Does Anyone Use This Chain Measuring Method?
 

I'm talking about the BicycleTutor method shown in this video:
http://bicycletutor.com/calculate-chain-length/

Does it work? I'm essentially done with a build, but my small chainring for a triple has not yet arrived. I need to have the bike rolling tomorrow afternoon due to the fact that I'm traveling abroad for a bit and need it completed. I also want to be able to use the same chain when I get and install the small ring. If this method of measuring and cutting is accurate, it should allow for the chain to work even with the new ring, right?

Thanks.

Well that's screwed up right off the bat since he's telling us to break the chain on an outerplate link where it needs an inner plate left on both ends. I'm sure he meant well but just put his finger in the wrong place.

It also depends on if you have a short or long cage rear derrailleur. Not by a lot but a long cage may require an extra link if the adjustment is close to the limit of going shorter.

What a lot of us do is run the chain through all the derrailleurs and then put the gearing onto the big to big combo. Then draw the chain up tight but so that there's still some give in the rear derrailleur. In other words if you flex the RD up a little it still gives you a touch of slack. It needs that slack to let the chain pop over the teeth just in case you ever change to the big to big combo by accident. With that set you should still have enough tension to operate when in the small to small combo which you can't test yet.

In truth some folks set it using the rear cog one or even two rings down and rely on their awareness to shift the front before selecting that high on the rear. But make one forgetful mistake and you'll do some serious harm. The least of which is blowing your chain apart.

In any event by using the big to big combo and including the rear derrailleur with a touch of give to it you're covering off the absolute worst possible combo.

That's the same method that Sheldon Brown recommended. A number of people on here recommend it too.
http://www.sheldonbrown.com/derailer...ent.html#chain
It will work for your situation because it does not use the small chainring.

I disagree, sort of. It depends upon how you plan to close the chain. It's unfortunate that the video overlooks that crucial detail. The video looks correct if you are connecting using a pin. But if using a Powerlink, then you'll need to add one more half-link (one more half-inch) in order to have each end be an inner link.

The suggested bib/big method suggest the shortest possible chain length. That's OK if you have the largest cog that the RD can handle, but if not, you would need to make the chain longer if the cassette was ever changed to one with a larger cog.

I still think it's smarter to use the little/little method where the chain is routed through the RD, as normal and made as long as possible without hanging loose or rubbing on the RD cage. This length will handle any cassette within the RD's wrap capacity without having to change the chain length.

If you deliberately exceed a RD's wrap capacity, then the big/big makes sense, but you should know that the chain will hang loose in the little ring and several of the smallest cogs.

The big-big technique is the one to use but you don't run the chain through the rear derailleur. Wrap the chain around the largest cog and the big chainring, overlap the ends and add 1" (2 half-links) then cut the chain at that point. If you need to adjust a half link to get the ends to match properly, go a half-link longer. Then install the chain through both derailleurs and join the ends with the special pin or master link.

Once the chain is properly set for big-big, the addition of a granny ring of whatever size you use is immaterial. If your rear derailleur can't wrap up all of the needed chain for small-small, just avoid the gears it won't handle. Going to a too small-small combination is just a nuisance. Using big-big, if the chain is too short can (read will) be a mechanical disaster.

DaveSSS hit upon a key issue.

However you measure a chain there are three possible lengths. The method described will give you the shortest length, big/big +2 links. You can also use BCRider's method for the same results. You can use the method DaveSSS describes to find the longest length, small/small with RD just taking up slack.

If your RD cage is long enough, the shortest length will be shorter than the longest length, otherwise you have a choice, change gearing, replace RD with longer cage, or cheat a bit using the shortest length and allowing the chain to sag if you accidentally shift to the small/small combination.

In the event that there's a range between the shortest and longest length you have choices. Sram recommends the shortest length method, which will obviously yield a lighter chain. Campagnolo recommends measuring by the longest length method who's advantages are more chain wrap on small sprockets, freedom to increase sprocket size later, and for MTBers the ability to cut out a damaged link and resplice the chain.

