nickc3

So, I bought a new Cassette last season.

I did approx. 2,000 miles on that cassette. Shimano 105.

I just checked my chain, and it needs replacement. If I'm measuring correctly, it appears to be at the 1% wear mark - which from what I've read means I really should replace the cassette too.

Do I really need to? Is there any harm in replacing the chain first and seeing if all appears to be in order (no bad shifts, etc.) before getting a cassette. Or should I bite the bullet and replace the cassette too at this time.

Perhaps the chain hit the 1% wear mark recently?

flaprao

No,it's not necessary.I've a 105 cassette,i replaced chain ,after 6000 km,but the cassette is still well.You can change, eventually,one or + elements of cassette.In my opinion ,that ins't necessary.your chain is still appropriate.How many Km did you make?

FBinNY 

No, there's no harm, and IMO this is the most logical process. Why replace a cassette before knowing you need to? And the only way to know, is to try.

BTW- often a new chain will skip only occasionally on a new cassette. If it's rare enough for you to live with it a while, it will usually resolve itself fairly quickly. However, if skipping is pretty regular, waiting it out isn't a real option.

Sometimes you can save money by buying a chain and cassette together, if so, fo ahead and do so, but hold off on installing he cassette for the moment.

By the same token. If the chain is now running fine, remove it but don't toss it. If the new chain skips, you might want to reinstall the original chain and ride another 1,000 "free" miles on the old drive train.

AlexCyclistRoch

FWIW, a LOT of those chain-stretch tools are not terribly accurate.

skiingfury

I would just replace the chain, and keep an eye on the next one. If the next chain stretches more quickly than the last, the cassette is probably shot. It's cheaper to watch and wait with a new chain than to preemptively replace a nice cassette.

dedhed

On my commuter 3K miles a year I put a new chain on every spring and a new cassette every 3-4 years and then usually because I think it's a good idea not because it skips. 10s Ultegra or 105 depending on what's on sale.

Bike Gremlin

Test the new chain - if it skips, replace cassette immediately, because a worn one will speed up the chain wear. If not - it's good to go.

Wrote about chain wear measurement here, not all the chain wear tools are correct:

When to replace the chain on a bicycle? - Cycle Gremlin

DrIsotope

I averaged 9,000 miles out of each of my XT cassettes, which came out pretty perfectly to 3 chains per cassette. A 105 cassette should last for similar miles, provided the chains are taken care of and replaced before they're excessively worn and have a chance to speed the wear on the cassette.

shelbyfv

Another vote for "no harm in trying." If it skips, put the old chain back on and ride the combo until it's done for, as others have said. Watch for sales and stock up on chains and cassettes when you find a good buy.

ramzilla

(IMHO) You can always just put a new chain on a bike. But, if you're changing out the rear cogs you must always put on a new chain. Be good.

HerrKaLeun

You should replace at 0.75% next time. for 10-speed maybe even sooner.
If you use all the rear cogs (and not just the small ones, which wear first) you may be OK. Look at the teeth if they are triangles or hooks already. If you have no chain-skipping, you may be OK.

easyupbug 

Interesting that you post 0.75% and "Before phrasing questions: Google, Read "Big Blue Book of Bicycle Repair", Watch Park Tool Repair Videos" when surely Park recommends the pretty universal 0.5%. There is gray.

gsa103

2000mi and already at 1%? That seems like a very high wear rate for a chain.
Do you ride in bad conditions?

The other possibility is the chain checker is pessimistic. Did you check the chain when it was new?

HerrKaLeun

In my Park tool chain checker tool the manual said new chains can show 0.25% to up to 0.5% when new. A bit under 0.25% is my experience with new chains. They also mention 0.75% for up to 9-speed chains (that is why Park tool sells the chain checkers that only show 0.75% and 1%). If they recommended universally 0.5%, what would you do with a chain checker that can't tell you anything under 0.75%? At 10+ they recommend 0.5%, but also say to consult chain manufacturer.
The internet says a lot, but what most sources will agree is 1% is too long. I assume the 105 is 10-speed, so at 0.5% it may be time to buy one. I stand corrected. If your cassette is very expensive compared to a chain, changing sooner may make sense. If the cassette is relatively cheap, maybe not. Changing a 10-speed at 0.6% is probably not a reason to lose sleep.

Marcus_Ti

This is why you measure with a good caliper...

caloso

I usually get 2 or 3 chains out of every cassette.

79pmooney

You don't need calipers. Any decent tape measure will do. Measure 12 pairs of links, pin to pin, The easy way to get accurate3 measurements is to measure from front edge to front edge. Much easier than trying to judge centers.

