I have a 2011 BH G5 (54cm) with Edge 45 Clinchers and Conti 20C race tires. Dura Ace shifters with 53-39 Rotor rings, Bontrager XXX carbon brakes, and Edge 45 Clincher wheels. 6.4 kgs. without pedals or water bottle cages.
At first, coming off a Defy Advanced 1, I found the ride to be a bit on the harsh side. On the flip side, climbing speed was much better. On my first ride, I improved a personal best time on a regular climb by about 45 seconds on a 13.30 min. climb. Riding on the river flats, the aero wheels seemed to cut the wind so well,that I literally stopped to feel if I had a tailwind behind me. (seriously) However, on long steep descents, I was a bit put off by the sound of the wheels, and also couldn't shake the visions of the wheel rims getting gooey from getting too hot.
I changed the wheels to a pair of Dura Ace 9700 C24's with Michelin Pro 4 23 C's. What a difference! The ride of the bike is now comparable to my Defy with Ksyrium Elites with Michelin Pro 3 23 C's. Descent stability is stellar with this combo. I like having my pedals at 9 and 3 o'clock, squeeze my legs tight on the seat, lean and carve into the turns. On a recent 105km bike race, on a long descent, I found myself getting caught by surprise on some sharp turns. My first instinct was to brake, but I resisted that urge, and just leaned in. The track was just so precise and so easy to hold, and everything felt incredibly stable, even when the road surface gets rough. No wandering out towards the edge of the road and needing to brake for lack of control if you dared to lean harder into the turn. With the G5, I found no fear of just leaning harder and harder into the turns. The slack seat angle gives my rear and the bike's rear a very planted and stable feel. The nice stiff Edge fork and Dura Ace worked in perfect concert with the front end going exactly where I wanted it to go.
With Rotor oval rings, I get the feel that they dull the "responsive" feel of a bike when climbing. That being said, I love the smoothness of the application of power both on the hills and on the flats. I experienced knee problems on my Defy with a click in my right knee, and soreness in my left knee on long extended climbs. I found my knees are noticeably more comfortable on the long rides with my BH G5. Rotor cranks? Geometry? 170, instead of 172.5 crank arms??? Not sure which one, but the difference is more than noticeable.
The G5's low 12mm head tube was an easy adjustment for me. But, I did find that my back aches a bit on the long climbs due to not being able to get my back perfectly straight when standing on the pedals. I might try a slightly shorter stem to get my whole body moved backwards just a little bit.
Confession: I also run a 11-32 Sram rear cassette with the 53-39 front gears. There were a couple bike shops that just refused to even try this combo. I finally found a shop that would give it a try. I had to buy a new chain because the original chain was just too short for the ultra low gear. However, once lengthened, everything works like a charm, even with the oval rings!!! I have been trying to train myself not to use that lowest gear on all but the steepest climbs or towards the end of a long ride with lots of climbing. The 39 - 32 combo puts me in prefect sync with other riders with 34-28 compact combo. The Sram cassette is louder, as most people have posted.. but I LOVE THE DURA ACE COMBO. QUICK SHIFTS, and a very obvious quick positive clunk when you change the gears. I just love coming out of stop lights, in full sprint mode, running up through the gears under full power... never letting up on the shifts, and feeling those hard hitting clunks! Acceleration compared to the Defy is beyond compare. The 6700 Ultegra hardware feels like slow motion with very silent but marshmallow feeling shifts. The frame and wheels don't respond like the G5 does either.
I find the G5 40cm 3T carbon aero ergo handlebars, just a tad too narrow for getting the best feel for me. Anybody have some 42's that wants to trade? I also find with the slack seat angle, I run the Fizik Carbon railed seat in a fairly forward position. At first I didn't like the long carbon railed Fizik Arione seat design. However, in actual riding, you find that there are so many different positions that you can have your body adapt to with the long flat plane of this seat all the way out to the pointed trailing edge. When your legs get tired in one position, you can shift a good 10 cm's backwards and engage a very different set of muscles.
I think that the paint job with Red/Sparkle Grey/ Black and white accents is just drop dead gorgeous. The clear coat is mirror smooth, and just shines until midnight. Ok... however, much that paint weighs.. I'll proudly pedal that dead weight, for sheer beauty's sake. Finally, the Bontrager Black carbon triple X brakes look like they were custom made for this bike. They look so cool with the G5 paint scheme, that it brings down the ambient temperature by 5 degrees within a 3 meter radius of the bike.
All in all, I am in G5 heaven, and just loving it.