smontanaro 

Last night I'm putting the finishing touches on my RRB that's been off the road after a rather lengthy hiatus for no real reason than I didn't like the 52/30 front ring setup and Rally-style long cage. I sold the 30T ring and cage plates, tracked down a 36. Got that all set up. I then discovered I needed to get a slightly longer BB. (The 30T managed to squeeze in right next to the chainstay with a small gap, but nothing bigger would.)

The last task was to install a chain and adjust the derailleur. Usually, I weave the chain through its little labyrinth with the gears on big/big, pull the ends together, then eyeball how much extra I have. Mark my spot with a Sharpie, punch out the proper pin, stick on the master link. Good to go. (These are generally 70s-80s vintage road bikes with 5-7sp rear freewheels, Nuovo Record rear derailleur, you know, the normal road bike of the era.) I like SRAM's 8xx chains, and stick with them.

Last night, for some reason, I decided to do it differently, the right way. I would measure and use math. I wound up at Park's site on their chain length sizing page, wherein I read:

Simple Equation: L = 2 (C) + (F/4 + R/4 + 1)

I measured my chain stay (C) at 16.5 inches. I have 52/24 bigs. Substituting, I got

2 * 16.5 + (52+24)/4 + 1

or 53 inches. Mark the bench for 53 inches, lay out the chain, including master link. Check again, Spot on. Poke out a pin, install the chain. Damn. It's too small. Or rather, ever-so-barely just big enough. The derailleur doesn't really like the big/big combo. I could move the rear wheel forward a smidgen, but it's already in the front half of the dropout, and I worry about the upper pulley interfering with the big cog.

So, I'd like to add another inch of chain. I don't recall how long it's been since I tried to push a pin back into a chain, so don't know how successful I'd be. I have an extra master link. Is it okay to just use that?

Shimagnolo

No reason you can't use as many master links as you like.
In fact you could replace every pair of outer plates with a master link, but it would be costly.

tyrion

Technically there's only one master link per chain. The other EZ links are assistant master links.

smontanaro 

Thanks, two master links it is, or a master and an assistant, or a captain and a first mate, or The Skipper and Gilligan. I now have two. What a difference an inch makes.

jetboy 

an inch can make all the difference for sure. you can be cheap like me and visit your local LBS and get all the cut off chain pieces they leave in a box.. then get to work building your own chain out of 12 chain cut offs (jsut pushing pins.. no master)

recommended only for the next el-cheapo build contest you find yourself in.

catgita

For an easier chain length, forget the math and measuring. For a double or tripple, wrap the chain around big-big (skip the detailler), then add one inch (2 half links), rounding up as required.
For a 1x, do the same, but add two inches.

randyjawa 

No mechanical engineer on the face of the planet would recommend running two master links on a single chain. In a pinch, go for it, but as normal practice, forgetaboutit.

daf1009

Randy

I am interested in your response...and as I am an "Imaginary" (Industrial) Engineer...I do not understand the mechanics...explanation?

Thanks!

Trsnrtr

Recumbents with their long chains, often 2-1/2 normal length, frequently use multiple quick links and yet they survive to ride another day.

smontanaro 

I never throw out chain leftovers. I figure in a couple years I might have enough extras for a mix-n-match chain.

nashvillebill

I'm a mechanical engineer, and under the conditions we're running, having multiple master links is not an issue.

For high speeds, high horsepower applications there could be a problem if someone puts a couple of brand new master links on a worn chain running on worn sprockets. New chain, and new sprockets, it's not much of an issue (if any) to have a second master link. Perhaps in the old days a hundred years ago, when chain and master link manufacturing wasn't as advanced, master links could literally be the weakest link in the chain, but I've seen todays chains run merrily along under the poorest operating conditions imaginable.

cdmurphy

This. I also play mechanical engineer when I'm not riding bikes (with a real degree and everything!). For straight line tension, I can't imagine a master link would be any sort of a weak point at all. Under conditions where the chain line is poor, with a large offset I could see the master being slightly weaker as the chain makes the transition from straight tension to being pulled at an angle as it either leaves the cog, or enters the chainring. That being said, adding more masters wouldn't ultimately make the chain any weaker than just one, there would just be more potential weak points. I would be a lot more concerned about a chain that had had a pin replaced to link it. The odds of getting the pin driven too far, or not enough are pretty high. That, along with the fact that reusing the pin removes a good part of the peening that keeps the unmolested pins in place makes it riskier than a good master link or quick link.

merziac

Going to chime in here and say that while there may be no technical reason not to be able to use more than one master link, I would refrain on principle, lets call it "mechanical correctness". As an ASE and FoMoCo Sr. Master technician I think it just isn't right. I would also imagine that the chain manufacturers say its a no go and may actually have a good reason besides just trying to sell.

