# Fulcrum Racing 1 vs. Fulcrum Racing 3



## uscsig51 (May 7, 2006)

It appears that the major difference between these two wheelsets is that the Racing 1 uses an alumunum bladed spoke while the Racing 3 uses a steel aero spoke and the Racing 1 has some additional cut-outs on the front rim to shave some weight.

What is the advantage/disadvantage between the aluminum (lighter weight) vs steel spoke with respect to ride/handling/performance?


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## hairscrambled (Nov 18, 2004)

uscsig51 said:


> It appears that the major difference between these two wheelsets is that the Racing 1 uses an alumunum bladed spoke while the Racing 3 uses a steel aero spoke and the Racing 1 has some additional cut-outs on the front rim to shave some weight.
> 
> What is the advantage/disadvantage between the aluminum (lighter weight) vs steel spoke with respect to ride/handling/performance?


Steel spokes are softer riding and more compliant. Aluminum spokes tend to be stiffer with snapper acceration. My comparison is based on Campy Eurus (aluminum) and Zondas (steel).


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## Mark McM (Jun 18, 2005)

*Stiffer? Snappier?*



hairscrambled said:


> Steel spokes are softer riding and more compliant. Aluminum spokes tend to be stiffer with snapper acceration. My comparison is based on Campy Eurus (aluminum) and Zondas (steel).


Please reconcile the above claims with the fact that aluminum has only 1/3 the stiffness of steel (Aluminum has a modulus of 10x10^6 psi, vs. 29x10^6 psi for steel), and that even the hardest alumunium alloys have a lower hardness than the stainless steel used for spokes. Also, how can one wheel accelerate better than another, when all tangential tension spoked wheels have negligible torsional compliance?


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## Cruzer2424 (Feb 8, 2005)

Mark McM said:


> Please reconcile the above claims with the fact that aluminum has only 1/3 the stiffness of steel (Aluminum has a modulus of 10x10^6 psi, vs. 29x10^6 psi for steel), and that even the hardest alumunium alloys have a lower hardness than the stainless steel used for spokes. Also, how can one wheel accelerate better than another, when all tangential tension spoked wheels have negligible torsional compliance?



Doesn't area have to do with it? 

I'm not exactly sure since its been a while since i've taken physics. Please explain. lol.


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## Mark McM (Jun 18, 2005)

*Aluminum is a poor choice for spokes.*



Cruzer2424 said:


> Doesn't area have to do with it?
> 
> I'm not exactly sure since its been a while since i've taken physics. Please explain. lol.


Yes, longitudinal stiffness is proportional to both area and modulus. So for the same stiffness, an aluminum spoke would need to have about 3 times the cross sectional area as a steel spoke.

Interestingly, the 3 common structural metals for bicycles (steel, aluminum and titanium) all have about the same specific modulus (specific modulus is the modulus per unit mass). Although aluminum has 1/3 the stiffness of steel, it also has about 1/3 the density, so an aluminum wire of equal weight to a steel wire would have 3 times the area, but equal stiffness. Which demonstrates one of the reasons that aluminum is a poor choice for spoke material - for equal stiffness, you end up with a fatter spoke with more aerodynamic drag. In addition, the aluminum is softers (way easier to get gauged by a wayward chain or anything else that might go into the spokes). Aluminum also has poorer fatigue performance, which is unfortunate since spokes undergo very high cyclic load - a 700c rotates about 800 times per mile, so the spoke see 800 load cycles per mile, or a million load cycles every 1250 miles.

Aluminum's properties lend itself well to many bicycle component applications. However, spokes is not one them - (stainless) steel is a much better choice for spokes.


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## Cruzer2424 (Feb 8, 2005)

Mark McM said:


> Yes, longitudinal stiffness is proportional to both area and modulus. So for the same stiffness, an aluminum spoke would need to have about 3 times the cross sectional area as a steel spoke.
> 
> Interestingly, the 3 common structural metals for bicycles (steel, aluminum and titanium) all have about the same specific modulus (specific modulus is the modulus per unit mass). Although aluminum has 1/3 the stiffness of steel, it also has about 1/3 the density, so an aluminum wire of equal weight to a steel wire would have 3 times the area, but equal stiffness. Which demonstrates one of the reasons that aluminum is a poor choice for spoke material - for equal stiffness, you end up with a fatter spoke with more aerodynamic drag. In addition, the aluminum is softers (way easier to get gauged by a wayward chain or anything else that might go into the spokes). Aluminum also has poorer fatigue performance, which is unfortunate since spokes undergo very high cyclic load - a 700c rotates about 800 times per mile, so the spoke see 800 load cycles per mile, or a million load cycles every 1250 miles.
> 
> Aluminum's properties lend itself well to many bicycle component applications. However, spokes is not one them - (stainless) steel is a much better choice for spokes.



Hmm... So lets take a ksyrium and a custom built stainless steel spoked wheel. Doesn't the ksyrium spoke have more than 3x the cross setional area of a regular custom built wheel? Would that make it stiffer?

Also, how does this affect double butted spokes?


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## Mark McM (Jun 18, 2005)

*Fat spokes, skinny spokes*



Cruzer2424 said:


> Hmm... So lets take a ksyrium and a custom built stainless steel spoked wheel. Doesn't the ksyrium spoke have more than 3x the cross setional area of a regular custom built wheel? Would that make it stiffer?
> 
> Also, how does this affect double butted spokes?


Ksyrium spokes are 1.7mm x 5.2mm. An ellipse of these dimension has a cross sectional area 6.9 mm^2. To have the same stiffness, a steel spoke would need 1/3 the cross section, or 2.3 mm^2. This is the cross-section of a 1.7 mm diameter circle. So, on a per spoke basis, a Ksyrium spoke would be less stiff than a 14 gauge (2.0 mm) straight, 15 gauge (1.8 mm) or 14/15/14 butted spoke, but more stiff than a 15/16/15 (1.8/1.6/1.8) butted spoke, or a 2.0/1.5/2.0 "super butted" spoke like a DT Revolution. In the spectrum of steel spoke stiffnesses, the Ksyrium spokes fit right around the middle.

Of course, Ksyriums only have 18 spokes in the front and 20 in the back, so they actually have less total spoke stiffness than typical custom built wheels, which have more spokes. This may explain why the actual measured stiffness of Ksyriums are on the low end - compared to "typical" standard wheels, Ksyriums are rather flexy.

See the data in Damon Rinards wheel stiffness test for some comparitive stiffness data of Ksyrium wheels.


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