guide!

[PJN]

Seems like the seat stays weren’t aligned before welding.

If the wheel is centered in the chainstays and in plane with the seat tubes you’ll be best leaving things as is. The alignment of the wheel in the seat stays maters for brake adjustment (can be fixed with spacers) and optics. It’s way way more important the wheel is inplane with the seat tube.

[marciero]

Another reason to put down the file is that alignment involves centering, toe-in, and camber. Filing the dropouts will affect both of the latter in proportion determined by the angle of the dropouts; i.e, you have no control over it.

[Tandem Rider]

I don't have access to a surface plate, so my method would involve a sturdy workstand and good light. First, take off the cranks, cables, front der, fork, headset cups, and rear brake caliper. Next, using your eyeballs and light, determine if both seat tubes are in the same plane, repeat this for the head tube, use a straight edge or level against the head tube to increase the accuracy. Using a long straight edge, held against the head tube, and rear seat tube, is the gap to the front seat tube the same on each side? Use calipers to make sure. Do this first because these errors are going to be nearly impossible to remove at home. Assuming this is good, take a perfectly dished and true rear wheel without a tire, and put it in the frame. Again, good light, how well does it align with the seat tube? I have used a 4 foot level held against the rim, as close to the hub as I can get before the level hits the spokes to help with this. If it's "cockeyed" to the seat tube, then it would be acceptable, in my opinion, to carefully file a dropout to bring it into alignment, it won't take much filing to move it.

[unterhausen]

I can't see the dropouts in the pictures, are they vertical? I might make the wheel center a little better than that with a file. After I was absolutely sure that the wheel was okay, that is.

Some builders use a T-tool to tell if the wheel will center. I'm not sure how to simulate that with a string test or something that you can easily do at home.

[C. Matthews]

Seems like the seat stays weren’t aligned before welding.

If the wheel is centered in the chainstays and in plane with the seat tubes you’ll be best leaving things as is. The alignment of the wheel in the seat stays maters for brake adjustment (can be fixed with spacers) and optics. It’s way way more important the wheel is inplane with the seat tube.

^^^This.
Also, filing a dropout to move the wheel at the seatstays can have a couple of unintended consequences.
1. The wheel will move at the chainstays too, not as musc as at the seatstays, but it will move.
2. The axle locknuts won't fit square against the dropouts so the drops will need realignment.

[Brian Smith]

How do I determine if the wheels are in the same plane?

If you don't know this already, then your questions about modifying the position of the wheel in the frame are not a framebuilding problem, they're a bike mechanic problem. Given the type of bike here, there's no need to spend disproportionately to fix what might (or might not) be wrong. You can fix the poor brake alignment by changing the washer positions in the brake pads and/or replacing the pads with some offering greater adjustment if that brake won't allow for the adjustment. You can split the difference in the rim position between the multiple sets of stays by either changing the rear axle spacing with a spacer washer and/or re-dishing the wheel - the possible resulting 1.5mm error at each set of stays would exceed all requirements. Enlarging the dropout slot by filing is more likely to result in the wheel being pulled out of position under the torque of two riders than it is to result in a functional benefit of a theoretically-centered rear wheel being created.

[Kontact]

^^^This.
Also, filing a dropout to move the wheel at the seatstays can have a couple of unintended consequences.
1. The wheel will move at the chainstays too, not as musc as at the seatstays, but it will move.
2. The axle locknuts won't fit square against the dropouts so the drops will need realignment.

I think some of you are misunderstanding the problem.

What the OP is describing is the dropout slots being out of line from the horizontal plane. They are in line from the vertical plane, which is why the wheel is centered behind the BB okay, but the top of the slot on one dropout is lower than the other by tiny amount - an amount much less than the amount of offset at the seat stay bridge.

If the OP wants to center the wheel at the seat stay without changing the centering at the chainstays, he would raise the slot vertically only by about 1/3 of the amount the wheel needs to move at the tire, while leaving the horizontal location of the slot alone. The result will be the top of the tire moving laterally while the front of the tire by the BB remaining where it is.

This will produce a tiny change in the squareness of the dropouts, but less than the amount that occurs when you put a 130 wheel in a 126 dropout.

Everyone who has horizontal dropouts is already familiar with what I'm pointing out, because tightening one dropout screw more than the other will kick the wheel off center at the chainstay while barely affecting the brake centering. We're just talking about doing that vertically to achieve the exact same kind of result.


In other words, you guys are over-thinking this.

[David Tollefson]

When I look at the OP shot on the left, it appears that the wheel is centered on the seat tube, but the seatstays, and maybe even just the bridge hole, are offset. It may simply be that the stays aren't centered... Unless this shows up as a handling issue, I'd be inclined to leave it alone.

[C. Matthews]

I think some of you are misunderstanding the problem.

.

Nope, OP says the wheel needs to move 3-4mm to the right. Filing the drop enough to move the wheel that much will do what I described, try it and see!

I'll reiterate that I agree with all the posts that advise to leave it alone,

[Kontact]

Nope, OP says the wheel needs to move 3-4mm to the right. Filing the drop enough to move the wheel that much will do what I described, try it and see!

