Corima MCC 47 S+ versus Lightweight Meilenstein
Moderator: robbosmans
- cyclespeed
- Posts: 1120
- Joined: Mon Jun 06, 2016 8:45 am
I disagree.
Yes, the tunnel will measure the effect of the spinning wheel on overall drag, but what it does NOT measure is how much power the rider is gaving to put in to keep those wheels spinning fast.
The best way to test for spoke drag would be to use an electric motor to spin up the wheel to say 40km/h, and measure how much power it takes to maintain that speed.
The result will show bearing drag and spoke drag.
Yes, the tunnel will measure the effect of the spinning wheel on overall drag, but what it does NOT measure is how much power the rider is gaving to put in to keep those wheels spinning fast.
The best way to test for spoke drag would be to use an electric motor to spin up the wheel to say 40km/h, and measure how much power it takes to maintain that speed.
The result will show bearing drag and spoke drag.
- cyclespeed
- Posts: 1120
- Joined: Mon Jun 06, 2016 8:45 am
Gratuitous shot of the Meilensteins in action at the Etape;
Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓ Broad Selection ✓ Worldwide Delivery ✓
www.starbike.com
cyclespeed wrote:Yes, the tunnel will measure the effect of the spinning wheel on overall drag, but what it does NOT measure is how much power the rider is gaving to put in to keep those wheels spinning fast.
I guess inertia is what you mean.
kgt wrote:cyclespeed wrote:Yes, the tunnel will measure the effect of the spinning wheel on overall drag, but what it does NOT measure is how much power the rider is gaving to put in to keep those wheels spinning fast.
I guess inertia is what you mean.
Inertia is different - it is the force needed to change the speed or direction of something (roughly speaking). Here he means that wheels with unaerodynamic spokes will slow down quicker because they have face wind resistance whilst spinning - imagine you had wheels with gigantic fan blades as spokes, the bike would stop pretty quickly and require lots of W to ride
----
No longer in the industry
No longer in the industry
- cyclespeed
- Posts: 1120
- Joined: Mon Jun 06, 2016 8:45 am
jever98 wrote:kgt wrote:cyclespeed wrote:Yes, the tunnel will measure the effect of the spinning wheel on overall drag, but what it does NOT measure is how much power the rider is gaving to put in to keep those wheels spinning fast.
I guess inertia is what you mean.
Inertia is different - it is the force needed to change the speed or direction of something (roughly speaking). Here he means that wheels with unaerodynamic spokes will slow down quicker because they have face wind resistance whilst spinning - imagine you had wheels with gigantic fan blades as spokes, the bike would stop pretty quickly and require lots of W to ride
Yes, exactly. Nothing to do with inertia.
An un-aero spoke has to be forced through the air. This takes power. That power comes from the rider.
The more aero your spoke setup, the better.
We already saw that when you add up the total surface area of the Corima's spokes, it's 230cm2. That's alot. More than a 1/3 of a sheet of A4 paper. Imagine pushing that through the air at 40km/h.
Mavics wheels (was it the R Sys?) were often criticised for their round spokes being un-aero. The Corima's were improved recently to make the front have bladed spokes, not round, but rear still has round ones.
Normal drag experiments on wheels in wind tunnels do not measure this factor. In my opinion, 50mm wheels are all very similar to each other in wind tunnel aero performance, certainly close enough for it not to matter. However, spoke performance could be significantly different, if said spokes are especially un-aero.
Ok, I see.
It's getting too complicated though, I doubt that is something easy to calculate. Total surface and shape of spokes are not enough parameters.
It's getting too complicated though, I doubt that is something easy to calculate. Total surface and shape of spokes are not enough parameters.
- cyclespeed
- Posts: 1120
- Joined: Mon Jun 06, 2016 8:45 am
kgt wrote:Ok, I see.
It's getting too complicated though, I doubt that is something easy to calculate. Total surface and shape of spokes are not enough parameters.
Agree that's it not a simple calc. As for any aero calc you need air density, the surface area, the Cd (i.e. round, oval, flat, etc), and the speed of the spoke, given that the spoke speed is low at the hub and very high at the rim.
We need a mathematician!
cyclespeed wrote:Normal drag experiments on wheels in wind tunnels do not measure this factor.
Thinking about it, I don't believe that's true. I think that a wind tunnel experiment where a motor turns the wheel will capture some, but not all the drag. Here is why:
If the wind tunnel experiment didn't capture any drag, then it would mean that there is no net drag on the bike (as in measured by the drag created from the wind blowing from the front), apart from the energy needed to turn the wheel. But there is:
As the spoke rotates, the different parts of the spoke will rotate through the air at different speed.
Take a (unrealistic, theoretical point) right at the tire: the moment it touches the ground its forward speed is 0. The moment it is at the top (furthest from the ground) it is at 2x speed (so, at 40kph: 80 kph). So that part of the spoke goes from 0 ->80 -> 0 -> 80....
Take a second (unrealistic, theoretical point) exactly at the middle of the hub. This point will keep traveling through the air at 40kph all the time.
So, the further away from the center, the greater the variance in speed of the spoke. But it is always >0 (it doesn't travel backwards). The rotation doesn't "cancel out" the drag direction, everything is always moving forward.
