Is there a reference manual or article available
for choosing front/rear sprocket combos.

I know:
For every one tooth you decrease from the front sprocket,
The effect is - you add two to the back sprocket.

But, I vaguely remember something about even/odd teeth
and certain combinations do not work as efficiently as others.

Anyone have anything on this subject?

Thanks, in advance for any help,


c.winterwoods

This may not be a direct answer, but is a cool website to calculate stuff like this. It is in our weblinks too.

I don't think it's quite that linear, but we can see!

Stock on my RT1 is 15/39. 39 divided by 15 equals a 2.6 ratio.

Take a tooth off and we have 14/39. That equals a 2.786 and change ratio.

To get a 2.786 ratio with my stock 15 we multiply by the ratio and get 41.79 teeth. Hey! That's close!

It depends on what you start with...

for 15/45 the ratio is 3:1 so one tooth on the front equals roughly three teeth on the back

For 15/30 the ratio is 2:1 so one tooth on the front equals roughly 2 teeth on the back...

or as pntrbl showed, for 15/39, the ratio is 2.6:1 so one tooth on the front equals roughly 2.6 teeth on the back

Going too small on the front sprocket is not a great idea... tighter radius and less teeth in contact with the chain at any one time so sprocket and chain wear faster. However there is a clearance limit to how big you can go on the front and still clear the cases...

Changing front is easier/cheaper than the rear... I generally like to choose a rear sprocket that lets me end up with a front that's one or two teeth smaller than the maximum that will fit. YMMV... and first you have to figure out what ratio you want.

I get the science behind ratios, this is the part I'm stuck on. 40+ years of existence, is there a good reference for what ratios work best for what situations? Or a recommendation for a good starting ratio for me? My scenario is a CT1 to be used on the street in stop and go traffic partly on a 50mph highway, mixed with 35mph back roads a majority of the time. Add to that a heavy rider.

James... it sounds to me like "stock" would be a good starting place for you...

likey

Thanks, I figured as much.

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I think you will find it is cheaper to change the front as you can run the same chain.You may not be so lucky if you do anything major to the rear.

hey guys i have a 1973 DT3, anybody know where i can find a new rear sprocket mines alittle chewed

The ebay item id given is invalid, no result has been sent26 on E-Bay. I think 44T is stock.