I recently converted my wife’s 650b mountain bike to a 1×10 setup. With this conversion, we simplified her set up, dropped some weight and reduced some redundancy in gearing. I have a lot of people ask me how to convert a mountain bike’s drivetrain to a 1x setup, and I see a lot of the same questions coming online as well. So I’ve decided to kick-off a new series of “how-to’s” with a How to Convert your drivetrain to a 1x setup. Here’s her build as it sat post conversion:
Overall, the conversion is rather simple. But what gets some people I think are some of the subtleties and the jargon involved. So let’s roll up our sleeves and get to work. First things first. Let’s talk about the overall options. The two main choices are between Shimano and Sram (Sram X9 Type 2 shown). I knew well ahead of time that Lynn would eventually go with a 1x setup, so we had originally spec’d a Sram Type 2 rear derailleur. Here’s what you need to know and it’s the first part of the system: Shimano produces what is called a “clutch” style rear derailleur (EDIT: Technically called a Shadow PLUS or a Shadow RD+ i.e. Shimano XTR Shadow+ Rear Derailleur). This has a switch on the rear derailleur that when thrown increases the return spring’s resistance and alleviates chainslap by putting more tension on the chain (EDIT: The lever can be positioned anywhere in between the on and off position so technically you can create more or less friction on that return spring mechanism. In addition, you can actually adjust the amount of tension INSIDE of the mechanism. Pinkbike has a great step by step guide showing you the details here). Sram deploys what is called a “Type 2″ rear derailleur. This has the same basic design element of a stronger spring but it’s always “on”. Shimano gives you the option of flipping the switch on/off. This heavier spring puts more tension on the chain, reducing chainslap and hence the chance of the chain to be thrown. Think of that old trick when you have a garden hose or an extension cord laid out in front of you and you whip it into the air to get a section of it to roll out in front of you. A chain does the same thing when your bike goes through a series of obstacles, and it’s those “jumps” that travel down the drivetrain and cause it to skip up and off the chainring/cog or both. The heavier duty spring on the Shimano Clutch and Sram Type 2 help to reduce that slap. Here’s Lynn’s X9 Type 2 rear derailleur for reference. Looks pretty much the same…
The second part of the system is the chainring. Sram introduced their “X-Sync” chainring tooth profile with the introduction of their XX1 11 speed group. The teeth have a thick/thin profile if you sight down on them from the vertical. This is the positive shape found between each chain link. Check out your chain. That negative space you’re seeing is the tooth profile of Sram’s X-Sync chainrings. This basically keys into place and “grabs” the chain, holding it onto the chainring. The only problem was that X-Sync was pretty much proprietary to Sram due to a proprietary mounting hole pattern that came with the new XX1 group… Bad news for pretty much everyone else running a 4-arm 104 BCD crank. That void was filled by Wolftooth and the result is their Drop Stop chainring. IMO, this actually has a superior tooth profile and does a really good job of holding onto your chain. Here’s a Wolftooth Drop Stop “Cinch” style chainring as a reference:
Shimano introduced their XTR 9000 series component line earlier this year, and FINALLY got on board with a 1x system. They come about the whole chain retention thing from a different angle. Literally. The chainring tooth has a kind of “hook” that grabs the chain link and holds onto it this way. So the chain pops on/off the tooth to be retained. Their cassette also does not require Sram’s XD driver but is backwards compatible with all existing hub shells from what I understand via a little fanciness with their largest cog. But, we’re talking about converting existing drivetrains, so chances are, you can keep your existing cassette. I personally recommend one which has a 36t cog as the largest cog tooth count. This makes a HEAP of a difference when climbing. We’ll also get into some hop up’s that further relieve the pain of climbing and really give you granny gear feel.
