# Bicycle Mechanics - newb question: what is chainring combination?

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sgt_singapore
04-20-05, 11:37 AM
Indeed, a true newb question, but what is chainring combination? what do these ratios explain? also, why would one use a triple rather than a double? Are these questions a newbie roadie should concern himself with? Thanks in advance

ofofhy
04-20-05, 12:06 PM
http://sheldonbrown.com/gearing/index.html

Try this site, loads of info.

MichaelW
04-20-05, 12:33 PM
Gearing matches your power output (in watts) with your ideal pedalling cadence (revs/min) and the drag on the bike (caused

The range of gearing that you need should suit your very best and very worst scenarios. If you carry big loads up steep hills on rough tracks, you need a lower gear than if you ride unladen on the flat.

The intermediate gears should be close enough that you can chose your ideal cadence under any conditions. More gears let you get closer to your optimum cadence but there are often many dupliate ratios and unusable ones. A rider on a flat time trial will want a closer selection of steps than a tourist who prefers the gears spread out into a wider range.

Triples permit a wider range of gears with acceptable steps.
Doubles are lighter, narrower and shift more cleanly.
Std doubles are ideal for racing athletes. Slower riders dont use the big gears and run out of low gears, hence the increasing popularity of compact doubles.
Single chainring setup are used by flat-land riders who need more than a singlespeed.

Al1943
04-20-05, 05:47 PM
Most of the gear numbers that are discussed are simply the numbers of teeth on the chain rings (front sprockets) or the cogs (rear sprockets). A combination like 53-15 means the chain is on a 53 tooth chain ring and a 15 tooth cog. A 13-26 cassette means that the smallest cog is a 13 and the largest is a 26.
The most common triple crankset is a 52-42-30, the tooth counts for the three chain rings. The most common double is a 53-39. There are many other possibilities.

Al

sgt_singapore
04-20-05, 09:58 PM
Thanks for the response.

So the next question is does one intuitively know what combination one is in, that is after memorizing the teeth numbers on cogs and chainwheels? Or is there another way of knowing?

Does one need to get so specific with the combination, and why not just 'feel' that a particular combination is right for a circumstance, instead of getting down to the numbers?

Thanks again.

MichaelW
04-21-05, 03:07 AM
When you ride, you just go by feel, not by numbers.
When you are setting the bike up and chosing the transmission system the numbers let you compare different setups.

John E
04-21-05, 10:23 AM
Thanks for the response.

So the next question is does one intuitively know what combination one is in, that is after memorizing the teeth numbers on cogs and chainwheels? Or is there another way of knowing?

Does one need to get so specific with the combination, and why not just 'feel' that a particular combination is right for a circumstance, instead of getting down to the numbers?

Thanks again. I actually go "by the numbers" at times, but I'm a gear-head. The rest of the time, I just do what everyone else does, i.e., move to a higher gear if I am spinning the cranks too fast, or to a lower gear if I am starting to mash the pedals.

neil0502
04-21-05, 10:30 AM
I've seen people punch up their combo in a gear calculator, then print out the resulting gear-inches chart and tape it to their stem.

I've always gone by them too da*ned fast to ask them exactly why they do it ;)

I guess it's to understand where they're overlapping, and help them formulate a 'strategy' for effective shifting. To each their own, huh?

As for me, reading 6pt fonts while pedaling 15mph means I'm broad-siding an SUV :(