How to tell when a chain is bad?

[2fun]

Originally posted by 3vrider
According to the manual for an 03 CFR:

The service limit of the drive chain is 10.20 inches for 17 pins.

Get a machinist ruler, count out and mark 17 pins, then measure from center to center of the pins. If you get more than 10.20" it needs to be replaced.

I haven't actually used this method as I use a little less scientific method, but it's nice to have an actuall measurement to refer to.

Hope this helps

Thanks for the added info!
Its nice to have a solid number to go by too!

[yamaha250F]

If you have a yz250F the manual says: 10 links should be a maximum of 6 inches. I just checked mine today and it was exectly 6 inches (stock chain 1 year of use). I am going to try to get 1 more month out of it than replace the set. The manual also says to change out the chains and sprockets as a set. There is ALOT of good info in the manual, sounds like some of you need to start reading

[Florida 393]

That is a good tech thread. If someone will summarize it I will authorize it being in the General Knowledge forum.

Bill

[Madman393]

Cast your vote and rate this thread to send it to the KB for all time!

[Florida 393]

I moved several tonight. Thanks for the prompts!

Bill

[Jaybird]

Wow! It has been awhile since I've been here. I hope the following will help clear up any issues that are still fuzzy to some on proper chain measurement.



To keep your chain properly adjusted you must be aware that the chain will in fact elongate or "grow" over a period of time. This change of pitch will change the adjustment that you initially placed on the chain at install (chain sag).

When this elongation occurs and your sag changes, you must re-adjust the chain tension to it's original setting. Although it may be a very long time before the chain requires adjustment, we recommend that you check your chain sag after every ride. Immediately adjust the chain when any change is noticed.

After many adjustments you will find that there may be some changing of the geometry of the sprocket teeth. This change is due to the fact that the chain is elongating and the pitch is actually changing. The change in the sprocket teeth is the sprockets way of showing pitch change.

A high quality roller chain will provide you with good service until it has reached a point of approx. 1.5% - 3% of it's initial length.

The method to check for this change of pitch is a very easy process and requires only a measuring tape or rule.

You will see many differing methods listed in owners manuals, but they all have the same theory involved. The only thing that is different about measuring recommendations is the percentage of growth that the Mfg. will recommend a change-out. You will see some chain manufacturers recommend a change out of chain at less than 1% growth. This would be a good recommendation if you never plan to change out your sprockets. Changing out a chain at that percentage of growth will probably never show any wear on your sprockets. However, I feel that there is much more life and service to be gotten out of good quality chains before a change is necessary.

To know when your chain has reached a growth limit you must measure the chain physically. We know that when a 520 chain is new, it has a pitch of 5/8" or .625"(15.875mm) To make measuring easy, you can measure several pins at a time. I like to use 10 chain links when measuring.

We know that a chain link has a pitch of .625" (15.875mm) So a measurement of ten new links should produce a measurement of 6.25" (158.75mm)

CHAIN MEASURE SKETCH

We must take care that we are measuring the proper points. You must measure from a point on the very first link to the identical point on the tenth pitch. (edge of pin on first pitch, edge of pin on tenth pitch) Also realize that when you are measuring ten chain pitches, or links, you will actually have 11 pins involved since the first pin is numbered zero. Between pin number zero and the next pin will be pitch number one. So, one pitch equals two pins...two pitches equals three pins, etc...

We must also realize that the chain needs to be taught when measuring to ensure that all the slack is out of the measurement area. To do this, put the bike in gear and hold pressure against the chain using the back wheel. You can also place a weighted object on the chain at the bottom side of the assembly. Measure the chain on the top side of the assembly when tightening the top side or weighting the bottom side. Another method to remove slack from the measuring area is to use a cargo strap and lift the top of the chain, creating tension on the bottom side for measurement.

Take the time to measure your chain when it is brand new to get a feel for where your measurements should take place and remember that with ten pitches on a 520 chain you will have a measurement of 6.25" (158.75mm)

You should have a target measurement that you want to see that alerts you to change out your chain. Let's assume you have decided to run your chain until it has reached 2% growth. A new measurement of 10 pitch's is 6.25"(15.875mm) and a measurement of 6.25" plus 2% equals a measurement of 6.375" (161.925mm).

According to your target measurement, once ten chain pitch's measures a distance of 6.375" (161.925mm) it is time to change it out. Remember that chains can remain in service as long as the pitch is anywhere between 1% - 3% of original length.

I recommend that you take your chain stretch measurements on several different parts of the chain. In a perfect world you should see identical measurements form one section to another, but there are times when the chain may have been damaged on one section. This damaged section can be trouble for the rest of the chain if not identified. One bad link or section can in fact cause the rest of the chain to wear prematurely.

Jaybird

[ossagp]

Bird doesnt mention it, but that part about checking in several places pays off. If you have a bike (particularly a road bike) that almost feels like it has a wheel out of balance,,but you can't seem to find it,,,and what some would call an "up and down" feeling to it under load; check to see if one section has outstretched the others.

Since I dont like to spend as much time as some do with chains, I check roller wear by using a couple of pencil points to lift and move the roller on the pins,,do this in a few places with a chain you tried it on when it was fresh. Lots of ways to get to the same point,,but just like checking for lateral movement, you need to be familiar with what the chain was like to begin with.