ogbigbird

i will try to keep this brief and actually need affirmation if i am on the right track. i recently converted a 86 murray monterey 1spd cruiser to a 5speed cruiser via adding caliper brakes, rear deraillur system a shimano 5speed sis freewheel and obviously new rear wheel. now i added links to the chain, actually replaced it with the appropriate length, but kept it 1/8" standard size so it would fit the oem single 46t chainring. now i coulda swapped it out with a narrower chainring so i could use the correct "10speed" chain with it and be compatability correct, but actually managed to get smooth shifts with the 1/8th and minimal gear lash. i wanted to keep the chainguard cuz since i commute to work, i don't want my work pants anywhere near moving, dirty parts.

my question: the whole system runs spot on untill i am cruising in 5th gear, when every once in awhile, the chain decided to jump off the chainring and rest on the pedels. this only happened twice to me in about 10 miles of riding, and i will also hear a little clunking when in high gear. is my chainline just off for this 5th gear position, and if so, can spacers or wshers aliviate this? i know i could shoehorn a 6speed in there, but id definatly have to go to the narrower chain for that. and b4 i am judged on riding an old murry, its really, really boring in my town and tinkering on a "frankenstein" project is better than watching tv.

operator

Your chainline is off or the chain is too long meaning excess chain slack leading to chain derailment.

Your chain should run straight to the 3rd cog of the freewheel, eyeball this when the bike is on the ground. If it's off by a lot then that could be a problem.

Read below link to confirm chain length is correct, use the big big + 1 method. And when you mean 5th or "high" gear, do you mean the largest rear cog, or smallest?

https://www.parktool.com/repair/readhowto.asp?id=26

Someone else should confirm whether or not the shimano 5 speed freewheel will accept 1/8 chains or not. I have no idea.

c_m_shooter

If your bike has those old one speed cranks, you can't move the chainring to alter the chainline. If you are brave and the frame is steel, you can bend the rear triangle of the bike to bring the whole cogset over to the left. Look up Sheldon Brown's article on respacing frames, except you will be moving both sides in the same direction. I beleive they had to do this to those old prewar schwinns when they were turning them into mountain bikes in the '70s.

ogbigbird

smallest cog, of course. good advice by doing the visual in third for alignment. its not that big of deal to have to space the frame and start bending stuff, but thanks for the idea. worse comes to worse, or if i get board, i'll just convert it back to a single speed with a freewheel on the rear ( i think a 34mm will screw right on). with 4 regular single speed cruisers, i just wanted something a little different. thanks for the help and i'll go check it out.