1/16" stretch (ie 12 pairs of links measuring 12-1/16") is 0.5%. This is a true reading. The common tools push the rollers apart and the play between the roller and pin gets added to the stretch, but the cogs never see that play since all the rollers are pushed against the pin from the same direction.

Save yourself a lot of confusion, can the fancy tool and use you tape measure. (You can calibrate the tool after using your tape for that brand of chain, but different brands may have different roller-pin play.)

Ben

dsbrantjr

What I would do (and have done) is throw the chain checker away and use a ruler.

grizzly59

This. And Dsbrantjr above. Chain check tools are like using a thermometer to take your blood pressure. I check 2 or 3 separate spots along the length of the chain with a steel rule. Chain should have a bit of tension.

DaveSSS 

None of the common chain wear measuring tools produces an accurate measurement of chain elongation (change in pitch) because they add roller wear to the measurement and most measure over a very short length. The roller wear can be as large as the elongation over this short length, so the tool may report twice the actual elongation. The result may be a chain tossed when it's half worn. Another problem with these tools is that roller diameters and clearances are not the same for all brands, so some chains will measure .25% worn when new. If that false wear is not subtracted from future readings, there will be even more error.

The best way to measure elongation is with a 12" scale. Place an accurate 12” scale on the edge of a pin. The pin at the opposite end will be totally covered when the chain is new. As the chain wears, this pin will begin to “peak out” from under the scale. Change the chain before ˝ of this pin is exposed. The maximum allowable wear is 1/16” (.063”) per foot. One half of a pin is slightly more (.070 inch).

Elongation is only half of the chain wear issue. The rollers also wear - often as much as 10 times more than the pins and bushings (which cause elongation). New rollers will measure about .200- .210 inch in between them. When this distance increases by .035-.040, I consider the chain to be shot. It is possible to have this much roller wear and very little elongation.

Changing a chain long before either of these wear criteria is met is not likely to increase cog life. It's entirely possible to wear out at least one or two cogs over the life of a single chain. I've used a single chain for 6000 miles, and worn out one cog, even though the chain showed little elongation. The only practical way to detect a worn cog is by installing a new chain. If the chain skips on a cog, while pedaling under a heavy load, then the cog is too worn to use with a new chain.

The best way to maximize cog life is to alternate the use of two (or more) chains, changing every 1-2000 miles. With this method a new chain will never be installed on worn cogs. When both chains are worn out, then most likely the cassette will be too. There might be a valid argument for including a third chain, but it all depends on the cost of the chain relative to the cost of the cassette. For example, if chains cost $40, the cassette cost $120, and chain life is 4000 miles, the cassette could be used for 8000 miles. The cost per mile is 2.5 cents. If a third chain was included in the rotation, the cassette might be useable for 12,000 miles and the cost drops to 2 cents per mile.

After measuring several chains, I know that my Campy chains will never come close the maximum elongation, even if used for 6000 miles. For that reason, I don’t even bother measuring elongation any more. I have a home made plug gage, made from a 6mm hex wrench, ground down to .070 inch thick. If it drops between any two rollers, the chain is shot and I trash it.

rfmarotti

+2

FBinNY 

While I wouldn't buy a chain checker, there's no reason no reason to discard or not use one that's already aid for.

Take a hint from the medical community, where a simple test that tends to false positives is used to screen, then if there's a positive, they follow up with a more reliable test to confirm or deny.

Likewise, use the chain checker to quickly verify that the chain is NOT stretched, but when it starts to show stretch, confirm with a ruler before replacing anything.

Joe Minton

A precision 12" scale.

Here's a cheap example:
https://www.harborfreight.com/12-inch...ler-66199.html

and another:
https://www.officedepot.com/a/product...s-Steel-Ruler/

I personally use a Mitutoyo 12" steel ruler which is a bit pricey these days.

Joe

BTW: Most of the popular chain wear checkers are inaccurate because they include roller wear.


Here are a couple of good ones:
Shimano TL-CN41 Chain Wear Indicator ($57 on Amazon)
Pedro's "Chain Checker Plus" ($16 MSRP)

These two checkers exclude roller wear and only measure pin-to-bushing wear. --- JM

DiabloScott

Old chains can damage cassettes.
Old cassettes cannot damage chains.

Chains wear out from grinding in the pins and bushings and rollers.

I love chain checker threads

DaveSSS 

The idea that a new chain will wear faster on a used cassette that causes no skipping is false. Cogs do not change pitch as they wear, only the tooth form changes. The chain pitch determines where the chain will contact the cog. As long as it doesn't skip, you're good to go.

Also, if a new chain skips on only one cog of a cassette, go ahead and put on a new cassette, but keep the old one. After as little as 2-300 miles of use on the new chain, you can put the old cassette back on and there will be no chain skip and no premature chain wear. You'll get another 2-3,000 miles from that cassette.