What I can't get my head around is whether this is "all" the drag there is, or whether the energy needed to keep the wheel turning is somehow dissociated from that.
Best
Jever
----
No longer in the industry
No longer in the industry
- cyclespeed
- Posts: 1120
- Joined: Mon Jun 06, 2016 8:45 am
Well, verdict time.
Albeit I haven't ridden the Corimas that much (about 400km), it's enough to already have a favourite.
The Lightweights had a strong position as my favourite wheels and psychologically that's a tough crown to take.
But there's a few things about the Corimas that I can't ignore;
1. Rougher, crashier ride. I set my tyres to 100psi every ride (as Vittorias lose pressure every day), so this is consistent. The Corimas are noticeably crashier over lumps and bumps, making me wonder if I put in 120, 130psi by mistake. This may be because they are stiffer than the LWs. Personally, for me, at 63kg, I don't need super stiff wheels. But this could be a benefit for a bigger more powerful rider.
2. Freewheel lash. You know when you are kind of half-pedalling and you get a bit of 'lash' in the freehub? That is accentuated on the Corimas. I don't notice any on the LWs, but with the Corimas it seems to happen more often. Maybe something to do with the number of pawls, engagement teeth in the freewheel??
3. Aero. In my opinion, all same size rims are equal or as near as dammit. (I don't believe that a Super Cresty Strikey 50mm rim is detectably any more aero than anyone elses 50mm rim). So that leaves spokes. And the Corimas have big fat non aero round spokes in the rear. They clearly recognised this as a problem as this latest edition now has flatter spokes in the front. But for me, this is a non-ideal aero setup.
There is just a touch of magic missing from these wheels that the LWs have in spades. My rear LW in currently in for a bearing change, but I can't wait to get them back on.
Albeit I haven't ridden the Corimas that much (about 400km), it's enough to already have a favourite.
The Lightweights had a strong position as my favourite wheels and psychologically that's a tough crown to take.
But there's a few things about the Corimas that I can't ignore;
1. Rougher, crashier ride. I set my tyres to 100psi every ride (as Vittorias lose pressure every day), so this is consistent. The Corimas are noticeably crashier over lumps and bumps, making me wonder if I put in 120, 130psi by mistake. This may be because they are stiffer than the LWs. Personally, for me, at 63kg, I don't need super stiff wheels. But this could be a benefit for a bigger more powerful rider.
2. Freewheel lash. You know when you are kind of half-pedalling and you get a bit of 'lash' in the freehub? That is accentuated on the Corimas. I don't notice any on the LWs, but with the Corimas it seems to happen more often. Maybe something to do with the number of pawls, engagement teeth in the freewheel??
3. Aero. In my opinion, all same size rims are equal or as near as dammit. (I don't believe that a Super Cresty Strikey 50mm rim is detectably any more aero than anyone elses 50mm rim). So that leaves spokes. And the Corimas have big fat non aero round spokes in the rear. They clearly recognised this as a problem as this latest edition now has flatter spokes in the front. But for me, this is a non-ideal aero setup.
There is just a touch of magic missing from these wheels that the LWs have in spades. My rear LW in currently in for a bearing change, but I can't wait to get them back on.
- jekyll man
- Posts: 1570
- Joined: Wed Apr 25, 2007 10:23 am
- Location: Pack filler
cyclespeed wrote:Well, verdict time.
2. Freewheel lash. You know when you are kind of half-pedalling and you get a bit of 'lash' in the freehub? That is accentuated on the Corimas. I don't notice any on the LWs, but with the Corimas it seems to happen more often. Maybe something to do with the number of pawls, engagement teeth in the freewheel??
.
I'm glad someone else has found this; I run a corima disc on my tt bike, and thought there was too big a delay taking up the drive, but I wasn't sure if running an osymetric chainring was a contributory factor. Obviously not, by the sounds of it
Official cafe stop tester
Gazelleer wrote:Forgive my ignorance but how does that rear wheel lacing work? There cannot be any tension on the spokes this way, can there?
These wheels have no tension in the spokes - also if you break a spoke it will still go straight. The spokes are strong enough to get a stiff wheel without tension in the spokes
we can`t compare Lightweight Meilenstein with Corima... Lightweight are the best wheels ever
Nice review.
Re spokes, have to admit for overall ride quality and aeroness (perceived or real) I prefer wheels with traditional bladed steel spokes (e.g. CX Rays) and so stick with Boras, Zipps etc in part for that reason. That alone would put me off LWs and these Corimas, and I never liked it with the CCUs I had, though the carbon spokes maybe do give a nice snappiness going uphill
Re spokes, have to admit for overall ride quality and aeroness (perceived or real) I prefer wheels with traditional bladed steel spokes (e.g. CX Rays) and so stick with Boras, Zipps etc in part for that reason. That alone would put me off LWs and these Corimas, and I never liked it with the CCUs I had, though the carbon spokes maybe do give a nice snappiness going uphill
----------------------------------------
Stiff, Light, Aero - Pick Three!!
Stiff, Light, Aero - Pick Three!!
Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓ Broad Selection ✓ Worldwide Delivery ✓
www.starbike.com