No.briztoon wrote:So if I am riding my road bike in it's 53 chain ring, with an 11 cog, I'll roll 130.1 inches or 3.3 meters with one revolution of the pedals.
130 is just a number. Big number = hard gear to pedal. Small number = easy to pedal.
Postby Derny Driver » Sun Aug 25, 2013 4:29 pm
No.briztoon wrote:So if I am riding my road bike in it's 53 chain ring, with an 11 cog, I'll roll 130.1 inches or 3.3 meters with one revolution of the pedals.
Postby Alex Simmons/RST » Sun Aug 25, 2013 6:12 pm
That's exactly the rollout it will have.foo on patrol wrote:Not a hope in hell that a 130" gear will roll out to 10.38 metres.
Foo
Postby Alex Simmons/RST » Sun Aug 25, 2013 6:23 pm
It's gearism, and shoud be banned.briztoon wrote:Can you explain why different figures are in different colours please.
Postby foo on patrol » Sun Aug 25, 2013 6:30 pm
Ok I'm confused now. I have always been of the belief that it was one full 360 revolution of the pedals!Alex Simmons/RST wrote:That's exactly the rollout it will have.foo on patrol wrote:Not a hope in hell that a 130" gear will roll out to 10.38 metres.
Foo
Rollout = gear x Pi
gear = wheel diameter x chainring teeth / cog teeth
In this case a 27" wheel x 53 chainring / 11 cog = 130.1" gear
The rollout of such a gear would then be 130.1" x Pi = 408.7" = 10.38m
Postby jaffaman » Sun Aug 25, 2013 7:30 pm
It is. Lets simplify it for ease of working. Say your front crank is a 55 and the rear is on an 11. Every time you turn the pedals 360 degrees, you move 55 chain links. At the back, the 55 links will spin the rear 11 tooth cog around exactly 5 times. So, one turn of the pedal, the wheel goes around 5 times.foo on patrol wrote:
Ok I'm confused now. I have always been of the belief that it was one full 360 revolution of the pedals!
Foo
Postby bigfriendlyvegan » Sun Aug 25, 2013 9:31 pm
The gear ratio gives you the number of times the cog will rotate for one revolution of the chainring. If you were running a 100 tooth chainring and a 25 tooth cog (for the sake of simplifying numbers), then one revolution of the chainring will give you 4 revolutions of the cog (100/25). If you had 20 teeth on the back, you would get 5 revolutions of the cog for one of the chainring, and so on.foo on patrol wrote: Ok I'm confused now. I have always been of the belief that it was one full 360 revolution of the pedals!
Foo
Postby HLC » Sun Aug 25, 2013 9:34 pm
Postby foo on patrol » Mon Aug 26, 2013 6:42 am
Postby ldrcycles » Mon Aug 26, 2013 7:07 am
Ahh that's why. My preferred cadence is significantly slower, more around 90rpm, entering that into Sheldon's calc for my 52-14 gives 43.3kmh, which is exactly where I feel most comfortable on that bike. Out of interest, I changed the cadence to 120 and got a figure of 57.8kmh, definitely getting pretty quick there!Derny Driver wrote: cadence 110
Postby Derny Driver » Mon Aug 26, 2013 5:10 pm
90 is about right for road riding. In an individual pursuit on the track the optimal cadence is around 106-108. From a standing start getting a 100 inch gear up to around 56kph in half a lap takes a big effort. Then the rider settles back to around 52 kph at that cadence around 105-110 and has to do 11 and a half more laps without losing any speed at all. For me, I find individual pursuits and points races the most fascinating to watch.ldrcycles wrote:Ahh that's why. My preferred cadence is significantly slower, more around 90rpm, entering that into Sheldon's calc for my 52-14 gives 43.3kmh, which is exactly where I feel most comfortable on that bike. Out of interest, I changed the cadence to 120 and got a figure of 57.8kmh, definitely getting pretty quick there!Derny Driver wrote: cadence 110
Postby dalai47 » Mon Aug 26, 2013 5:53 pm
Great to watch, hard to race well...Derny Driver wrote:For me, I find individual pursuits and points races the most fascinating to watch.
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