Length Does Matter: Chain length is one of those important setup points that often gets overlooked both when building up a bike from scratch, or when replacing a worn chain. In fact, it is so common that there is a good chance that many of the bikes on your local shop's showroom floor are sporting too long of a chain, an oversight from the factory that can often lead to dropped chains or inconsistent shifting. While an over-length chain can cause some annoying issues, one that is too short can be downright catastrophic. The best case scenario is that your bike will refuse to shift to the larger sized cogs or chain rings due to too much chain tension. Worst case: you could not only rip off your bike's derailleur hanger or destroy the chain and derailleur itself but even bend over the chainring due to the massive forces involved. It's fair to say that a bit of carelessness when it comes to chain length can quickly make for an expensive repair bill.
Derailleur Cage Counts: Your bike's rear derailleur also plays an important role in managing chain length. Its hanging cage and pulley wheels take up the chain's extra slack when in small cog and chain ring gearing combos, but the spring-loaded cage can also rotate forward to compensate for added chain tension when you are in a larger sized cog or chain ring. Derailleurs are available with short, medium, and long cage lengths depending on what your bike requires. The general rule of thumb is that the larger the gearing range, the longer the derailleur cage needs to be. This is because of the massive difference in chain slack when in certain gearing combos on bikes with three rings and wide range cassettes, while bikes with only a single chain ring can often get away with a short cage derailleur. Using a short cage derailleur on a bike with a very wide gearing range (
a triple crankset, for example) will require a chain that is overly long to compensate for the lack of capacity in the derailleur's short cage, while the opposite is true of a long cage derailleur on a bike that doesn't necessitate it - there will be no happy medium setup. In short, the wrong length derailleur cage will make determining proper chain length nearly impossible.
Too much chain length and you'll have shifting issues and suffer from dropped chains, but too little could rip your bike's derailleur right off. Have we scared you into checking the chain length on your bike?
Some helpful pointers
• The term 'chain growth' refers to the distance between the bottom bracket and rear axle lengthening as the bike goes through its travel. It is important to determine chain length on a full suspension bike when it is in its fully compressed position, and with the chain in the largest cog and chain ring. This will tell you the maximum chain length required. • While today's 10-speed, dual chainring setups can often be ridden in the big ring and big cog combo (otherwise known as being 'cross geared'), it isn't recommended for bikes with triple ring cranksets. Even so, it is best to set chain length when in the big and big combo simply because it isn't uncommon to accidentally shift into such a gear by accident when out on the trail. Better to be safe than sorry! • Advanced riders on bikes with double or triple ring setups will sometimes purposely run the chain too short for the bike to fully bottom when in the big cog and big chain ring combo. This setup puts the onus on the rider to not shift into such a gear in order to prevent damage, but is done to add chain tension when in more common gearing combos to limit noise and the chance of losing a chain. No, we don't recommend it. • New bikes will often ship from the factory with a stock chain length that is far too long. Just because your bike is brand new from the shop doesn't mean that its chain length is correct. It's always best to double check. • Derailleur cage length varies between Shimano and SRAM, and there can even be differences between different model years of the same derailleur. This means that a new derailleur necessitates checking chain length.
The Full Suspension Factor: Setting up your bike with the proper chain length isn't a difficult task, but the job does become more complicated if you ride a full suspension bike. How so? Many designs use a layout that, whether employed intentionally to increase pedaling performance or not, moves the bike's axle further away from the bottom bracket as the bike goes through its travel (this is known as 'chain growth'). This rearward axle path may be present throughout the entirety of the travel, or only during part of it, but it does mean that a full suspension bike will nearly always require more chain length to compensate.
Bottom the suspension - Full suspension bikes will often have the most chain growth when at full travel, so this is where you'll have to size the chain. If your bike uses an air shock, simply let all of the air out by depressing the shock's schrader valve as you compress the suspension (be sure to write down your air pressure before doing so), or remove the valve core to allow all of the air to escape. Bikes with a coil shock will require the shock to be removed, the coil taken off, and the shock to be reinstalled.
