I’m building up a new BMC TT02 (SWEET deal on a frameset, BTW!). The TT02 comes standard with an Easton EC90 Aero fork, but I had used an Oval Concepts A900 on my previous Cervelo–does anyone have experience in the tunnel or the track with the Oval Concepts? Is it ACTUALLY that much faster with a Zipp 1080?
The rims have become so deep now that the maximum velocity of the spokes is no longer twice the velocity of the bicycle (i.e. at the top of the tire the velocity is 60mph when you’re traveling 30mph). Instead, it is:
(VELOCITY) * = 30 * = 48.2mph
The spokes are further from the fork blades because they effectively make a smaller triangle between the hub flanges and the rim. There are also only 16 of these babies spinning through the fork blades, and the larger nipples are even hidden. I would imagine this really negates the benefits of the “pressure-relieving” vents in the A900.
The A900 is a solid aero fork. It rivals the Reynolds Ouzo Pro Aero in most circumstances.
The fork was manufactured with the air reliefs facing the wrong direction (from outside to inside instead of inside to outside). On principle, you should not buy this fork so that Oval will get off their ass and retool the molds to work correctly.
While the aerodynamic benefits of this (vented fork blade) design are quantifiable and provable in the wind tunnel they may not offer a tangible benefit in the real world since many riders spend enough time *below *the minimum speed required to appreciate much of a benefit.
In other words: If you have to stay over 24 M.P.H. to appreciate a tangible time savings but the course doesn’t allow you too because there is too much cornering, too many hills, the rider themself is not fit enough, the value of the design diminishes.
If you were going extremely fast for the entire ride the benefit may be there. If not, it is debatable at the best. Additionally, as the previous fellow pointed out, there is a school of thought that the design is less than optimal for aerodynamics even at extremely high average speeds.
Reynolds touts their TS20 as their most aero time trial fork. Is this the same as the “Ouzo Pro Aero” referred to?
Anyone know how the 3T Funda forks compare to either of these, or how any of these compare to the stock fork on a Trek Equinox 9.x?
Would it be worth it to change from a stock Trek fork to any of these?
I am headed to the wind tunnel and I could try an alternate fork, but only if there was a realistic chance of gains.
I’ve heard about wheels travelling 2x the speed of the bike before and don’t doubt it’s true but am having trouble visualizing. do you have a link to where the formula in your post comes from as I’d like to see it explained / think it through.
You can also imagine that every point on the wheel is traveling in the +x direction at 30mph, and then you account for the rotational velocity separately and add them together. This is what must be done when looking at points that do not lie on the vertical line extending from the ground to the hub.
If you wanted to be exact, the spokes are traveling through the fork blades at a ~73 degree angle, not 90 as is assumed in these calculations. The spokes would still be traveling through the fork blades at (R/11.1) mph, i.e. 30mph at the maximum point on the tire, but the air velocity tangent to the spokes and fork blades is actually SIN(73)(R/11.1)=0.956(R/11.1).
The angle of the fork reduces the tangential velocity of the wind through the fork blades, but not by much. If you were to assume (like my paper calculations do) that the fork blades are vertical, then you could formally say SIN(90)(R/11.1)=1.000(R/11.1)=(R/11.1). The SIN() term drops out.