TC1

As I said to the other individual, fine, let's pretend that calculation is off by 300%. It's not, but let's pretend for the sake of argument. Now it's 3 layers of paint, or 3 thin human hairs. Does that make this operation plausible with naked-eye measurements and crude hand tools? No, it doesn't -- not to the level of precision that is being claimed, anyway.

How did you set and align them? What tolerance are you able to hold? If such is not a trade secret, please share.

Kontact 

You're an odd fellow. So little experience with actually doing stuff, yet such strong opinions about matters related to doing stuff that no one else thinks about or cares about.

The point of squaring the dropouts is to serve the hub. Centering is a function of other parts of frame geometry. No one needs super accurate frame alignment, nor has anyone suggested this is necessary.

The point you keep ignoring, I will restate for you: Bending 425mm stays with the crude methods that we use does not result in a .25 degree change in the dropout from parallel. The actual number is unknown, variable, and usually great enough to benefit from dropout alignment. Which you'd realize if you had done this enough.


I agree with your strawman argument, though: One hair of misalignment is unimportant. Everyone agrees with that. No one is arguing with you about that. So you can stop bringing that up as if you are having an argument about that. You aren't.

FBinNY 

To clarify ----- what I thought I might have missed, and therefore the apology, was a post saying essentially the same as what I was contributing (?).

As for the acceptable tolerance, I explained my reasoning working from what Campagnolo said in their tech info back in the sixties, and the tool they provided for the job. So, IMO half a degree is probably fine and 1/4 22nddegree about the limit of what's achievable.

Also keep in mind that changes in hub design, probably make the entire system more forgiving than was the case 50 years ago.

FWIW, I consider most of this argument based on a 4mm change in width pointless. IMO, if you have the tools, skill, and desire, you might as well do the job. But, no big deal if you lack any of the 3.

TC1

You haven't the slightest idea about my experience, and you are the one who apparently eyeballs frames and believes that you are accomplishing a precise adjustment -- so you've revealed quite some about yours.

And much of the point is exactly that people are not thinking about what they are doing in this instance.

Then learn the correct terminology. If you are just making the dropouts parallel, without concern for their location, then you are not squaring the frame.


I did not ignore this point -- I specifically said that if it makes you happy, you can pretend that that calculation is off by 300%, and triple that value, but the point does not change.

I note with amusement that you completely ignored that remark.

So how many hairs are required before it does become important?

Kontact 

You are inexperienced with dropout tools - it doesn't sound like you have ever tried one, or even seen one before. How do you know how much the dropouts are off after spreading?

Quote where I said "squaring the frame". I said "squaring the dropouts", which refers to making them both parallel and directly across from each other - like the sides of a square, but not like the sides of a rhombus. Read.

Where did I say I "eyeball" frames? There's an alignment tool for dropout centering, and a separate tool for the dropouts themselves. But I guess you wouldn't know that, because of your inexperience?

Again, you have no idea how far the dropouts are off, because - instead of checking - you have a theory about how the stays bend. And your theory is simplistic and wrong. Because the dropouts are at the end of two stays each, and the chain and seat stays are very different in stiffness, the dropouts can end up slightly twisted and otherwise off far more than 300% of .25 degrees. And that's assuming that neither dropout was tweaked by the act of spreading itself, depending on the tool used.


You don't know what happens to the dropouts during spreading, because you haven't checked. You assume you know because you have a simplistic theory about what is happening. And you don't see the downsides to having dropouts well out of square - not just two hairs.

TC1

I have owned a dropout alignment tool, but it didn't do the job that was required, so I gave it to a friend who is less meticulous. I now use other tools, and metrology instruments.

Ironically, way back up top, before you started getting all defensive and arguing nonsensical points for no reason, you agreed with me:

When I inquired as to how you assure that your dropouts are squared to the frame, you said:

When pressed for a description of how that comparison to the frame tubes takes place, you had no reply -- seemingly because your method is that which most people use, taking a step back, closing one eye, and havin' a look at it.

Which is fine, but let's not pretend that such offers real precision. And your first sentence in that quote isn't correct, either, at least with respect to the precision that we are discussing. Of which you would be aware, had you the experience you are now claiming to have.

When did I say that I do not check them? I am simply realistic about what can be accomplished by the crude hand tools and eyeball measurements being discussed here. I'm also aware, as I mentioned a page or so ago, that most dropouts are not even manufactured to sufficient tolerances to make the operations that you are claiming, possible to the precision you claim.

Just for the record and all, I manufactured a couple (non-bicycle) parts for a friend two days ago, and my CNC rig held +/- .0012" on the critical dimensions ( roughly 1/5th of a hair ). In case you wanted to blather on some more about my experience, ya know.

What tools are you using to spread frames that cause you to routinely fubar them so completely? A proper tool that will not mangle your frame costs less than $5 to make, with parts available at any hardware store. Are you using that half-assed 2x4 method? If so, no wonder you have such problems.

Kontact 

To spread I use my hands. But we are speaking about all the techniques, not just your favorite one. There's no reason to be overly precise with one part of the process if it is followed up with a more precise step.

grumpus

Yeah but do you have "metrology instruments"? Do you even have a calibration certificate for your eyecrometer?

smd4

I don’t. I need to google it now.

Googled.

Oh.

smd4

We have to have our steam gauge certified. Afterwards we get a certificate of certification.

No joke.

well biked

I miss Sheldon. Would have been awesome to have him pop into this thread.

Kontact 

Leave it to someone in a specialized field to grossly overcomplicate something simple and well understood. If you have a hammer, everything looks like a nail...

