claude

Hi to all,

sorry if this question might seem banal to you people, but I just realised (about time I did ??) that newer bikes have got much smaller chainrings than my 10 year old MTB... want to make sure before I buy some bits...

Is the gear ratio measured as the difference between the number of teeth between the chain ring and cog ? Would a, for example 44-11 gear ratio feel exactly the same as a 48-15 ??

thanks for any feedback

claude

madsnake

The formula is:

number of teeth on chainring/number of teeth on cog x wheel diameter = gear inches. The result is the distance travelled for one pedal revolution.

Hence 44:11 = 104 gear inches.
48:15 = 83 gear inches.

52:13 would give you 104.

A good cycle mechanics book should give give you a table of gear inch equivalents.

claude

so, if I understood correctly, my older bike with a 48:13 ratio would actually be slower than a newer bike with 44:11 ratio, although the difference in teeth is actually more in the older bike....

claude

Ciufalon

You could always play around with the gear inches calculator on this page. https://sheldonbrown.com/gear-calc.html

Bill Kapaun

IF the "engine" is spinning at the same RPM.
Unlikely for a "casual" cyclist. It would require an extreme degree of fitness to do so at those speeds due to wind resistance. For somebody my age, it would be torture feeling my knees grinding away slowly.

MaxKatt

epic thread dredge.

urbanknight

I think this is the oldest zombie I've ever seen!

veganbikes

I think this was probably solved, it has been over 23 years. Though Sheldon Brown has always provided good info it is new posts with it are best left to current active threads rather than almost 24 year old threads.

grumpus

You're replying to someone who hasn't posted in 22 years.

tomtomtom123

I wonder if Claude ever figured out how to calculate gear ratios.

DiabloScott

Well as long as someone already woke the corpse -
That's the right formula but the wrong definition. The result is the equivalent diameter of a wheel that would travel the same distance in one revolution (like a penny farthing's wheel).
In other words, the distance travelled per pedal revolution is the (gear inches) * π.

Camilo

Not the difference between front and rear teeth, but the ratio. And yes, that ration would be a good point of comparison if the wheel /tire circumference is held constant. It's an easy way of comparing two similar bikes, for examle, two 700c road bikes or two 29'er MTBs. Gear inches - which a lot of people are well versed in - is a better way to compare if the wheel size changes as well as the gearing. For example, comparing two mtb with different size wheels