I am just kind of wondering, when I spin the Dura Ace wheels they stop kind of quick and also doesn't let the valve settle to the bottom, they came factory preset and I never touched them. It just seems like they don't roll very fast either, kind of hit a wall at 35-36mph. When I was quite sure my other wheels could reach 39-40mph easy. Is it the bearings or the rim shape? They are great wheels but it's hard to compare with cartridge bearing or more aero shape wheels. They are the clincher version with more boxy rim shape.

Eh? Same terrain? Same wattage? Same position? How measured?

Shimano DA hubs are as good as any on the market. In fact, they're vastly superior to most. They're cup & cone, so maybe your cones are a bit snug? Worth checking.

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Could be right
I was told they would loosen up but never did after some miles

Won't touch the question regarding rim profile and personal speeds achieved......

Valve at the bottom is an assumed point of reference.....but not all rims are weight toleranced for that to happen - case in point is Bora wheels where Campagnolo places extra material opposite the valve to offset the weight of the valve - therefore those wheels (specifically the ones I have) never come to a stop with the valve at the very bottom.

Cup and cone (such as the higher level wheels from Shimano and Campagnolo) are infinitely adjustable and far superior to cartridge bearings (easier future maintenance, lower drag).

In my experiance, high end cup and cone wheels don't require a break in period. In your case possibly the factory adjustment is less than idea. Do you know how to adjust them as it sounds like that would be a good first thing to play with on your own.....nothing hard to do.

Skewers clamping pressure may require your cones being backed off slightly.
Just make sure there isn't any play when then wheels are fitted in the frame.

i'm pretty sure the DA axle design does away with clamping forces acting on the bearings.

My DA C35 needed adjusting off to match the smoothness of my friends Eurus setup, however, even before that i was amazed how quick they rolled but really i doubt that the wheels are knocking of 5mph of your top end that would be an impressive loss... to many variables.

i had the same problem...did some servicing to the bearings...still same problem...

did a side by side test with my wife's alex rim...my DA wheels indeed stop faster...

sold it and bought custom wheels with DT240s hub...problem solved!!

Odd. I'd say adjust them as a first try. Should be ever so slight movement of the axel in your hands. Or tight, minus 1/4 turn. Play around with it if your skewers (are they Shimano?) don't make up the difference. An extra pair of hands can help if you're not used to cone adjustments.

As others have said, the DA hub/bearing arrangement is as good as they come. I have two sets of C24 wheels and one needed adjustment right off the bat. I think some ship a little tight and its not worth waiting for them to loosen up. Just have them adjusted as its easy, and they will virtually spin forever.

shimano hub indeed have this problem，dura ace ride over 1000km can solve it，it's seem no a big problem，it wouldn't effect you when you cycling

+1 on an adjustment issue. The Shimano DA hubs are stalwarts of the industry. If there is a problem after adjusting them, Shimano will make it good. The axel is very stiff. You only need a tiny amount of play off-the-bike. If it is perfectly adjusted off-the bike, you may find it too tight when you install it. Are you test-spinning it in the dropout? When you adjust the bearings, you have to account for the tightness of the skewer, so always test the wheel in the dropout.

How do I adjust the cone? Normally there is a locknut, so on this one, is it just the 5mm key instead of the lock nut?

Just a tightening torque but doesn't tell me how to adjust it.

Picture included.

I think they are land-anchors but they spin really well normally so this is odd.
It could be a folded dust seal, or as others have suggested, over-tight bearing setting (unusual for DA). Check bearing settings by backing the QR right off and re-spinning it then tightening it beyond normal pressures and comparing the 2 spins.
Re adjustment. Back the outer lock-cap off using the allen key while holding the cone in place with a cone spanner. The cone can now spin comparatively easily and you'll be able to "back it off" ( only go about 1/4 turn as the threads are reasonably coarse) then re-lock the lock cap. It only takes about 1 min to do BUT you may have to have a few goes at finding the "sweet spot" where you have perfect clamping force from the QR and no movement at the rim near the brakes but free spinning.

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Used to race....got too wrinkly and old Updated: Racing again! Thought this was unlikely! Eventually, I may even have a decent race!