5 Mar 2015

5th March 2015 Shimano 11 speed options.

It seems that Shimano has added 11 speed kit while my attention was wandering elsewhere. Their 11-32 x 11 speeds Ultegra cassette costs about £45[equiv] or £30 for the 105 version online. Both need an 11 speed chains at £15, £25 and £30 for 105/Ultegra or Dura-ace. I doubt 10 speed TA chainrings will be a problem with the difference in width between 10/11 being so small. [Less than half a millimetre] An 11 speed system should work well with my 11 speed Chorus Ergo levers too. It seems the former incompatibility between different manufacturers gear components has been erased with the arrival of 11 speed. Except that Campagnolo still uses different splines on their free hubs. The special Trykit 2WD freehub will take any Shimano cassette, including 11 speed, but is not available with Campag splines.

A 43/33 double chainset with 11-32 11speed sp cassette will give me road speeds from 5 up to nearly 30mph @ 90-95rpm. I find my present 28 x 30 bottom gear too low to be very useful for anything. So a slightly higher 33 x 32 should be fine for climbing walls. A trike is not balance limited at very low speeds so there is never any point in "getting off" on a hill to walk. Pushing a trike uphill is hard work anyway. Because the nearest rear wheel constantly tries to run you over. If you walk behind the trike it doesn't self-steer like a bike. A 30mph top gear capacity is strictly for downhill use these days and I can always pedal faster to go any quicker. 120rpm is no effort at all for somebody used to high 90s average cadence.

The need for multiple, close ratio gears as analogous to a small racing motorcycle. The very high [pedal] rpm requires that there is never too much resistance to pedalling forces. If resistance increases beyond the comfort zone then pedalling speed drops rapidly. The twiddler becomes a pusher without the physical resources to be one.

While the true pusher is the equivalent of the big V8 engine. The brute power at low rpm from large muscles allows him to accelerate rapidly but he uses up lots of energy in doing so. As soon as his energy reserves are depleted he becomes weakened by lactic acid build up. Every hill becomes a vicious interval. Most sprinters are heavily built and often struggle on the big hills. Their own weight is an obvious disadvantage but they still cannot [usually] spin freely enough against a lighter load, for long enough, because of their greater muscle mass.

Being able to match rpm to their natural power band makes the skinny climber able to maintain a higher speed uphill. The "leverage" applied to the pedals is high but the load lifted per pedal stroke is very low. This is compensated for by using much lower gears and higher rpm. There are many more, but much smaller pushes per minute or per mile. Lactic acid build up can be much better avoided at higher rpm than ploughing on in a big gear at low rpm.

So the more gears, the better the climber can exactly match his desired cadence to road speed while still maintaining a low enough pedal resistance to avoid fatigue on a given incline. Climbing in a low enough gear should essentially become a normal training ride. Spinning freely without serious effort per pedal stroke avoids fatigue. Since the cyclists is always fighting a headwind, of his own making, the need for close ratio gears holds true even on the flat.

The trick is to have the fitness and stamina to be able to keep spinning for long periods. While pushing a slightly higher gear, or using even higher rpm than the opposition, will maintain a higher road speed to reach the finish line first. Chris Froome shows the skinny climber's ability to spin very freely but lacks the raw power to accelerate. While the crafty opposition dances on the pedals in higher gears to pull away they use much more energy in doing so and seriously risk burning up on lactic acid.      

Here's a brilliant visual gear calculator where the sprockets and chain rings can be changed simply by dragging them along with the cursor:


If you want a triple just drag the left chainwheel onto the scales and then adjust the chainring sizes to taste by sliding them along until the required tooth numbers appear.

Gear-calculator screen shot: Note the speed scale along the bottom below the tooth count scales. Having lots of gears around your average cruising speed allows for variations in tiredness level, headwind and changing incline.

I can still remember working out my gears longhand back in the 1960s  before electronic calculators became commonplace. Now this clever software completely eclipses dry tables and raises usability to a whole new level of sophistication!

Gear inches = [Wheel diameter in inches x No. of chainwheel teeth] / No. of sprocket teeth.
For example: 27" x 48 / 18 = 72" Which used to be a popular gear for fixed gear time trialling.
This was the highest fixed gear allowed for young competitive cyclists and probably led to a lifetime of twiddling. Riding fixed gear in a hilly area is a wonderful way of learning to pedal really fast!

BTW: Gear inches represents the equivalent size of an Ordinary [slang: penny farthing] wheel with fixed cranks and no gears. Before gears were invented the wheel size of the "high wheeler" was limited by the inside leg measurement of the rider. Since the wheel size sets the direct drive [fixed] gear ratio a high cadence [very rapid pedalling] was the order of the day to achieve high speeds. The rider would usually lift their feet off the pedals on steep or long descents. Given the parlous state of the roads at the time "doing a header" was a common occurrence! Yet ironically the large wheel smoothed the rough roads far better than the early safety bicycles and tricycles. Hence the invention of the pneumatic tyre and the sensible standardisation on 26-28" wheels despite some [arguably minor] road improvements over the last century or more.

Click on any image for an enlargement.

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