Okay maybe I was getting the definition mixed up. (I'm used to seeing arguing as ending up messy, that's all)

In all truthfulness, I like your posts when they are educational. And I honestly thank you AND the others who have unknowingly taught me things here.

Disagreeing with people is not where you are going wrong Pete.
Different views are a good thing and should be voiced.

It's also obvious that you do know bikes.
That's not where you are going wrong either.

The part where you are going wrong is in the way you present your side and in how you present your self.
You don't debate, you attack the personality and the person rather than just the issue.
It's just as obvious as your above stated bike knowledge, that you have no respect for the other people around you and you actually seem to like putting them down to make your self look better.
It's obviously a respect issue, you have no respect for your fellow members on here.

I think you have a lot of good knowledge to share, but your delivery and your people skills both absolutely suck.
So does your ability to even make the attempt to see the other side of things.
That's where you are going wrong, that's what Siu Blue Wind and Pheard are both telling you.
And by the way, the elitest attitude sucks too.

You ladies done yet?

As for the OP, think about this. I've seen some old(er) school road headsets that used needle bearings top and bottom and had ultra low stack heights. They were threaded though, but depending on the design you might get away with just ditching the threaded locknut (further reducing stack height), and replacing it with a single thin 1 1/8" spacer or perhaps nothing at all.

It might not be the most durable or practical thing in the world, but then again, neither is the lefty:D

Oh my...you forgot the baling wire and scotch tape, heee hooo:D

Just do it right.

Was actually leaning toward duct tape.

So, just to recap - what I'm getting from all this is that grinding down the top or bottom of the head tube will not change the geometry? There's not too much available to reduce off the bottom (@ 2 mm before you'd hit the weld).

Here is the correct information:

1) DO NOT "grind" the headtube. Get the bike shop to use their facing tool to mill it down.

2) Removing material from the top of the headtube will make the headtube shorter

3) Removing material from the bottom of the headtube will steepen the effective head angle and make the headtube shorter.

Got it, gastro. Thanks!

ap: You're like the coolest mom ever. My mom doesn't know the diff. betw. an X-mart bike and a "y-mart" bike, hehe.

One last plea...check out ebay. I've done really well on ebay buying AND selling. You could sell the Carbon Lefty and get the adjustable one. There shouldn't be a terrible weight penalty, and the bike would be built right. It just scares me to think you would mill down the head tube to fit a fork that's not made for the bike.

I guess there's a bright side. It doesn't sound like your boy is too terribly aggressive, right? Just XC riding/racing? Maybe a few mm of head tube wouldn't matter. For me though...I'd be afraid that I'd end up snapping the head tube off or something catastrophic.

As Gastro said though...don't use a grinder. Use a "facing tool" to take it down.

I just got done doing a little "homework" on this end to show you exactly how this works..

AP is working on a Lefty fork.
Lefty fork has both an upper and lower clamp.
She is contemplating cutting the head tube to make room for a head set.

There is both an upper and lower clamp.
Head tube with headset essentially needs to be shorter to fit.
Cutting the top side will allow the frame's head tube to sit that little bit higher between the 2 clamps or crowns. Gets more slack of an angle.
Maybe 1/4 degree difference or so, but still a slight change none the less.
Cutting the bottom in the 2 clamp systems such as your lefty will make room, but will not change head angle.

Now on a single clamp or crown fork, just the opposite is true because it's lined up with the lower and not the upper.
Therefore when cutting the top side of a single crown or clamp fork, nothing happens but a shorter overall headtube/stack height.
But when cutting the bottom side on a single crown fork, the frame lowers on the fork slightly and thus, affects head angle slightly, Lowering the front end makes it more steep.
Again, only a slight difference, but still a difference.

The fork height does not change.
The headset bearings will obviously sit at the max height that they can or she would not be looking at cutting the frame.
So it's back to cutting the head tube down to make it fit the given space.
The head tube is going to be as high up in the fork as possible as there is no room for anything different.

So this boils down to cutting materiel off the top and effectively raising the frame head tube that 1/4" or so, or cutting the materiel off of the bottom and leaving the top of the frame at the same height it was.
I drew a quick picture and attached it. I know I'm not an artist, but it does show what I'm explaining on how it will effect head angle slightly.

Now look at above picture. (I know I'm no artist) Click on it, it gets larger to see better.

What will happen when you cut the top of the head tube on the dual clamp type and have to leave the top clamp where it sits? Frame and lower clamp go up and thus change head angle.
The Lefty fork will work on this same principal

What will happen on a single clamp (or crown) equipped bike when you cut the bottom of the head tube and have to leave the lower clamp where it sits? Frame goes down and sharpens head angle.

It's really not that hard to fathom.
Other people really can get things right even when you can not, PETE.

I've done exactly this a few years ago on a 98 FSR frame that we put a 7" Risse Trixxxy fork and 3" tires on. We had to to make the clearance for the larger tires as it would BARELY accept a 2.35", and so I did the cutting with the fore mentioned facing tool (look back on page 1 where I said to use this)
The Kevin Risse rear linkage and shock choice gave us 6.5" in the rear and I cut most of the materiel off the top of the head tube (3/8" to be exact) and was able to get almost a half degree more slack at the head tube because of this.

