kysrium sl vs cosmic sl

Hanners

I currently have a set of Kysrium sl's but like the look of deep sections and like an ali braking track and hanker after a set of cosmic sl's or something else around the same same price but am i going to gain anything apart from looks?
I will be mostly concentrating on sportives as a shattered elbow has put paid to my racing ambitions

rpd_steve

The Cosmics will be better for aero - the gain is about 12W over the Kysriums at 18mph. That means they are better overall unless
-You stop more frequently than every 3.5 miles using your brakes
-You spend more than 10% of your ride on a gradient of 8%, particularly if you brake on the way down.

Do note though that the Cosmics will feel more sluggish to accelerate as they have a higher MOI, and it depends is this feeling of them being a bit slower to respond will bother you if you know they are better overall. The 'sluggishness' you will feel, the increase in speed/energy savings you will not, but the Garmin/power meter and average speed will show it.

EKIMIKE

Dude, i'd love to know where you're getting you incredibly precise figures (i smell bullshit)

Basically, Cosmics for the flat, Ksyrium for the hills. Sportive organisers love to stack the hills in. Stick with the Ksyriums. The Cosmics don't have a particularly aerodynamic profile and are pretty heavy so not ideal for your hilly sportives.

On the other hand, if you just want some bling for blings sake - get the Cosmics.

rpd_steve

I dont want to get into a stupid taff on here.

rozzer32

RPD Steve wrote:

I'm an engineer with 2 degrees in mechanical engineering and aerodynamics, and spent significant time and effort both wind tunnel testing and performing CFD analysis on every wheel out there for my research project...
The proof of the savings of NACA based wheel profiles is very well understood and the savings are provable in black and white in CFD and real wind tunnel tests. The figures I quoted are for moving from an open pro type 20mm box rim to an 'average' 50 mm toroidal/NACA based profile.

The stats on aero vs weight/inertia are quite simple maths that any 2nd year engineering student could do, but there seems to be a big misconception about the negative effects of inertia - think of it like a battery, you DO get it back when you freewheel, and it is only 'wasted' is it goes into heating the rim under braking. The increace in impulse required to accelerate the mass in speed is then the same as for any other part of the bike - if essance the wheels act like a flywheel on an engine to smooth out speed changes in both directions, but does not use up energy overall.
The gains are there and provable, (the % improvement BTW remains the same in a pack or alone, though the absolute improvement obviously reduces)

The real question is
-will you like the feeling of 'sluggish' wheels
-do they suit your riding style (crits etc are not the right use)
-Do you care if technicly you are saving x% energy, and does it matter to you?

So Steve you're in your final year at Brookes this year but you've already done 2 degrees, that's impressive for a 21/22 year old.

You've done testing on ALL wheels out there? Was that using Star CCM+? Because the computers at Uni are so shit that they struggled to do CFD of a rotating 30mm wheel when I investigated wheels for my project, along with frames and rider position.

Also where did you do the wind tunnel testing? The tunnel at Uni is sh*t and so small that you can't do real world testing. Also you can only use the force balance for lift at Uni, not for drag which is what you want as a wheel.

Can we have a look at these research projects you've done seeing as you've tested every wheel, I'd be interested to look at the data, as I'm sure other people would.

Wheel aerodynamics isn't difficult to understand really. Deeper rims allow the flow to stay attached for longer, the longer the flow stays attached the more aerodynamic the wheel is, quite simple really.

(Yes I go to the same Uni as RPD Steve. Also if people want a copy of my dissertation looking into aerodynamics of wheels, frames and rider position then drop me a PM and I'll send it you).

EKIMIKE

EKIMIKE

Also NB how i only called bullshit on your incredibly precise figures. I get aerodynamic benefits. I don't buy the calculations that claim 'x(precise)' real world performance gain.

All you can categorically say is there will be a gain in certain circumstances.

