Gitane TdF Frame is lopsided
 

I'm on my second Gitane TdF. I bought the first one when I was in high school, and loved the way it rode, even though the frame was always a little bit small for me. I stumbled on a larger one a couple of years ago, so passed the first one on to Pastor Bob. This second bike is a great rider, too. It's the only one of my bikes that I can comfortably ride with no hands, though I seldom do that.

Anyhow, I was looking at it today and taking some measurements to see if it would work as a 650b conversion. (I have 32s on it now, but there's hardly any clearance at the fork crown.)

In the process, I happened to notice that the tire is way off center between the chainstays. Just below the brake bridge, there's about 20mm of clearance on on side, and 30mm on the other. My first thought was to wonder how I'd ridden the bike for years without noticing that the rear wheel was wildly mis-dished. But then I realized that the wheel is perfectly centered between the chainstays. I don't think it has anything to do with dish.

Just for the heck of it, I strung a line from the rear dropouts around the head tube. The seat tube is centered between the stays almost perfectly--the side-to-side difference is something like one millimeter. The rear rim is perfectly centered between the seat stays at the string line, just behind the seat tube.

Has anyone an explanation for this? It's not something I plan to worry about, since the bike tracks and handles perfectly. I just don't see how the seat stays can be so far out of whack when the chain stays and seat tube are not. But them, I'm not at all knowledgeable about frame alignment.

These are pretty crappy pictures, but I hope they illustrate the issue I've tried to describe.

EDIT: Looking at my own photos on the screen gives me an idea. Perhaps the chainstays are correctly spaced and aligned from side to side, but are a little off vertically? That is, the right dropout could be a couple of mm higher than the left one? It seems to me that that would make the wheel tilt leftward at the top.

An artifact of pushing as many bikes as possible out the door of the Gitane factory in 1972, I would guess.It probably wouldn't be all that hard to cold-set it back into line, although it hardly seems necessary.

Re-dish right, move further back in the left dropout

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Good detective work; you're on the right path.

a) if wheel dish correct

b) if string test good

c) if dropouts aligned

d) then the effective length of one seat stay must be greater than the other. :(

prior to taking any remedial measures you can do a corrobabtive check of the rear triangle alignment with the straightedge test. with bb fittings & rear wheel removed place straightedge against face of shell and see where the other end comes out vis a vis the dropout

this is essentially a no-fix problem

one can fudge a bit by opening up the dropout on the short stay side a bit and closing down the one on the long stay side a bit

solution works a bit easier if rear wheel solid axle. if hollow axle it is somewhat of a nuisance to get things lined up each time wheel is installed.

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In a case where I found a longer chainstay I filed the top surface of one dropout and/or the bottom of the other to tip the wheel to the desired side.

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suspect you meant to write "seatstay"...


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Right. Filed the dropout regardless.

Have you actually checked the dish? I thought aligned between one but not the other would be a sure sign of a wheel out of dish

A set of dropout alignment tools will check/correct any issues with dropouts not being parallel to each other and otherwise catty-wampus. :foo:

After that check/fix set the dropout adjuster screws to center the properly dished wheel between the chainstays, they are provided for just that purpose when perfection in stay length on horizontal dropouts was a wish more than a reality in production. If still off at the brake bridge nudge the caliper one way or the other and proceed in true '70's fashion by ignoring what can't be "fixed" that does not affect handling. :twitchy:

-Bandera

It appears to me that an out-of-dish wheel on a correctly aligned frame would necessarily be off by the same amount at both the seatstays and chainstays. If not, what am I overlooking?

I did check the dish when I trued the wheel on a truing stand when first overhauling the bike.

Good idea about checking with dropout alignment tools. I've been meaning to buy a set for years. Maybe this is my chance.

On the other hand, I agree that letting well enough alone is probably the way to go. Unless one is very good at frame alignment and has a frame table available, it's probably very easy to "correct" a frame irregularity that doesn't effect bike handling by replacing it with one that does effect bike handling.

There's a great Yiddish word for that, which I can only spell phonetically: Farpotchket, which means, approximately, "something that is broken as a result of an attempt to fix it."

only if the wheel axle is bumped against "known true" stops (eg fully at the back of perfectly built dropouts, or against known-perfect adjustment screws). It's easy to align an out-of-dish wheel between chain stays, since the horizontal dropouts freely allow for yaw and you may not notice you're riding down the road a tad sideways. But not so with seat stays; the brake bridge often tells the truth...

I would certainly take it to an Old School shop with dropout alignment tools and have it checked by someone who knows how to use them. It was SOP to do so F&R back when a 531 frame like yours came out the box as they were usually "close" but not correct.

