Wheel stiffness: Thick spokes v's fat rims ?

[one-eyed_jim]

I wasn't thinking 'lateral' ;-)

Lateral stiffness is the only aspect of wheel stiffness that matters - in a healthy wheel, at least. Radial deflections are of the order of fractions of a millimetre.

iirc - Swaged / butted spokes have higher tension than 'thick' spokes so they make a tighter/stiffer/stronger wheel.

The tension should be the same in each case. Butted spokes undergo a smaller drop in tension for a given vertical deflection (because they're more flexible) which means that a wheel built with butted (or thinner) spokes is less stiff, but normally more durable, as more spokes share the load cycle.

 

[one-eyed_jim]

By the way, Jobst Brandt's "The Bicycle Wheel" is the Old Testament of bicycle wheel theory, and well worth a read. It's mostly concerned with traditional road bike wheels, but much of the theory applies to other wheels, even if the specifics differ.

Jobst is currently recovering from a nasty crash and a spell in hospital.

 

[mikesnowdon]

http://www.sheldonbrown.com/rinard/wheel/index.htm

Thanks!

7. How does spoke gauge affect stiffness?

Thicker spokes make a wheel stiffer, if all else is equal. A typical 32 spoke wheel built with 2.0mm spokes is about 11% stiffer than a similar wheel built with 2.0-1.45mm swaged spokes.

Compare the deflection of two wheels: numbers 39 and 47. Wheel 39 is built with 2.0-1.45mm swaged spokes, but wheel 47 is built with 2.0mm straight gauge spokes. Hub dimensions are effectively identical, spoke count is the same and the rims are the same make and model, so the only structural difference is the spoke gauge.

Result? The wheel with thinner spokes deflected 0.051" (1.30mm) in font and 0.067"1.70mm) in the rear, but the wheel with thicker spokes deflected less: only 0.046" (1.17mm) and 0.055" (1.40mm) for front and rear, respectively. That's an 11% increase in stiffness for the thicker spoked wheels.

Interestingly, wheel stiffness depends on more than just spoke thickness; the rim and other factors also contribute, so only part of the increase in raw spoke stiffness shows up in measured wheel stiffness. The thicker spoke by itself is nearly twice as stiff axially as the thinner spoke!

 

[Rio]

according to DT the butted spokes are about 10% stronger than the plane gauge spokes (1000-1100 Nm/mm2 vs 1200 Nm/mm2). But as the example above shows, stronger doesn't always mean stiffer.
I think the DT comp is a great spoke, not to heavy, and very strong. But I never had any problems with revo's either. Maybee go for DT comp on the drive side, and revo on the other side?

 

[mikesnowdon]

Nice idea revo