Another NB: I'm not an engineer and don't have any interest in engineering schlong measuring. In this instance i am more than willing to be labelled an engineering bigot.

jimmurray

I've got both. Cosmics look and sound much better plus easier to hold a higer speed. The kysriums feel snappier when accelerating, initially, and feel easier if doing a lot of climbing. All pretty subjective and nice when changing from one to another as they you do notice a difference.

rpd_steve

It wasn't don't at brookes. I CBA to get into a bitching match on here. You have an opinion on me and what I have/haven't done in the past as you have made that quite clear. But opening an account pretending to be someone else is being ridiculous. For the record the testing was done elsewhere with someone else at Southampton for a body of work. It would be ridiculous to say all wheels were tested, but a good representative sample of available designs were.

rozzer32

RPD Steve wrote:

It wasn't don't at brookes. I CBA to get into a bitching match on here. You have an opinion on me and what I have/haven't done in the past as you have made that quite clear. But opening an account pretending to be someone else is being ridiculous. For the record the testing was done elsewhere with someone else at Southampton for a body of work. It would be ridiculous to say all wheels were tested, but a good representative sample of available designs were.

So when you graduate this year will it mean you have 3 degrees?

"It would be ridiculous to say all wheels were tested" - well it's what you said in your post above, so obviously not that ridiculous. Also what you mean by a good representative sample?

Anyway I'm still very interested to read the reports you made on your findings. Is there any where I can see them?

rpd_steve

It was done last summer with a friend who is completing an aero based thesis at Southampton. His uncle owns a bike shop so he was lucky enough to be able to have access to a good selection of wheel sets. And stop impersonating Laura please Rory, its not really on to be dragging her name into any of this, particularly publicly on here.

rozzer32

RPD Steve wrote:

It was done last summer with a friend who is completing an aero based thesis at Southampton. His uncle owns a bike shop so he was lucky enough to be able to have access to a good selection of wheel sets. And stop impersonating Laura please Rory, its not really on to be dragging her name into any of this, particularly publicly on here.

Well cheers for throwing accusations out there but it definitely wasn't me who set that account up, I think I have disproved your comments already (still waiting for those reports). Although whoever has done this does have a good sense of humor.


On another note did you pick between the normal 404's or the firecrest ones???

rpd_steve

Well surely you can see why I would think it was you... Can only be someone who knows a bit about me, but looks like they have gone now anyway.

Couldn't really afford the 404s and was trying to justify spending that much... Think it will end up being something more down to earth like Cosmic carbons as the convenience of a clincher is always nice. Though the low weight of tubs is appealing, I doubt I'd use them enough to justify it.

Zoomer37

Aero wars. Love it.

Sammyw23

Just to take it back to the OP's question......

I have just switched from Ksyrium Elite's to Cosmic SLE's - they are both great but I (much) prefer the Cosmics. The Ksyriums are ultra stiff, great for racing but not so great for longer rides/sportives. The Cosmics look better, feel a little softer and they do hold their speed better. Plus I couldn't notice the added 200g weight at all.

Overall the statistical differences will probably be minimal but for me the difference in how I felt at the end of riding my bike on both wheels is chalk and cheese. With the Cosmics its just a more pleasurable experience (for me).

I'll be keeping my Ksyriums for racing but the cosmics for my weekend rides and sportives.

styxd

Since you guys know so much about wheels, how does a "semi" aero rim (like a velocity aerohead) compare?

Is it the best of both worlds? Obviously they are pretty light like the ksyrium, so they climb well, but does the fact they are about 30mm deep offer any aero benefit?

rick_chasey

Best to keep spats in real life away from the boards.

Apologies to the OP!

rozzer32

styxd wrote:

Since you guys know so much about wheels, how does a "semi" aero rim (like a velocity aerohead) compare?

Is it the best of both worlds? Obviously they are pretty light like the ksyrium, so they climb well, but does the fact they are about 30mm deep offer any aero benefit?

To be honest you'll get hardly any aero benefit, when I did my testing I used a 30mm rim as the base rim to compare against. You won't really see a significant aero benefit from the rim until you go above 50mm.

If you want to try and make a 30mm rim aero the best thing to do would be to keep the number of spokes down. Naturally the more spokes you have the more turbulence and drag is created. So you want to keep the number of spokes as low as possible for aero reasons but obviously this needs to be balanced against stiffness and strength.

styxd

Thanks for the reply. I realise theres going to be very little in it, but I assume they do offer some sort of advantage over a rim with a flat profile such as the classic Mavic Open Pro?

rozzer32

styxd wrote:

Thanks for the reply. I realise theres going to be very little in it, but I assume they do offer some sort of advantage over a rim with a flat profile such as the classic Mavic Open Pro?

Yes maybe, but then you have to take things like rim profile into account to give a definite answer.

