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3-cross verses 2-cross: all the pros & cons

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3-cross verses 2-cross: all the pros & cons

Old 08-27-05, 10:50 PM
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531Aussie
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I'm thinking of getting my next rear wheel 2-cross to give me a stiffer wheel.

Apart from possibly being too stiff, what are the drawbacks of a 2-cross rear?

most likely 32 hole
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Old 08-28-05, 04:53 AM
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I doubt you'll notice much difference in any regard.

Honestly, now, aren't you really considering 2 cross just to be different?
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Old 08-28-05, 08:39 AM
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If you want something different try a Crow Foot lacing.
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Old 08-28-05, 09:44 AM
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Originally Posted by Retro Grouch
Honestly, now, aren't you really considering 2 cross just to be different?
No. What the hell are you talking about?

I built up a 3-cross 28 hole Mavic CXP30 rear, and it doesn't feel as stiff as my 32 hole CXP30s, so I'm thinking of rebuilding it as 2-cross in the hope that it will stiffen up.

I bought the 28 hole rim instead of a 32 because it was dirt cheap.
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Old 08-28-05, 12:27 PM
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Correct me if I'm wrong (woudn't be the first time..) but aren't MORE crosses supposed to provide a stiffer wheel?
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Old 08-28-05, 01:31 PM
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Originally Posted by 531Aussie
No. What the hell are you talking about?

I built up a 3-cross 28 hole Mavic CXP30 rear, and it doesn't feel as stiff as my 32 hole CXP30s, so I'm thinking of rebuilding it as 2-cross in the hope that it will stiffen up.

I bought the 28 hole rim instead of a 32 because it was dirt cheap.
Yes, You are right (and wrong thinking).
A 2-cross wheel are stiffer because the loss of slack, but it can give you broken spokes.
When you add cosses you will get a longer spoke. That will give you a more flexible spoke who will take care of the slack. The same result will you get with a reduced spoke.

I think you will have to check the spoke tension. A 28-spoke wheel should not be more instable than a 32-spoke.
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Old 08-28-05, 10:37 PM
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"I built up a 3-cross 28 hole Mavic CXP30 rear, and it doesn't feel as stiff as my 32 hole CXP30s, so I'm thinking of rebuilding it as 2-cross in the hope that it will stiffen up."

"Correct me if I'm wrong (woudn't be the first time..) but aren't MORE crosses supposed to provide a stiffer wheel?"

Well... the reason you have crosses at all is to angle spoke more tangentially to the flange. This allows it to transmit torque/twisting forces from the hub to the rim without winding up the spokes. Under torque from the hub, 1/2 the spokes increase in tension and the other 1/2 decrease in tension ever so slightly. The pull on the spokes then spins the rim. If you were to lace the rear radially, then there's a lot of flexing and winding up of the spokes under torque. So while a radial wheel may be stiffest in vertical loading, it's the softest under torque and twisting. That's why I like crow-feet lacing, the best of both worlds!

But the difference between 2x vs. 3x is probably way to small to be noticed. What 531Aussie is feeling as the differnece between the two wheels as far as "stiffness" goes can be attributed to more significant factors other than spoke-crossings (in order of importance):

1. spoke-tension, have you verified that both wheels are tensioned identically with a spoke-tensiometer?

2. tyre-pressure (same tyre, same pressures on both wheels?)

3. hubs, flange-width and height. Wider flanges give the rim more lateral support and will feel stiffer when leaned over. Taller flanges also increase the angle of the spokes, giving more lateral support as well. I can definitely tell the difference between my road wheels with small-flange hubs vs. my track wheels with large-flange hubs.

4. 28-spokes vs. 32-spokes. For the same tension, more spokes will make for a stiffer wheel, in vertical AND lateral directions

5. spoke gauges used? Double-butted spokes will have more springiness and feel more "soft". But they will hold the wheel true for longer as they have stretch more under the same tension. Thus they can face more compression before losing all tension. It's the loose-spokes at the bottom resting on the ground that lose tension. If they relax completely, the nipples can rattle around and work themselves free and cause the wheel to go out of true.
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Old 08-28-05, 10:51 PM
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http://www.geocities.com/spokeanwheel/lacinggw.htm


i found this website to be helpful.
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Old 08-28-05, 11:02 PM
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thanks for the replies.

Same hubs (Ultegra 9 speed), same rim, same tyres, same pressure, same spokes: 'straight' DTs

the only difference is the 28 vs 32.

I considered the spoke tension, but aren't the spokes "longer" in the 28 hole? I just measured the distance between the rim and the hub holes to be about 3.5mm longer on the 28 verses the 32. So, I thought this would make more difference than a slight tension variance. My thinking was that shortening this distance with a 2-cross pattern would reduce the flex.

Last edited by 531Aussie; 08-28-05 at 11:08 PM.
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Old 08-29-05, 12:17 AM
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Actual tension on the spokes makes the biggest difference in the stiffness "feel" of the wheel. You really should check and verify that both wheels are tensioned identically.