I'll reiterate that I agree with all the posts that advise to leave it alone,

I think you need to re-read the OP:

The rear wheel does not sit correctly up near the brake bridge, chainstay area is fine. the dish is fine, dropouts aligned, string test is spot on on both seat tubes

the wheel needs to move about 3-4mm to the right. would filing the top of the left dropout help this situation

He's saying that it is centered at the chainstay and off center at the brake bridge by 3-4mm. The wheel is canted out of the vertical plane by about .6° counterclockwise.

[cachagua]

If you can get hold of a laser level with a vertical beam, remove the tires from the wheels then mount them in the frame. Align so that the plane of the laser goes past both wheels at a reasonably close distance, then lean the bike so that one wheel is in plane with the beam (within the tolerance of your measurements). Then check the other wheel and see if it's in plane too.

And if they *are* in plane, then consider of the possibility that the stays , not the wheels, are out of line. Especially if the bike rides well, in addition, then maybe everything's exactly where it needs to be, and you don't have to "fix" anything.

[dddd]

As a last thing before removing any metal, I would do a few sighting-down tests about the rear wheel, along the sides of the wheel, and the seat tube, removing the saddle first to allow a fuller view.
I would think that this much of a wheel tilt might actually be visible as such if viewed from the right angle.

Having said all of the above, I have ultimately had to remove metal from a front or rear dropout slot on several occasions, at such point that I felt I had established that one seatstay or fork leg was effectively longer than the other.

There is a ratio of roughly 2:1 of axle length to 700c rim radius, so a rim that is offset from true center by 2mm would need a full 1mm of metal removed from the axle seating surface inside of the dropout slot.
And in the case of a horizontal dropout slot, you can only remove so much from the top surface of one slot before the locknut might lose contact with the lower rung of the dropout, something that would cause very serious problems with axle twist and slippage.
On one Peugeot PKN-10 here I removed metal from the top of one dropout slot and from the bottom of the other dropout slot so that enough corrective axle tilt could be effected without compromising the grip of the locknuts on both sides of the slots. I now properly install that bike's rear wheel by tilting it forcefully before closing the QR lever, and the wheel stays nicely in plane.

[pinkshogun]

What DDDD wrote was and may be my plan of action from the start...removing metal from the top of the left dropout and now that he brings it up, the bottom of the right dropout as well to get the tilt i need.

i too have filed forks and the ends of dropouts to achieve correct alignment but never the top/bottom of a rear dropout and was not sure this method would work

i already have a tandem so this raleigh would be for sale but i cannot in good faith send it out with a crooked rear wheel

i will see if i can get Chapman to eyeball it before i do anything drastic

DDDD...did you use a round file directly on the area the axle with sit to provide a little recessed support?

[Kontact]

What DDDD wrote was and may be my plan of action from the start...removing metal from the top of the left dropout and now that he brings it up, the bottom of the right dropout as well to get the tilt i need.

i too have filed forks and the ends of dropouts to achieve correct alignment but never the top/bottom of a rear dropout and was not sure this method would work

i already have a tandem so this raleigh would be for sale but i cannot in good faith send it out with a crooked rear wheel

i will see if i can get Chapman to eyeball it before i do anything drastic

DDDD...did you use a round file directly on the area the axle with sit to provide a little recessed support?

There is no "bottom" of the dropout to file - you'll just make it harder to get the wheel in right if you remove metal from the lower side of the right dropout because it will just become sloppy.

Use a round file just a bit smaller than the axle size.


With a "vertical" style dropout, you remove material on the "ceiling" of one dropout to lift the low side of the axle up. If the wheel is crooked right to left, you remove material from the back side of the appropriate dropout.

The reason you do it this way is because of how you hold the wheel in place to tighten it - by pulling it up and back. So you only want to make changes that are either up or to the rear.

[David Tollefson]

Before you start filling, PLEASE confirm that the wheel is misaligned with the seat tube and not just the seatstays.

[dddd]

What DDDD wrote was and may be my plan of action from the start...removing metal from the top of the left dropout and now that he brings it up, the bottom of the right dropout as well to get the tilt i need.

i too have filed forks and the ends of dropouts to achieve correct alignment but never the top/bottom of a rear dropout and was not sure this method would work...

DDDD...did you use a round file directly on the area the axle with sit to provide a little recessed support?

I did indeed cut a pocket for each axle end, since I didn't feel that I would ever be changing the fore/aft position of the axle in the slot, and since I removed the least amount of metal so as to leave more around each pocket to grip against the locknuts.
My file was a 3/8" round file, but a tapered "rat tail" file could work as well.
This frame has axle stops so I only need to put weight on the saddle to hold the axle against the stops position and against the chain's sprung tension as I tilt the wheel fully and close the QR lever. It's pretty fool-proof that way, even for anyone that I might sell it to, and can be done nearly as quickly as a regular setup.
Mostly I couldn't stand the look of the caliper hanging sideways at the seatstays, and I did have to re-adjust the left and right pad heights after making the correction to prevent rub against the tire.

The bike now looks and rides really well, so I feel that the efforts were worth it!
https://c1.staticflickr.com/5/4580/38017375765_bfab631a4b_c.jpg

[pinkshogun]

I took the tandem to Chapman and after measuring again with string and another device, ground then filed a bit of the top of the left dropout. now the wheel sits much straighter.

[v531xc]

Nice! glad this worked out for you.