Open mold wide profile carbon wheels

[Beaver]

Even the "best in the test" Zipp 303 FC Disc are not really optimized for 25mm tires (real 28mm width) - like the Roval CLX 50 it's 21C, 29.9mm at the widest point but narrower at the brake track. These wheels perform best with 23mm (real 26mm width) tires.

That's why the differences between 25 and 28mm aren't that big, as already with the 25mm tire, the airstreem will lose contact to the wheel very early. So between 23 and 25mm tires it will be a few watts more, especially in the very high angles. It's just the 105% rule again...


http://bikeblather.blogspot.de/2016/03/ ... party.html

But you are right, the differences in rolling resistance - especially on very rough tarmac - are much higher.


https://silca.cc/blogs/journal/part-4b- ... -impedance

[Beaver]

I have both LB 46mm and Venn 507 (50.7mm).
Their shape are similar but the LB is more blunt at the fairing end. It's like Venn 507 is the LB 46mm that extend further and end at sharper V.
Venn got their shape from computer simulation but did not aero tested in real world.

The new Bontrager Aeorus (also modern wide V shape) are very close in shape to Venn 507, and it aero tested to be better than other leading brands.
We can only guess How Aeorus 's test hint Venn 507 (which is computer simulated well) and the LB's real word performance.

The perfect rim shape doesn't exist. My guess is, that torodial will always offer the best aerodynamics, but is most prone to crosswinds.

Bontrager got back to V-shape because of its better stability in crosswinds, not better aerodynamics. A sharper V-shape handles better in crosswinds, Reynolds are best in this category, but add a few watts.



Rounder V-shapes are a good compromise, and the fact, that the higher Bontrager rims get "sharper" shows their wish for stability.

[emotive]

it looks like there's only ~1w difference between 25mm and 28mm tires on most of those rims at typical yaw? So that probably needs to be factored against the rolling resistance difference for the wider tires.

Good perspective. I'll happily take a 1W aero penalty to run a more comfortable 28mm tyre.

Buying new wheels to save 1w sounds extreme, but I would definitely agree that buying a wheelset that has been aero tested is the only thing that makes sense if looking for these marginal gains.

(I threw away 1w aero savings by using Laser spokes, so clearly I did not build these wheels to time trial; I just like how they ride.)

I agree, I can't justify new wheels for a 1W gain. I can re-purpose the older wheels to my gravel bike, as I need another set anyway, but I'll wait for wheels that provide bigger gains. Hopefully in 6-12 months Hunt will have their 'optimised for Pro One 28' wheels. Imagine how wide they will be, 35mm perhaps?

[Beaver]

For a real 33mm wide tire, the rim should be around 34,65 to 36,3mm wide for best aerodynamics. But at this width the lower rolling resistance will not even out the higher drag at higher speeds anymore, because of the now really wide frontal area. On normal roads it only makes sense for slower riders with less than 30km/h average speed. For Gravel one should question the 105% rule, because a wider than the rim tire will protect the rim and aerodynamics are less important here.

[emotive]

For a real 33mm wide tire, the rim should be around 34,65 to 36,3mm wide for best aerodynamics. But at this width the lower rolling resistance will not even out the higher drag at higher speeds anymore, because of the now really wide frontal area.

DT Swiss did their Road Revolution crossover test for the 25mm vs 28mm GP4000II, and concluded that the 28mm is faster if you average less than 35km/h. That was on their 27mm wide ERC1100 wheel. I'd say the 28mm GP4000 measured 31mm on the DT Swiss wheels. How much extra drag do we get increasing to a 33mm wide tyre on a 35mm wheel?

On normal roads it only makes sense for slower riders with less than 30km/h average speed.

I'd estimate for a club rider on an endurance bike with 28mm tyres, the average speed is closer to 25km/h than 35km/h. At 25km/h, or even 28km/h, I expect the rolling resistance of 33mm wide tyres is a bigger benefit than the aero penalty.

That's without considering the comfort/fatigue benefits of a 33mm measured tyre.

[Beaver]

This?



I agree, at 25km/h aero is nearly unimportant. But again: Have a look at the drag and rr watt differences, low one digit.

And did they use the same tire pressure or not? And both tires are wider than the 27mm rim (19C), what would be the result with a matching 30 or 32/35mm wide rim with 21C and 23/25C? But the differences will always be tiny, on the one hand you have a lower rolling resistance, on the other hand a larger frontal area.

For aero assure to have a tire that is not wider than the brake track (and very fast riders should keep 23mm tires up front), for bad roads pick a wide inner width and mount a tire with low pressure. I will try the LB 23C 30mm rim with 25mm tires on rough roads and my 35km/h average.

Edit: And mcfk has the right rim for you. http://www.mcfk.de/2/felge/felge-mtb/felge-29.html

Those with Carbon-TI X-hubs, CX-Ray and 28mm Schwalbe Pro One and maybe 3bar (?) should be comfy and fast.

[Svetty]

Noticed my LB rims don't have drain holes for water to escape/evaporate via. My other wheels generally do.
Is this a problem in practice?

[Klaster_1]

Noticed my LB rims don't have drain holes for water to escape/evaporate via. My other wheels generally do.
Is this a problem in practice?

I never had any issues with water drain, but then again tend I keep away from it: no creek crossings or riding through puddles.

[krafra]

Just received some Farsports wheels

Can anyone tell me if this is normal?

[alcatraz]

Just received some Farsports wheels

20180515_121958.jpg

Can anyone tell me if this is normal?

