Gearing - terminology, what does it all mean?

[AndyR]

Reading the spec of myEzee Forte the 8 speed hub gear is described as folows.

Shimano Nexus Inter 8 hub
12, 14, 16, 20, 24, 27, 31, 38T 307% range

What do the numbers mean? Also does this give a good range of gearing? I'm thinking in terms of cycling without electrical assistance should I run out of juice. Do these type of gear systems need much maintenance and are they reliable?

AndyR

 

[Ian]

The quoted numbers are cassette sprocket teeth, but as the gears are in the hub there is no cassette

I would guess the numbers are the number of teeth the sprockets on a cassette would need to give the equivalent to what you have with the Nexus Inter 8.

The 307% refers to the overall range available and means that for a fixed cadence (crank speed) top gear would be just over 3 times faster than bottom gear. That is quite a wide range for a road bike, many unpowered bikes are fitted with similar gears.

Maintenance requirements are minimal, just a drop of oil dribbled into the spindle once in a while and given that minimal maintenance they are usually very reliable.

 

[coops]

Hi AndyR

As Ian said, the numbers mean the equivalent number of gearteeth on each rear sprocket, if it was a derailleur not a hub gear, and are given that way I think in order to make it easier to work out the gear ratios (which gives the number of turns of rear wheel for each full turn of pedals), when the number of teeth on the front chainwheel is known:

e.g. If your front chainwheel has 48 teeth (I think thats right, maybe 50 or 52 though), your top gear ratio is about 48/12 = 4.0, so 1 turn of pedals gives 4 turns of wheels, and the lowest gear ratio is 48/38 = 1.26 so likewise just over 1 and a quarter wheel turns for 1 full pedal turn.

The given equivalent 'teeth' numbers are fairly accurate, except that the top gear is nearer 12.4 so more like 4/12.4 = 3.87 top gear ratio.

That range of gears is very good, about as good as you could get with one chainwheel, & should be fine for most except very hilly areas, but should you want to increase or decrease gearing you can I think change the front chainwheel and/or rear sprocket on the hub to adjust them . I've never had hub gears, but I think they are relatively low fuss & maintainance & are reliable .

PS There was more detailed information & discussion of the gearing of the F-series bikes when they first appeared in this thread, (scroll down page a little) in case its useful .

I hope thats helpful,

Stuart.

 

[AndyR]

Thanks very much for the info.
AndyR