I’ve been intrigued by single chainring drivetrains for mountain bikes since friends started using them 4 or 5 years ago. Back then, with a max rear cog of 34 teeth it was somewhat limiting for climbing since I REALLY like my granny gear. I end up riding at Henry Coe and other locales with long, sustained climbs and really appreciate a 22/34 or 24/36 combination for the steep grades.
With SRAM out-innovating Shimano again ( just a few years ago they made double front chainrings for mountain bikes mainstream) this time with their 1 X 11 offering it’s finally possible to run a single front chainring and get pretty much the full range available with a conventional drivetrain.
Where SRAM impresses me the last few years is their willingness to ignore conventional wisdom and just solve a problem. In this case they said ‘Why not offer a cassette that goes from 10 teeth to 42?’ The challenge was that the smallest conventional cog offered for years had 11 teeth and rear hubs were designed around this ‘standard’. SRAM decided that this was too limiting and got the hub manufacturers to support them in their move to the smaller cog. Of course, all this comes at a substantial cost. If you already have a bike it means buying a complete drivetrain and rear wheel (or freehub). This can easily hit $1500 or more likely $2000 and up depending on your appetite.
So when a number of (mostly) small manufacturers started to offer upgrade options for 10 speed users I was very intrigued. The premise was to install a 42 tooth cog next to the existing 36 tooth cog and toss out one of the smaller cogs (usually the 15 or 17 tooth). Then if you paired this new cassette with a 30 tooth (in my case) chainring you could get almost the equivalent gearing of many riders granny gear setups. You still have to compromise a bit since there is no 10 tooth option but if you aren’t racing the lack of top-end speed probably won’t hurt too much.
The advertised advantages of a 1X drivetrain are:
- Simplicity (front derailleurs are notoriously fickle in muddy conditions)
- Lower weight
- Excellent integration with dropper posts (no more accidental front derailleur shifts when you were reaching for your dropper post control)
- Fewer dropped chains (with or even without a chain guide)
One of the impressive things about the SRAM setup was using a chainring that has alternating thin/wide teeth. This allows a closer fit of the chain to the teeth on the cog resulting in better chain retention. A ‘full profile’ tooth also helps and is possible since the chain doesn’t need to be derailed from the chainring. Fortunately several manufacturers are offering similar chainrings that will adapt to most common cranksets.
One other important aspect of the setup is having a ‘clutch-type’ rear derailleur (introduced in the last few years by both drivetrain companies) that does a better job of keeping consistent chain tension than conventional derailleurs. Fortunately I already had one since I smashed my old derailleur about 6 months ago and upgraded when I bought the replacement. If you don’t want to pay for a new derailleur you could try the conversion and upgrade the rear derailleur only if you notice a lot of dropped chains.
In my case I decided to go with the Wolf Tooth Components hardware. I liked their website and their approach to solving the problem and they are getting good reviews. Installation and setup was pretty easy. If you are used to doing your own maintenance it won’t be a problem. If you aren’t comfortable making derailleur adjustments and removing a chain definitely have a shop do the upgrade for you so it’s done right.
The first thing you have to do is take a bunch of parts off your bike. Get rid of the left shifter and cable. Remove the front derailleur. Take the chainrings off your cranks (in my case 3 rings). Then install the new chainring – that’s easy. Then it’s on to the cassette. If you’ve installed a cassette before this will be simple for you. Remove the cassette from the freehub. Then put the new 42 tooth cog on the hub followed by the other cogs. You’ll need to discard one of the cogs. In my case the only individual cogs were the 15 and the 17. Per Wolf Tooth’s recommendation I chucked the 17 but some people toss the 15 I’m told. There is a bigger percentage jump between adjacent gears if you get rid of the 15 so it made sense from me to ditch the 17 as they recommend. Then just tighten up the cassette lockring and put the wheel back on.
The next thing you need to do is determine chain length. I was surprised that my chain didn’t need to be shortened. It was the correct length already so that saved a bit of hassle. With everything back together the next step was to adjust the mysterious B tension screw on the derailleur. I turned mine all the way in but still got pulley to cog contact. Fortunately my Wolf Tooth cog included a long screw just for this case. Be aware that they no longer include the screw so you may need to order the long screw from them (fortunately it’s only $1). Their instructions for this adjustment were very clear and I had this one done in about 5 minutes. I didn’t even need to adjust the derailleur limit screws. Then a quick ride outside to confirm it was working and I was ready to go to the trails.
Usually when I try out new hardware I ride alone so that I don’t disappoint friends by breaking down and ruining their day. But I figured I would take a chance this time. We were doing a relatively short loop at Skeggs Point so even if I had to walk back to the car it would be a short walk. The setup instantly felt right. Shifting was crisp and quick and there was no noticeable difference in performance when shifting in and out of the 42 tooth cog. The simplicity of using just a single derailleur is great – even though I’ve shifted front chainrings for a long time it was nice to have one less thing to think about and I found I was using my dropper post more since I didn’t have to worry about accidental front derailleur shifting.
We happened to hit Skeggs on a misty, slightly rainy day so there was plenty of grit thrown up on my bike and a few puddles. But not a single bad shift or dropped chain. Since that first ride I’ve had 2 more with the setup and it’s been perfection every time.
For my Yeti ASR 5C I would never go back to a dual or triple chainring setup – there is just no need. However for my other mountain bike – a 29er hardtail I will stick with the 2X10 setup. I use that bike for longer rides and often ride to and from the trailhead on roads so having taller gearing is a real plus on that bike. I know I would have to compromise either on the climbing capability or top end if I went with a 1X10 setup on the hardtail. Now if I could only afford the SRAM 1X11 offering with their wide range I would be very tempted to try that out. Reportedly SRAM will be offering 1X11 in lower pricepoints in the near future so that just may be an option.
- 42 tooth cog: $89.95 (available in black, silver, red and blue)
- 104 BCD chainring: $75.00
- 25mm b screw: $1.00
One unusual aspect of this upgrade is that you’ll take so many parts off your bike that you might pay for your purchase by selling your old shifter and chainrings if they are in decent shape. So consider the resale value of your takeoff parts when you budget for this upgrade.
For more information check out the Wolf Creek website at http://www.wolftoothcycling.com/
Any questions about my setup? Just let me know and I’ll try to answer