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need a new pair of wheels and choices have come down to AC 350 (420?) and Spinergy XAerolite...

first option would be the AC's but since I've injured my lower back a few months ago, now I'm quite tempted by the Spin's

watching some reviews the Spin's seem to be more confortable in spite of some 200gr more..

are the Spin's more confy than the AC's?
are the AC's more stiff?
aerodynamics?
can one really feel the difference?

any comments/experiences on this would be great...

 

[HeronTodd]

There is no noticeable difference in the vertical compliance of bicycle wheels. Any vertical deflection is so small as to be masked by the deflection of tires, fork, seatpost, saddle, stem, and handlebars. You cannot feel the difference.

 

[hairscrambled]

The biggest difference is spoke material. Aluminum spokes like Kysriums are stiffer and less compliant than steel.

 

[bigbill]

Tires make the biggest difference IMHO. Get some 25mm tires, Michelin or Specialized make some nice 25s that fit most frames. Roly Poly tires are nice but at 27mm, don't fit all frames. The Michelin, Specialized, or other quality tire will go a long way in making your ride comfortable. FWIW, I have a set of Spinergy Xaeros and I really like the ride. Not very stiff, but very forgiving. Tire mounting is a chore though.

 

[Mark McM]

Metal spokes and wheel compliance

The biggest difference is spoke material. Aluminum spokes like Kysriums are stiffer and less compliant than steel.

This is not true. All metal spokes, be they steel or aluminum, are so stiff, that they might as well be perfectly rigid. Consider - the very thinnest, most flexible spoke (such as a DT Revolution or Sapim X-Ray) has a stiffness of about 5,000 lb/in for a single spoke. When you put a bunch of them together in a wheel, the resulting stiffness of the entire wheel assembly (including rim, hub and nipples) is typically about 15,000 lb/in. This is almost two orders of magnitude greater than the stiffness of a pneumatic tire. The difference in vertical compliance between the very stiffest and the very flexiest wheel is about the same as a a 1psi difference in pressure in the tires - and it is highly unlikely that someone would notice whether their tires are inflated to 99psi instead of 100 psi.

Anybody who tells you that one metal spoke wheel is "more comfortable" or "more compliant" than another is just blowing smoke.

 

[Reynolds531]

True

This is not true. All metal spokes, be they steel or aluminum, are so stiff, that they might as well be perfectly rigid. Consider - the very thinnest, most flexible spoke (such as a DT Revolution or Sapim X-Ray) has a stiffness of about 5,000 lb/in for a single spoke. When you put a bunch of them together in a wheel, the resulting stiffness of the entire wheel assembly (including rim, hub and nipples) is typically about 15,000 lb/in. This is almost two orders of magnitude greater than the stiffness of a pneumatic tire. The difference in vertical compliance between the very stiffest and the very flexiest wheel is about the same as a a 1psi difference in pressure in the tires - and it is highly unlikely that someone would notice whether their tires are inflated to 99psi instead of 100 psi.

Anybody who tells you that one metal spoke wheel is "more comfortable" or "more compliant" than another is just blowing smoke.

And if they tell you they can tell a speed and efficiency improvement vecause of a 200 g wheel weight reduction they're also blowing smoke. So, there will be no difference in comfort or speed between these two wheelsets.

 

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thank´s everyone...think I got the idea...

 

[rruff]

The biggest difference is spoke material. Aluminum spokes like Kysriums are stiffer and less compliant than steel.

Another placebo induced assertion.

Aluminum in fact has about 1/3 the elastic modulus of steel... or in other words it is 1/3 as stiff. Ksyrium SSCs have well below average stiffness. See #96 and #97: http://www.sheldonbrown.com/rinard/wheel/data.htm

I suspect that many riders look at SSCs, see those fat spokes, think "wow those must be stiff!", and then their feelings and sensations go along. The vertical compliance of frames is another myth.

 

[FTF]

The biggest difference is spoke material. Aluminum spokes like Kysriums are stiffer and less compliant than steel.

K's are NOT stiff, infact they test very low, esp. the rear.

 

[ttug]

hmmmmmm

ALL SPOKES FLEX. Otherwise, we would be up to our armpits in failed wheels......

 

[howardpowered]

Aluminum in fact has about 1/3 the elastic modulus of steel... or in other words it is 1/3 as stiff. Ksyrium SSCs have well below average stiffness.

This is only partly true. Axial spoke stiffness is a function of modulus, x-sectional area, and length (EA/L). Spoke lengths (L) don't vary much, and while its modulus (E) is less, an aluminum spoke usually has a significantly larger area (A) than a steel spoke. I would expect the axial stiffness of a Ksyrium spoke to be close to the average steel spoke. The reduced lateral stiffness of a Ksyrium wheel is most likely due to the low spoke count. The space between hub flanges may also be a factor, but I'm not sure how various wheels compare in this regard.

 

[Mark McM]

ALL SPOKES FLEX. Otherwise, we would be up to our armpits in failed wheels......