When setting up race bikes sometimes a length between the shortest and longest length will allow the RD to be set higher improving shift response, and I try for the length which allows that using either chainring.

Regardless of how you measure it, consider big/big +2 links to be the absolutely shortest length. You may say to yourself I never crosschain, so I don't have to worry, but chains are incredibly strong and if you ever shift into a combination it can't wrap, kiss either your RD, wheel axle, or chainrings goodbye.

DaveSSS is correct that the big-big+1" method isn't valid if you ever change the cassette for one with a bigger largest cog. However, I think it's safe to assume you would either fit a new chain with a new cassette or, at least be aware that the old chain wasn't sized for the new cassette.

His little-little method assumes your rear derailleur has the wrap capacity to handle any other gearing changes and I'm not sure that's a always valid assumption either. I tend to violate most rear derailleurs published capacity by substituting 26T grannny ring for the stock 30T on triple road cranks. Setting the chain by small-small would leave me with a chain too short for big-big.

DOH! ! ! You're right. I'm so used to using SRAM or KMC chains with links that I'm conditioned now to doing it the "Powerlink Way". I went over to the link method many years ago just for the ease of being able to remove a chain when required without needing to punch links. I guess I'm so conditioned to it that I immediately saw his finger as pointing out the wrong link. Sorry for any confusion.

OK. The cassette is a 13-24 (I believe) Hyperglide. The crankset is an older RSX triple without the little ring currently attached. The derailleur is also older RSX, long cage.

So what I'm hearing is that if I use this method, I won't be able to cross-chain. I mean, I know it wears things down faster, but this is my brother's bike. He sometimes does the cross-chain thing before settling into a better gear. The chain I'm using is an SRAM one with a Powerlink. I figured in the video he would just be using a pin, and I would actually cut the chain before that outer link he pointed to. Eliminate that link, and the Powerlink pops in as its substitute offering the same length. But are you guys saying I should cut at the end of the next inner link in order to have adequate chain length?

Use the method in the video. You should then be able to cross-chain.

Leave an extra couple of half-links if you're concerned and want to be extra sure. It won't hurt to have two inches of slack rather than one.

The problem with these tutorials is they don't mention what to do if the ends of the chain that come together can't be joined - like two sets of inner plates. The ends that comes together don't magically match up. In that case you add 3 links or 1-1/2 inches and if you use a master link, that counts for 1/2 inch.

The little/little method is not ambiguous. The chain either has enough tension or it doesn't. There is no guessing. If you use that method with a long cage RD, the chain will be long enough, with a 24T largest cog.

This is the SRAM method - that's what they recommend on their web site, subtleties such as inner vs outer link aside; it's know as big+big + 1 (or 2, depending on the flavor of the moethod used). Shimano goes another way - big front, small rear, vertical alignment of RD rollers. At the end of the day, you still need to check that you can ride big-big without the RD being bent out of shape, and small-small without the chain sucking into the chainring.

+10 Big/big +2

^ Always works for me!

I alternate between cassettes that are 12-25 and 12-27. I size my chains on the 12-27 using big/big+2, and I cross-chain sometimes. So far, so good. No issues whatsoever.

it doesn't need 2 inner plates unless you are using a quick link. You don't have to go that route but if you do, you are correct. The display shows an inner link on the chain coming off the top of the gear (it's there). If you pop the pin of the outer link where he has his finger pointed, it will fit to the inner link coming off the top. It's kind of hard to see. I use this method and I like it too on my Campy chain. On another of my bikes I do use a quick link though.
I also don't think it matters if it's a long cage or short cage as this is the longest length you will see on your gears and you have to have the chain at least fit this. Cage length is to take up the loose chain when you use the small chain ring and does not come into play on "minimum length necessary", which is what measuring chain length is all about.