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Old 05-27-08, 11:18 PM   #1
bcody
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4 cross spoke pattern?

I'm having a wheel set built and I asked for a 3 cross pattern, but then the builder said he'd do a "4 cross pattern since the wheels will be used for loaded touring." The wheel set is being built with Shimano 105 hubs, Alex Adventurer rims, and double butted spoke. The wheels are 700c and 36 spokes.

From searching the forums I gather that the 4 cross pattern is better for disc brakes because of the high torque they create. But what about for rim (cantilever) brakes, that I will be using?

Are there any advantages or disadvantages to the 4 cross pattern? Which one should I go with?

Some people in the forums seem to thing that the 4 cross pattern can create problems. What do you think?

The wheels will be put on a vintage Nishiki Riviera frame.

Thanks.

Last edited by bcody; 05-28-08 at 06:23 AM.
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Old 05-27-08, 11:38 PM   #2
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Wheels

My 26" wheels are built with 4X method using PW 48 hole hubs and Rhyno-Lite rims.

The wheels are heavy (lets face it - 48 spokes/nipples are a LOT heavier than a 32 spoke version). They are strong. In my across outback trip (Cairns to Darwin) I never had a problem with wheel strength. Even when my RD disintegrated and went into the rear wheel breaking spokes, the wheel was still pretty good.

Heavy.. No problems with "rim brakes"
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Old 05-27-08, 11:52 PM   #3
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From what I have read, spoke pattern has almost no effect on the vertical stiffness and strength of the wheel (less than 5% difference between 3 cross and radial).

Based on this analysis: http://www.astounding.org.uk/ian/wheel/patterns.html

Where it matters is in torsional stiffness. For a touring bike, the main load is vertical load, so lacing pattern shouldn't affect things much. Having more spokes of course makes the wheel stronger.
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Old 05-28-08, 12:43 AM   #4
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From what I have read, spoke pattern has almost no effect on the vertical stiffness and strength of the wheel (less than 5% difference between 3 cross and radial).

Based on this analysis: http://www.astounding.org.uk/ian/wheel/patterns.html

Where it matters is in torsional stiffness. For a touring bike, the main load is vertical load, so lacing pattern shouldn't affect things much. Having more spokes of course makes the wheel stronger.
I'm by no means an expert but I've read the same thing. One note on radial lacing, it should be front wheel only on bikes that do not have disc brakes because they don't transmit torque (be it pedalling or braking with disc brakes) very well.
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Old 05-28-08, 02:17 AM   #5
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Stiffness per se may not be as important as strength and durability. The more crosses, the more the load (stress, not deflection) on the wheel is spread out to different spokes -- that is, the wheel is more 'pliable' and resilient.

I have no quantitative data, though.

Last edited by Pedaleur; 05-28-08 at 02:31 AM.
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Old 05-28-08, 02:31 AM   #6
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While qualitatively similar to other models, I would question the author's abilities on the grounds that there is an obvious flaw in his modelling.

Anyone?
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Old 05-28-08, 07:12 AM   #7
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Sheldon Brown writes this:

"Most wheels are built cross 3. Higher cross numbers cause the spokes to leave the hub flange more nearly at a tangent. This makes them better able to withstand the twisting forces of hard pedaling in low gears, and also braking forces in the case of hub brakes. "

http://www.sheldonbrown.com/wheelbuild.html

"[H]ard pedaling in low gears" sounds like climbing a hill with a loaded touring bike -- I'd go for the 4-cross pattern.
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Old 05-28-08, 07:10 PM   #8
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For a touring bike, the main load is vertical load, so lacing pattern shouldn't affect things much.
This statement is incorrect. A touring bike sees significant torsion loads, above and beyond those experienced by an unloaded bike, due to leverage exerted by panniers mounted at a distance from the bicycle's centerline. More spokes, and to a lesser extent the spoking pattern, affect a wheel's lateral stiffness much more than they do its vertical stiffness. If the main load on a touring bike wheel were vertical, you could tour quite happily on Ksyriums.

