Easy Dual Rear Sprocket Setup 45T/50T
These instructions require no cutting, no grinding, no fabricating, and should take less than ½ hour. This whole project costs less than $75 and uses all new stuff. Because I had swapped the original 50T rear sprocket for a 42T (and needed to shorten my chain), this post includes directions and materials to start from scratch.
After looking at this thread for a while I finally decided to give it a go. I took bits and pieces from everyone’s advice and complied what I thought would be the easiest and ideal setup.
As a few suggested, I went with the recessed JT Sprockets. I believe this is what made everything go so easily. This setup uses the 45T sprocket on the inside and the 50T on the outside. The 45T will be mounted against the wheel hub with the RECESSED SIDE FACING IN (facing the hub and wheel spokes). This will very slightly offset this sprocket from its original alignment and creates a similar slight misalignment for the other sprocket. The outside 50T sprocket will be mounted with the RECESSED SIDE FACING OUT.
JT Sprockets JTC428HDR122SL 428 HDR 122-Link Heavy Duty Drive Chain ($21.29)
JT Sprockets JTR1842.45 45T Steel Rear Sprocket ($23.17)
JT Sprockets JTR1842.50 50T Steel Rear Sprocket ($21.09)
(6) Bolts (8.8 Grade) M8 x 1.25 x 40mm
(18) Washers, M8
(6) Nuts, M8 x 1.25 (regular sized nuts)
(6) Jam Nuts, M8 x 1.25 (half the thickness of common nuts)
(6) Lock Nuts/Stop Nuts M8 x 1.25 (blue or white nylon inside)
NOTE: This is the order things need to go on, from outside to inside:
Bolt, Washer, 50T Sprocket, Nut, 45T Sprocket, Wheel Hub, Washer, Jam Nut, Locknut
Remove the chain guard and the sprocket protector thing. Remove the wheel entirely and remove original sprocket. You will not need any of the original bolts or other pieces. Lay the wheel flat with the hub facing up.
1.) First thread all 6 bolts (with a washer on each) through the 50T sprocket. The bolt head and washers should be sitting inside the recessed part of the sprocket. Remember, this 50T will be the outside sprocket and the RECESSED SIDE will be facing OUT.
2.) Using the regular size nuts and 6 washers, spin them on to each of the bolts. DO NOT tighten yet. (There needs to be some play to get through the hub.)
3.) Mount the 45T sprocket on the wheel hub, RECESSED SIDE DOWN, facing the hub. It should be a nice snug fit. Make sure the wholes are lined up.
4.) Mount the 50T sprocket onto the 45T sprocket (and through the hub). Since the bolts were left loose it should slip right in.
5.) Add a washer and jam nut (the thinner nuts) to each bolt, and hand-tighten.
6.) Now you will need to tighten the nuts in between the two sprockets. There should be plenty of room for a wrench because we are using regular sized nuts in between.
7.) Now you can tighten the Jams Nuts on the inside of the hub (the ones we hand-tightened earlier).
8.) Finally, add a Lock Nut to each of the bolts and tighten.
9.) NOTE: The white nylon, sprocket protector thing, can be remounted BUT you will need to add about two or three thin washers on each bolt or these little bolts will interfere with the 50T sprocket. You WILL need to bend the metal mount the sprocket protector thing screws into out of the way a little bit or the bolt heads will rub. The chain guard cannot be remounted unless you do some modifications.
This specific setup allows for plenty of slack to easily slip the chain from one gear to the other. You’ll notice that at this chain length, the 45T sprocket is pretty much as high of a gear you could put on the inside. The chain is maxed out and the axle is all the way back. However, there seems to be enough slack up front if you wanted to experiment with even lower gearing than the 50T used here.
I hope this helps.