Aero TT Framesets

Raffy Varona said:

Since all of these new aero tt frames are being released with more integration on the frames like integrated front brakes, how can one tell which one is faster/ more aero? Any personal preferences/experiences? I'm not going to take the frames to a wind tunnel because I don't live near one nor do I have the time to go to one.

You can't without taking the frames to a wind tunnel. The wind tunnel tests that manufacturers and other entities use do not tell you which is best. They tell you which has least drag given the set of wheels, the rider on the bike (or without a rider on the bike), with the wheels spinning (or not),........... Frame A with wheel set B might be faster in one tunnel than Frame B with wheel set B, but Frame B might be faster with wheel set C. You should note that there's a fair bit of agonizing done by people going to test about the number of tests they will do, the number of pieces they will test, and how they're going to set up each test. Keep well in mind that a bicycle frame/fork produces only a small amount of drag, and it's entirely possible that the difference between frames in a given test is within the noise of the wind tunnel and test measurement. The best option is to buy the TT frame that fits best, rides best, minimizes wallet damage, and trips your happy triggers.

+1 on, but especially on this part

Quoted post said:

Originally Posted by alienator [IMG]/img/forum/go_quote.gif[/IMG]

...The best option is to buy the TT frame that fits best, rides best, minimizes wallet damage, and trips your happy triggers.

The bike that fits best in terms of TT stack and reach is almost certainly going to be more aerodynamic in the end (with you on board) than the latest uber bike if you can't achieve your best fit or have to start adding a lot of front end spacers or otherwise disturbing the clean lines of a properly fitted TT bike. And not all frames fit the same as there are differences in stack, reach, TT length, ST angle, HT length, etc. that impact rider fit.

This is from last year but provides a good summary of stack and reach differences among commercial bikes: http://www.slowtwitch.com/stackreach.html

More info on TT bike geometry variations here: http://www.slowtwitch.com/Bike_Fit/Geometry_and_Handling/Graphing_geometric_themes_1321.html

Start with fit, but it you're looking for the fastest TT setup it also makes sense to pay attention to the well accepted and common features that have been shown to reduce drag including:
- Internal cable runs with minimal exposed cabling
- Low profile integrated headsets, either running a spacerless flat (-17 degree) stem or one of the modern designs with a flush integrated stem that nearly every major manufacturer has offered following the success of the Shiv with their ultra clean lines leading flush into the top tube.
- Hidden or low profile brakes (or run a set of Tririg Omegas, very cool small and yet powerful aero brake)
- Curved seat tube that partially fares in the rear wheel
- Highest aspect ratio frame tubes legal under your racing class (3:1 max for UCI racing)

So you end up with one of perhaps six or eight bikes developed in the last couple of years and you run it in a size that doesn't defeat the design (for instance run a big enough frame that you don't need to add a ton of spacers above your super sleek integrated stem or worse have to run a bunch of round stem spacers and an uptilt stem to achieve your best fit on a bike a size or two too small).

That's the 'money's no object, gotta have the newest' approach. Personally my TT bike is six or seven years old, still has exposed cable runs, conventional -17 degree stem, exposed brakes in the normal places (though I went to the Omegas and dig 'em) and it's plenty fast. I've ridden faster times than some folks on uber bikes like the Shiv or P4 and have had my clock cleaned by some fast folks on very low tech round tubed steel and alloy TT bikes but their positions were good and their fitness trumped mine.

Pretty decent discussion on frame drag charts and interpreting the results here: http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=2477448;page=1;sb=post_latest_reply;so=ASC;mh=25;

Good luck,
-Dave