I'll be adding "Farpotchket" to my vocabulary, a term of great utility. ;)

-Bandera

FWIW, it's a 531 Gitane. I've never put my Super Corsa in a jig or aligned it on a frame table and it's one of my keepers. Think of the hung-over tube cutter with a Gaulious hanging from the corner from his mouth.....They really are more than the sum of their parts.

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I'll be adding it to my vocabulary as well. Great word, and you were really close on the spelling, [MENTION=52458]jonwvara[/MENTION]! :thumb:

What is Farpotshket in English? - Yiddish Slang Dictionary

As I began reading this thread, my worst fear was of the dropout height being off.


I've suspected that jigs were used for positioning rear-frame parts in the mass-production shops in France, as I've had a Gitane (and have a Peugeot PKN10) that both were out of whack in just this way. I suspect that hasty assembly in the jig may have resulted in parts not being fully "settled" into their proper positions, but I am probably wrong as I am just guessing, as in maybe thermal expansion wasn't accounted for(?).


My fix for this problem is to mark my preferred fore/aft location of the axle at the dropouts, then remove a minimum of metal from the inside of the dropout slot there, at the top on one side and at the bottom on the other. This keeps an acceptable amount of purchase of the locknut on both the upper and lower runs of each dropout (needed to safely secure the axle).
Then, upon installation of the wheel, I force the rim over fully at the rear caliper as I tighten the QR.
The amount of metal removal should be strictly limited to the amount of correction needed (there is some freeplay there to play with already), and this all should be verified using a perfectly-dished wheel up to and during any dropout modification.
In use, I find that the "tilted" installation of the wheel is not much of a hassle at all, and that if I forget to tilt the wheel then the rubbing caliper will remind me.
Lastly, like the OP, I never noticed any symptom of the tilted wheel while riding, even with hands off the bars, and correcting the wheel tilt caused no such problems, so is hardly a functional problem, just looks like heck (and makes the frame seem defective) seeing the tire off-center within the frame and caliper. Oh, and I've also seen this problem on lower level Japanese frames.


Editing here, it likely will be necessary to re-set the brake pad heights after the lateral rim position changes this much at the caliper!

I'm gonna' go with the DO surfaces not being 'zactly the same height, which is to say the wheel is leaning to one side even while aimed straight ahead. The thing is, it doesn't take much at the axle to move the rim a noticeable amount.

Note the string method doesn't show alignment as bad as it really is, which is to say a 1mm discrepency at the ST means more at the DOs. You can can check the wheel dish by flipping the wheel over. In theory you can correct DO spacing by re-dishing the wheel since there is no reason the DO offset from centerline has to be the same on each side. But I doubt anyone ever does this. It also makes the wheel inappropriate for any other bike.

I had a bike with this problem once. Riding it was a chore.

Thanks to all. If I ever have the bike stripped to a frame again, I'll consider having a frame shop do an alignment. It seems nuts to me to file the dropouts. Even if that eliminated what's basically a cosmetic problem--the appearance of an off-center wheel at the brake bridge--it would replace it with an asymmetry at the dropouts, albeit a much less visible one. Handling is fine now. Who knows how that would affect things? And in general, I have a real aversion to trying to fix things by filing or grinding.

A riding friend of mine who is a museum conservator of historic furniture would say that any irregularities that are original to the frame are the work of the builder, and therefore a part of its history that should be preserved. Maybe that sounds overly grandiose for a bike-boom Gitane, but it seems right to me in this case.

I have witnessed this aberration on a number of occasions. I have never noticed it affecting ride quality; only my (imperfect) sense of perfection when I notice it visually.

I should have 'splained this a bit better, was working with minimal time or on a smarffone keyboard or something, sorry.

The rear wheel can be out of alignment in three different ways. It can be pointing in slightly different direction from the front wheel; when viewed from above the wheels track in different directions. It can be offset to one side so that the wheels point the same way but not in a single line. It can be tilted to one side at the top though the tires' contact patches are still parallel and co-linear. Or to describe them by their axles, the two axles aren't parallel and point different directions when viewed from above. Or they are parallel but the rear is offset to the side w.r.t. to the front. Or they aren't parallel and point in different directions when viewed from the rear.

Your situation sounds like the third case. The second case is what you detect with the string test. Theoretically the second case can be solved by customizing the wheel dish for it. In fact, for a spoke-challenged bike one could design a frame with more offset on the DS and build wheels with less dish to be stronger.

