Road Bike, Cycling Forums banner
1 - 11 of 11 Posts

·
Registered
Joined
·
47 Posts
Discussion Starter · #1 ·
I just checked my chain with a tape measure and a Park Tool CC 3.2. According to the Park tool it exceeds both the .5 and the .75 spec's, that is to say the tool drops into the links easily on both sides of the tool. Yet according to the tape measure, over a foot, there is only 1/32" stretch. What gives?
View attachment 275997
 

·
Registered
Joined
·
765 Posts
Possibly your tape measure method isn't as accurate? I have switched over to using a chain tool as well. Chains are cheaper than replacing cassettes. I buy 'mid' level chains for a good deal at my LBS. Chains and jockey wheels... when in doubt, swap it out
 

·
Registered
Joined
·
1,846 Posts
I just checked my chain with a tape measure and a Park Tool CC 3.2. According to the Park tool it exceeds both the .5 and the .75 spec's, that is to say the tool drops into the links easily on both sides of the tool. Yet according to the tape measure, over a foot, there is only 1/32" stretch. What gives?
Chain checker tools are notorious for reading high, especially at low stretch. Some will show a brand new chain as 1/2 way to to the 1/16"/12" replace point. The reason is twofold.

One, since you're reading over a short length of chain, you're looking at smaller changes, so making an accurate tool s more difficult.

Two, there's also play in the rollers which increases with wear. Tools which measure the same way yours does, push the rollers apart adding twice that amount of roller play to the measured stretch value.

So the 12' steel tape measurement is the more accurate, but be aware that roller play also does count. For a typical chain wearing normally, the 1/16"/12 guideline is about right, but some chains can see roller wear disproportionate to pin wear (stretch) so you want to be aware of both.
 

·
Registered
Joined
·
1,846 Posts
Do you think I should play it safe and replace my chain then?
Yes---- and No.

Replacing and discarding the chain prematurely may be as wasteful as waiting too long. You measure for good answers, otherwise why bother.

In your shoes, I'd replace the chain, but save it for later use. Ride the new chain until it's worn somewhat more than this one, then switch back, rotating the 2 chains back and forth as they wear. This method is the best way to get the most miles for your drive train dollar.

I rotate 3-4 chains for any cassette, switching about every 1,000 miles.

The advantage or rotating multiple chains vs. sequentially replacing chains at 1/2% stretch is that the chains are always a close wear match to the sprockets so they tend to run smoother. Also, since you never plan to introduce a new chain to a worn sprocket, you're no longer bound by the 1/2% limit and can run everything until it just won't run at all. Typically this will be at 1-2% stretch so we're talking roughly 2-3x the total life on chains and cassettes.

Be aware that if you run the rotated chains out to 2% or more stretch, the chainrings will also suffer, so factor that cost in the decision and consider starting a new cassette and new chains at a but over 1% rather than taking it to the end.
 

·
Registered
Joined
·
223 Posts
seriously just get into a habit of replacing your chain every **4500kms or so and be done with the chain checking crap! chains are cheap.

like with your car, you don't buy a device to measure the clarity and viscosity of the oil before replacing it.....you just change it when u do a service which is X amount of kms (sorry miles).

** first time i changed my chain it had done 6000kms, and found i had to replace the cassette as the chain was slipping. so next time i changed it after about 4500kms and sweet....so between 4500 and 5000kms for me.
 

·
Registered
Joined
·
1,904 Posts
seriously just get into a habit of replacing your chain every **4500kms or so and be done with the chain checking crap! chains are cheap.
I agree.

I like performing much of my normal maintenance in the winter. So come spring the bike is in as near perfect condition as I can make it. Sure... over a period of years... I might be able to save a few bucks by waiting for each and everything to wear out or even break. But then I'd lose a lot of the cycling season repairing and replacing parts.
 

·
Registered
Joined
·
10 Posts
The best way to compare apples to apples is to measure bike wear with a chain checker is to make sure the chain is clean, no grip in between the pins and rollers. I get varying yes/no answers for different sections of the same chain when I do this test on a dirty chain.

I would never use a tape measure to check a chain. The go/no go tolerance is as small as the smallest division on the tape. Also, the chain checker pulls the cahin taught. Remember that as your chain is rotating the cassette, it will be stretched. This is difficult to duplicate with a tape.
 

·
Registered
Joined
·
7,161 Posts
Others that point out that chain checkers are faulty are correct. They not only measure chain lengthening from wear between the pins a the bushings formed in the side plates, they then add in roller wear, twice, which is much less relevant. A good ruler (recommend a steel machinist's rule) is a much better tool for determining chain wear.

I had occasion to discuss this with a manufacturer of one of the popular chain gauges and they agreed. They still sell zobs of chain gauges.
 

·
Registered
Joined
·
21,726 Posts
seriously just get into a habit of replacing your chain every **4500kms or so and be done with the chain checking crap! chains are cheap.

like with your car, you don't buy a device to measure the clarity and viscosity of the oil before replacing it.....you just change it when u do a service which is X amount of kms (sorry miles).

** first time i changed my chain it had done 6000kms, and found i had to replace the cassette as the chain was slipping. so next time i changed it after about 4500kms and sweet....so between 4500 and 5000kms for me.
So you're saying I should replace my chains 3X more often than I actually need to because I cannot be bothered to simply measure with a ruler? Doesn't make sense to me but if it works for you . . .

subguy658 said:
I would never use a tape measure to check a chain. The go/no go tolerance is as small as the smallest division on the tape.
Actually no, it isn't. It's roughly half (or less) than the smallest division. It's pretty easy to see less than 1/16" and that is the cutoff for elongation in 12" of original chain length. The go/no go measure is not a cliff anyway, it's a guideline.
 

·
Registered
Joined
·
985 Posts
One, since you're reading over a short length of chain, you're looking at smaller changes, so making an accurate tool s more difficult.
It is very easy to measure the wear if your chain has a reusable connector. If you take the chain off and measure 48 inches, the recommended maximum length would be 48 + 4/16 of an inch.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top