building a bike help

[arthurdunne]

i am building a Little mountain bike its gonna be a measly 7 speed but it i need a special chain cause i have two different kinds of wheels how do i figure out how many links i need for it i dont have a pic currently cause my account is still new but when i can i will link a picture

[Criminal]

(12-21-2020, 04:26 AM)arthurdunne Wrote:  i am building a Little mountain bike its gonna be a measly 7 speed but it i need a special chain cause i have two different kinds of wheels how do i figure out how many links i need for it i dont have a pic currently cause my account is still new but when i can i will link a picture

When you say " two different kinds of wheels"; do you mean chainwheels or road wheels; different sizes and/or brands?
Basic set-up is to run your new chain around the largest cassette/freewheel cog through the front derailleur cage (if applicable) and around the largest chain ring; do not "thread" through rear pulleys. Add 2 full links/2 pins/1" of chain to where you pulled it snug to on the chain ring. If you have any suspension that changes the distance between rear axle and crank axle centerpoints when being compressed and/or extended, you may have to add another link or two. Best to fit a chain on a suspension system with suspension disconnected and the frame set at its maximum normal travel point to where axles would be at their farthest points, then add the extra length. Depending on some other factors (specific components, worn components, chainline, etc.) you may still have to add or subtract a link. Don't forget to get the proper width chain!

[ReapThaWhirlwind]

You don't need a special chain.

You need to match the cassette and the shifter. Otherwise, in your case, the chain may be too narrow, and present stability issues.

You can typically go one Speed up or down—mix-matching components.

One great exception is 9 speed—for the rear derailleur, shifter, and cassette. Because 9 Speed uses a special spacing and pull ratio apart from 7/8 and 10/11. You can only mix "9 speed cranks/chainrings" with other speed components.

You will always need to match the shifter, rear derailleur, and chain to the same speed as the cassette.