The elongation of the spoke under that same tension is a different measurement altogether. Hang 100kg from a spoke and 100kg from a rubberband and they will stretch different amounts, but the tension will be the same 100kg. On the difference in spoke-lengths, 3.5mm is just over 1% difference in length, not significant. Considering that the modulus of elasticity of stainless-steel under tension is about 190 Gpa (28,000,000psi), the actual amount that the spokes of either length stretches is insignificant. The tyre deformation is easily 1000x more than the spoke-stretch.

I suspect it's the spoke tension. For example, an nicely tensioned wheel near the upper limit will have a lateral deflection of about 5mm when a 50kg load is applied sideways at the rim. A wheel with barely enough tension to hold the rim true and round will have a lateral deflection of over 60mm. No other wheel-building factor has such a significant contribution to wheel stiffness in the lateral direction. If you're talking about vertical stiffness that you can actually feel, then the spokes are definitely way too loose because the differences in vertical stiffness isn't as pronounced as with lateral stiffness.

Last edited by DannoXYZ; 08-29-05 at 01:26 AM.
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Old 08-29-05, 12:29 AM
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Originally Posted by DannoXYZ
Actual tension on the spokes makes the biggest difference in the stiffness "feel" of the wheel. You really should check and verify that both wheels are tensioned identically.

The elongation of the spoke under that same tension is a different measurement altogether. Hang 100kg from a spoke and 100kg from a rubberband and they will stretch different amounts, but the tension will be the same 100kg. On the difference in spoke-lengths, 3.5mm is just over 1% difference in length, not significant. Considering that the modulus of elasticity stainless-steel under tension is about 190 Gpa (28,000,000psi), the actual amount that the spokes of either length stretches is insignificant. The tyre deformation is easily 1000x more than the spoke-stretch.

I suspect it's the spoke tension. For example, an nicely tensioned wheel near the upper limit will have a lateral deflection of about 5mm when a 50kg load is applied sideways at the rim. A wheel with barely enough tension to hold the rim true and round will have a lateral deflection of over 60mm. No other wheel-building factor has such a significant contribution to wheel stiffness in the lateral direction. If you're talking about vertical stiffness that you can actually feel, then the spokes are definitely way too loose because the differences in vertical stiffness isn't as pronounced as with lateral stiffness.
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Old 08-29-05, 02:38 AM
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Originally Posted by DannoXYZ
Actual tension on the spokes makes the biggest difference in the stiffness "feel" of the wheel. You really should check and verify that both wheels are tensioned identically.
.
thanks again. My LBS is good enough to occasionally lend me their DT 'Tensiometer'.
DO you know what figures I should be seeing on the DT meter with the 28 hole, 30mm deep rim?

I think the last time I checked a rear wheel with the DT meter, the tighter spokes on the drive side were around 2.3 (red or black numbers on the DT gauge....can't remember). I'll get it tomorrow
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Old 08-29-05, 08:31 AM
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You might consider double crossing the non-drive side, and triple crossing the drive side. This will help even out the tension between the two sides, and build a stronger wheel. But, as others have pointed out, the difference in crossings/spoke lengths we're talking about is pretty small, not something you're likely to feel.

One thing that makes a rear wheel feel less stiff is when there's not enough tension in the non-drive side spokes.
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Old 08-29-05, 09:44 AM
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Originally Posted by 531Aussie
thanks again. My LBS is good enough to occasionally lend me their DT 'Tensiometer'.
DO you know what figures I should be seeing on the DT meter with the 28 hole, 30mm deep rim?

I think the last time I checked a rear wheel with the DT meter, the tighter spokes on the drive side were around 2.3 (red or black numbers on the DT gauge....can't remember). I'll get it tomorrow
Park has a spreadsheet tool that may be useful.
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Old 08-29-05, 10:51 AM
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thanks.

One of my old rear wheels has 2-cross on the left and 3-cross on the right -- i might do that.
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Old 08-29-05, 01:51 PM
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You should be able to tell by feel whether the spoke tension is similar between the two wheels by feel -- i.e., squeezing two nearby spokes together. Not as accurate as a spoke tension gauge, but it should be enough to ballpark it.
Certainly Sheldon Brown doesn't think that spoke length itself will contribute to a soft or harsh ride.

The thing I'd be concerned with on a 2x rear wheel is the increased likelihood of breaking the hub flange. But I'm a over 190lbs, so I worry about that sort of thing.
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Old 08-29-05, 03:07 PM
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Originally Posted by 531Aussie
thanks again. My LBS is good enough to occasionally lend me their DT 'Tensiometer'.
DO you know what figures I should be seeing on the DT meter with the 28 hole, 30mm deep rim?

I think the last time I checked a rear wheel with the DT meter, the tighter spokes on the drive side were around 2.3 (red or black numbers on the DT gauge....can't remember). I'll get it tomorrow
The various tensiometers have their own units. They usually come with a conversion table to calculate actual spoke tension. You want about 100kg of tension per spoke on average. Obviously the rear wheel will have lower tension on the non-drive side.

But what I would do is measure the spoke-tension on your previous 32-hole rim first, then measure the spoke-tension on your new 28-hole rim. Are they identical?

if not, I would re-tension the 28-hole rim to be the saem as the 32-hole one and then compare their riding stiffness characteristics.
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Old 08-29-05, 08:44 PM
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will do
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