28h rear wheel lacing ?

[ergott]

Originally Posted by Mark McM

Yes, obviously a longer spokes will have less longitudinal stiffness than shorter spokes. A 290 mm spoke is 7% longer than 270mm spoke, and will stretch 7% more under the same load. In turn, if the spokes stretch more, the wheel will deflect more. Similarly, a thinner spoke will have less longitidunal stiffness than thicker spokes, so thinner spokes make less stiff wheels.

If it isn't written about, its probably because for a given rim and hub combination, there is little difference in possible spoke lengths, so differences in spoke length will have result in only minor differences in the stiffness of that wheel. The number and thickness of the spokes and the bracing angle have much more variability, so variations in these will have much larger affects on stiffness.

290mm to 270mm is a practical different in spoke length when changing patterns from cross to radial. If that's a 7% increase in lateral stiffness then that's a bigger improvement than some of the other changes mentioned.

[ergott]

Originally Posted by AngryScientist

ok, so should i go heads in or out on the radial side then??


by the way, i've built a whole bunch of wheels now, just want to do something a little different than the usual for this one.

Due to the large flange diameter and spoke hole placement on those hubs I would definitely lace heads out. Heads in would put stresses on the flange I'm not sure CK recommends. It might even be mentioned somewhere in their literature with regards to radial lacing.

[AngryScientist]

thanks eric.

heads out it is.

[Mark McM]

Originally Posted by ergott

290mm to 270mm is a practical different in spoke length when changing patterns from cross to radial. If that's a 7% increase in lateral stiffness then that's a bigger improvement than some of the other changes mentioned.

The 7% stiffness change is just for the spokes. The spoke stiffness is just one contributor to wheel stiffness - the rim stiffness and the hub/axle stiffness are also important contributors. Changing the spoke stiffness by 7% may result in a wheel stiffness difference of only a few percent. Even for the same hub and rim, there are other variable that make bigger differences. For example, a 2.0 straight spoke has nearly twice the longitudinal stiffness of a 2.0/1.5/2.0 spoke, so switching between these two spoke types will have a bigger affect on wheel stiffness.

As I first said, spoke lacing pattern has only a minor affect on wheel performance - other design variables have much larger affects. I think that people sometimes focus on wheel lacing pattern because it tends to be more visible than other variables.

[charliedid]

Originally Posted by Mark McM

While the degree of difference can vary depending on other factors, lacing radial spokes heads out can result in a small increase in stiffness over a crossed lacing pattern. Keith Bontrager tested otherwise identical wheels with either radial (heads-out) or 3x lacing, and found that the radially laced wheel was 5% stiffer laterally. There is little difference in bracing angle between radially heads out and 3x, so the difference in stiffness is mainly due to length of the spokes (3x spokes are about 5% longer than radial spokes).



As you note, radial heads-in lacing can result in an even greater difference in lateral stiffness, because this lacing pattern can result in a meaningful difference in bracing angle. In Damon Rinardl stiffness's test of whee, he found that otherwise identical radially laced wheels, lacing heads in resulted in 13% more lateral stiffness than lacing heads-out.







Yes, obviously a longer spokes will have less longitudinal stiffness than shorter spokes. A 290 mm spoke is 7% longer than 270mm spoke, and will stretch 7% more under the same load. In turn, if the spokes stretch more, the wheel will deflect more. Similarly, a thinner spoke will have less longitidunal stiffness than thicker spokes, so thinner spokes make less stiff wheels.



If it isn't written about, its probably because for a given rim and hub combination, there is little difference in possible spoke lengths, so differences in spoke length will have result in only minor differences in the stiffness of that wheel. The number and thickness of the spokes and the bracing angle have much more variability, so variations in these will have much larger affects on stiffness.

I wonder if Keith could pick the correct wheel out of a blind taste test. Is 5%. Stiffer really discernible? I wonder.


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[oldpotatoe]

Originally Posted by AngryScientist

ok, so should i go heads in or out on the radial side then??


by the way, i've built a whole bunch of wheels now, just want to do something a little different than the usual for this one.

Twisty spokes then!!

[AngryScientist]

pretty happy with the way these came out.

hopefully they ride as nicely as they look.

side note: these are really nice rims. built up very easily. perfectly round/flat out of the box.

[Spaghetti Legs]

Nicely done - looks good! BTW, I just did a first ride on Tirreno Zeros and liked ‘em.

[AngryScientist]

Originally Posted by Spaghetti Legs

Nicely done - looks good! BTW, I just did a first ride on Tirreno Zeros and liked ‘em.

yea, the casing on them feels pretty nice, looking forward to rolling some miles on them. these are the 32c version.