Originally Posted by
mstateglfr
So do you want the same 31.8mm diameter for 10 inches across the middle of the bar? Most bars taper from 31.8mm at the center clamp down to 23.8mm for the ramps, hooks, and drops. Are you wanting 31.8mm all the way across the tops? I cant tell if what you call 'flare' is really just the taper that is normal for most all bars.
If you want 31.8mm all the way across the top, consider this in the round option(there are 3 options)-
https://www.bikethomson.com/product/alloy-drop-bars/
If you just mean you dont want the tops to rise or cant towards/away from the rider and instead you want bars that are straight, then consider Zipp Service Course bars. They come in multiple bends and widths. Here is just one example-
https://www.biketiresdirect.com/prod...gaAsq6EALw_wcB
For my aerobar attachment sites, I need 31.8mm across for the middle for at least 8 inches. The bars I have seen in my searches have an insufficient length of truly round 31.8mm diameter, but instead an oblong flat or top area (for aerodynamic or ergonomic reasons I suppose) that begins a couple inches +/- outside center. The Zipp bar you presented looks to be one example. The Thomson bar looked like the correct choice, but reading through the FAQ, it says that there is only a 90mm center area that is safe for clamping accessories. IDK, maybe the bar that is on my gravel bike (A Diverge that is setup like I'm wanting to do this bike, a Roubaix) has that limitation also and was never brought to my attention. Or are they strictly talking about their carbon handlebars here? Not really clear on that.