DrIsotope

When I initially switched from an 11-28 to an 11-32 cassette, I had two quick links with 3 normal links between them. Ran it that way every day for the ~3,500 miles until the chain was due for replacement. The extra links weren't even the same brand of chain.

USAZorro

My preference is for zero. I have quite a collection of brand spanking new master links.

Darth Lefty 

Another engineer here. Your engineering judgement saying it's probably ok is not the same thing as your signature

RaleighSport

Done it, never had an issue. Great for adjusting chains with mushroom headed pins.

Trsnrtr

I agree with this. A friend of mine had a crank, I think FSA, with chainrings with very pronounced shifting nubbins or hooks to help shifting. Being a bent, he had 2-1/2 chains with 3 quick links. Occasionally, he would get a jump in his chain when one of the links would happen to catch a protrusion. Didn't matter until he caught one downshifting on a hill and the link opened. This was in the winter and 1/2 of the link disappeared into a snow bank never to be seen again.

randyjawa 

I really can't remember exactly why we were instructed, and taught in Industrial Mechanic School, to use only one master link per installation but that is how we were trained. My guess is because the master link is not as strong as a standard link and subject to human error during installation. Also, some fools, including me from time to time, reuse a master link, rather than getting a new one. Also, the links we used in industry for smaller chains had to be installed in the proper direction. Other than that, the reasons escape me.

That said, I have seen more broken master links that standard links and I have installed a lot of drive chains in my life. None the less...

I still bet that no mechanical engineer would recommend using two masters, in a single installation, unless there was no other way to implement the installation. Obviously, I forgot to mention that the above was my opinion, rather than fact, although it does seem like fact to me, not to mention simple common sense.

Oh boy, that is the absolute truth. We had a couple of hot shot engineers who would say "go ahead and just get it done". Well, when we were doing a lift, in the middle or the night and not sure of the weight or if a beam would support the load, we insisted on the engineer's opinion, backed up by his or her signature. To heck with I will take the heat if something went wrong. I want to be sure and why...

Because when I was working in industry, at the last place I worked, five guys got killed, and sometimes it was a lack of understanding that killed them. In my job, then I wanted to be positive before I went ahead and just got it done. And, these days, I am still a by the book, know for sure guy.

USAZorro

I'm sticking with zero as my standard. A Park Chain Tool and 70-ish seconds is all it takes for supreme peace of mind.

jimmuller 

When the style police are around keep a low profile. Otherwise you should be fine.

SJX426 

Its about risk and your assessment about how much of it you will tolerate.

I vaguely remember the first time I "broke" a chain to remove it from the frame with those poor quality chain breaker tools from the 60's and 70's. It takes a lot of force to move a pin, initially. LOL, I think I pushed it all the way out and getting it back in was a challenge. That is a part of being young I can do without!

As a ME student at the time, I wondered about the peening "removal" during the process. I thought the pin would just slide back in, nope. there is a fair amount of elasticity allowing for continued interference fit when pushing the pin back in. Far more that the lack of a snap when a master is reused! the pin does not loose any dimension. That is it is still straight with maybe less of a taper due to the peening modification during removal. But the diameter of the pin does not get smaller than the smallest dimension prior to removal.

All the masters I have seen, which are very few, have a grove cut in the end of the pin for the plate's slot to fit into when installing. The diameter of that grooved portion of the pin is significantly smaller than the main pin. If a master was going to break, I would expect the pin to fail where this groove is. Oh and there are two pins on the master with the grove. Not having seen any failures, it is pure speculation. Perhaps this crowd has some data to support the assessment?

So as a Mechanical Engineer with a degree and everything, I disagree that replacing a pin is worse than a master. I have less confidence in the master than reusing a pin. The trick to installing the pin is to make sure that the plate the pin is being pushed through, is spaced enough away from the internal link. This is easily accomplished with the right tool and the knowledge of how to use it. Turn the chain over like you were going to push the pin the opposite way out. Only force it far enough that the chain no longer binds. And by the way, you can eye ball the pin position by comparing it with the untouched neighboring pins or pull out your digital calipers if you are OCD ME (or wannabe)!