The question isn't whether spokes flex (everything flexes under an applied to load to some degree), but whether that flex makes a meaningful difference. When it comes to "comfort" and shock absorption, the amount of flex in the spokes is far too small to make any difference.

It is not simply enough to know that something happens - you have to know if the magnitude of the affect is meaningful. When I run east, the earth's rotation about its axis slows down ever so slightly (every action has an equal and opposite reaction). When I run west, the earth's rotation speeds up slightly. A few moments ago I ran down the hallway - did you notice any difference in the earth's motion?

As stated above, a single spoke has a stiffness between 5,000 and 10,000 lb/in., depending on diameter and length. When build into a wheel, the entire assembly has a stiffness between about 13,000 and 20,000 lb/in. So a 200 lb. load may result only a wheel flex of only 0.0100" for the stiffest wheel, and 0.0067" for the flexiest. And yet, we know that a tire can pitch flat when we hit a sharp edge, so the tire itself can deflect at least an inch. Do you think you would be able to tell the difference between a tire/wheel deflecting 1.0100" and 1.0067" (a difference of 0.32%)? I doubt it - especially when you further add in the other deflections of the other components (fork, stem, handlebars, saddle, seatpost, etc.). Any small deflection of the wheels just gets lost in the noise, and has no meaningful contribution to "comfort" or shock absorption.

 

[ttug]

yup

The question isn't whether spokes flex (everything flexes under an applied to load to some degree), but whether that flex makes a meaningful difference. When it comes to "comfort" and shock absorption, the amount of flex in the spokes is far too small to make any difference.

It is not simply enough to know that something happens - you have to know if the magnitude of the affect is meaningful. When I run east, the earth's rotation about its axis slows down ever so slightly (every action has an equal and opposite reaction). When I run west, the earth's rotation speeds up slightly. A few moments ago I ran down the hallway - did you notice any difference in the earth's motion?

As stated above, a single spoke has a stiffness between 5,000 and 10,000 lb/in., depending on diameter and length. When build into a wheel, the entire assembly has a stiffness between about 13,000 and 20,000 lb/in. So a 200 lb. load may result only a wheel flex of only 0.0100" for the stiffest wheel, and 0.0067" for the flexiest. And yet, we know that a tire can pitch flat when we hit a sharp edge, so the tire itself can deflect at least an inch. Do you think you would be able to tell the difference between a tire/wheel deflecting 1.0100" and 1.0067" (a difference of 0.32%)? I doubt it - especially when you further add in the other deflections of the other components (fork, stem, handlebars, saddle, seatpost, etc.). Any small deflection of the wheels just gets lost in the noise, and has no meaningful contribution to "comfort" or shock absorption.

Yes, however, I do have a real world detection of too much flex, its called a broken spoke or a wheel that untrues too often.

I agree that the tire will have the max deflection and that the wheel itself had better have very little of that. However, as to wheel deflecvtion getting lost, yes, most of it is, UNLESS, that wheel fails then all of a sudden, that tiny diff is not so tiny anymore.

 

[Kakah!]

I only have about 300km on my new ac 350's but I love them. I dropped the extra cash and got the sapim c-xray spoke option. I think if there is 28.32 spokes flying around c-xrays are nice because they arer bladed and super small, along with slightly higher tension allowed on the wheel. My set came in at 1294gms, I think some of the lightest clicher wheels around mabye.

 

[hairscrambled]

This is not true. All metal spokes, be they steel or aluminum, are so stiff, that they might as well be perfectly rigid. Consider - the very thinnest, most flexible spoke (such as a DT Revolution or Sapim X-Ray) has a stiffness of about 5,000 lb/in for a single spoke. When you put a bunch of them together in a wheel, the resulting stiffness of the entire wheel assembly (including rim, hub and nipples) is typically about 15,000 lb/in. This is almost two orders of magnitude greater than the stiffness of a pneumatic tire. The difference in vertical compliance between the very stiffest and the very flexiest wheel is about the same as a a 1psi difference in pressure in the tires - and it is highly unlikely that someone would notice whether their tires are inflated to 99psi instead of 100 psi.

Anybody who tells you that one metal spoke wheel is "more comfortable" or "more compliant" than another is just blowing smoke.

OK. I'll blow smoke again. Steel spoke wheels are more comfortable.

 

[ergott]

I only have about 300km on my new ac 350's but I love them. I dropped the extra cash and got the sapim c-xray spoke option. I think if there is 28.32 spokes flying around c-xrays are nice because they arer bladed and super small, along with slightly higher tension allowed on the wheel. My set came in at 1294gms, I think some of the lightest clicher wheels around mabye.

CX-Rays are nice spokes. One thing I will correct you one is that spoke choice will not determine the tension of a wheel. The limiting factor in tension is usually the rim and sometimes the hub. Any spoke that is used in wheels today are capable of tensions far higher than possible in a wheel.

-Eric