Now go attack someone who won't take the time to prove their point.

PS
Is there a spell checker on this forum some where?
I could really use that.

I, for one, and presumably others who consider accurate information to be a valuable asset and people who spew poorly thought out speculation compunded by incorrect terminolgy to be a hindrance.

Your fears are unfounded. Shortening the head tube would only make that junction stronger.

So it's bad for a person to gain some experience and share in that experience because they did not swallow the same dictionary as some one else?
That's interesting.

And so what if he is a poser. It really doesn't hurt to just considder the source and move on to a more experienced member.
How do you suppose those more experienced members got their experience?
At least Pheard has enough interest in bikes to want to be on here.
Last I checked, there is not an entrance exam.

As for the poorly thought out speculation compounded by incorrect terminology part.
I'm assuming that part's about me since I seem to be taking the brunt on this one.
That's OK though.
I know my qualifications and experience, and afterall, experience really IS the best teacher.
That's what I speak from, experience.

You want to know where that experience comes from?
I'll tell you anyway.

My Mom was an AMA race official at the old Holiday Hills motocross track in spokane many years ago.
I was born into it.
Got my first mini bike for my 5th birthday and have been racing since I was 8.

I took a 4 year break from racing and just rode when ever I had the chance when in the Army, and took up mountain bikes when I got out. Army was in 84 through 88.
That's 19 years now on the mountain bikes and in that time, I started in beginner class like everyone else and promply moved up to sport that same year. I did work up to Expert 18 to 34 age group for Norba races (at that time) and raced semi pro in the non norba Wild Rockies series. Of course, now I'm in an older age group and that's good.
All the while, I was my own mechanic as I could afford the parts, but labor was normally another story at that time.
Now I've got over 30 years of working on bikes, both motorized and nonmotorized.
I didn't go to school for this, I learned from the school of hard knocks and messed up parts.

Now several years later and still riding and working on my own stuff, but out of the love of working on it now, rather than the financial reasons in the beginning, I moved my company to the bike industry along with the snowmobile parts that I've been building and selling.
Experience really is the best teacher.

Please don't get all butt-hurt again, Darin.

I agree that experience can be a valuable teacher - I have a bit of experience myself, although I will spare you the boring and irrelevant details.

Suffice it to say that without the ability to effectively communicate with others, any experience and/or derived knowledge is absolutely worthless.

P.S. despite your formidable resume, defending Phred will not help your credibility amongst the cognoscenti on this forum.

Add me to the list of people that know this is not true.

The top of the head tube is being cut to fit inside the top and bottom crowns. The frame position does not change. The distance between the lower clamp and the ground has not changed. The lower clamp on this lefty is fixed to the fork, so if the lower clamp goes up as you say, then the front wheel is magically levitating off the ground.

Experience is a great teacher, but successfully completing high school geometry can be helpful too.

I miss meme.

OK.
Here's another picture.

C= Max height as defined by the bottom of the upper clamp of the fork.
The top of the head tube/headset bearing can not go above point C for the obvious reasons.

A= Head tube/headset bearing stack height.
B= Allotted space as defined by the 2 clamps on the fork.

Point C on the head tube will not rise above point C on the fork.
This is your fixed point of reference.

To make dimention A the same size of dimention B you must subtract or cut materiel in this case.
By cutting the lower part of the head tube, there is no change in head angle.

Now here is the important part that I think you are missing.
By cutting the top of the head tube you are making point C on the head tube lower than point C on the fork by the exact ammount as the difference in dimention A and Dimention B.

The frame did not move yet.
It still sits too low in the bottom and now also in the top.
So we move the frame up to the level of the opening in-between the 2 crowns and hopefully measured out acurately.

The fork height stayed the same, but we took some materiel off of the top of the head tube.
We had to make the Point C on each the head tube and on the fork match again, so we lift the frame up into position.
It does, in fact, have an effect on head angle.

And PS
I'm not butt hurt Gastro, no need to worry about that.
This has actually turned out to be an interesting debate.
I'm just thinking that it needs to stay to just the issue.

I also don't really care one way or another about F3 or what ever his name will be this week.
He will, in time, either show that he's a good contributing member, or not.
That's up to him, and not mine to judge

Good point. Just stay away from the weld, eh?:D

That's what I was going to say...the fork that apclassic9 is installing has a fixed lower crown, so there's no way to slide the tube up/down in the crowns.

The lower crown in this case will not move.
That is the whole reason for AP having to cut head tube.
The upper crown is obviously maxxed out too.
The stack height needs to fit in-between.

No magically levitating, just cutting metal to make it fit.
All I'm saying is that the location of where the cut is made can have an effect, and that effect can, in fact be controlled by making the cut on the bottom side or by splitting the ammount of materiel by making 2 smaller cuts, 1 on top and bottom.
This way, the geometry can be slightly manipulated.
Cutting the bottom of the frame head tube just moves the lowest point on the stack to where it fits.
Cutting the materiel from the top of the head tube effectively lowers the top point on the stack in relation to the rest of the frame.

