Disc wheels - J-Bend vs Straight Pull

[jever98]

Hi folks,

again a topic that the search function doesn't like to help with :-/, so sorry if discussed before:

For disc wheels, J-bend versions of hubs (e.g., Carbon-Ti, Dt Swiss, etc) tend to have a bigger flange diameter in the J-bend version. E.g., on the Carbonti it's 48mm / 43.5mm for the straight pull version and 54.5mm for the J-bend version. A wheelbuilder said to me he prefers to use J-bend spokes in stead of straight pull for this reason, to achieve better results (lower torsion).

What's your feedback? Agree / disagree?

Thanks!

[alcatraz]

I imagine the torsional advantage of the larger diameter flange can't be that big. On road wheels the spokes are quite long and would need a _really_ big flange to noticeably change the braking characteristics.

Straight pull has the advantage of being less fatigue sensitive at the head so probably they can be run at higher tensions which I think would improve torsional strength even better.

Also wouldn't a 3x lacing pattern be more efficient than 2x in this regard? Just change the lacing pattern if you need more torsional strength.

/a

(I am a newbie to wheelbuilding. Just built two wheelsets so far and none of them were disc brake wheels.)

[WinterRider]

Hi folks,

again a topic that the search function doesn't like to help with :-/, so sorry if discussed before:

For disc wheels, J-bend versions of hubs (e.g., Carbon-Ti, Dt Swiss, etc) tend to have a bigger flange diameter in the J-bend version. E.g., on the Carbonti it's 48mm / 43.5mm for the straight pull version and 54.5mm for the J-bend version. A wheelbuilder said to me he prefers to use J-bend spokes in stead of straight pull for this reason, to achieve better results (lower torsion).

What's your feedback? Agree / disagree?

Thanks!

I would think offhand the actual building stats for the hub more important than flange diameter and j-bend vs straight pull. Given equal tension ratio's the straight pull will always have some durability advantage in the most trying circumstances. J-bend builds done correctly are more than durable for most all builds though. Given equal spoke butting/configuration the straight is going to stretch less.. if that translates into enough difference to matter in your application is doubtful.

[bm0p700f]

The J bend carbon Ti hub does not give better tension balance that you can measure over the SP version.

SP spoke in theory have longer service life but there is no emperical evidence to back this up. Straight pull hubs are mainly used for ease of building I think. A machine can lace these easier, I think.

[charlieboy52000]

Hi folks,

again a topic that the search function doesn't like to help with :-/, so sorry if discussed before:

For disc wheels, J-bend versions of hubs (e.g., Carbon-Ti, Dt Swiss, etc) tend to have a bigger flange diameter in the J-bend version. E.g., on the Carbonti it's 48mm / 43.5mm for the straight pull version and 54.5mm for the J-bend version. A wheelbuilder said to me he prefers to use J-bend spokes in stead of straight pull for this reason, to achieve better results (lower torsion).

What's your feedback? Agree / disagree?

Thanks!

He is on the money. I had straight pull and the spokes move around like if it is a normal thing when the wheel deforms. This results in more truing needed during the life of te wheel.
J bend makes the wheel sturdier because it doesn't allow for so much deformation by torsion of the spokes.


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[Nefarious86]

Deformation is deformation, how does the attachment point of the spoke change this?

[CycloTron]

I think straight pull vs J-bend doesn't matter as much as lacing pattern and spoke tension.
All things being equal, then I think straight pulls are easier to build with, AS LONG AS you use aero spokes, otherwise it's very painful to reverse/prevent spoke twist.

[TheKaiser]

Hi folks,

again a topic that the search function doesn't like to help with :-/, so sorry if discussed before:

For disc wheels, J-bend versions of hubs (e.g., Carbon-Ti, Dt Swiss, etc) tend to have a bigger flange diameter in the J-bend version. E.g., on the Carbonti it's 48mm / 43.5mm for the straight pull version and 54.5mm for the J-bend version. A wheelbuilder said to me he prefers to use J-bend spokes in stead of straight pull for this reason, to achieve better results (lower torsion).

What's your feedback? Agree / disagree?

Thanks!

Did he mean "torsion" under braking loads/pedaling loads, which a lot of people will refer to as "wind up", or did he mean "torsion" under lateral loads, which a lot of people will refer to as lateral flex?

Larger flange dia may help the former, but "wind up" typically isn't an issue on most modern wheels wheels anyway. In this case, the J-bend advantage would be mostly theoretical.

Wider bracing angle can help the latter, as with several manufacturers the J bend flange model provides a wider spoke bracing angle than the straight pull one, so it would be advantageous in that way.

[joejack951]

I'm not sure of the exact reason other than the geometry forced by a straight pull hub but the straight pull builds I've seen don't lace the spokes at their nearest cross to the hub like all j-bend spoke builds do. This would seem to create a weaker wheel as the spokes no longer 'work together' under tension, perhaps offsetting any advantage of the straight pull arrangement.