But getting back on track, and we’ll come back to this Cinch stuff in a bit (for the record, it’s a technology thanks to Race Face that FINALLY eliminates the spider and all 4 or 5 chainring bolts…). So, back to the chain and the chainring. Having this “thick/thin” chainring profile which keys into the chain and grabs the chain holds it onto the ring. Believe me, I’ve pounded the living hell out of my set up and haven’t dropped a chain to date. Well correction , I have dropped a chain twice in the last 2 years basically. That’s a lot of riding and only 2 chain drops. For the record, these were due to two extremes: The first was the temperature dropped significantly while out on a fat bike ride, so what was water on the ring turned to ice and began to build up and over the course of about an hour or so, eventually picked the chain up and off the ring. Kicked the ice off, and no problems. The second incident was out for a 40 mile ride after a big storm and having to ride through endless mud holes and stretches of thick mud chewed up by racers I was cleaning the track for… I had mud build up and get so gunked up on the ring that again, it picked the chain up and walked it off. So two extreme cases, and with a little watchful eye can be avoided. Under pretty much every other condition, no problems. We can call these “typical” trail conditions I suppose! Basically, beating the living hell out of the system. But what makes the whole 1x system go is this thick / thin chainring IN COMBINATION with a Sram Type 2 or Shimano Clutch style rear derailleur. That is paramount to ensure the best chain retention in a truly guileless, 1x setup. If you sport only the ring or only the derailleur, you cut the system in half. So if you are thinking about converting, check what you have and make sure you plan accordingly if you don’t have one or both of the systems in place. My hunch is you “might” not have the proper rear derailleur.. But that’s just a hunch. Check to be sure first before ordering parts.
The next piece of the puzzle is choosing chainrings and tooth counts for your set up that closely matches the gears you’re most often in. Wolftooth by default… Honestly, they offer the widest variety of chainring BCD’s, and mounting options. Check them out if you haven’t. Made in the USA and bullet proof. I can’t speak highly enough about their product. The equation to use to figure out what closest matches your current setup’s variety is the gear inch calculation. Sheldon Brown has a nice one with many “finer points” to fill in, while there are other ones that are more simple. The basic calculation is the drive wheel diameter multiplied by the front chainring tooth count which sum is divided by the rear cog’s tooth count. This has little to do with it’s original intention, but it does give us an idea of “feel” of different gear ratio’s. So by doing a little calculations, you can put a finger on where a good place would be to start with a front chainring tooth count. IMO: 32t is a really great place to start for a true trail setup. Not too high nor too low, it’s “just so”. Direct mount chainrings (aka Race Face’s Cinch Platform) now gives you the option of choosing chainring size/teeth counts that are no longer restricted by the BCD of the crank. So a 28 or 30t chainring is not a problem with cranks who have share this direct mount technology. Basically, if your crank has a removable spider, there’s a good chance that Wolftooth or Absolute Black may make an option for you in addition to the stock offerings from the crank’s manufacturer. But, there’s a good chance you’re running a crank with a 4-arm crank with a 104BCD mounting pattern, like so:
Honestly, I always felt that when I was running a 34, I wanted to run a 32t ring and I’ve been running 32t chainrings ever since I got my first 104 BCD crank and haven’t looked back. What we always needed was a little bit bigger cogs out back, and we’ve certainly gotten our fill now with XX1, X1 and Shimano’s XTR 9000 offerings. Now we also have what I’d refer to as a Poor Man’s 11 speed with One Up’s 40t cogs (First came out as a 42t cog…) and Wolftooth’s GC (Giant Cog) in a 40t configuration for both Sram and Shimano. This 40t cog acts as an additional set of teeth for when the going gets tough, you can chew your way through or rather gnaw your way up a climb. You’ll have noted that I have introduced one of these on Lynn’s build in the form of Wolftooth’s 40t GC (i’ve also been running one since the fall and LOVING it) – I’ll use this image… again. It’s the black gear behind the last one of the cassette which is a 36t:
The basics of this is you remove your cassette, slide on that large cog, ditch the 15 or 17t cog and spacer (I’ve been actually ditching the 15t cog as I find the jump without the 17t much too great and I actually really LIKE the 17t cog), reassemble everything and tighten it all back together. Blam.
