Larger Tire, Bigger Sprocket?

[clark4131]

I tried a 120/100 on the rear and wasn't really sure about it for a variety of reasons. However, I just switched back to the 110/100 and I like it less so I'm gonna go back to the 120 when I bogart my current tire. Here's my question...Since I'm gonna be increasing my rotational diameter by just under 2/5 inch, what kind of effect with that have on my gearing? I know it will detract from the power, but will it be negligible to the point of not noticing or should I think about bouncing up a couple of teeth on the rear or dropping a tooth on the front? I can't remember what the difference felt like, plus I was still in the process of getting my jetting right for max performance. My current chain and sprockets are OEM and look like new, so I figured I could get away with using one or two of those parts. Also, I'm running a TM Designworks guide and was wondering if that would have clearance issues with a larger rear. I was thinking about running a 13/49 combo to account for the larger tire. Thoughts, opinions, ridicule, Bueller, Bueller, Bueller...SC

[SJMC_DON]

You say you are running OEM sprockets and you are concerned with clearance on your chainguide with a 49T rear? Your OEM rear is a 50T. I run 13/50 and love it but the 49 rear should give it some legs!

I don't know if one would notice the difference with the tire diameter

Good luck

[clark4131]

My post was confusing, my apologies. I'm concerned with chain guide clearance due to a larger-than-stock sprocket, i.e a 51 or 52...SC

[clark4131]

Okay, so I'm replying to my own thread...but I just crunched some numbers and want to know if they make sense to anyone else...

The stock wheel w/ tire measures 22.33" (18" wheel plus tire sidewall height of 110mm, or 4.33 inches)

Stock gearing is 14/50 or .28

With a 120mm sidewall (4.72"), the tire measures 22.72", a difference of .39 inches, or 1.75% over stock

To figure out the new gearing ratio for the new tire, I subtracted 1.75% from the stock ratio for a final gearing of .275.

A sprocket combo of 14/51 gives me just that, but a combo of 13/48 gives me .271 and the tiniest bit more low end with no problem regarding clearance, but I may have to lose a link in my chain.

So kids, what to do? Gimme some direction, I'm a ship without a rudder...boohoo ...SC

[SJMC_DON]

Good question........ let us know if you upsize, I run the same chain guide

[clark4131]

I think I'm going to give the Sunstar Z-Sprocket a try. It looks kind of funky and I can't find a whole lot of info on it, but what I did find was all positive. For $30, why not?...SC