rear sprocket info

[Target30]

ok, those with 17" rims might be able to help more, but anyone with info can chime in!

the skinny, I have a 17" rim (tzr250) going on my bike. originally i had a 14/47 520 setup. i will still have the 14 front, but the rear rim came with a couple sprockets that i would like to use if possible, but i have no idea how the bike will react. the biggest is a 40tooth. now, does the 17" rim make a difference with the tooth size, or am i going to get relatively the same reaction from the 17 as i did with the 18, with the same tooth rear sprocket? the bike the rim came off of was a race bike, do the 20's typically use a smaller rear sprocket? will the 40 work ok with the 14 front, knowing that i will loose excelleration? btw, gonna be a 160 rear, cant remember the sidewall, but i'll look it up and edit the post.

[cad600]

Stock FZR600 was 15/45 With a 18" rim
Stock YZF600 (if I remember correctly) was 15/47 with a 17" rim

I have a feeling you need a different sprocket, but again,

[haro504]

i would assume if you used the same size sprocket and have a smaller wheel diamiter than it would be like putting bigger sprocket on giving more torque. i dont know weather it would change enough to be noticable. if you want to keep the gearing the same or close than i would use the same sprocket or down a tooth. the 40 tooth sprocket is made for speed less power i dont think you would like it.

[95FZR600]

you might have to test them both. I know the newer bikes have a for instance 520 for them would be 16 48.

This is what we studied and calculated in class last quarter. Give me your teeth sizes and gear ratios and tire size and I can do the math to see which ratio would be best. Ill do it for both sizes if you want. Just give me a day.

[Luke-a-Tron]

The change in wheel size works out to about a 5-6% change in gearing. A 45 tooth rear sprocket would put your gearing pretty close to where it would be with a 47 tooth sprocket on an 18 inch rim.

The math:

[ 100% - (18" / 17") = -5.5% ] This is roughly the difference in ratio between the two wheels.

[ 47 teeth * 0.945% = 44.415 teeth ] This the adjustment to sprocket to bring the gearing back to where it was with the 18" rim. I fudged it upwards because I didn't account for the thickness of the tire in the first calculation.

[Luke-a-Tron]

you might have to test them both. I know the newer bikes have a for instance 520 for them would be 16 48.

This is what we studied and calculated in class last quarter. Give me your teeth sizes and gear ratios and tire size and I can do the math to see which ratio would be best. Ill do it for both sizes if you want. Just give me a day.

The final drive ratio choice has to be made with the consideration of the power output from the transmission. You can't directly compare the sprockets on a new r6 against the FZR for instance. It's not useful to consider what any other bike is using.

[PIMPMYFZR]

before i put yzf wheel on i had 14-47
now with yzf wheel i have 14-47
seemed like it pulled harder with the fzr wheel compared to yzf wheel .. but i dont know the stats ..

[mszilves]

before i put yzf wheel on i had 14-47
now with yzf wheel i have 14-47
seemed like it pulled harder with the fzr wheel compared to yzf wheel .. but i dont know the stats ..

Same here. Kept the same sprocket combo with the YZF as i had with the FZR wheel, and it does feel like it had more pull with the FZR wheel. Not sure if this is psychological yet, or maybe the YZF wheel is a bit heavier and thus robs some of the power?

[Luke-a-Tron]

Could be the wheel is heavier. If the tire you put on more than an inch taller than the tire you were coming from then you'll actually be moving the other way in gearing. That's entirely possible if you switched brands and your old tire was fairly worn.