Here’s another view of Lynn’s converted drivetrain:
So to review, the essence of a 1x setup is a thick / thin chainring and a Sram Type 2 or Shimano Clutch style rear derailleur in combination with your existing cassette. Additionally, a 40t hop up cog from Wolftooth, Absolute Black or OneUp all provide a little extra something in the can of whoop-ass when the going gets tough. If you don’t already have it, consider getting a cassette which has a 36t cog at the top end of the cassette. Choose the right chainring tooth count for your conditions (honestly, you can’t go wrong with defaulting to 32t) and match up your mounting pattern with the appropriate one. Pretty simple, but as you can see, it’s a lot of info possibly to sift through. The rest is pretty easy:
Remove your front derailleur. Remove your front shifter and all the cables/housing associated. Check out Lynn’s cockpit post removal of all those shifty bits… Clean. Mean:
Remove your drive side crank arm. Remove all the chainrings, bash guards and/or guides. Clean all interfaces, and add a little grease to them to reduce creaks. Install the new thick / thin ring. If it’s spiderless, same applies (or if you have a removable spider, chuck that thing as far as you can see…). Assemble everything, again be sure to grease all interfaces and while you’re at it, take a minute to clean and grease up the spindle / bearing interfaces while you have it apart. Torque to spec. *Note I’ve found that for me, Race Face’s Cinch torque specs are not high enough. I actually went to 50Nm for the cinch retaining bolt, and upped the spindle bolts to 50Nm as well – hasn’t come loose since. A lot of the new direct mount aftermarket chainrings are BEEFY. IMO: You would have to make an effort of slamming it purposely onto obstacles to bend it – the chains going to pay before the chainring will (That comes from experience on my end ATMO). I’m more of a finesse rider myself and I don’t use one. But if you want extra safety, you can always mount a bash or a dog bone type bash on a set of 104 BCD cranks. Here’s Lynn’s stock X9 GXP cranks. Gone are the spider, 36/22t chainrings and bash. Wolf tooth 30t Cinch Direct mount chainring in it’s place. Light. Stiff. Simple. And it works.
Now break the chain/master link. I’ve got myself a set of Park Tool MLP-1.2’s which are a Master Link plier. A must have tool IMO now… Double check that the chain is the correct length by wrapping around the largest cog and around the chainring and checking the overlap. I think Sram and Shimano are about the same. Basically 2 links overlapped and then add the master link. But check it with the manufacturers spec! I always have to go back to the instructions for this one. Reassemble with the master link if applicable and snap it back in place. Run through the gears to make sure all is still working smoothly and you’re done. I know when using the 40t hop up cogs, sometimes I have to add a little bit more b-tension so the rear derailleur’s pulleys clear the cog. So run through them several times. You’ll know as it has a knocking or “bump-bump-bump” type sound as the derailleur moves into position. Just add a little b-tension and you’re good. Head out onto the trail and shred. Here’s my own personal rig as of this past fall:
That’s pretty much it in a nutshell. Again, the most important key is the combination of the correct chainring tooth profile with the appropriate rear derailleur. If you’ve got a shimano drivetrain, stick with a Shimano Clutch style rear derailleur. If Sram, go with a Sram Type 2 rear derailleur (which are available pretty much throughout their line). One thing to note: 10spd rear derailleurs ARE NOT COMPATIBLE WITH 9spd drivetrains. So be sure to match everything up appropriately, get the right gear and choose the right chainring tooth count that is a nice, happy balance of your riding style and the demands of your typical rides and terrain. Right now, I’m trying out a 30t Wolftooth Direct Mount Cinch chainring with a sram X9 Type 2 rear derailleur, 1080 12/36t cassette with a Wolftooth 40t GC hop up cog. All 10 speed and so far so good. The only thing I’m finding “odd” if you want to call it that is when doing technical climbs, picking the right gears that have a balance of power, traction and forward momentum. I find if I am too high in the cassette, I have so little forward momentum and forward progress that sometimes I simply can’t get through sections I could with ease. So relearning that gear choice/s has been a slight challenge but with a 30t ring, I’m finding I’m using even more of the cassette in it’s entirety throughout the ride instead of sticking to the upper half the majority of the ride. More on that soon. But there you have it: Get out and ride while the gettin’s good!