BMX Bike - Chain Tensioning

[ChrisKH]

Proving that n+1 works for all ages (!) I bought my eldest son a second bike yesterday. It's a BMX style bike which was for sale at a neighbouring house in very good condition; wheels true, brakes working (though poorly adjusted etc.). He's going to use it to ride the 1 mile to school.

Anyhoo, I cleaned it up, adjusted it to his size and adjusted the brakes and then looked at the chain and cogs. The cogs are hardly worn but the chain was a bit loose. I released the back wheel and tightened two silver adjusting clamps at the back of the rear facing drop-outs. Then had a thought this morning that I may have tensioned the chain too tight to get it back on the cogs if the chain ever came off. Is there any rule of thumb for this sort of bikes chain?

 

[Landslide]

If it's too tight, you'll be able to hear it creaking when the pedals are turning. Too loose and it'll flap up and down if you poke the chain when stationary. Somewhere in-between is what you want.

 

[jimboalee]

Most of the time, unless you have a well built bike, the chain will vary in slack when the pedals are turned.
Identify where the tightest place is and adjust the rear wheel so there is about 1/2" up-down movement in the chain.
When the chain is in its tightest position, you should be able to lift the first engaged link off the chainring about 1/8".

 

[ChrisKH]

Cheers Guys. It's a bit tight at the moment, I suspect given the advice. Will adjust tonight.