OneUp Components 42T Sprocket Cassette Add-On

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by Evan Turpen

Over the last couple of years there have been major advancements in the drivetrains of our bikes (clutch derailleurs, mega-wide gear ranges, and almost derail-able chain retention techniques). Everything is simpler, lighter, smoother, and in most cases...more expensive.

The OneUp 42-tooth cassette sprocket is a simple and affordable alternative to spending the coin on one of these complete drivetrain systems (in reality there's only one at the moment). It effectively gives you that 1x11 "climb up a wall" granny gear without causing that 1x11 hole in your bank account. For this reason I was intrigued. I like when companies offer affordable alternatives that improve my bike and therefore I wanted to give it a go. So was the OneUp a magical solution for my 1x10 and my poor legs up those steep climbs? Read on to find out. My answer may surprise you...

Setup and Initial Impressions

Installation onto the freehub body was straightforward with removal of the 17-tooth cog from my Shimano XT 11 to 36-tooth 10-speed cassette. OneUp provides the 42-tooth cog with a thin steel shim which is oriented either behind the cog (Shimano) or in front of the cog (SRAM). I have Shimano so I installed the whole cassette+cog contraption with the spacer behind the 42-tooth cog.

Once my wheel was back in the bike some adjustment was necessary to get things to work. I did have to remove the small plastic piece that the B-tension threads through on my XT derailleur in order to make the pulley clear the 42-tooth cog. After removing it you get a few more turns of adjustment (which you'll need all of) and I added blue Loctite to the threads in order to keep it from rattling loose. I also had to add a couple links to my chain and I'm currently running a double KMC MissingLink setup.

On The Trail

The big positive of the OneUp system is that it does drastically improve your gear range and climbing gear for the steep ups. It also shifts very well from the 36 to the 42-tooth and vice versa. Additionally, despite my best efforts, I could not strip out my aluminum freehub body when in the 42 even under my hardest sprinting efforts uphill. I think this is due to the much wider base of the 42-tooth (roughly twice as wide as a traditional cog) and possibly my lack of high peak wattage.

Unfortunately performance further down the cassette has been compromised, and from the very first ride I was immediately unhappy with the huge jump from the 19-tooth to the 15. It is VERY noticeable as I would go from spinning out big time to bogging (cadence wise) with one shift or vice versa. I also noticed less precise/sluggish shifting as I got down to the smaller cogs on the cassette. This is due to the upper derailleur pulley now being VERY far away from the smaller cogs. Apparently this is less noticeable on certain SRAM rear derailleurs as they have an offset upper pulley resembling XX1's actuation where it follows the contour of the cassette more closely. I'm a Shimano guy and with this setup my shifting went from previously stellar to very sub-par. There's simply too much slop in this system with the pulley so far away.

In my quest to try to make things work I tracked down a 16-tooth Shimano 10-speed cog to replace the 15 so the gearing went: 21,19,16,13,11 instead of 21,19,15,13,11. OneUp also has recently started including a 16-tooth cog with their 40 and 42-tooth cogs. The more consistent jump in gears is a significant improvement, but is still not ideal. The 3-tooth gearing jump from the 19 to 16 and 16 to 13, although better, is still noticeable, especially on the flats at speed where cadence is everything. I often ride on the road for a few miles to get to the trailhead and these larger-than-usual gearing jumps nearly drove me insane.

Unfortunately the 19-tooth cog is not removable (it is anchored to the other easier cogs) as I feel it would be much better to remove both the 19 and 17 and replace these with an 18 so the full range went: 42,36,32,28,24,21,18,15,13,11 with jumps of 6,4,4,4,3,3,3,2,2 instead of the stock OneUp 6,4,4,4,3,3,4,2,2 or 6,4,4,4,3,2,3,3,2 with a 16-tooth inserted.

Messing with any of these gears further throws off the shifting performance as the cassette is not designed to shift properly with different jumps in teeth-count than what is provided from the factory. Simply put, a complete cassette designed to shift with the given wide-range cogs would have been better in my eyes, but obviously much more expensive. A bit of a double-edged sword...

Things That Could Be Improved

Most everything is listed above, but to sum things up I would much rather see an entire (from the ground up) cassette designed specifically for this wide range. Even if it costs a bit more it would be worth it if the shifting performance and predictable gear ratios were there. Also including a longer B-tension screw with the product would make setup much easier.

Long Term Durability

I do not see any issues with the 42-tooth cog itself durability wise. The rest of the cassette and chain however will see accelerated wear in my opinion. Because the B-tension adjustment has to be run so far in the chain doesn't wrap around the cogs as much as before. This means there are less teeth on your cassette engaged by the chain at any given time. Less teeth + same pedal force = higher forces per tooth on your cassette and faster wear rates. Science.

What's The Bottom Line?

I’m torn here because I like the added gear range and the shifting to/from the OneUp cog, but the negative impact it has on shifting performance and ratio jumps throughout the rest of the cassette is very tough to overlook. Any drivetrain component that overlooks proper gear ratio, shift performance further down the cassette, and derailleur design is difficult to recommend. While using a derailleur other than the Shimano XT used in this test may improve performance, it's still a tough compromise from my point of view.

I'd suggest riders seeking more range but a crisper shifting experience try OneUp's new 40-tooth ring with the 16-tooth add on before jumping to the 42. Another alternative is to keep saving those pennies for a proper SRAM XX1/X01 setup.

Following Up

OneUp had this feedback to add given my experience on the trail:

"We totally agree that our product is bit of a compromise, you sacrifice some shifting crispness in the lower end of the cassette for the huge increase in range. This might not be for everyone, but we all run it on our bikes and honestly believe the benefits outweigh the downsides for most riders.

SRAM rear derailleurs (particularly X5,X7,X9) provide more exact shifting in the lower cogs. For Shimano users, the current 10x XTR rear derailleur shifts much better than all other models.

If you're a rider who focuses on a smooth cadence, then even with the addition of our 16-tooth, OneUp might not be the product for you, and XX1 or the new XTR will a better product choice.

For most of our customers our 42-tooth finally allows them to upgrade their current 2/3X setups and reap all the awesome benefits of a narrow/wide chain ring for a fraction of the cost of XX1/X01."

Visit www.oneupcomponents.com for more details.

About The Reviewer

Evan Turpen has been racing mountain bikes for over 12 years. He raced downhill as a pro for the last 8 years with his career highlight being selected to represent the U.S. in the 2006 World Championships. More recently he can be found competing in enduro races and having a blast with it. He is an aggressive yet smooth rider who loves to flick the bike around to put it on the fastest line or to smooth out the rough sections. With an extensive knowledge of the mountain bike industry and its technologies, Evan is able to take all things in to perspective during a review. He has helped design, develop, and test products for multiple major mountain bike companies and has an attention to detail well above most. When he's not out ripping around on a bike he helps run the California Enduro Series and is also in charge of the bike park at China Peak Mountain Resort.