My blogging has been delayed due to having my priorities straight, I’ve been on my bike.
About 2 weeks ago I touched on the subject of chain stretch in my post called “Random Thoughts and a Eureka Moment.”
Borrowed from Sheldon Brown: Using a steel rule and measuring 12″ center to center on the rivets.
“If the rivet is less than 1/16″ past the mark, all is well.
- If the rivet is 1/16″ past the mark, you should replace the chain, but the sprockets are probably undamaged.
- If the rivet is 1/8″ past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8″ point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.
- If the rivet is past the 1/8″ mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.”
- The major cause of chain “stretch” is wearing away of the metal where the rivet rotates inside of the bushing (or the “bushing” part of the inside plate) as the chain links flex and straighten as the chain goes onto and off of the sprockets.”
Using the steel rule I can see that my Ultegra 6700 chain with 4700 miles on it has stretched, but it’s hard to see exactly how much. I picked up a Park Tool CC-3.2 Chain Wear Indicator. It’s a pass fail indication tool. The tool will indicate .5% wear on one side and .75% wear on the other. Other versions of this tool measured 1% stretch as fail. I was curious enough about this to write an email to Park Tool and their response was:
“Hello, The CC-2 still will read up to 1% wear. The CC-3.2 reads at 0.5 and then 0.75% wear. The modern narrow 10 and 11 speed chains are best replaced before the 1% wear mark. Older chains did use the 1% wear standard, but all newer chains are best replaced before this.
Using the chain wear indicator the chain passed the stretch measurement, <.5% stretch, I’m good to go. This will buy me the time I want to talk to more people about this. Everything you need to know about the bicycle chain and how it works plus it’s relationship with the cassette can be found by clicking here. All I really want to know is when to change the chain on a bike. The guys I ride with don’t seem to be of one mind on any topic including this one. Everything from run to fail to change it before 1/16th inch of stretch. Nothing definitive, some share their experience while others are just anecdotal. The most interesting answer was “I only use 3 gears here in Florida so I’m gonna start just rebuilding the cassette, replace those 3 gears when it’s time for a chain.” Looking only at cost the run to fail camp makes a strong argument. I actually did run to fail on my other bike. The chain was skipping in high gear. I had the shop install a new chain and discovered it did not work with the old cassette. At that point I changed the cassette and all is well. This may be the way to go.
The Shimano Ultegra 6700 cassette. can be rebuilt. I use all my gears but the primary 3 would be 14T /15T /16T. To estimate the cost I need a list of the parts I’ll need . I’m riding a 12/25 cassette so the parts would be:
1-14T sprocket part#Y1Z81400D $13.89
2-15T sprocket part#Y1Z81500D $13.89
3-16T sprocket part#Y1Z81600D $13.89
Sub Total $41.67
Tools required: (Prices from Amazon)
1- Shimano TL-LR15 Lock Ring Tool $32.89
2-Park Chain Whip Tool $19.95
3-Park Chain Break CT-3 $30.00
Sub Total $82.84
New Ultegra CS 6700 complete cassette = $67.00 (Amazon)
New Ultegra 6700 chain $37.00 (Amazon)
The grand total to tool up , rebuild the cassette + new chain = $161.51
The grand total using cassette complete,tools + new chain = $ 186.84
Savings = $25.33
Let the shop do it; new cassette & chain using these prices + $30.00 labor = $134
( my estimate.)
It’s nice to have options. Buying the tools, complete cassette and chain and doing the job myself appeals to me. I would then have the tools on hand and the next time the cost would be minimized. I like buying tools, I always have, and it ain’t like I’m rebuilding the transmission in the truck. There are step by step procedures on line for replacing the chain and the cassette. Who knows, I might learn something. What stops me from rebuilding the cassette is the wear on other components that would not be addressed causing premature chain failure. If nothing else now I can show the wife my data when it’s time to ask her for the money. My bike shop estimate looks really reasonable, the labor is based on < 1hr. This will be my fall back position. I noticed that when I plugged in the part numbers for the Ultegra sprockets the name Dura-Ace appeared on the parts bag. “Are you suggesting that last years Dura-Ace is this year’s Ultegra ?” Interesting.
Anyway, the chain passed the stretch test and I’m feeling a bike ride coming on so……..
“WAIT WAIT!!! You didn’t answer the question! Do I change the chain or do I ride to fail?”
I’m leaning towards ride to fail. When it starts to skip I’ll replace the chain. If the new chain doesn’t mesh with the old cassette then I’ll replace the cassette. That’s what I’ve done in the past, my experience, and also the advise from the life long bike mechanic I know. He suggested that to maximize the chain life that I keep the chain and cassette clean, it’s that simple.
1-If I run to fail how many miles will I have?
2- Even if the new new chain works with the old cassette how long will it last?
“What should you do? Answer…………YOU”RE ON YOUR OWN.”
Thanks for reading this and I look forward to your comments.