When re-assembling the bike, there will be a slight difference in head angle if the cut is made on the top side of the head tube.

You were good right up to the point you started typing this.^ I am glad you acknowledged that the axle to crown height of the fork is fixed. Let's use the crown race (which rests atop the lower crown) as a fixed point of reference.

Now visualize if you will a bike sitting at rest. If you remove material from the bottom of the head tube the attitude of the frame will rotate forward around the rear axle. This will reduce the absolute height of the bottom of the head tube from the ground, shorten the wheelbase, and steepen the head angle. Got it?

Now visualize removing material from the top of the head tube. What will happen to the absolute height of the bottom of the head tube/crown race from the ground? That's right, absolutely nothing. Which, not coincidentally, is the exact amount of head angle change you will see.

<fingers crossed that you will get it this time around>

edited for clarity

Fixed crown height, single crown fork, you are right.
Cutting the bottom will sharpen head angle.

It really depends on your point of reference as to where the frame moves.
Starting with the top of the frame lined up with the bottom of the top crown, there is X head angle.
Cutting the top off the frame, you need to lift the frame to make that top line up with the bottom of the upper crown again.

The same is true if using the starting point of the bottom of the crown as you just stated.
The bottom of the head tube/stack is the same as the top of the bottom crown and you have Y head angle.
Cutting the bottom changes the point of referance on the frame and so you have a sharper head angle.

In reading your post 1 thing did occur to me.
That is that we are starting from different reference points.
I'm starting from everything lined up at the top side and you are starting with everything lined up at the bottom side.
This difference will make the opposite true or untrue to each depending on where you start from and make 2 (or more) grown adults debate pretty harshly when saying the same things with in the same principals.

Think about it.
What was the original head angle and at what height?
We don't know as the bike wasn't assembled yet. The difference is going to be approximately 1/4" to 3/8" and so the angle is going to be altered very little.
Little enough that it will probably never be noticed. A different brand fork with the same travel will have a different height difference than what we are talking about.
So which starting point is correct?

As being a DH rider, I've normally set up as slack as possible making my starting points at the bottom of the upper clamp and lining the head and all up to there.
In "our world" for lack of a better term, this is the propper set up and starting point.
We would line up to the top side and then cut the top to make it more slack by most available means.

As an XC rider (I'm assuming here, so please correct me if I'm wrong) you've ridden the single crowns primarily, and so your starting point is always fixed at the lower crown.
There fore you would want to start at the lower end and either cut the top in that senerio to not effect head angle, or possible cut the bottom to make it more steep for tighter cornering etc.

In short, I'm wondering if we are hammering at the same point, but from litterally opposite ends of the Stack height.

I do know that either starting point does validate my original point that cutting head tube can and will effect head angle. That is what started this and so Thank you, you actually validated my original point, but from the other end.

Fingers also crossed that we can put this to bed now.

Yes, moving the triple clamps up and down on the fork tubes is the best way to change or tune head angle.
This technique has been around since before either of us was born.

The possibility of a different point of refference is the one mechanical block that you have on this.
The other block is that you are now trying to argue simply for the sake of arguing, I think you like it.

Starting with the opposite point of refference actually does make the same theory work in reverse.
Fork height will not change with this, so we either move the frame upwards and cut off the top, or move the frame downwards and cut off the bottom, depending on where we start from, if we are just trying to show that it can be done..
The frame can't hang below the lower crown just as it can not rise above the upper.
Either way, it has to fit in the given area and it will be cut or a smaller headset will be located.
Given that we are discussing a 1/4 or so inch difference, this really is just academic.

It would seem to me if you mill the head tube at the bottom, it would change the effective head tube angle, because it's relationship to the fork crown race has changed.

However if you milled the top of the head tube, no geometry changes take place, except stem height.

I've learned that bearded surveyors know their geometry.

http://www.developindianola.com/imag...yor%5B1%5D.gif

This is the perfect explination Pete.^^

Now lets take this 1 step further and I think you will see where I've been coming from on this, and hopefully we can put this to rest.

Visualize the same bike, but with a triple clamp fork.
Now cut some materiel off the top of the head tube, then loosen the clamp bolts on the lower clamp and slide them upwards until the head tube sits where it should in relation to the top triple clamp as we did not move it.
Obviously there is more to it than just this. Cutting the top of the steerer tube or spacing the stem, etc, but it shows the same theory at work.

When we slid the lower triple clamp upwards, what did it do th the frame?
It rotated around the rear axel in an upward direction.
The only difference is that I started from the upper starting point as that is normally where I've set up my forks with the triple clamps, as slack as possible, and thus, the top side is the chosen starting point my general use.

There fore, Gastro did actually validate my original point with his description here by making a visual of the theory at hand.

It had nothing to do with your picture, rather what I carry around in my head :)

I actually hope I am wrong on your motivation.