Sprocket for 29"?

Discussion in 'Performance Mods' started by Ryan, May 6, 2011.

  1. Ryan

    Ryan New Member

    Can anyone recommend a sprocket for a 29" tire? Top speed is not my main focus, Im looking for low speed torque. I would be happy with 25 mph (30 would be great) as long as it has good hill climbing ability. The kit I bought came with a 41 tooth, but I think that is way too small. Would a 48, 50, or even 56 work? I have a 66cc engine that I am planning on doing some work to.

  2. bigkahuna

    bigkahuna Member

    I'm also looking to do a build with 29" wheels and it was recommended to me to use a 50t sprocket. As I also am more concerned about hill climbing than speed, I'm thinking a 56t sprocket might be even better. Not an expert myself, just passing along advice that was given to me on another forum.
  3. skrufryder

    skrufryder Member

    So the taller the rear sproket will give you much more tourqe. i think the 48 46 maybe the best way to go. me and my bud got i think its a 56 it had great tourqe and unbelivable exceleration but the top speed must of been like 12
    haha it went from a stand still to 12 in maybe 15 feet. it was like instant top speed but so so disapointing
  4. skrufryder

    skrufryder Member

    how steep of hills you trying to climb anyways on or off road?
  5. Ryan

    Ryan New Member

    It will be mostly off road trail riding. I definitely want higher than 12 mph top speed, I would like double that. Im thinking about a 48 or 50 tooth.
  6. shell shock

    shell shock Member

    man, 29" tires. those are massive! with that size, i think it would be safe to say a 56 tooth is what your looking for. just my 2c but hope it helps. best part is, its just a sprocket. if it doesnt work out for you, its not the most risky upgrade.

  7. spad4me

    spad4me Member

    Are you using a happytime 66cc two stroke engine.
    If so count on about 6500 rpm.
    Here is a link to a program that may help you decide on what driven ( rear) sprocket to use.
    A happy time has a built in four to one reduction before the output sprocket.
    The output sprocket usually has ten teeth you decide on the rear sprocket to determine the top speed.
    Anything over thirty five is hard to do without a shift kit or lots of tuning and porting , a tuned chamber, bigger carb, ignition work.


    With a 56 tooth rear sprocket I get 22.40:1 which at 6500 rpm yields 25 mph.
    With a 48 tooth rear sprocket I get 19.20:1 which at 6500 rpm yields 29.2 mph.

    22.40 to 1 is very good for cruising.
    This program works on Windows and GNU/linux under WINE.

    I usually use ten to 40 for the first stage, leave the second stage at 1 to 1 or ten to ten. And use the final window to insert the values for the ten tooth drive sprocket on the happytime the last value is for the rear sprocket. Enter your wheel size, and the expected rpm.
    Last edited: May 10, 2011
  8. retromike3

    retromike3 Member

    think tires

    If you are using a 29/700c wheel its a bigger rim than a 26 but its not double the size. I would think about dropping the size of your tire first. Maybe down to a 700 by 30 then maybe use the stock size 44 tooth sprocket. I have a "happy time" 66 and use a 36 tooth on my 26 by 1.5 tires and it scoots around at a pretty good clip. I don't have a speedometer though. I can keep up with traffic in a lot of city streets.

    I also have a tuned pipe and it really helps with the low end pull on the bike.

  9. bigkahuna

    bigkahuna Member

    @spad4me - Thanks for the thorough explanation. For me, 25 mph is fine. I'd rather have more torque for hill climbing than speed, so I'll definitely go with the 56t sprocket.