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Testing the stiffness of frames...(5 posts)

Testing the stiffness of frames...Ride-Fly
Feb 22, 2003 2:38 PM
do any of you ever do this: stand at the side of the bike, facing it, place hands on seat and bar, and foot on center of crank/bottombracket. Then apply steady even pressure. I know this is a very subjective test as the lateral stiffness of the wheels play a huge role, as well as the fact there is no torque or PSI meter in my foot but I think you can roughly gauge the stiffness of frames with this method. BTW, I wouldn't recommend trying this on some frames such as Bianchis or Williers (frames that have a reputation for using extremely thin walls and breakage history) I usually do this to all the mountain bikes I am interested in purchasing (or just out of curiousity in how it compares to my MTBs). I decided to try this on my '00 Klein Quantum Race and '02 Fondriest Carb Level. I was a bit suprised by the results. First of all, the difference in lateral stiffness of Rolf Vector Comps and Mavic Ksyriums were fairly noticable. The Rolfs made both bikes a lot stiffer than the Ks. So I did this fairly unscientific test with both sets of wheels on each bike. I am suprised because I didn't think I would be able to tell the difference with this test as I could barely notice it when riding the 2 bikes. I suspected the Klein felt just a micrscopic hair stiffer while riding but I thought a lot of that was the effect of the carbon stays on the Fondy. The Fondy is buttery smooth, as smooth as the DeRosa Corum I had tested on a short 7 mile slightly hilly, not-so-smooth route earlier in the year. Also, the Fondy has a reputation for being a stiff frame (with its CNC chainstay/BB juncture). Basically, I think it illustrates to me that the Klein frames are just a notch above others, even my much more expensive, (yes I'll admit it-overpriced Italian) Fondriest. My point (not that I have a real point) I am trying to make is that I would love to see an objective test on frame stiffness like the one Cannondale did with their CAAD 7 ads featuring "OTTO" frameflex measuring machine. They tested their Optimo tubed CAAD 7 frame against the C-40, Trek 5900, and LS Vortex. I wish CDale would have included others. Then again, maybe the results wouldn't have supported the intended purpose of their ads (meaning CDales were not the stiffest and lightest frames out). Thanks for reading my dribble...Ride ON!!!
old data but...Akirasho
Feb 22, 2003 4:14 PM
http://www.sheldonbrown.com/rinard/rinard_frametest.html

Time for someone to take up Damon's reins...

In the past, Cannondale frames were noted for their stiffness and strength... I no of no independent data for the CAAD7.

Be the bike.
Better make sure the tire pressure is the same in all the testsupandcomer
Feb 22, 2003 4:42 PM
re: Testing the stiffness of frames...gtx
Feb 22, 2003 11:43 PM
A customer cracked a Kestrel frame doing that at a shop my friend worked at (this was 10+ years ago). I don't think that "test" proves much of anything--kind of like kicking tires. Check out KB's article on stiffness:

http://www.bontrager.com/keith/rants.asp?id=32
Bicycling Magazine used to do that.Spoke Wrench
Feb 23, 2003 11:40 AM
They had a machine that I think was designed by Gary Klein they called the Tarentula. The bicycle minus the wheels was clamped into it by the dropouts and a measured load was placed on a crankarm. Dial indicators measured frame and fork flex.