Mavic R-Sys wheels

[airwise]

Phil, I thought you said you had some understanding of engineering/physics?

[Phill P]

I've been miss understood

If you have two wheels with the same total weight, but one has higher rotational inertia (missed that bit out, was saying rotational mass instead), the low inertia wheels will accelerate faster and feel better/snappier, but the high rotation mass wheels will store the energy put into them and help prevent deceleration.

I didn't say heavy wheels climb the same as light wheels. I said if you do a lot of braking and sprinting back up to speed again you want low rotational inertia. So for crits and single track you want low inertia

If you don't understand this don't criticise.

[Tinea Pedis]

(but then you'd also not want the most unaero wheels tested either..)

As asked previously, if you could point me in the direction of the tunnel tests of the 2013 R-sys that would be great Phil.


Ta.

[airwise]

Phil, what happens as you climb up a 7% gradient with regards to wheel velocity and gravity?

[Phill P]

from earlier in this thread, and around the forum for some time now

Rouesartisanales found the Ksyrium ES to be the very worst wheel in their big aero test. (http://www.rouesartisanales.com/article-15505311.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;) and R-SYS wheels to be 1.35 time worse still (http://www.rouesartisanales.com/article-6833227.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;). That's what you would expect with large unaero hubs, shallow rims with a lot of square edges, and especialy the large diameter round spokes. Can you can "barn door"? Or "parachute"?

When the roads get step lighter wheels will gain advantage and aero will be less and less important as the speeds drop. What is your point? I've not denied this. This is why Zipp have the 202-a light weight more climbing orientated wheelset for their range which still has the Zipp trade mark aero qualities (no not a *super* light weight wheelset though)
What I'm saying is for climbing on the road, a 1400 gram wheelset with light rims and heavy hubs will have no advantage over a 1400gram wheelset with a heavy rim and light hubs. The light rim will feel snappier, but on roads where you don't do so much braking the stored energy in a heavy will will get returned to you and help maintain the speed you have built.

[TrekUk]

Can somebody explain rotational mass to this guy.

[davidalone]

actually, the whole rotational mass argument is a wash. the physics is sound, true that there is some advantage, but it is minute. not even in the order of aero gains we usually talk about.

anyone who rides a lighter rim wheel and a heavier rim wheel ( all else being equal) and says they can 'feel' them accelerate faster is speaking out of placebo effect.

a larger contributor to this would probably be spoke tension rather than the rim weight. low height rim usually = higher tension = stiffer wheel = feels 'snappier'. its not really because of the rim weight.

[Penthousepete]

This makes really interesting reading and so far I've established this:

-C24s wear quickly, but are light and recommended by a few in this debate. Is there a thought whether this wear issue will be improved for the new DA 9000 2013 variation?
-Easton EA90 SLX may have a slightly less strong set of spokes.
-Extralites are made of noodles(!)
-R-sys wheels are definitely non aero, light, stiff, but potentially expensive should they fail.
-Fulcrum R3 I believe was mentioned above, and approved, albeit slightly heavier. What about the Racing Zero? A smidgeon heavier than the 1400g benchmark and a couple of hundred quid more expensive are these worth a mention?

Ultimately, I can see the points all are making about mass, rotating and otherwise. I guess thats why we try to lower both! I'm no engineer, but surely though the comparison to maintaining momentum in a slightly heavier versus lighter rim on a climb would be only applicable if a climb were exactly the same gradient throughout? And the rider able to exert exactly the same power throughout? Even then surely gravity would win eventually? As accelerating out of hairpins requires a boost of power due to the gradient change would this mean a lighter rim wins? Agree with the placebo effect too and the talk of greater tension in spokes makes sense.

Like I said, interesting stuff and a different wheel for every ride and its peculiarities would be ideal, but in a real world not many people can do that. Your experiences here are great to learn from, but I think the lighter rotating mass argument seems more logical to me when combined to greater tension.

...and even with the wear issue, Im still thinking the C24s are winning unless the Fulcrum Zero supporters jump in...........?!

[eric]

summary: R-sys have 1.35x greater aero drag than the next worst wheel in the test I linked to

What I'm saying is for climbing on the road, a 1400 gram wheelset with light rims and heavy hubs will have no advantage over a 1400gram wheelset with a heavy rim and light hubs.

I agree with this. You're assuming steady state speed or close to it. Then it doesn't matter where on the bike the weight is, it is all weigh that needs to be moved up hill. Even for hard accellerations the difference in inertia between the R-SYS rims and other light clincher rims will be so small it's effectively zero. Weight on the rim has about 2x the inertia of weight elsewhere. I don't know the R-SYS rim weights but I doubt they are significantly lower than Stans 340s or other light clincher rims.

But that has nothing to do with the aerodynamic qualities I was discussing. Perhaps you quoted the wrong post?

[Tinea Pedis]

Phil, I'll even bold it

the tunnel tests of the 2013 R-sys

Otherwise, just stick with the "in my opinion..." engineering stuff. As I would like some real world tests that are less than half a decade old.

[ergott]

Has anything significantly changed in the design of the R-sys to make older aero tests invalid? I thought the rim shape, spoke count and spoke profile has remained unchanged.

[Tinea Pedis]

I'm not sure.

But given Mavic design their wheels as a system and the tyres have certainly changed since those tests (assuming they were even done with their tyre, which is not stated and I highly doubt) then I'd say they would be well due being tested again.

[MajorMantra]

a larger contributor to this would probably be spoke tension rather than the rim weight. low height rim usually = higher tension = stiffer wheel = feels 'snappier'. its not really because of the rim weight.

Spoke tension, within normal parameters, does not affect wheel stiffness.

I do think you may be right in saying that a stiff wheel will tend to feel snappier and that increasing stiffness has more of an effect than weight reduction. Maybe.

[HillRPete]

Ok here's another opinion, if you haven't had enough already :p

Whether a lighter wheel feels snappier under acceleration, hmm, I like to think that you actually feel the difference in some situations, like climbing out of the saddle. Talking about my 1200ish tubs vs 1900ish WH-R500 here.

In any case, what you can certainly feel is the quicker steering of a lighter wheel, because of the reduced rotational mass. This certainly translates into a snappier feeling, because the faster you go, the bigger the difference between the light and the heavy wheel are.

[ergott]

I'm not sure.

But given Mavic design their wheels as a system and the tyres have certainly changed since those tests (assuming they were even done with their tyre, which is not stated and I highly doubt) then I'd say they would be well due being tested again.

Not even Mavic claims any aerodynamic benefit with the Rsys. That's CX01