Bicycle Frame Stiffness : The Numbers

Twelve top end bicycles that you can buy for money and the wheelsets they had were recently thrown into mechanical tests by the German magazine RoadBike.de. Which means, lots of interesting figures for you guys with fat wallets and zilch to lose. For people modest with finances like me, I just like to see the data that these state-of-the-art bicycles are putting out these days.

Methodologies of the tests maybe read here, if you know German. The bikes were all sub 6.8 kg. The models and the figures they posted are shown below.

• BMC Team Machine SLR01 : Link
  
• Canyon Ultimate CF SLX Ete 201 : Link
  
• Cervélo R3 SL : Link
  
• Cube Litening Super HPC Race : Link
  
• Focus Izalco Team Milram : Link
  
• Haibike Affair RX : Link
  
• Lapierre Xelius 900 : Link
  
• Red Bull Carbon X-Lite 8800 : Link
  
• Scott Addict R1 : Link
  
• Simplon Pavo Red : Link
  
• Storck Fascenario 0.7 IS : Link
  
• Trek Madone 6.9 Pro (this is what Contador won the '09 Tour de France on) : Link
  

Bottom Bracket Stiffness

Headtube Stiffness

Fork Stiffness

Comfort Related Stiffness (lower stiffness, or more the compliant, is better)

Wheelset Stiffness (front & rear respectively from left to right

Observe that Mavic R-Sys, whose notoriety is second only to the spectacular failures it suffered out on the field, posted 5% lower stiffness than the average of the 12. Overall, the Canyon Ultimate was rated the best bike in this test.

Readers may recall that last year, I posted stiffness data for Museeuw's MF5 Flax-CF bike. I'm also interested in what another exotic frame - the Delta 7 Isotruss - shows in comparison. So here are those two that I plug into one chart. Really interesting.

Delta 7 vs Museeuw MP5 Flax. Courtesy for data : German Tour Magazine

The Ascent bike is described by the company as "extremely stiff" due to its structure and so light it is "exhilarating". However, the numbers Museeuw's Flax frame has posted put the isotruss slightly down. Both frames are however no where in comparison to the bikes above for bottom bracket and headtube stiffness, although they seem to be relatively more compliant for comfort. The flax bike is second only to the BMC Team Machine in comfort and I wonder if the benefits of the flax are tied into this.

This exercise only compares stiffness of these frames. Do remember that stiffness is not the only yardstick by which bicycles are measured. Lot of stiffness is beneficial in some spots but unnecessary in others. Lot of stiffness may suit some riders but not others. See, if stiffness alone were the holy grail of bike design, we'd all be riding on reinforced concrete by now. And you'll need lots of chamie cream for that.

ADDITIONAL READING :

Rational Bicycle Frame Design : Giving Consideration To Functionality
Buckling In A Bicycle Frame
Dynamic Ride Comfort & Measuring Vibration In Bicycles
Carbon Nano-Tube Technology In Bikes
Nanotechnology Application In Bicycles : How Good?

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