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Old 02-02-07, 07:16 AM   #1
jonwvara 
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Four-cross valve hole problem

I recently built a four-cross back wheel for the first time--it's on an old but nice high-flange Campy hub that had originally been spoked four-cross. Using a new Mavic clincher rim, I built it just the way you'd build a three-cross wheel, except that I moved the crossing spokes over an extra two holes to get the fourth cross.
As in building a three-cross wheel, I started with the first drive-side spoke to the left of the valve hole. When I was done lacing the wheel, though, I noticed that instead of ending up between one of the nine pairs of nearly-parallel spokes on the wheel (it's a 36-spoke wheel), as on a three-cross wheel, it's offset by one hole, so it's between two spokes that converge as they move from the rim toward the hub.
"Bummer," said I to myself. "I'm going to have to take it all apart and relace it with everything shifted one hole clockwise to get the valve hole to come out in the right place."
But then when I started thinking about it--and believe me, I sat and stared at the wheel for a long time--I realized that you CAN'T shift one hole clockwise, because the spoke hole to the left of the valve hole is offset above the rim center line, and the spoke hole to the right of the valve hole is offset below the center line. So if you offset everything by one spoke, you'd be taking a spoke from the top flange (as you sit lacing the wheel on your lap) and threading it into one of the spokes below the center line, and that every spoke from then on would be in the wrong position relative to the rim. Of course, you could offset by TWO spokes, but that leaves the valve hole in the same position it it now, just on the other side of the two parallel spokes.
What the hell? I went back and looked at the old rim--a 70-'s vintage Mavic tubular rim--and noticed that the valve hole is in a different position: the spoke hole to the left is offset BELOW the center line and the spoke to the right is offset ABOVE it.
So it appears to me that if you four-cross a standard modern rim, configured so the spoke to the left of the valve hole comes off the top flange (I assume that's the current industry standard, because all the wheels on my other bikes are drilled that way, too) you've got to live with the valve stem in a less-than-ideal position. I think it's going to be possible to fit a pump head in there, but it still bugs me.
I guess this just caught me by surprise, and I'm wondering how others who build four-cross wheels deal with it. Can you order wheels with the valve hole correctly positioned for four-cross lacing, as it was on the old tubular rim? I'd never heard anything about that. I suppose I could cover the factory valve hole with a piece of tape and drill another one elsewhere, but that seems pretty half-assed. Or I could buy a new set of spokes and relace the wheel as a three-cross, but I don't really want to spend the 50 bucks on that either (I also bought spokes for the front wheel, which I haven't started on yet.)
Any experienced wheelbuilders have any comments or suggestions? I'm obviously not the sharpest tool in the shed in this area.
JV
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Old 02-02-07, 08:20 AM   #2
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You've made a mistake somewhere in the lacing procedure.

The first spoke which you seem to have placed correctly will be the same regardless of number of crosses. Okay, place that first spoke and complete this side - 9 spokes. Look at one spoke and sight across the hub, select hole to left and lace through this hole and place in rim to left of sighting spoke. Rotate hub so that the spokes adjacent to the valve hole slope away from it. Complete the wheel. My guide for lacing and building came from this book, I've done 2 and 3 cross no problem, plus half radial rears.
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Old 02-02-07, 10:38 AM   #3
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Four-cross valve hole problem

Quote:
Originally Posted by RayGreen3
You've made a mistake somewhere in the lacing procedure.

The first spoke which you seem to have placed correctly will be the same regardless of number of crosses. Okay, place that first spoke and complete this side - 9 spokes. Look at one spoke and sight across the hub, select hole to left and lace through this hole and place in rim to left of sighting spoke. Rotate hub so that the spokes adjacent to the valve hole slope away from it. Complete the wheel. My guide for lacing and building came from this book, I've done 2 and 3 cross no problem, plus half radial rears.
Yes, I know this works for 3-cross. Have you ever done a four-cross? I can orient the hub as you describe, but only if I run the spokes from the top flange to the rim holes that are below the centerl line of the rim, and vice-versa. Can that be right? It seems unlikely to me.
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Old 02-02-07, 12:47 PM   #4
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Most likely(and depending on how you build), you went the wrong direction when you installed the second set of spokes, or twisted the hub the wrong way for the build pattern.
The build method I use places the spokes in order and making either of these mistakes will cross over the valve hole.
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Old 02-02-07, 08:30 PM   #5
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Four-cross valve hole problem

