A disc is a disc is a disc.......

Not worth worrying about

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/

This was discussed in a different thread a while back.
http://forum.slowtwitch.com/...y;so=ASC;t=riaivbsah

Jens was pretty adamant that a lenticular disc was a little faster. There has also been discussion about the faster disc being dependent on the frame and whether it had a cutout or a no down tube etc. I know Grill (who is a stud time trialist) has said he's tested or seen tests in the velodrome where Hed and the Aerocoach discs (both lenticular) have tested faster than the flat Super 9.

In the end the end you are probably splitting hairs with the difference being pretty small.

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Matt

In some frames a flat disc may be worth 1-3w faster than a lenticular disc. In other frames a lenticular disc may be 1-3w faster than a flat disc,

The trick is to know which frames favors which wheel.

For instance I'm redoing my Scott Plasma 3, drilling the frame out to route electronic shifting, new aero bars etc.

I know my current disc is 2-3w slower than the disc I recently bought to complete Project Plasma.

I know where the Plasma 3 that I currently have built will place in the Aerobike shoot out (pretty damn high!). Once I get done with Project Plasma I've got a good idea how much closer, if not faster than a P5-6 it'll be!

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

I know a lot of people's aero data is private, but any insight on which is better for an old p2c? I'm planning on buying a wheel cover for my flo 90 rear, and I'm just curious how that stacks up.

Faster than the P5-6 will be quite the accomplishment. I am still waiting to see a WT test where someone 's alternative is significantly faster (not counting the P5X, which is barely faster). Keep us posted on progress and good luck

Gerard Vroomen stated that flat discs are faster on the P3C, P2C and P4
http://forum.slowtwitch.com/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Cervelo_P3_Owners_P3095831/

In normal circumstances, a flat plate will be significantly slower than a more typical convex aerofoil except, possibly, at very low angles of attack. This is because flow separation and stagnation will occur much earlier on a flat plate. In the case of a bicycle rear wheel where the surface is rotating, it's in an already turbulent airflow, and there's a tyre on the leading and trailing edges, it's much harder to predict. It's feasible that as others have said, it depends hugely on the configuration it's used in (i.e. frame, tyre and rider) and the conditions (airspeed, AoA/yaw).

Interesting. I am doing the same. Got a NOS Plasma 3 last week,
Using some of the info I found here on ST for the drilling.

For reference I'm building a Felt DA.

I’m not aero expert but have been running Jet6 with cover on my DA. I figured the “newer” frames were made to have a bigger gap for wheels so they were also made to be better suited for a leticular disc. And older frames, p2c, were better for flat discs since the clearance was an issue.

I could be totally wrong and am watching this thread to see if DD has an answer since I am likely going to purchase a disc for racing this season.

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Twitter - Instagram

As I stated before I was running a Flo 90 with a disc cover on my Cervelo P2 but I'm currently in the process of building my da and was considering changing to a full disk rather than a cover

Hopefully you both realize the most important part of any Plasma 3 build is sourcing the flat shark tooth stem ;)

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I got what you were saying. I was trying to say that for the DA I would assume that either a cover or a lenticular disc would be best on that frame. Since the 90 plus disc cover is pretty much the FLO disc I would go with that one, again, unless someone chimes in who knows way more than me! But my plan is to get a FLO disc as well.

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Twitter - Instagram

[quote]is sourcing the flat shark tooth stem ;) [/quote]

oh I have one of those!

I use it to lift weights. I can almost do a bicep curl with it!

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

Yeah it doesn't make sense to drop money on some, well many, probably > 50% anyway, of the newer aero bikes when they can't even beat an 6yo stock plasma 3.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

a good rule of thumb is less aero frame = lenticular disc. Highly shielded back wheel = flat disc.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

It doesn't really matter much. Though a lenticular disk will often be a little stiffer and might not flex back and forth as much. But it is highly bike dependent for what disc to use. I wouldn't overthink it.

To add to the OP topic: flat disc vs lenticular??? Don't forget, there was also the Zipp SUB-9 disc. Basically a bulged 404 with a flat disc in the middle. Zipp made the claim that it actually produced speed in the tunnel at certain angles.

Just a thought to add into the discussion.

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Team Zoot-Texas, and Pickle Juice

HED says their Stinger Disc, Stinger 9, and Jets 9 and 9+ provide forward thrust, can assume the Jet Disc does as well. Always wondered why Zipp had such a short run with the Sub9.
https://docs.google.com/...jNFbFpSa0ZfM3c#gid=0
Courtesy of Aeroweenie

Every disc has made that claim since the advent of the zipp 900. At high yaw they produce lift, that is translated into "negative drag" which isn't quite the same as propulsion, but the exact semantics don't quite matter

Although we've never tested a covered FLO 90 in a tunnel, I'm guessing that it would test very close to a FLO DISC. I say that because the lenticular shape in our disc is based on the shape of our FLO 90.

I sell wheels for a living, but this is a case where I'd likely encourage you to save your money. Now if you want one for convenience sake and are tired of installing the cover, then I completely understand that.

I hope that helps,

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling