I think the size of tyre you use for Flanders depends on your size/weight and frame stiffness, I used 23mm on an alloy frame and was grand but I'm heavier now and would use 25mm tyres and a frame which allowed me expose more seatpost (such as a TCR) as the flex in this gives me just as much comfort as wider tyres does. With stiffer carbon frames I would consider lower profile rims and wider tyres for comfort , plus it means the tyres and not the frame is taking the shock.

I don't think any mainstream current production frame is "too light for Flanders"....Its not about the frame its about your wheels and tire choice. EM3

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My 2013 Cervelo R5

The pave´s in Flandern (I´m assuming you mean de Ronde) is not so bad compared to Paris-Roubaix. I use old style 32 spoke 3 cross handbuilts on both sportives but I dont think using stiffer wheels is really a hindrance in de Ronde but in P-R it definitely is. That said i´ve seen plenty of people on high profile wheels in both sportives. I use 27 mm FMB Paris-Roubaix tubulars and I´ve also used the 24 mm Vittoria Pave clincher. FMB´s get my recommendation for pave´s

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The unbearable wallet lightness of being a weightweenie