As the originator of this thread, I'd like to cast a slightly wider net, because I think that neither of the responses so far addresses my fundamental question. Here's a request for anyone who has a 36-hole four-cross wheel in their possession on which the valve hole is in the correct position, between a pair of parallel spokes: When you look at the wheel with the valve stem hole in the 12 o'clock position, does the spoke to the immediate left of the valve hole come off the TOP flange (that is, the flange facing toward you) or the BOTTOM flange? It seems to me that in every case it would have to come off the bottom flange. If anyone reports otherwise, I would love to see a photo of the wheel to try to figure out how that's possible.
Is anyone from the classic and vintage forum looking in on this? Don't you have a four-cross wheel you'd be willing to look at and report back?
Thanks!
JV
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Old 02-02-07, 09:22 PM   #6
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I think your responses were more complicated than you needed. Your mistake was moving the spokes over 2 holes. You wanted to move it over 4. I have built many 4x wheels, and that is how I remembered to get the valve hole to line up.
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Old 02-02-07, 10:02 PM   #7
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I looked at several wheels including two I built today. The older ones often have the upper spoke left and lower spoke right, when the valve hole is a twelve. The newer ones tend to be opposite. Depends on the offset drilling in the rim. You have to accomodate the way the rim is drilled and it is easy to get backwards if you are used to doing one drilling and then do the opposite.
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Old 02-03-07, 05:00 AM   #8
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JV

Try this exercise...

1. Take a 3 cross wheel that is built with the correct valve orientation.
2. Look at the left spoke adjacent to the valve hole and trace its path back to the hub.
3. The only difference with a 4 cross wheel is that the spoke will enter the hub through the next counter-clockwise hub hole, nothing at the rim changes. Obviously the spoke will be longer.

Hope this helps.

The geometry of wheels really clicked when I read the previously mentioned book.
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Old 02-03-07, 06:25 AM   #9
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I just did the same thing with a 4 cross build. If you build it with the "key" spoke adjacent to the valve hole being a leading spoke rather than a trailing spoke it should correct the lacing.
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Old 02-04-07, 06:58 PM   #10
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Quote:
Originally Posted by dck
I just did the same thing with a 4 cross build. If you build it with the "key" spoke adjacent to the valve hole being a leading spoke rather than a trailing spoke it should correct the lacing.
DING! (sound of light bulb going on). Thanks, dck, your comment clears it all up. For what it's worth, my mistake was in exactly duplicating the original spoke position on the old hub--so the new spokes would lie in the original grooves--without allowing for the fact that the spoke-hole positions on the new rim were different, as I explained earlier. I'll have to live with the old grooves in the hub not matching the new spokes.
Thanks to everyone who took the time to respond.
JV
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Old 02-05-07, 06:16 AM   #11
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Quote:
Originally Posted by jonwvara
I'll have to live with the old grooves in the hub not matching the new spokes.
You should still be able to match up the existing grooves. Did you try the exercise I mentioned previously? Look at that 3 cross wheel and imagine rotating the hub counter-clockwise (with longer spokes). Similarly if you were to build it 2 cross then you would rotate it clockwise one hole pitch. Nothing is changing - rim or groove-wise.

This book shows you how to draw a wheel and demistifies the lacing procedure.

Ray
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Old 02-05-07, 11:53 AM   #12
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four-cross valve hole problem

Quote:
Originally Posted by RayGreen3
You should still be able to match up the existing grooves. Did you try the exercise I mentioned previously? Look at that 3 cross wheel and imagine rotating the hub counter-clockwise (with longer spokes). Similarly if you were to build it 2 cross then you would rotate it clockwise one hole pitch. Nothing is changing - rim or groove-wise.

This book shows you how to draw a wheel and demistifies the lacing procedure.

Ray
Yes, Ray, you're right. Things have clicked into focus for me. There's nothing like screwing something up the first time to really enjoy making sense of it later!
JV
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