Uncle Ted

I noticed today for the first time that I get a rattling from my rear derailuer area when I have shifted into a certain cog. I only get the rattling/skipping of the chain when i've shifted up, and not when i've shifted down into said cog. I've been periodically checking my chain and it hasn't reached .75% yet with the tool i'm using, however upon looking closer at the chain and how it fits into the slots in the rear cog I noticed that it fits snugly except in two locations where it rides up the tooth. So, my questions: Should I replace the chain? If so might I also have to replace the rear cogs?

urbanknight

Yep, I'd replace the chain. If the cogs are showing wear on the teeth (look like a shark fin) replace those too.

n4zou

Anything over .50% is too much. Trash that useless chain stretch tool which only tells you to replace your chain after you've also damaged your cogs. Use a 12" steel ruler and replace the chain when the chain measures 12 and 1/16 inches (.50%) between the pins on 24 links.

brianappleby

my ultegra chain STARTS at .5%

OP, if this happened I would adjust my rear derailluer trim before I started replacing things.

Al1943

Check the chain with a good steel ruler.

Bill Kapaun

Does it always ride up the same teeth? Or do the same links ride up?

operator

Check for stiff links?

DMF 

+1

womble

My PC991 started at .50

operator

Did you use a real chain checker or a ruler?

n4zou

Standard 1/2" chain should measure exactly 1/2" (.5") between each link pin when new. 24 links should measure exactly 12 inches for new chain. Damage to standard sprocket teeth machined for 1/2" chain starts at 12 1/16 (.50%) inches as the chain starts riding up on the teeth under load. Do not confuse decimal .50 inches with .50% chain stretch.

Nessism

I've measured several new chains with a ruler, Shimano and SRAM, and I've never seen one that wasn't dead on length wise when new.

Al.canoe

I've got a Park CC-3 chain stretch gauge. It's got two labeled go/no-go positions of 0.75 and 1.0. Is that percent?

I've been using 0.75 for years and get very good drive-line wear both road and ATB.

Al

operator

This simply cannot be true.

DogBoy

My guess is the difference between measuring pin to pin and measuring end to end is why some are finding .5% when new.

rm -rf

My original sram chain measured .5% when new, using the park chain checker. Slop in the rollers accounts for this, since the tool pushes the two end rollers away from each other. My new campagnolo chain measured 0%, the two prongs barely fit in between the rollers.