OneUp ISCG05 chain guide review

Minimalist guide with real benefit

BikeRadar score4.5/5

Narrow/wide chainrings came with the promise of holding chain to chainring without a chain guide. They certainly do a far better job than a regular ring, but as anyone who rides aggressively, or slams through rocky, jarring terrain knows, they're far from infallible. 

Even if the chain derails from the bottom, the chain cannot bounce off the top teeth
Even if the chain derails from the bottom, the chain cannot bounce off the top teeth

I've been riding narrow/wide chainrings for a few seasons on both my hardtail and full-suspension bikes and have thrown the chain on both bikes numerous times. Chain drops definitely get more frequent as the ring wears down, as well. Enter the new crop of mini chain guides. Instead of the usual chain retention device that has guides top and bottom, OneUp’s ISCG05 only features a small top guide. 

OneUp ISCG05 chain guide specs

  • Weight: 35g 
  • Capacity: 26-38T 
  • Chainline: 5.5mm adjustment 
  • Mount: ISCG05 
  • Color: Green and black top guides Included
  • Material: 7075 aluminum, top guide glass-reinforced thermoplastic
  • *Incompatible when used with Oval chainrings on the following frames: Santa Cruz Bronson 2 and 5010 2, Intense Tracer T275, Rocky Mountain Altitude 27.5 (out of spec ISCG tab placement)

OneUp ISCG05 chain guide installation

The installation video on OneUp's site is a mere 46 seconds long, but surprisingly manages to cover all the basics. Mounting the guide took more than 46 seconds, but honestly not much more. I did not have to remove my crankarm or even the chainring.

After setting the guide's chainring size, the backplate simply mounts to two out of three ISCG05 holes. (If you're unfamiliar, ISCG stands for international standard chain guide and, as you may have guessed, this 05 'standard' is an updated version.)

A quick check with the included spacer guide said add one spacer to the top guide and bolt it all together. It really was that simple and painless. 

The backplate mounts to the ISCG05 tabs with the crank and ring still installed
The backplate mounts to the ISCG05 tabs with the crank and ring still installed

Does it actually work?

In answer to the above question, I'm delighted to say: "Yeah, it does." To test its mettle I spent a day at a bike park riding downhill and smashing into way too many rocks. Numerous times when waiting at trail junctions, I looked down to see my chain derailed to the outside, but not off the top where the OneUp guide was. A quick half crank forward was all it took to get the chain back on track.

 I'm certain there will have been many more times my chain popped off while I was in motion and a quick crank revolution righted the wrong. 

There's just enough space to run smoothly in all gears, with no rubbing
There's just enough space to run smoothly in all gears, with no rubbing

Russell Eich

Tech Writer, US
Russell fell head over heels in love with bikes in the '90s, and has been involved in the bike industry ever since. Between wrenching in bike shops, guiding professionally, and writing about bikes, Russell has honed an appreciation for what works, gained knowledge of what doesn't, and can barely contain his enthusiasm for what comes next. His two-wheeled passion continues in the Rocky Mountains high above Boulder, Colorado.
  • Age: 39
  • Height: 6'3"/190cm
  • Weight: 175lb/79kg
  • Waist: 34in/86cm
  • Chest: 42in / 107cm
  • Discipline: Mountain, road, cyclocross
  • Preferred Terrain: High altitudes, forgotten singletracks, bike parks, roads without cars
  • Current Bikes: Custom Meriwether steel hardtail, Specialized S-Works Enduro 29, Kona Jake the Snake, Trek 69er, and a bunch more
  • Dream Bike: Yeti SB5c, Intense Tracer 275C, Black Cat custom road
  • Beer of Choice: Gin + Tonic
  • Location: Rollinsville, CO, USA

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