Chain Skip
 

Good Morning to Everyone on the Board –

I have a technical question that I hope someone can shed some light on…

Recently, I cleaned the chainrings, cassette and chain on my touring bike. The large and medium chainrings were unbolted, removed and cleaned; as I left the crank arms attached, the small chainring was cleaned on the bike. The cassette was removed and cleaned as well. The chain was not removed from the bike and cleaned using the Park Tool chain cleaner device and oiled afterward.

Now that everything is back together, the chain skips on the center ring, specifically when I apply power to the cranks when taking off from a light. Sometimes, it’s so bad, the chain comes completely off of the chainring on to the bottom bracket. When this happens, I’m usually the middle gear of the cassette (gear 4 of 7). A check of the front derailleur showed that it had not drifted inwards towards the small ring. The FD is also appears to be in good alignment.

A visual check of the chainrings showed that they are not out of alignment (no lateral movement when I spin the cranks). When I reassembled the crank, I tightened the bolts in a star pattern (like one would tighten lug nuts on a car wheel). The chain ring tooth counts are facing outwards (I was told that was important, not exactly sure why). I’ve checked the chain, and there are no stiff links (all the same – the chain was not removed).

The only thing that was odd during reassembly is that four of the five stack bolts tightened without the need of a screwdriver to hold the back in place; one, however, did. That said, I was able to tighten it.

The problem is intermittent, but it only seems to occur when I’m on the center chainring. Further, if I start off in a lower gear, there’s no problem.

Thoughts on this?

Thanks.

How many miles have you put on that middle chainring? I don't need a number, just a few, 2 or 3 thousand, miles and miles. If it is "miles and miles" the chainring may be worn out. You need to change you chain at the same time you replace the chainring.

I'm interested in what others have to say.

What kind of crankset is it? On a Shimano triple the big ring tooth count stamping should face away from the frame, the other two rings should face toward the frame.

Other brands are not that way.

I have about 400 miles or so on it. It was installed about fall of 2010.

It's a Sugino triple.

Thanks for the help.

That sounds like a potential cause to me. Chainrings wear where the front side of the tooth goes over the top. If you have reversed the chainring, you are mateing a new tooth profile to a worn chain. That would definitely cause it to skip in high torque applications.

If you really replaced the chainring only 400 miles ago, that's not very many. If, however, you didn't replace the chain at the same time, 400 miles is plenty of time for a worn chain to transfer it's wear pattern into a new chainring.

You have the middle ring on backwards. The lettering on the middle ring faces in, toward the frame. I just checked the Sugino on my bike.

Fixed it! Thank you for the responses...
 

Right, then...

So I figured it out... I was able to finally tear the cranks down...it turns out that the large chain ring goes on the outside of the spider...not on the inside, immediately next to the middle ring:innocent:. Now, we're running smooth! :thumb:

Thanks for all the responses...

I normally take a photo of something that I am about to take apart to make sure that it goes back the right way, I did that with my snow blower when I replaced the auger belt.

Thats the great thing with digital cameras.

Oh, indeed! That's a lesson that I learned while tearing down the bike after this one. I used to think I could remember where everything went or just sort of intuitively know by looking at how the parts fit together...I don't think that any more :D

This is fascinating, you guys are awesome.

This is not a message with a hidden agenda requesting memberships, just an honest coment:

If I were not a paying member of this message board, I would become one right after reading a thread like this one.

A skipping chain on a traffic light, damaged chainring, blunt force facial trauma, the list goes on...

How much does it cost to avoid all of that!!!

Thank you for sharing ( both the issue in details as well as the solutions presented)