Bigger sprockets, longer chain?

[bakeLit]

Hello fellow riders/builders,

I'm wondering - will I need to get a longer chain if I go one up on front (17) and four up (43) on rear sprocket? It is a lot, so I suppose I would. But just in general, is there a rule of thumb to calculate this? And more importantly, will I be able to extend a brand new chain?

P.S. I'm doing this to get a better gear ratio for more powerful bottom end (2.53, 2.44 being stock) AND to gain some clearance between the chain and swingarm, running 365mm shocks. (the primary goal)

Thank you very much!

 

[XSLeo]

The way I figure out chain length is to measure from the center of the front sprocket shaft to the center of the rear axle. This is the length of the chain run at both the top and bottom of the chain run. The 530 chain pitch is 5/8 inch. So each link is 5/8 inch long. Or .625 inch. So if your center to center is 18 inches, then multiply it by two, one top run, one bottom run. 18x2=36, take this and divide by .625, As in 36 divided by .625= 57.6. 57.6 links for the top and bottom run.
This is only the top and bottom runs, you need to add enough to go around the sprockets. Your front choice is a 17, divide by two, the chain runs on 1/2 the sprocket. 17 divided by 2 is 8.5 links.
The rear a 43 then by two is 21.5 links.
Now add these to the chain runs. 57.6+8.5+21.5=87.6 links. Your chain runs are probably more than 18 inches.
A bit simpler method is to figure out the increase by finding how many links more your new sprockets need than stock. One up on the front plus four up on the rear is 5 links. Add this to the stock chain length. If your stock chain is a 102 then you need a 107. You might not find a 107 length chain. Buying a chain too long and cutting off the extra is better than trying to add a few links. In this case buy a 110 and cut to length.
Leo

 

[BBS360]

The 530 chain pitch is 5/8 inch. So each link is 5/8 inch long. Or .625 inch. So if your center to center is 18 inches, then multiply it by two, one top run, one bottom run. 18x2=36, take this and multiply by .625, As in 36x.625= 22.5. 22.5 links for the top and bottom run.

If the links are less than an inch each, shouldn't there be more links than inches.
36/.625=57.6 links?

 

[XSLeo]

Yes, My mistake. I'll correct this.
Leo