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Common Tread

Chain final drive redux: 12 things you might not know

Mar 21, 2017

I thought I’d written all I needed to on chains. All I could, really. Hell, it's just some teeth and rollers, right?

Looking through the CT archives, I found I'd kind of beat this horse dead. I wrote article after article after article that mentioned drive chains. We’ve also done a few videos on them, with more planned.

And yet there seemed to be more to say on the topic. There were so many interesting tidbits I didn't delve into more deeply! Roller chains and sprockets are a bit more intricate than they appear. I thought some of the notes I was taking were pretty engaging. If you’ve watched our videos on the topic or installed a few chains yourself, some of the following points might be interesting, helpful, or educational for you, too.

Leonardo's drawings
"One of these babies is gonna look badass on a Ducati in like 500 years." Illustration by Leonardo da Vinci.

Fact: Hans Renold patented the roller chain in 1880, but sketches by Leonardo da Vinci in the 16th century clearly show chains using roller bearings.

Tech tip: The closed end of a clip-style master link’s clip should always lead in the direction of chain travel.

Keychain master link
It's been on my keychain (first in 520 form, then in 530) since my salad days. Photo by Lemmy.

Product recommendation: Keep a clip-style master link on your keychain the same pitch of your bike. Regardless of what type of master link you normally use, a clip-type can often be installed without special tools in the field, and it will likely get you home. A spare master link is useful if your chain breaks at the master, which is typically the weakest part of the chain and the one most prone to breakage.

Low-tech tech tip: Surprisingly, you might actually get better chain life from a plain chain because it forces you to stay on top of cleaning and lubing. Keeping a sealed chain with damaged O-/X-rings lubricated can be nigh on impossible. Of course, the downside to this is that you do have lots more cleaning and lubing to take care of.

Tip: Some people swear by a pickle to clean their chain! I haven’t tried it, but I guess if I broke down at a nice Jewish deli that had no rags, I’d give it a whirl.

Product recommendation: Companies like Supersprox and Renthal make sprockets I feel are truly innovative for the offroad crowd. Riders often struggle over which sprocket material to choose. Steel sure is durable, but it’s much heavier than aluminum (whose softness makes it a less-hardy contender for longevity, especially in the dirt). Bi-metallic sprockies solve both problems. Let’s examine the Twinring, for example. The large inner portion of the sprocket is made from 7075 T6 aluminum. The outer ring that makes contact with the chain is made of nickel-coated steel, giving the benefits of both materials where they are needed. The outer rings are heated and pressed onto the inners, and then locked into place with flat grub screws.

Chain-drive hardtail
Here's a rigid bike. Note that the rear sprocket can't really move relative to the front, so the chain can be run with much less slack than a bike featuring a rear suspension. Photo by Dan Venditto, bike by Bryan Hagaman.

Fact: If you ride a hardtail, you probably know that rigids don’t need much chain slack — 0.75 inches should do the trick. If you have stretch or drop in your frame, though, a tensioner might be necessary to keep the lower run of chain from becoming a chainsaw.

Tech Tip: If you’re planning on converting a belt-driven bike to chain, you might not have enough adjustment in the swingarm slots. In that case, you should know about half-links and one-and-a-half links, which can help get the correct slack adjustment on a bike with a small adjustment window. I also find them helpful when working with a chopper with a fender that sits very tight to the tire.

Sprocket ratio chart
We did the math. It's an older code, but it checks out. Table courtesy of Drag Specialties.

Fact: Sprocket gear ratios are specifically formulated to decrease wear. One of the principles of chain design is to have a specific chain roller and sprocket tooth mate up as infrequently as possible to prevent wear and spread wear evenly, especially from damaged teeth or roller bushings. (Your factory-engineered ratio took this into account.) Often, an “extra tooth” is built in somewhere. This concept is called a hunting tooth design. Ideally, the design incorporates a chain that has a number of links that is not evenly divisible by the number of teeth in either sprocket. Interestingly, this same theory applies across other final-drive methods, too, like belts and pulleys or the gear teeth on drive shafts.

Tech tip: Switching from a 530 to a 520 (narrower) chain is a popular modification to make on many sport bikes or race bikes. The 520 chain and sprockets are a bit narrower, so that means the chain typically gives up some length and some life, however, the benefits are two-fold. The lower contact area between the rollers and sprocket frees up horsepower and also helps you shed weight.

Tech tip: If you’re installing a rivet-style master link, correct pin deformation varies according to tool and chain manufacturer. Generally, ideal “mushrooming” is around 0.025 inches. Here are a couple of manufacturer’s examples:

  • 0.020 to 0.028 inches over the un-riveted diameter. (RK)
  • 0.217 to 0.236 inches outer diameter depending on type chain (D.I.D.)

Product recommendation & tech tip: The battle between ease of installation (with clip-style master links) and strength in service (rivet-style master links) has been solved by EK chain. They have a patented master link design that’s ingenious, and many riders don’t even know it exists. It’s called a screw-type master link and it does not require a rivet tool to install, nor does it require a user to measure pin head deformation. The screw-style master link has extra long pins with a threaded section on them. All you need to do is tighten the nuts with an 8 mm wrench until they bottom out. Remove the nuts, snap off the excess pin length with a pair of pliers, and your chain is perfectly riveted!