Those three case are nearly independent except for how people compensate. The third case would be totally independent of the other two if the DO slots were absolutely parallel to the ground. But they aren't, so if one end of the axle were a bit too far back it would also be a tiny bit too high. The first two cases are related by the fact that most people lock down the rear wheel by aligning it with the ST. If one DO is further from the bike's centerline than the other this results in the wheels not pointing in the same direction though the top of the wheel would be directly under the brake mounting bolt. An incorrectly dished wheel would result in the same thing, pointing the front of the wheel at the ST even though it "should be" offset to one side. But with an incorrectly dished wheel the top of the wheel will not line up with the brake mounting bolt because tweaking the direction the wheel is pointing won't reposition the top. With an incorrectly dished wheel, flipping the wheel over will make it offset to the other side. With offset DOs it will not.

I would image the third case is least likely to affect handling. So @gugie and @seedsbelize are correct - if it ain't obviously broke and you haven't noticed a problem all this time, then just ignore it.

If it rides straight and tracks true, the only issue is the rear brake is off center, which you can adjust for.

Yes, that's the case.

Also, the problem, such as it is, is not as bad as I had thought. It turns out that the dish in the wheel was off significantly--about a 3mm gap on one side of the dishing gauge. I was sure I remembered checking the dish when I trued the wheel a couple of years back, but not so. That is probably a function of my gradually improving memory. When I was younger, I could only remember things that had actually happened, but now I can even remember some things that didn't happen. Soon I will remember things that couldn't have happened--hunting elephants with Teddy Roosevelt out in our back field and things like that.

Anyway, once I tweaked the wheel and adjusted the dropout adjusters, about half of the disparity went away. Original spacing was about 20mm to the seatstay on one side and 30 on the other. Now it's 22.5 on one side and 26.5 on the other (I know those don't add upper perfectly--there's a stray millimeter in there somewhere.) That's still visible but a lot less bothersome.

I'm a little embarrassed to have to explain this after being so sure that wheel dish wasn't a factor. But a little embarrassment has its place from time to time. It keeps us humble.

Thanks for this great thread.

Without your error I wouldn't have learned "farpotshket", nor would I have understood that my memory, like yours, is getting better.

You probably did he work very quickly and consumed considerable energy, thus the millimeter of mass loss. Modern physics ftw!

My memory is improving but in the opposite direction. As I get older I can remember fewer things to forget, so I forget them at a much slower rate.

The important point is that we are both continuously improving. Kaizen!

This may not be entirely your fault. I've had rear wheels that I've built up seeminly de-dish themselves by a few mm after their first ride or two. I suspect I hadn't fully bedded the drive side spokes as I was tensioning / stress relieving the wheels. After a ride or two, the spoke heads bedded in a bit better, and effectively reduced their tension, allowing the wheel to move back over a bit.

Regarding your alignment problem, it's actually pretty common for the dropouts to be at slightly different heights. No problem centering a perfectly dished wheel between the chainstays, but the top will be off at the brake bridge. It's the one aspect of frame alignment that can't be fixed after the fact on an alignment table. (If the chainstays are slightly different lengths, you would never know it on a horizontal dropout.) That's one of the reasons no one really used vertical dropouts until the 80s. Production (and even most custom) frame building and alignment just wasn't precise enough to guarantee you wouldn't have the wheel way out of whack. It wasn't until the Japanese got their act together, and pressured everyone else to up their game that you would see vertical dropouts on production frames.

On one or two bikes that I cared about, I've actually gone through the trouble of heating the dropout / seatstay junction on the higher side to reflow the brass, and then tweaked the dropout back to where it should be. I would only consider this on a frame destined for re-paint, and I wouldn't try it on a chromed dropout / seatstay.

One last point -- you might want to consider re-dishing your wheel back to where it was. All that the bike cares about for purposes of riding no-hands is that your center of gravity is right in line with the contact patch of the front and rear wheels. With your wheel slightly off in the frame, a perfectly dished wheel will in effect put the tire in the same spot as a frame with a crooked rear triangle. You might find it doesn't ride no-hands quite as well now that you've "fixed" the wheel. Really, the point of a perfectly dished wheel is so that you can interchange it with any other, on a perfectly aligned frame. If the frame is off in ways you can't fix, you have to choose between easily interchangeable wheels, or a functionally mis-aligned frame. (It might not be enough to matter, but keep in mind that the goal is getting your body right between the wheels, not necessarily in having every component perfectly centered and aligned.)

I've done the same.

Sometimes I think we're twin brothers of different mothers. I've often thought that you could intentionally offset a frame's rear triangle and reduce dish for a stronger wheel. You'd have to accomodate chain line, and make sure the crank arm doesn't hit, but it would be an interesting design proposition.

Thanks Gugie, that's high praise coming from you. I like to think it comes from a unique combination of having a machine / fabrication shop, and a border-line pathological desire to "make it right". Sometimes it's even a good thing :-)

Kind works, thanks! It'll be great to meet you at Eroica, we can talk about some potential projects we can work on together.