alanyu wrote: ↑Sun Jan 12, 2020 4:33 pm
Adrien wrote: ↑Sun Jan 12, 2020 9:44 am
alanyu wrote: ↑Sun Jan 12, 2020 12:56 am
I'd like to see a 2:1 design for rim brake like fulcrum (unequal spacing) to have a more balence left right tension and a better overall wheel performance.
We used the 2x/x spoke design in the 2009/2012 years. We went back to x/x design later.
What we found out so far is:
- reduced lateral stiffness when the left side flange is within the range of regular x/x design
- lateral stiffness can be pretty high when the left side flange is pushed very far from the center, but it does not exceed the x/x design
- 2x/x spoke design is a nightmare when a non drive side spoke failure occurs. The wheel is absolutely unusable because of the huge distance between 2 non drive side spokes
Because of these reasons, we prefered to stick with regular x/x design. Both for performance and safety/security reasons.
I disagree with your idea on rim brake hub.
A spoke failure on NDS can be a nightmare for 2:1 hub, but for a good designed wheel it can be greatly avoid if it's not an accident. For an accident where the spokes are broken by something, I don't think anything can be thought as safe. Many big brands are on the 2:1 triplet side for rim brake, including shimano, roval, fulcrum, campy, etc, whose quality and performance are both proved to be solid. Moreover, shimano's DA C24 is 1:1 2X:2X instead of 2X:0X, if the later is better why not? Why do they go to triplet for deeper rims?
As to super light hubs, extralite also released their sp rim brake hub with 2:1 triplet lancing long ago It was claimed, and also proved to be better than the old sp 1:1 2X:0X hub.
I have to agree with you on the spoke failure side: I don't remember seeing a broken spoke due to fatigue on our RARs. It has become extremely rare, probably 2 or 3 a year break suddenly for no apparent reason (less than 0,0001%). And I think large manufacturers are in the same case.
Fact is that a 12/12 - 24 spokes wheel will still be rideable with 1 less NDS spoke while the one with 16/8 won't.
Also in term of performance, I confirm we found out the 2:1 to come with no stiffness gain because the non drive side of the wheel actually has a huge impact on wheel stability due to its wider bracing angle. Dropping the number of spokes this side reduces wheel stiffness significantly unless you compensate with a super wide bracing angle. Then you get back the stiffness of a 12/12 design, no more.
It's merely a question of choice and marketing. We chose the safe side after trying 2:1 a few years, no bling bling.
Concerning the major brands, you have to keep in mind that, the 2:1 spoke pattern actually is easier/faster to build as long as the rim is super stiff.
That is due to 2 things.
First, the spoke tension is equal on both sides, depending on bracing angle choice of course.
Second, the NDS spokes, or non disc side for a front wheel, are so few that if one has a spoke tension out of average, the wheel is obligatory out of true. Take this sentence the other sense you can read: if the wheel is out of true, then a spoke has its tension out of range. And the culprit is super easy to find because of the huge space between the 7 (if 14/7) or 8 (if 16/8) spokes.
Finally, your remark about the Shimano C24 having 12/12 spokes is relevant.
I don't have the exact reply, but my bet is that it is a question of rim stiffness, as explain before, i.e. the C24 is not stiff enough to handle the 2:1 tensions, and torsionnal stiffness. I explain the torque stiffness assumption.
The shallow rim has very long spokes. Those long spokes always come with an important drop in wheel torsionnal stiffness because they can flex pretty much along their length. I remember removing the large teeth ring on Tune hubs in the past (those having the insane creaking sound), and we had to lock the ring tool in a vice, take the rim in hand and rotate it as a steering wheel. The amount of deflection of the deep wheels was far lower than the one of shallow wheels where you could see the rim taking an angle in relation to the hub. It was a direct translation of wheel torsionnal stiffness.
Back to the C24: because Shimano sells worldwide and have pro Tour guys, they beef up this "light" wheel using a 12/12 spoke design and a 2x/2x cross pattern. This must help to avoid many warranty cases for large or strong riders.
edit: edited many typos sorry