Place the bike in a repair stand and shift to the largest chain ring and cog combination before lifting up on the rear wheel in order to fully bottom the suspension. Either have a friend hold the bike in this position, or place it on the ground. Chain too short - Your bike's rear derailleur will tell you the entire story. The photo above, taken when the the bike is fully bottomed out, shows the derailleur cage pulled fully forward and nearly parallel with the bike's chainstay, and the upper pulley wheel is also making contact with the largest cog. This setup would equal disaster if the rider was to bottom the suspension while in this gearing combo, likely resulting in damage to both the derailleur hanger and the derailleur itself. Links must be added to the chain. Chain just right - Note the angle of the derailleur cage compared to its postion in the second step. Adding just two links to the chain allowed the derailleur cage to relax, leaving enough slack to prevent any damage from occurring. Just loose enough - Shift the bike to the smallest chain ring and smallest cog - the combination that will result in the most chain slack. The photo on the left is close to the ideal setup, with the chain still having enough tension from the derailleur cage to keep it from hanging loosely. Conversely, the photo on the right shows the derailleur's cage in its fully relaxed position, letting the chain hang too freely with not enough tension. This setup could result in sloppy shifting or dropped chains over rough terrain.
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Author Info:
mikelevy
Member since Oct 18, 2005
2,032 articles
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It doesn't matter what it "looks like", your eyes can deceive you. If the derailleur has reached its maximum extension, as PB has suggested, it will be under less tension than that on the left; therefore more likely to drop, and that is the point PB want you to understand. So no, the photos therefore are not the wrong way round.
This MTBR thread post about rear cage length is a good place to start to understand if your cage length is correct, and from there there is an alternative method of getting chain length right without using the rear derailleur. It is one I have used for years on both single and twin ring setups and works.
forums.mtbr.com/2019042-post2.html
Read again and look at the pics.
It's not chain length by links.
Bypassing the derailleur and adding two links works for all cage lengths in my experience IF you have checked that your cage length can handle your ratio of biggest to smallest cogs/rings (and that is where you use the formula).
If you don't check whether your cage length can handle the ratios you have on the drivetrain there is an increased possibility that something might go wrong.
They have since edited the article, (correcting it to left = tensioned correctly).
Also thatgeeza is still incorrect, he thinks the pic on the right is tensioned correctly.
How is thatgeeza absolutely correct?
Seems like a fairly comprehensive write-up but one thing it might fail to mention, depending upon your perspective, is that having a little longer chain is a bit of a fail-safe for long distance trail riders. If you permanently damage a link you can remove it and still have the proper chain length, assuming you have everything to adequately repair the chain.
But my favorite, or at least most memorable trail repair is turning a geared hardtail into a singlespeed because of a destroyed chain /and or derailleur. You can usually find a somewhat tight gear.
shift to Biggest ring up front + smallest cog in back, then install the chain at a length that allows the der. to be perpendicular to the chainstay.
-this is only for hardtails, rear suspension usually necessitates at least 2 extra links
But yeah the chain tools are not much good with them. I knackered two on my last bike, one bent pin, one bent tool. I always carried a solid tube long enough for the pin and a strong a.f. Nail. Always a rock or a brick lying around to hammer with and it weighs a lot less than a tool.
The guidance on chain length provided in the MTBR link is the same guidance that is provided by both SRAM and Shimano.
Bottom line: Unlike what this article is saying, chain length is independent of derailleur choice.
Ok they were ugly but you never got a destroyed bike with one fitted due to spoke collision.
Even with the screws set it only takes a knock or twist from something to cause drama.
Maybe mrp will make carbon ones for only a few hundred quid :p
www.bike24.com/p240525.html
When in doubt, go long cage. It's what a vast majority of complete bikes ship with. I think SRAM med cage was designed for 1x10 or maybe micro geared double+bash (ex. 24/32/bash + 11-32).
