Chain Size Query

When I inherited my bike, it had Shimano Ultegra 6700 53-39 front rings and a 28-11 (10 speed) on the back.

When I got my Kickr Core, it came with a 25-11 (10 speed) cassette. And I’m still using the same chain (maybe I shouldn’t, but I don’t know better).

I’ve been considering for a long time to update my rear cassette to a 30 tooth set. Tho it looks like that would be a 30-12 10-speed (unless a 30-11 exists, but I can see why that may now work due to the ratios) to put on my Kickr Core, but then to also to be able to move to my rear wheel when I get back to outdoor riding.

I likely need a new chain sometime soon since this one is at least 4 years old. I have a brand new chain that my dad gave me with the bike 4 years ago that’s the same size as the one that was on the bike when he gave it to me with the 28-11. If I upsize my rear cassette to a 30-12 will my current size chain still work? Or will I need the next size chain?

Have a look on Park Tool about how to size a chain. I would say that almost certainly the chain should be longer than it is now, unless it was a little long to begin with. I imagine your chain is well overdue being replaced if it’s 4 years old, definitely change it when you change the cassette, I’d check the chain rings at the same time as they may have been worn with an old chain.

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The only reason I feel like it may not need a larger chain size is simply because this chain was originally installed with a 28-11, so moving to a 30-12 isn’t that much bigger. But then I’m definitely no bike maintenance expert, so it could very well need to be larger if I move to a 30-12.

And you’re probably right about the front rings, too. I have considered that it may be wise to replace those at the same time. Probably needs a good overhaul. Trying to decided if I want to buy everything and do it myself or if I should drop it all off at the LBS and get a tune-up at the same time. If you listen to my shifting you would know I have not mastered gear indexing in the slightest. :grinning_face_with_smiling_eyes:

If you wanted to be strict about it, the chain for the 30-12 cassette should be 2 links longer than the chain for the 28-11 (assuming you keep the chainring size the same).

If the 30-12 is on your trainer, and you never completely cross-chain from big chainring to big cog, you should be able to get away without lengthening the chain.

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I do this all the time, unfortunately. lol! :rofl:

Although I’ve quit doing it as much lately since my chain drops onto the small ring or completely off almost every time I do it. Probably better that I not. heh.

If you do cross-chain, and the chain is not long enough, things might get ugly! I’d suggest getting a new chain that you can shorten to the correct length - not worth risking damaging derailleurs or cassettes.

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You don’t buy chain by size, only speed, i.e. 10s.
generally they all come with 118 links, you have to measure and remove the excess links for your bike.

Before you do that, Fit the 30tooth cassette, put wheel in frame, change to 53 front and second largest rear, see how much slack the rear mech is taking up. If it can extend further, v then shift gently into the 30 and check again for slack.
If so some slack then good to go. (This is most likely as most people are conservative when fitting chains and leave slack.
If no slack you need 2 extra links, so get new chain and shorten it to 2 links bigger than current one.

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Right. I was using the term size since I’m not very experienced in bike maintenance. Now I see that what I was saying as size meant the number of links.

I have a 116L chain that I inherited.

So, essentially what you’re saying is really the only way to know if this 116L chain will still be the right size is to try to put it on and then figure it out from there? From what I’ve been finding thru Google that makes sense since even if two people had the same hearing they may not have the same size frame and even people with similar size frames from different brands could have different geometry and need a different sized chain.

So that does makes sense. But it doesn’t make me feel any more confident in being able to do it myself. :grinning_face_with_smiling_eyes:

At minimum I will collect the parts so I can then either figure it out for myself or have the LBS take care of for me. :see_no_evil:

@emacdoug Installing a chain via quick link is easy - connect the link, hold the rear brake and stomp on the pedal to click the link into place. However, Shimano doesn’t make a quick link for their 10 speed chain. I think SRAM or KMC links may work but check before buying.

If you are installing via chain pin then you need a chain repair tool (which you will need anyway to get the old chain off). It is a more tedious process and you really want to seat the pin properly. Shimano does make replacement pins that are a bit easier to install.

Four years is a long time for one chain if you have been using the bike regularly so the bike shop might be the best option as they can check your front rings and cassette for wear as well.

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I use KMC or Sram links on my Shimano Chain regularly if that helps. The KMC ones seem more durable in terms of undoing them for chain cleaning


Given that the chain is brand new, I think there’s a very good chance that it will be long enough. You may even need to remove some links to get it to the correct length.

If you look at the Park Tool website (Chain Length Sizing | Park Tool, Section 4) you can see a way of doing the measurement. As long as you have at least the two extra links they talk about after you wrap the chain around the big chainring and big cog, you’re good to go.