To keeps things simple if you're looking at a 30mm wheel I wouldn't consider aerodynamics as a factor. I'd just look at weight and stiffness/strength.

okgo

Sammyw23 wrote:

The Ksyriums are ultra stiff, great for racing but not so great for longer rides/sportives. The Cosmics look better, feel a little softer and they do hold their speed better. Plus I couldn't notice the added 200g weight at all.

So you couldn't notice 200g, yet the light, stiff wheels that are great for racing are no good for longer rides(be interested to hear what is a longer ride, and WHY they're no good, but they are fine for a race of 80 miles?), that sounds like utter toss to me.

styxd

I already have the wheels, I picked them purely because they were cheap and light (or least lighter than the open pros)

But then I wondered why Velocity bothered to give them an aerodynamic profile, just as a selling point? Or is there actually any difference?

Tom Dean

RPD Steve wrote:

The Cosmics will be better for aero - the gain is about 12W over the Kysriums at 18mph.

The old Roues Artisanales wheel test showed this kind of gain at 50kph. 12w at 29kph sounds very optimistic

Sammyw23

okgo wrote:

Sammyw23 wrote:

The Ksyriums are ultra stiff, great for racing but not so great for longer rides/sportives. The Cosmics look better, feel a little softer and they do hold their speed better. Plus I couldn't notice the added 200g weight at all.

So you couldn't notice 200g, yet the light, stiff wheels that are great for racing are no good for longer rides(be interested to hear what is a longer ride, and WHY they're no good, but they are fine for a race of 80 miles?), that sounds like utter toss to me.

The races I was talking about are 60-90 minute crit races. My longer rides are 60-100 miles. I am not saying that the Ksyriums are no good for longer rides, if you were trying to ride longer and as quickly as possible then they would be very good.

The point I was trying to make (and clearly failed) is that to me, the cosmics feel like a nicer ride. Ultimately, whilst I always listen to other's opinions the one that I take most notice of is my own.

Either way, I wasn't trying to state facts about the benefits of either wheel, I have no right to given I am no expert.
It was simply my own opinion so call it utter toss if you want but my feedback stands.

MattC59

I've got a set of Aeolus 5.0 ACC wheels. They work equally well on short or long rides, hold speed well and are very stiff. They go up hills well, go down hills well and go along the flats well. I don't race, and have no intention to, so can't comment on how much snappier something like a Ksyrium might be in a sprint or climb.

But................

They look and sound ace, so I'm happy.

If you're not into racing, ride what makes you happy !

Sammyw23

MattC59 wrote:

If you're not into racing, ride what makes you happy !

What I should have said originally

rpd_steve

At the end of the day the enjoyment is what it is all about outside of the pro ranks. Even for those of use who race only do so because we enjoy it... Even if the gains are marginal/non-existant or counter productive if they make you happy and enjoy the ride more then why not? I'm afraid that I must agree that for £1k i would be much better of having some good level coaching than wheels - as would most if the overall goal is to be as good/fast as you can be. But then 90% of us then buy what we WANT. Thats fine, so long as we dont kid ourselves that x% power saving will take my lame average speed and mean i can pull 25 all day long - coz it wont! But you (and I) may enjoy our poor performances more!

rake

some of the bumf i have read suggests that the gains from cx ray spokes are around 50% of going from box rims to aero rims. so maybe thats a good compromise for light weight box rims and not having to go too low on the spoke numbers and have a wheel like a wobble board.

ugo.santalucia

rake wrote:

some of the bumf i have read suggests that the gains from cx ray spokes are around 50% of going from box rims to aero rims. so maybe thats a good compromise for light weight box rims and not having to go too low on the spoke numbers and have a wheel like a wobble board.

If wheels aerodymanics were as important as suggested on magazines, then one should be able to reach higher speeds, when descending with profiled wheels. I have to admit I have never noticed any difference in top speed going down well known descents (steep and less steep) with and without aero rims/flat spokes and the likes. Wearing or not wearing a jacket seems to make a difference though... hence the aero effect of wheels must be something pretty insignificant compared to clothing, riding position etc... I think there are cheaper ways to be aerodynamic than a £ 1000 + set of wheels

okgo

I notice a huge difference going downhill on Zipps over Kysriums.

Endless research has been done into aero wheels, they work, obviously, why would anyone dispute that?

The person creates most of the drag, that is common knowledge, after that (who wears big flappy jackets if they're trying to go fast?!) the next best thing for dynamics are obviously wheels, with frames after that I suppose.