ZenForest

Newbie bike owner here.

Brand new bike. 21 speed (3x7)

Have yet to lube the chain or sprockets yet.
After assembly, took for test ride, up and down the street.

Noticed when I stopped pedaling for a few seconds, like when drifting down a hill, that the chain loses quite a bit of tension, and gets very loose unless I apply some slight forward pedaling pressure, at which point it tightens right back up. Also happens if I pedal backwards, even if very slightly.

I presume this is not normal.

Is there an adjustment I should make ?

Note: Visit to local bike shop not an option.

Thanks !

HillRider

The freewheeling mechanism (freewheel or freehub body) is stiff and drags when you stop pedaling or back pedal. Drip some light oil between the outer shell and inner core.

ZenForest

Do I need to (should I) disassemble the freewheel to do this, or can I just oil it with wheel attached to bike ?

Thanks for the tip !!

FBinNY 

Chains normally operate at two tension levels.

The first tension level is that imposed by the spring in the return arm. This is always the same in the lower loop, but only true in the upper loop when at rest or coasting.

The second affects only the upper loop and is the added tension you create by pedaling and what transmits the power to the rear.

So, every time you coast the upper loop tension drops back to the at rest level.

However it's also possible for the upper loop to drop below the rest tension when coasting or back pedaling, depending on the drag in the freehub. High freehub drag, will negate the "freeness" in the freewheel mechanism, ad the force needed to keep it from spinning is subtracted from the rest tension in the upper loop.

Whether you're seeing the normal drop to rest tension, or an excessive drop in tension is something I can't gauge from here, but as a guideline, the upper loop shouldn't sag more than 1/4-1/2" at the most.

Bill Kapaun

It IS a new bike. Chances are that things will "loosen up" a bit with a few miles.

Besides, HOW MUCH?
Vagueness results in this threads going way longer then needed.

ZenForest

It seemed excessive to the point where I was concerned the chain might fall off, (didn't bother to measure as I am certain it's not normal operational behavior), but w/a quick slight pedal what seemed like the proper tension was quickly regained. Will try the oil idea tmro and see what happens.

Txs.

FBinNY 

Try this to get a sense of how bad the problem is.

Remove the wheel and spin it in your hands, then put your thumb or one finger on the cassette to feel the drag. You should be able to hold it from spinning with very light finger pressure. If acts like a runaway buzz saw that's too tight.

Once you know it's too tight, then you can try to divine the reason and deal with accordingly. Of course, if your fingers can leep it stopped easily, then all is OK and your chain tension is within bounds.

However, while it's hard to diagnose bike problems blind, I have one other possibility to have you check. If the issue is limited to when using the inner chainring, especially combined with the smaller rear sprockets, then it's possible that your chain is long. Shift to small/small, and take a look at the chain. the lower loop shod not sag, and if you push the lower pulley forward (or down) to make it sag, it should snap back cleanly when you let go. I doubt this is your problem, but wanted to cover the bases.

dabac

You don't need to disassemble the f/w.


(That's only rarely done BTW. Standard ones are cheap enough that replacement is the normal cure to more serious issues.)


But removing the wheel from the bike will offer better access and make it easier to see what you're doing.
And it'll give you a better chance to poke, prod and twirl the f/w by hand a Little to judge how it's doing.