I built my touring bike wheels myself: 26", 36 hole, 4-cross. Is it any stronger than 3-cross? Probably a small amount. But if I ever break a spoke, there's a good chance I'm going to have to loosen one or two more to get the broken one out. Things wouldn't be quite as tight with 700c 36h, but 4-cross is probably best left for 40h or greater wheels

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Old 05-28-08, 11:20 PM   #9
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I used 4X lacing with large flange hubs on my track bike when I competed. I tied and soldered the spokes for added strength. That was the only way I wouldn't break spokes. That was back in the 1960's when ss spoke technology was not very good.
8 years ago I laced up a set of 36H SF Campy hubs using 4X for a cross bike and have had no problems. I have ridden on a lot of dirt and haven't broken any spokes. The only problem is that the head-in spokes tend to rub across the head-out spoke ever so slightly. Some site that as a disadvantage but, so far I have had no problems. I think that it is a toss up between 3X or 4X lacing. It is a little easier on the pulling spokes as the spokes meet the hub at a better angle.
In any case, one needs to think about the loads on the wheels when touring a fully loaded bike and rider.
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Old 05-29-08, 12:26 AM   #10
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just in reference to the last post, for large flange hubs i (and others) recommend, in general, fewer crosses. This allows a more moderate angle of incidence between the spoke nipple, eyelet, and spoke bed. ie, the spoke is allowed to create a less radically acute angle where it meets the rim.

I've built many mountain bike wheels, nearly all for disk equipped bikes, and i've always gone 3x. 4x requires longer spokes, and makes for a more jumbled looking wheel. i've found it harder to replace spokes on 4x wheels. i guess the decision is up to you, is the theoretical structural strength gain worth the longer (heavier) spokes and marginally more complex build?
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Old 05-29-08, 01:55 PM   #11
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I ended up going with a 3 cross pattern for both wheels. It seems like people think that there isn't much advantage to a 4 cross pattern. Furthermore, the heads of spokes could overlap in a 4 cross, and thus make changing a broken spoke more complicated. Not to mention that I'm not sure whether the Shimano 105 hubs have a high enough flange for a 4 cross pattern.

Thanks for all of the input. What would I do without this forum?
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Old 05-29-08, 06:30 PM   #12
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Originally Posted by Thasiet View Post
This statement is incorrect. A touring bike sees significant torsion loads, above and beyond those experienced by an unloaded bike, due to leverage exerted by panniers mounted at a distance from the bicycle's centerline. More spokes, and to a lesser extent the spoking pattern, affect a wheel's lateral stiffness much more than they do its vertical stiffness. If the main load on a touring bike wheel were vertical, you could tour quite happily on Ksyriums.
The only way that the distance of your panniers from the bicycle centre of gravity could affect wheel torsion would be if you were braking hard with disc brakes. In that case, the height of the centre of gravity of the panniers above the bicycle centre of gravity would add extra torque to the front spokes and be countered by the torque at the disc brake. Other than that, the only effect on wheel torque will be the straight addition of mass (irrelevant of the distance from the centre of gravity) which means you need to pedal harder to accelerate.

The "leverage" effect that you talk about cannot apply any torque to the wheel. The torque you refer to in that case is taken by the bicycle frame, which rests on the two wheel axles. The mass of you and the bicycle creates the opposing torque (like a see-saw) that is holding your panniers up. The axles cannot transmit any torque to the wheels, only the drive train can, and it should be obvious that your panniers are not being held up by your drive train.

If you need further proof, put your panniers on, and lift up each wheel. You will see that they are free to spin; the panniers mass is still there, applying the same leverage as always, but there is no torque being applied to those wheels.

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Old 05-29-08, 08:23 PM   #13
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Dan, the torsion loads I refer to are exerted in the direction the wheel's axle _points_, i.e., lateral. Your rebuttal describes torsion in the direction the wheel turns. I could have been more clear; a wheel sees torsion loads from multiple directions. Your first statement about vertical loads nevertheless remains incorrect. The most relevant forces that act on a touring bike wheel are neither vertical, nor torsion coming from the drivetrain, but instead are torsional loads that apply laterally. All bicycle wheels are more than strong enough vertically. The vertical strength of any spoked bike wheel is actually a significant fraction of the strength it would have were it made of a solid disc of steel. It is quite possible to run a bike straight into a wall at high speed, destroy the frame, and have have the front wheel come out undamaged. Thus, even embarrassingly low spoke count wheels have more than ample vertical strength to handle a fully loaded touring bike, but what they do not have is sufficient lateral strength to withstand the torsion that is applied by heavy panniers acting as powerful levers to bend the rim towards either side's stay cluster/fork blade. A wheel is made stronger against this kind of torsion by adding more spokes. Per the original topic, the spoking pattern strengthens a wheel not against these lateral torsion loads, but against the kind of torque which, as you describe, goes with the direction of rotation. Thus, a 4x wheel would not bear weight in panniers any better than a 3x wheel would. The 4x wheel would, however, better withstand the large amounts of torque applied by a lowest-gear mash up a steep hill, and by hard disc braking.
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