Bikesarecool21

Hi I was out for a ride today and about half way thru the cog started to slip while pedaling any idea of what's going on?

alo

You probably should explain more clearly what you mean by cog slipping.

If it is the freewheel not engaging, I would start by putting oil into it, and see how it goes. The oil may loosen the internal parts. If It continues to be a problem, you may have to buy a new one.

If it is the chain jumping over teeth on the sprocket, you will probably need a new sprocket. You could check the chain for stretch. You will probably need a new chain too.

Helderberg

All of the above and the rear derailleur might need to be adjusted. As said above, a better explanation of what is happening and when would help to narrow down what might be happening. Be safe.

Bikesarecool21

I've notice it the most when I coast for a while then start pedaling again that's when it slips the most or when I use hard. Pedal pressure it will skip gears hope this narrows it down thankyou

ARider2

Does it have a front and rear derailleur and in what gear combinations does it occur? Can you get it to happen every time or is it intermittent? It's either a freewheel or freehub problem, shifting out of adjustment, worn cog or worn chain. I would start by checking the chain for stretch. If the problem only happens when you are pushing hard on the pedals when in the smallest cog then it's likely time for a new chain and gear sprocket.

Bikesarecool21

Yes it does have from and rear derailleur and i don't know the count on them

Bikesarecool21

All I know is its a 7 spd

Bikesarecool21

Was out on a 33mile ride yesterday and the cog would slip when shifting from a higher gear to a lower one

Bikesarecool21

The rear cog is a 14-34 tooth

Bikesarecool21

Just put a new chain on the bike a month ago

alo

You probably need a new freewheel or cassette. Of course, I haven't seen it for myself. I'm just going by what you have said.

One option. Buy the new parts, and the tools needed to change it. It's what I would do.

Another option. Take it to a bikes shop.

hokiefyd 

I think we probably need a better description of "slipping". Bikesarecool21 later clarified that it's "slipping" when shifting from a higher gear to a lower one. I presume this means when shifting from a larger sprocket to a smaller sprocket, though this would more correctly be stated as "shifting from a lower gear to a higher one". Regardless, it sounds as though the indexing of the rear derailleur may not be correct and the chain is sometimes caught "between gears". When this happens, it's not uncommon for the chain to skate across the tops of the sprocket teeth and quite literally feel like it's slipping. If this is the case, then the freewheel may be fine and the bike may just need a rear derailleur adjustment.

Because it sounds like the bike will need some repair in any event, it may not hurt matters to try an adjustment yourself, Bikesarecool21 . Look at the freewheel and derailleur from directly behind the bike. The top pulley of the derailleur, usually called the guide pulley, should have the chain directly under each respective sprocket. If it looks like it's slightly inboard of centered (the chain is slightly off center towards the hub of the bike), then you can try tightening the barrel adjuster on the rear of the derailleur (where the cable housing enters the derailleur). This will effectively shorten the cable housing length and give some cable slack back to the derailleur and should center the chain. If the chain is slightly outboard of centered on the sprocket, towards the derailleur side, then you can try loosening the barrel adjuster. This will effectively lengthen the cable housing and pull some cable back from the derailleur and cause it to move slightly inboard.

It sometimes doesn't take much to make an improvement. Try a half turn at a time and see how that goes for you.

Bikesarecool21

Okay I will give that a try and some of the teeth on the cog are shaped like peeks is this something to worry about?

Bikesarecool21

And every time I hit a bump even the smallest one the chain jumps

hokiefyd 

We may be able to help more if you can take a picture and post here (you have enough posts to do so). It's hard to judge cassette or freewheel teeth based on their shape -- some of them look rather odd, even when new.

Bikesarecool21

Okay

Bikesarecool21

In pretty sure its a freewheel.

hokiefyd 

If it's a 14-34, it's almost certainly a freewheel (vs. a cassette). Most cassettes have an 11- or 12-tooth sprocket as the smallest sprocket, and freewheels usually have a 14-tooth sprocket as the smallest sprocket.

Bikesarecool21

hokiefyd 

That is a freewheel and the teeth shapes do not look unusual to me. Some of them appear to be "twisted" at the top...this is normal and is an aid to shifting cleanly.

Based on your description of the problem, it doesn't sound like the chain is jumping teeth on the freewheel because either the freewheel or the chain is worn (though either or both certainly could be). I think the description of the problem points to a derailleur indexing issue, where the barrel adjuster needs tending to a little bit. I would try that first. If it doesn't seem to help, then you might consider taking it to a local bike shop or a bike mechanic to further diagnose the problem.

Bikesarecool21

Okay thank you.

Riveting

Dirty pawls? or bad pawl springs?

Bikesarecool21

I will look in tobthat thankyou

Trakhak

Literally four out of five threads reporting "I replaced the chain, and now the cog/gear/sprocket is slipping" (or vice versa) elicit a dozen theories and end with the problem being solved by replacement of the freewheel or cassette or replacement of the chain, as appropriate. The chain is new, and the freewheel in the picture looks as though it has a lot of miles on it and might be ready to be replaced.

The problem could be elsewhere, but if the skipping didn't show up until after the chain was replaced (or if the chain was replaced to address the skipping problem), that's a strong indication that replacing the freewheel will fix the problem.

That's assuming that the chain was installed correctly and was shortened to the correct length.

Bikesarecool21

I will most likely change the cog.