TC1

No wonder your results are so poor. Scratch together $5 and make an appropriate tool that avoids winding up with a crookedly-bent rear triangle in the first place.

Also, you may want to consider the ramifications of my comment way above about the consistency of the thickness of cast dropouts. Specifically that such is insufficient to enable your ***-2 to measure what you are trying to use it to measure to the precision you are claiming. ( Edit: apparently this site does not allow mentioning the name of that particular Park Tool, so folks will have to use their imaginations. )

I can't really believe I just spent a dozen comments arguing about precision with someone who a) agreed with me initially, before deciding to have an argument about nothing and b) uses their hands to mangle a frame instead of simple, superior methods.

Kontact 

I don't get poor or inconsistent results. I am a superlative mechanic, craftsman, metalworker and electrician. There are all sorts of ways of manipulating steel frames, and I use my hands because they distribute force across a larger area and never marr the paint. It is also much faster than using two bending tools.

But, as I pointed out already, we aren't talking about what I do, but what everyone should do. Whether you use a jig, a lever, your hands, etc - you should check the dropouts with an alignment tool after you check the dropout centering (yes, the alignment tool or a taut string and calipers are sufficiently accurate), because you just applied a bunch of weird forces to complex metal shapes, and they don't always behave predictably.

So you make incremental changes to stays, stop when you are within a millimeter each side, then square the dropouts (which might not have started square in the first place). It takes less than five minutes with shop tools, maybe a few more with homemade dropout tools.


The important concepts in this discussion are Significant Digits and Tolerance Stacking. How close does each measure have to be, considering how a bicycle works; and how much does each alteration effect other measures? Steel bikes aren't made of rods, but tubes that don't just bend linearly but twist and interfere with each other. We cold set frames because of concern with putting the tubing under constant tension - but there is really no way to remove all of it because we can't measure how much the final position of the dropout is actually the result of opposing tensions between the seatstay and chainstay.

Given that complexity, you should check/correct your dropout alignment last, so your wheel goes in and out easily and your axle has a minimum of asymmetric forces acting on it. And if you see no point, why bother to cold set the frame at all? Like I said, if you do nothing at all it will be fine - Shimano originally planned for users to just cram the 130 wheel into the 126 frame.


As for you TC1, I don't think there is a single person on this thread that thinks whatever point you're making is sensible. You are simultaneously saying that all bike techniques are too crude measurement wise, yet insist that something you never measure is fine. Which is why no one agrees with you.

FBinNY 

Is this shtick? How long do you two intend to keep thr act going?

If it's not an act, one might fairly infer that each of you considers the other to be an ignoramus, (or worse). If you keep it up much longer you'll convince folks that you're both right.

Kontact 

Always making friends, eh? Are you passing on the love after getting told off in the oval HT thread?

I don't think TC1 is stupid, but I do think he has a forest for the trees problem.

FBinNY 

Yes, I've been known to poke a stick into a hornets' nest. However, it's not about who's right, but who's willing to let go and move on.

As for the other thread, I've been called worse, and am happy to let him stew in his own sauce.

Kontact 

I think the guy in the other thread knows what's going on much better than the responses he's gotten.

bboy314

Never let a bunch of real world experience get in the way of someone’s theory.

Trakhak

The common methods of spreading rear dropouts (or "fork ends," per Sheldon Brown's strongly expressed preference) were mentioned only once in this thread that I remember (those being the use of 2 x 4's, washers and nuts and a threaded rod. etc.).

Just dropping in to point out that, while the left and right dropouts often move equal distances from the frame's center line when a threaded rod is used, or when the mechanic just grabs and pulls the sides apart, equal movement is not guaranteed.

The advantage of the 2 x 4 method is that, if you begin with a frame whose alignment has been measured to be correct, you can bend one side at a time the correct distance. In the case of a 124-mm OLD being changed to 130 mm, that would be 3 mm per side, obviously.

Once you've moved each side 3 mm, all that's left to do is align the dropouts using the Campy H dropout tool or the Park equivalent and then reconfirm that the frame's alignment is still good.

Homebrew01

OK Kids, please stay on topic, and skip the "personal" remarks.

grumpus

You're the one telling a pro mechanic his methods are wrong, when they're SOP and "good enough". But the discussion got turned around and from "insignificantly small" fractional degree changes in alignment you're now arguing that the gauges we use aren't accurate enough. His Park Tool Frame Alignment Gauge No.2 is fine, it's quicker than my string but that is also fine, and the Campagnolo model H style end alignment gauges are sufficiently accurate and easy to use. Is it within a third of a degree? Who knows, who cares?
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grumpus

Tell me about it. I was replacing the rear ends on a frame, and when I took out the old pieces the seat stays sprang out a load, probably because the brake bridge was forced in. I slotted in the new pieces to check for fit and promptly forgot about the imbalance. When I was brazing it up I must have got the stays a bit too warm, because one of them cracked and released the spring tension - cue much ribbing from colleagues, and careful filing to make my mistake disappear.

grumpus

My 2x4 method is not your 2x4 method - I just put the two pieces inside the chainstays next to the dropouts and lever them against each other - if the ends are 6 inches above the stays and the pieces are 2 ft long I have 4x mechanical advantage. If the stays don't bend the same on each side I clamp the bottom bracket shell in the bench vise and push/pull them into alignment, but the 2x4 works well enough most of the time.

Trakhak

It's clear from your posts that you know what you're doing. Both methods work fine. The (admittedly fairly minor) reason I changed from your method to mine was that I liked not having to go back and rebend one or both sides if I could avoid it. Given a frame that starts out straight, I bend one side to 3 mm and then the other, I check the dropouts with the Campy H tool, and I'm done.