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New School BMX 2004 - Now => New School Park, Street & Dirt => Topic started by: JT71 on March 18, 2008, 08:25 AM

Title: chain ring / sprocket ratios (again)
Post by: JT71 on March 18, 2008, 08:25 AM

there was a really useful thread about this before, think it went down with the previous new school section.   :'(

basically, if I'm using an 11t cassette driver on the back what do I want up front.

park and street and popping to the shops.  :LolLolLolLol:

Title: Re: chain ring / sprocket ratios (again)
Post by: zed4130 on March 18, 2008, 08:33 AM

i did put up a site with a good chart before, wish it was kept as a sticky, ill see if i can find the site  :daumenhoch:

paul

Title: Re: chain ring / sprocket ratios (again)
Post by: zed4130 on March 18, 2008, 08:36 AM

not sure if this helps  ??? as only runs to 12  ::) isnt it 11-30 ?
http://rocketbmx.com/Merchant2/merchant.mvc'screen=CTGY&Store_Code=RB&Category_Code=xC

Title: Re: chain ring / sprocket ratios (again)
Post by: perry on March 18, 2008, 08:51 AM

http://www.bmxultra.com/downloads/flash/gearchart.htm

make a note of the ratio and then have a play  :) ( higher ratio means harder to pedal  ;) )

Title: Re: chain ring / sprocket ratios (again)
Post by: zed4130 on March 18, 2008, 08:57 AM

thats a cool chart perry, ive saved that now, so 30-11 is kinda normal then, mine is 33-12  :)

Title: Re: chain ring / sprocket ratios (again)
Post by: JT71 on March 18, 2008, 09:08 AM

thanks for the help chaps, the chart would be a good technical sticky,

30 it is...if i win the wheel on evilbay that it.  :LolLolLolLol:

Title: Re: chain ring / sprocket ratios (again)
Post by: dodgydave on March 18, 2008, 09:18 AM

this what was on the last thread...if its any help .. :daumenhoch:

44/16
39/14
36/13
28/10
25/9

Title: Re: chain ring / sprocket ratios (again)
Post by: Dark Diggler on March 18, 2008, 09:38 AM

In old money 44/16 with 20" wheels represents 55" gearing.

the equation for any size wheels is:  Front cog divided by Rear cog multiply by wheel size I. E   44 Div by 16 (2.75) multiply by 20 - 55" gearing

The higher then end number the harder you gearing will be.

My jump bike has 24" wheels and runs 25/11 so is pretty close to 44/16 bmx gearing at 54.55" gearing


SIMPLE  :LolLolLolLol:

Title: Re: chain ring / sprocket ratios (again)
Post by: zed4130 on March 18, 2008, 09:40 AM

Quote from: 94 Performer on March 18, 2008, 09:38 AM

In old money 44/16 with 20" wheels represents 55" gearing.

the equation for any size wheels is:  Front cog divided by Rear cog multiply by wheel size I. E   44 Div by 16 (2.75) multiply by 20 - 55" gearing

The higher then end number the harder you gearing will be.

My jump bike has 24" wheels and runs 25/11 so is pretty close to 44/16 bmx gearing at 54.55" gearing


SIMPLE  :LolLolLolLol:

yeah just as he said    :LolLolLolLol:

Title: Re: chain ring / sprocket ratios (again)
Post by: Gary72 on March 18, 2008, 10:14 AM

if you win the wheel, Stevie B has some lovely 30t Colony sprockets. £20 posted

Title: Re: chain ring / sprocket ratios (again)
Post by: pickle on March 18, 2008, 01:52 PM

they sure are nice!! 

(http://www.radbmx.co.uk/archive/albums/b339/robertbransby/Picture012.jpg)

Title: Re: chain ring / sprocket ratios (again)
Post by: zed4130 on March 18, 2008, 01:53 PM

that does look nice rob ,  :daumenhoch:

Title: Re: chain ring / sprocket ratios (again)
Post by: SaMAlex on March 21, 2008, 08:03 PM

Quote from: 94 Performer on March 18, 2008, 09:38 AM

the equation for any size wheels is:  Front cog divided by Rear cog multiply by wheel size I. E   44 Div by 16 (2.75) multiply by 20 - 55" gearing

Almost right but the "wheel size" needs to be the "wheel Circumference". (Put a tyre on a wheel and measure the outer Circumference and I bet it aint 20" (or 24" for a cruiser wheel)).

Then the number you end up with (ie 55") is the distance the bike will travel in one turn of the cranks.