It doesn't look pretty but it doesn't prevent using the wheel is my take. I have several chinese wheels and on few of them I had to grind down a few rough edges with the dremel. I use veloplugs (no rimtape) so it's important to have a smooth rim bed. For rim tape users it's no big deal what you are showing. An exposed spoke nipple hole is a greater threat to your inner tubes than these bumps.

With anything chinese you need to have some common sense and observe anything weird. Maybe someone else with more knowledge about carbon can tell you more about the specific marks in your picture.

/a

[alcatraz]

Having a sharp edge on one side and a comparatively wide and blunt shaped tire on the opposite side can't be good for crosswind stability is my guess.

These new bontrager rim shapes to me look like a kind of mix between aerodynamics, crosswind stability and ability to take a wide tire if needed while maintaining a low weight.

Whereas Zipp shapes may actually be less aero, their much larger depth obtains the aerodynamics while still being crosswind stable, bus loses in the weight department.

Fishtail V-shape I think is a way to add lower weight aero properties to a shallow rim that doesn't suffer from crosswind issues. For max aero you won't find this because they will all be toroidal and much deeper, for stability.

An amateur's analysis...

Also never mentioned in the discussion above is rider weight. A rider with 50% more weight 90kg vs 60kg might benefit from 28mm tires but lightweights need to focus much more on staying aero over rolling resistance. A narrower rim and 23mm tires might be the right way to go. Using the same principle that a heavier rider might run a 23c in front maybe us lightweights actually could use a 21c-22c in front. Of course I'm exaggerating but it's not as crazy as saying 28mm is great for everyone. (not claiming that you did)

/a

[krafra]

Just received some Farsports wheels

20180515_121958.jpg

Can anyone tell me if this is normal?

It doesn't look pretty but it doesn't prevent using the wheel is my take. I have several chinese wheels and on few of them I had to grind down a few rough edges with the dremel. I use veloplugs (no rimtape) so it's important to have a smooth rim bed. For rim tape users it's no big deal what you are showing. An exposed spoke nipple hole is a greater threat to your inner tubes than these bumps.

With anything chinese you need to have some common sense and observe anything weird. Maybe someone else with more knowledge about carbon can tell you more about the specific marks in your picture.

/a

Thanks for the reply. Compared to the rear wheel it's much more rough. The spoke hole entry is much more smooth. See this for example.

[Beaver]

That's how it should look like. Everything else it low manufacturing quality. ACE Bike/Yishun and especially Light Bicycle are a better choice.

[Beaver]

Having a sharp edge on one side and a comparatively wide and blunt shaped tire on the opposite side can't be good for crosswind stability is my guess.

That's what everybody thought, but real life testing showed the opposite. Triathletes were the first to recommend Reynolds wheels for strong winds. The Tour Test 2016 proved them to be right, with that 1 Nm side force as on Mavic Ksyrium wheels, whereas the Zipp 808 had 11 Nm, so 1.1kg pulling on your front wheel...

The last test of Triathlon Mag. showed the same (sorry German only): https://www.google.com/url?sa=t&rct=j&q ... kaXSYxl_uI

And they didn't even mind to show the wind tunnel data as the differences where too low (1.8 watt between Zipp 808 NSW and Mavic Cosmic Pro 40mm at 45km/h)...

They concentrated on ride quality, brake quality and crosswind stability (and also state that it's more important, that the tire is not wider than the rim).

These new bontrager rim shapes to me look like a kind of mix between aerodynamics, crosswind stability and ability to take a wide tire if needed while maintaining a low weight.

Their aim was to reduce side forces, even with more aero drag: http://trek.scene7.com/is/content/TrekB ... epaper.pdf

Whereas Zipp shapes may actually be less aero, their much larger depth obtains the aerodynamics while still being crosswind stable, bus loses in the weight department.

Zipp are most aero and most prone to cross winds. That seems odd, but the new BMWs lead the wind around the front wheels too, are more aerodynamic but also a pain in cross winds. But it's always only the initial drag, then there's no problem (as long as the wind speed is stable).

Fishtail V-shape I think is a way to add lower weight aero properties to a shallow rim that doesn't suffer from crosswind issues. For max aero you won't find this because they will all be toroidal and much deeper, for stability.

Sharp V-shapes are worst aerodynamically (mainly in high yaw angles) but most stable in cross winds. It's really true.

Also never mentioned in the discussion above is rider weight. A rider with 50% more weight 90kg vs 60kg might benefit from 28mm tires but lightweights need to focus much more on staying aero over rolling resistance. A narrower rim and 23mm tires might be the right way to go. Using the same principle that a heavier rider might run a 23c in front maybe us lightweights actually could use a 21c-22c in front. Of course I'm exaggerating but it's not as crazy as saying 28mm is great for everyone. (not claiming that you did)

That's also true. The comfort and rolling resistance is influenced by the tire pressure. A very light rider may be happy with 23mm on 19C even on worst roads as he may run very low pressures and a very heavy rider needs 28mm on 25C. But again, don't worry too much about this topic, the differences are tiny.

An interesting test result from SwissSide: leaving your optimal aerodynamic position increases aero drag by 10 watts per centimeter.

[krafra]

That's how it should look like. Everything else it low manufacturing quality. ACE Bike/Yishun and especially Light Bicycle are a better choice.

I have now contacted Farsports regarding the issue. Hopefully a new rim will be provided under warranty.