Hey, simply, yes it will be fine! I use my steel frame bike on my Kickr which has a setup of 53/39 and 11/25 - my Kickr cassette is an 11/32 and all sprockets work fine, no stretching👌🏽 you’re good to go my friend!!

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Measured my chain, today. 108 links. So essentially all I should have to do to my new chain, when I moved up from my 28/11 cassette to the 30/12, is to add 2 links and make it 110 instead?

The biggest problem I’m having is finding 53/39 teeth ultegra 6700 chainrings.They’re getting a bit older and harder to find. I like to avoid eBay, but that may my best recourse if my LBS doesn’t have them. But it’s amazing how much more expensive they are than the cassettes.

You only have to add 1 link per 2 tooth total increase.

Shimano chainrings are so expensive its often cheaper to just to replace the crankset, check Ebay for New Old Stock . Chainrings from a FC-5700 chainset will also work if you are on a budget. Shimano call them a “B” match which indicates that the parts are usable, but differ in materials, appearance, finish & size etc.


@emacdoug Try FSA as an alternative to Shimano parts. They sometimes have some of the legacy stuff still available. Be sure you match the BCD. Also use some Locktite on the threads before you torque the bolts so that the rings don’t start to loosen. I learned that one from experience when I bent my ring during a ride.

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My Kickr Core developed a wobbly noise and vibration 2 or 3 weeks ago. I contacted Wahoo and they sent me out a warranty replacement (refurbished, but working). So I decided that was a good a time as any to switch things out.

So I put in the 30-12 cassette I bought. I had to buy a chain link tool and links. I put my new chain in on Tues night.

The new chain and cassette feel great and have no “new” issues with them.

However, I have 2 overall issues.

  1. The first is that while doing a sprint effort a few months ago (inside on my Core) my chain popped off violently and loudly. I don’t see anything obviously bent or broken. However, ever since then I’ve had more and more issues over time with my chain dropping when I’m in the big ring and try to sprint or put in a big power surge.

Now, with the new chain and cassette, my chain is dropping from my front rings when in the big ring and I either stand up or stay sitting and increase my power unless I do it very overly gently. Today I quit riding with the big ring after the 3rd drop and used the small ring only. I was still able to get 800w in erg mode during The Shovel, but I don’t know if I can get 1190w in FF in level mode. I’m probably going to have to take my bike into the LBS some day soon. Will at least need an adjustment and most likely also either new rings or a new front crankset.

  1. The one other thing I’ve noticed is the “new” Core feels “tighter”. It holds my power much closer to the target than my original one. And, i feels like I’m putting out more effort to get the same power. I swear that if I do a new power test I’ll get lower numbers because it just feels tougher.

Here are comparison profiles from May (I just got the Core last year in Oct) and from my new Core from yesterday.

Igniter on the “old” Core (May):

Luberon on the “new” Core Friday:

Is the new one too tight or was my old/original one too “loose”?

It sounds like a new chain is highlighting a worn chainring.
Put the chain on the big ring and just see if you can almost push the chain off onto the inner ring. Worn teeth will not hold onto the chain and you will be able to see daylight and move it about with ease.
Ten speed Shimano rings will be very hard to find, although probably easier then 12 speed :wink:
As mentioned before it might be better going for a new chain set. Go for a five bolt standard so you are not locked into Shinamo rings.

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Re 1. As Adam says, worn chainring.
2. That’s the kickr applying power smoothing in is settings, before it send data to Systm.

Kickrs have it switched on by default, most brands don’t. It’s down to whether you like the perfect line or sessions the reality of your pedalling style.

The kickr config app will allow you to switch it off.

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Ah, thank you for the power smoothing reminder. I have it turned off in SYSTM, but didn’t remember there was a setting in the Wahoo app that affected it, too. I’ve just turned that off, so I’ll see tomorrow if that fixes that (which it should). Thank you!

Yep, not surprised that the front ring is worn. Guess I’ll need to figure out the best way to get it replaced. Hard to find new rings, let alone reasonably priced ones. I saw one matching used 53 ring on ebay for $125. And it didn’t look any better than mine.

Maybe a newer Ultegra or 105 model crankset is available and would still be compatible with my new 10-speed 6700 rear cassette. I’ll need to keep riding on the little ring and save up for some kind of replacement. Maybe if I can suffer thru the holidays supplies will improve in 2022.

@emacdoug Check FSA and Wolftooth as well. They sometimes make rings that are no longer manufactured by Shimano or SRAM.