Are Sapim CX-Ray spokes worth it over DT Comp/Revolutions? For a Carbon XC Wh...

The real question is, will they build a stiffer wheel?

No.
CX Rays are Lasers (Sapim equivalent of the Revo) that are rolled flat.
No more steel in the cross section = no more stiffness.
Same weight, same performance. The only differences are aerodynamics, which are moot on a mountain bike, and the ease of preventing wind-up. Whether that's worth $120 to you is your call. It ain't to me.

 

Bladed spokes like CX-Rays are simply easier to build than round butted spokes like Sapim Laser or DT Revs as you can see if they are winding up and use a tool to hold them strait. They are basically Lasers with the middle section flattened. Since aerodynamics aren't in play on mountain wheels there are no other advantages.

 

If you use revolutions you could put a small dot on one side of the spokes near the nipple with a sharpie so you can see any windup and return them to neutral after each adjustment.

 

+10

I can't believe how many posts I see on a regular basis implying that you need bladed spokes to be able to keep track of spoke wind up. What non-sense...

 

I had a chance to ride same rim tire (blunt sl, karma) combination with dt and cx rays on the same course. I found the deflection to be less in a g outs and stiffness in corners to be much better with the wheel built using the cx rays. I changed the order I had already placed with revo to upgrade to cx rays. I highly recommend cx ray spokes for xc/light weight builds.

 

that's called confirmation bias

 

Perhaps one unintended advantage of the cx rays is their ability to cut / chop through small branches and twigs. I always use cx rays because I have had good luck with them and my experience has been that the bladed profile of the spoke is pretty good at handling small debris that gets into the spokes from time to time whereas a rounded profile may not work as well.

 

Lots of the information here falls in that category except many have not tried both/several options available. i.e

This is the best bike ever....but I haven't tried anything else.

Having tried multiple options and like one over the other is call an informed opinion. Although it is based on subjective measurement like "feel".

Or maybe I do need to feel better about liking expensive spokes.

 

Does anyone have side to side comparison with equal rims? I know the cross sectional area between Lasers and Cx Rays is the same, but does the further work and shape do anything to enhance the strength and stiffness, or is it all power of suggestion that makes them better?

Does anyone have side by side or any tests to prove?

 

Do not confuse strength and stiffness.
Steels differs in strength a lot (tempering state, machining), but steel stiffness is pretty much a constant.

Look at matwebb.com the difference in elasticity modulus for a given steel (4130 for example) at different hardness: it's the same.

Look at difference in elasticity modulus between 4130 steel (chromo) and 431 (stainless): pretty much the same (205 vs 200GPa).
There is more variation between steels and stainless because of the nickel/chromium content, 316 stainless for example is 193GPa, but again, this is only 5%.

 

Are Sapim CX-Ray spokes worth it over DT Comp/Revolutions? For a Carbon XC Wh...

Steels differs in strength a lot (tempering state, machining), but steel stiffness is pretty much a constant.

Exactly.
Stiffness/elasticity is attributable to atomic-level forces, which are not affected by cold work... or temper (heat treatment).
Indisputable facts .. despite the persistent MTBR misinformation express train.

 

Do not confuse stiffness with elasticity either.

Rather than just these generic property specs, would like to see the ratings of the alloys after they have gone through various forming/shaping/treatment processes. A part machined from a cast block is not going to perform the same as a cold forged part.

 

Are Sapim CX-Ray spokes worth it over DT Comp/Revolutions? For a Carbon XC Wh...

Do not confuse stiffness with elasticity either.

Whatever, dood.
Elasticity=stiffness
Two ways of saying the same thing (force:deflection)
You should know that.

 

Modulus of elasticity is "stiffness" for a material, but there are more mudules to consider. In reality only constructions and parts have a stiffness.

Also ausenitic stainless can only be hardened through cold working, and the harder it gets the more brittle it gets (toughness-resistance to impacts).

Cast material will always be lower strength due to microscopic faults I believe its about 20% or so weaker compared to forged. Btw all steels are forged already at the mill, except those that are cast or powedered, sintered and hip'ed.

I believe drawn spokes are actually "cold forged" but maybe not reduced as much?

Cold forging is usually only used on metals that are not heat treatable.

Work hardening - Wikipedia, the free encyclopedia

 

But is any of those materials austenitic stainless? If i know my uddeholm/sandvik lingo correct one is plain 1%C steel with possibly Mn in it. Will reach a minimum of 64hrc or so as quenched, and the last one is a 0,35%C stainless with Mn in it, martensitic and thus hardenable, well somewhat at least. The flex one sounds like sandvik grade too. I have no idea what. i found it quite interesting though that those 3 grades responded bad to cold rolling (in the longitudal direction but not the trasverse), at least until tempered again to remove the effects of it.

I guess the lesson here is don't cold roll steel that are heat treatable if you want ultimate stiffness and don't intend to temper them after rolling.
Or?

I don't know but I at least could care less about the E-module of the different grades of steel used in spokes. Since there are only a few of the grades used, possibly only 2. And since you can obviously make the spokes out of crappy alu, expensive ti or carbon, and it doesn't make the wheels any worse or better. and the alu is at most 1/3 the GPa of steel and Ti is half e-module.

 

But is any of those materials austenitic stainless?

It doesn't matter. Modulus is an intensive property and stiffness is an extensive property, end of story. I posted a few tables to make the point that the somewhat assertive response above was incorrect without having me digging deeper into theory. If you would like to show I am wrong, I am curious to hear your perspective. I used a widely-accessible reference in hope that it might clarify the discussion.

I don't know but I at least could care less about the E-module of the different grades of steel used in spokes.

This is the point of Shiggy's post. I found it odd his comment was disputed (it was claimed that modulus and stiffness are equivalent), so I posted the above. I hope it helped.

 

I dunno what's worse - you guys having/taking the time to argue about discuss this stuff, or me having/taking the time to read it.

 

Why are people talking about modulus vs stiffness?--spokes are two force members in tension so it really doesn't matter which you use in a comparison if the weight is about the same.

 

1. Lots of misinformation floating around about stiffness and different spokes and performance.
2. Human tendency to assume that our interpretation of a given personal experience indicates some universal rule or property of physical systems. In general we have a low tolerance for not knowing/understanding things and our brains tend to fill in the gaps so we feel more comfortable negotiating our environment.
3. Provocateurs who come to MTBR looking for a fight and learn whatever topic is at hand via Google so they can, without any real understanding of the topic, copy-and-paste out-of-context information to further confuse the issue in the interest of coming out what they perceive to be "on top" in an internet discussion.

You'll find very little disagreement between those posters who actually know what they are talking about based on training or experience, because the concepts that are discussed here are not that complicated or mysterious.

 

I rebuilt a straight gauge spoked wheels with races and it stopped rubbing the stay.

Seriously too.

It wasn't the spokes that did it though. I've rebuilt wheels with the same spokes and they stopped flexing.

 

I rebuilt a straight gauge spoked wheels with races and it stopped rubbing the stay.

Seriously too.

It wasn't the spokes that did it though. I've rebuilt wheels with the same spokes and they stopped flexing.

Stay rubbing is not the straightforward indicator of wheel stiffness that many seem to think it is.