Patrick in VT wrote: Would I rather shave 5lbs bike/body or increase my functional threshold power from 300w to 325w? It's a no-brainer.
You are absolutely right. And that is why frame flex is so important. Imagine a bike that allows you to put out 325W instead of 300W for the same fatigue! From our testing, that is how "planing" works - the frame isn't more efficient for a given power output, but our power outputs vary with different frames. From our observations, it appears that you build up less lactic acid when the frame smoothes your pedal stroke, by storing energy during the downstrokes and releasing it during the dead spots. For those who think power output is constant, no matter the bike, it may help to think about pushing against a concrete wall. The wall doesn't move, so no work is done. Zero Watts. Yet you'll get tired pushing against the wall in no time. Similarly, if your frame doesn't move during the downstroke, it seems to limit how much power you can put into the system before the bike "pushes back" like that concrete wall. Then your legs start to hurt, and muscle fatigue limits your power output. On a bike that "planes," your legs don't hurt, and your cardiovascular fitness becomes the (higher) limiting factor. That explains why in our experience, performance correlates only very weakly with weight, but very strongly with optimized frame flex characteristics. (Of course, weight and optimized frame flex characteristics are correlated on most bikes, hence lightweight bikes often perform better than heavier ones.) Jan Heine Editor Bicycle Quarterly Follow our blog at http://janheine.wordpress.com/ On Tuesday, January 15, 2013 8:33:36 AM UTC-8, Patrick in VT wrote: > > On Monday, January 14, 2013 2:58:13 PM UTC-5, Skenry wrote: >> >> >> The only real way to compair weights is to have a frame built up with >> normal duty "heavy" Riv-ish parts and then build it again with lighter >> "racing" parts. Then you'd be able to notice a weight diffence. >> Scott >> > > If that's the case, I'll weigh in. I have two identical steel frame bikes > - same exact fit on both. One has a full-on race build for CX and weighs > about 17lbs. The other has a stouter build for gravel-grinding/rough-stuff > and is around at 20-21lbs - but is still worthy as a pit-bike for CX racing > and/or fast club riding. I absolutely notice a difference between the > bikes, but that difference is irrelevant to 90% of riding I do ... it > doesn't matter and I don't think about it. We're talking seconds (and not > a lot of them) on a long climb or a TT. That's what any "performance" gain > amounts to from dropping a few pounds off a "go-fast" bike, or a rider's > weight for that matter. Seconds. Maybe a couple minutes on a long ride. > > In my experience, step function improvement in performance primarily comes > from improved fitness/power, particularly functional threshold power > (basically the max power one can sustain for an hour). Far bigger gains in > performance can be had there. Would I rather shave 5lbs bike/body or > increase my functional threshold power from 300w to 325w? It's a > no-brainer. Lightweight might feel good, but being strong and fit feels > better - in my case, to the point where I don't sweat a carrying a few > extra pounds on my frame or a bike frame. > > It's not all that different with running. A general rule of thumb that > gets kicked around is 2 seconds per mile per extra pound of body weight. > So if I weigh an extra 5lbs for a local 5k, i can expect to be about 30-45 > seconds slower unless I improved my run fitness along with the weight > gain. in any event, we're still talking seconds or maybe a couple of > minutes on a 10 mile run. doesn't matter unless it matters, like trying to > qualify for the Boston marathon or if somebody is serious about setting > personal records (which a lot of runners are). > > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To view this discussion on the web visit https://groups.google.com/d/msg/rbw-owners-bunch/-/ixuj4ebYfMsJ. To post to this group, send email to rbw-owners-bunch@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
