marcus987
10-26-05, 11:40 AM
does any of you guys know any sites with gear ratio calculators on them?
BMX - online gear ratio calculators?
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PunkGuy
10-26-05, 11:48 AM
http://www.gsportbmx.co.uk/support/rideuktech/super_small_gears.html
article on gearing
from the site:
"So let's compare a 44 tooth sprocket a 36 tooth sprocket and a 25 tooth sprocket.
A 44 has a working radius of about 89mm so on a 180mm crank that’s almost bang on 1/2 way out. Therefore if you can press down with a force of 1000 Newtons (which you might well be capable of) the chain will have to take a load of around 2000 N.
A 36 has a radius of about 72mm so on a 180mm crank the chain tension will be 180/72 x 1000 which is about 2500 Newtons.
A 25 has a radius of only 50mm. With our 180mm crank we get a chain load of 3600 Newtons!
So on a 25-9 gear set up the chain has to take nearly twice the tension of an old school 44-16."
article on gearing
from the site:
"So let's compare a 44 tooth sprocket a 36 tooth sprocket and a 25 tooth sprocket.
A 44 has a working radius of about 89mm so on a 180mm crank that’s almost bang on 1/2 way out. Therefore if you can press down with a force of 1000 Newtons (which you might well be capable of) the chain will have to take a load of around 2000 N.
A 36 has a radius of about 72mm so on a 180mm crank the chain tension will be 180/72 x 1000 which is about 2500 Newtons.
A 25 has a radius of only 50mm. With our 180mm crank we get a chain load of 3600 Newtons!
So on a 25-9 gear set up the chain has to take nearly twice the tension of an old school 44-16."
Brian
10-26-05, 03:38 PM
So what does all that mean?
racersk66
10-26-05, 03:53 PM
So what does all that mean?
Thats what i want to know. I didn't pay attention in science in 7th grade to remember it.
Thats what i want to know. I didn't pay attention in science in 7th grade to remember it.
* jack *
10-26-05, 03:56 PM
http://sheldonbrown.com/gears/
Brian
10-26-05, 04:03 PM
I busted a side plate on my chain with 180mm cranks and 39x16 gearing.
sxe fbm rider
10-27-05, 11:32 AM
Iy your are just riding street or park or dirt bmx you dont need a gear ration calculator. There are the basic gear ratios. just pick one that you want.
CMcMahon
10-27-05, 01:34 PM
45,44,43-16
39-14
36-13
33-12
30-11
28-10
25-9
39-14
36-13
33-12
30-11
28-10
25-9
marcus987
10-27-05, 02:13 PM
what would be better for park: 36-13 or 44-13. i'm just wondering because i've just got a bmx for park riding and its got 36-13 and somewhere i have a pretty decent 44 tooth sprocket.
marcus987
10-27-05, 02:15 PM
forget that last post, it dont matter any more.
sxe fbm rider
10-27-05, 07:38 PM
36-13 is just fine for park.
marcus987
10-28-05, 01:50 PM
what would be better for dirt?
39-16
39-17
39-18
39-16
39-17
39-18
queensrider86
10-28-05, 09:03 PM
39-16, but just get a 44t