I learned my lesson the hard way. I heard/read people mentioning that med cage provides better tension, with chain drops being one thing that was noticeable reduced, which I really wanted to address, and wrongly assumed that it'd work with my 11-36 and 28/42 setup on my FS trail bike.
I used the big to big, shock fully compressed + 2 links method which is what is detailed in the instructions that came with my SRAM chain. Shifting is fine generally but the chain slack on the small chainring is ridiculous.
Why can't you accept that the UBI method works fine? Were you molested by UBI? Where did they touch you? Show me on the doll.
making yourself look like the tools you apparently don't know how to use.
It's a poor method which can lead to either having too long or too short of a chain than what is ideal. If it was the best way to size a chain the chain manufacturers would recommend it, because it is easier. But they don't, only shitty UBI does. Why do you think that is?
And since I see you have no sense of humor, I must assume that you were indeed molested by someone at some time. Maybe by a mechanic? Show me on the doll where he touched you.
The UBI method is especially bad considering the wide range of todays cassette's. According to the UBI method, you would put the exact same length chain on a bike that has 48-36-24 gearing in front and an 11-36 in the rear as a bike that has 32-24 gearing up front and an 11-28 in the back, assuming they both had a long cage derailleur. The second bike would have an unnecessary slack chain, it would be more likely to fall off and get chain sucked and damage the frame, more likely to rattle around on rough downhills
(more frame damage), and more
likely to have sloppy shifting. But all that would be "just fine" with you and your amateur UBI method.
If I have no sense of humor then why are you lamely attempting to
copy my jokes? Pull something more creative out of your toolbox. But I don't want to see your doll, I think we've all heard enough about your obsession with that. Must suck to not get the real thing, but hey, your obviously the kinky type.
And you honestly think that I would just leave a chain too long on a customer's bike? If it's too long after I install it, I take out a few links. It's really easy. You make it sound like cosmetic surgery.
you just flushed your whole argument down the toilet?
Not only do I honestly think you would leave a chain too long, I'm sure you have left customers chains too long more than a few times since you've been using this crap method for 10 years.
Funny that you say I'm coming at you with "bullshit mechanical
methods" when I have never explained on this thread exactly what my method is.
With everything in life"rules of thumb" rely on the person applying the rule to appreciate and understand the principles behind why the rule will generally work and equally importantly why, where, when and how that application may not be appropriate.
I see Protour has a very valid point. I run a 1x9 Sram drivetrain on three bikes. These have anywhere from a 32 to a 38 front ring and an 11-28 through to 11-34 cassette. I also used to run the same two cassettes on a 2x9 where both grannies were 22, giving me 38-22 and 32-22.
Using the small-small method would give me the same chain length on both the twin front ring bikes yet different lengths on the single ring bikes. Using the big-big method would give me different chain lengths on all.
At first sight then surely the small small method is a short cut...many may think.
An amateur with no or little mechanical experience or who does not bother to do the necessary research to inform themselves is left with no option other than to plump for one and hope for the best - not a good option Instead, as you have said, use your own expereince.... listen to your drive train people... pay attention to how it behaves in the more extreme ratios out on the trial.... get to know your ride for pete's sake....
None of the optinos are the only way, TRY THEM YOURSELF people and get a sense of achievement from feeling more connected to the bike bneath you and how it reacts to how you set it up. Try small-small and take your bike out and see how it works. Try big-big and do the same, get a few cheap mechs of different cage lengths and try, try, try.
Cinfidence on the trails that your drivetrain is not going to be the reason you walk home makes for a better ride.
You need to stop trolling my posts and get a life. Worry about your own shit.
I have a SRAM x.0 short cage mech, but a 11-36t casette (10 spd). I was told this should work just fine, but the jockey wheel feels constantly like it's skipping, and I can;t get into 1st gear.
Is my chain too short, or will that set up never quite work well?
I currently use a long cage derailleur to minimize chain damage on the bottom of my chainstay.
Thinking about going with a short cage and a Bionicon C-Guide.
So a few mm's
I'll have to ease it out and see how that runs. :[
N1 for the tip.
so TLDR...