GearCalc Pro Provides Certification For Your Bike Gears

The table below shows what I currently use on my training bike. I use six speed freewheels because they are relatively cheap. This means I can afford to wear them out frequently. When I decided on this, I could have gone for a seven speed freewheel, I was having a new wheel built anyhow. But the seven speed freewheels available from my local shops offered no advantage for my needs.

This setup works quite well. The disadvantage is that the lowest two gears are a bit too close together, and the highest pair are slightly too far apart (but not impossibly so).

The information enclosed in the frame shows the kind of printed output you get when you click Print from GearCalc's 'Assessment of Groupset' window. I have reconstructed it in HTML (because this transmit faster than a scanned bitmap), so its appearance might be slightly different to what comes out of your printer. But the content is the same.

This is how the GearCalc Pro bicycle gear calculator provides certification for a set of bicycle gears:

**Assessment of Groupset**
	C.R.	F.W.	Step (in)	Down (mph)	Up (mph)	Down (rpm)	Up (rpm)
1	28	28			7.3		92
2	28	24	4.42	7.3	8.4	79	91
3	28	21	4.42	8.4	9.7	80	93
4	38	24	6.63	9.7	11.4	78	91
5	38	21	5.99	11.4	13.1	80	92
6	38	18	7.99	13.1	15.0	79	90
7	38	16	6.99	15.0	16.9	80	90
8	48	18	7.73	16.9	18.9	80	90
9	48	16	8.83	18.9	21.5	80	91
10	48	14	11.36	21.5		80

Average step between gearchanges = 7.15 inches

Target cadence = 85 rpm

Range = 6.2-25.1 mph, at 78.1-92.7 rpm
Gear Usage Table

28 24 21 18 16 14

28 + + + - - -

38 - + + + + -

48 - - - + + +

700 X 25C Tyre Diameter (inches) = 26.5

Output from: Gearcalc Pro c:\gear_pro\nigel.def

Comments: Best I gould find 'off the shelf'. £13 from Shamano

The gear set below is much better. So why can't I buy one off the shelf?
The lowest gears are further apart, and the highest gears are closer together. As a bonus, a small amount of 'chain line abuse' allows me to squeeze an extra gear out of the set. The gears spacing is closest at the kind of speeds I spend most time on the Railway Path.
Bottom gear is a tiny bit higher - but still low enough to get me up the dreaded Tog Hill
Top gear is exactly the same. There comes a point where there is more to be gained by 'tucking in' and having a rest ready for the next climb.

**Assessment of Groupset**
	C.R.	F.W.	Step (in)	Down (mph)	Up (mph)	Down (rpm)	Up (rpm)
1	28	26			8.0		95
2	28	21	6.79	8.0	9.6	76	92
3	28	18	5.89	9.6	11.3	79	92
4	38	21	6.73	11.3	13.1	79	92
5	38	18	7.99	13.1	15.0	79	90
6	38	16	6.99	15.0	16.5	80	88
7	38	15	4.20	16.5	17.6	82	88
8	38	14	4.80	17.6	19.1	82	89
9	48	16	7.57	19.1	20.8	81	88
10	48	15	5.30	20.8	22.2	82	88
11	48	14	6.06	22.2		82

Average step between gearchanges = 6.23 inches

Target cadence = 85 rpm

Range = 6.5-25.5 mph, at 76.3-94.5 rpm
Gear Usage Table

26 21 18 16 15 14

28 + + + - - -

38 - + + + + +

48 - - - + + +

700 X 25C Tyre Diameter (inches) = 26.5

Output from: Gearcalc Pro c:\gear_pro\nice18.def

Comments: Ideal for my needs. £32 from a specialist

I have done some colouring in in the table above:

Step (in)
Refers to the difference between the inch ratio (or metre ratio) of the current and previous gears. In other words this represents how big each gear change will 'feel' after using the Gear Usage Table to weed out the duplicates.

Up (mph)
Refers to the ideal speed (mph or kmh) for each gear change. I.e. the upper end of the speed range for each gear, assuming the rider wants to stay as close as possible to the target cadence (85 rpm in above example). I use a sticker with these numbers on my handlebar stem to provide a cadence check on the road.

Important Note
Although the above examples both refer to 18 gear bikes, with three cogs on the (front) chain ring, and six cogs on the freewheel (rear block). You can use GearCalc Pro (v1.4 or higher) to assess bikes with up to 33 gears comprising up to three cogs on the chain ring and up to eleven cogs on the cassette (rear block), although as far as I am aware, no one has made an eleven cog cassette yet!

Gear Calculator For Single Speed Fixed Wheel Bicycles
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