One on One with the Mosaic GS1 Disc All-Road

Remember this one? From NAHBS? It was one of my favorites in the show. Everything about it just looked right. First impressions are everything you see and these days, with the whole bigger is better mentality about tire clearances, it was nice to see something embrace a modest tire so elegantly.

Mosaic‘s GS1 disc all-road bike is a custom steel or titanium frameset, offered by the Colorado-based frame builders.

Let me reiterate that: this is not a production model with stock sizing. It’s made with 100% custom geometry. A custom geometry ensures this bike will fit you like a tailored suit.

The GS1 is a road bike with disc brakes and room for around a 38mm tire. It has a road bottom-bracket drop (72.5mm) and a slightly slacker head tube than your average road frame (72.5º). Side note: I like how those two numbers match up so perfectly. The 420mm stays and 1033.5mm wheelbase can be best interpreted as smooth sailin’ down your favorite road, be it dirt or sealed.

Mosaic GS1 Disc All-Road

Frame and Feel:

The most elegant detail on this bike, by far is the rear triangle, particularly the seat stays. They bend carefully around the tire, giving just enough clearance to make it look like the frame is suggesting the tire size, not opening itself to whatever you can cram in there. Moves like this show confidence in the builder and a very specific visual language about what this bike’s intent is.

Mosaic GS1 Disc All-Road

No, you can’t fit RockNRoad tires on it, no you can’t fit big knobbies either. But you can fit a supple, smooth rolling tire like the Barlow Pass or as it came spec’d on this build, the Clement XPlor MSO. If you need a bigger tire than either of those, then it’s strictly preferential, or the terrain is entering a different realm. Personally, I don’t view this bike as a back-country explorer, more of a road bike with a little extra cushion for when the washboard roads get washed out. Had I not just got my Firefly in the mail, I would have ridden this at Grinduro.

Because it’s steel, there’s already a good amount of vibration dampening going on and because it’s True Temper S3 tubing, it’s lightweight and stiff where it counts. The ride quality of S3 is unmatched, in my opinion. The tear-drop top tube and oversized downtube are reminiscent of an old Eddy Merckx MXL, yet the butting and thicknesses of these tubes are much more advanced than what Columbus was producing at the time.

This thing ain’t a tank like the old MXLs were. It weighs in at 20lbs on the dot for the size 58cm!

With steel comes a few responsibilities. First: Frame Saver it! If you ride it in the rain, make sure it’s allowed to drain. With S3, you don’t exactly want to throw it in a bike pile. It’s a thin tubeset but you don’t have to baby it either. If you get to a nice, fast dirt descent, open it up! Let me tell you, as you’re descending that service road, the sounds of rocks pinging the downtube and stays get a little unnerving. Yet at the end of my ride, not a chip was found in the beautiful blue, wet paint job.

The 44mm head tube has a nice and elegant machined shape.

Mosaic GS1 Disc All-Road

There’s a threaded bottom bracket, internal rear brake routing, down-tube routed shifter cabling, rack mounts and fender mounts. The GS1 has it all.

Mosaic GS1 Disc All-Road

These days, something like the lack of thru-axles might seem like a missed opportunity, yet on a bike with such sexy, confident detailing, the quick releases compliment it as much visually as they do functionally. Personally, I’ve found QR with disc brakes to be concerning on frames with more compliance. Sometimes you get an annoying disc and brake pad rub when out of the saddle (my Indy Fab does this a lot) yet with the tubing spec and frame engineering, it’s not an issue on the GS1.

Mosaic GS1 Disc All-Road

Build Notes:

Woah! Ultegra. Woah! A double. That’s nice. It even has a brazed-on front derailleur hanger! Like I said, my interpretation of this bike is not for back-country, excursion style riding. Personally, I gravitate towards 1x setups on my own rigs but that’s because the kind of riding I do on my all-road bikes are similar to what I’ll do on my XC MTB rig and I like the simplicity of a 1x setup with a large cluster on the back.

The GS1 however made me embrace not only the functionally of a road double, but really begin to miss riding with a front derailleur in certain applications. I’d also like to just note that the hydro Ultegra feels great. Ergonomics, modulation, everything feels amazing.

Mosaic GS1 Disc All-Road

PRO is normally not the way I go, but I have to admit, the Shimano PRO lineup makes some pretty trick components. The saddle, even though it’s not the best looking profile out there is incredibly comfortable, the bars have a great feel to them as well but I cannot for the life of me get behind the stem. It slips when you hit big bumps, regardless of torque and it seems too form-driven. Just give me four bolts and call it a day, guys…

Wheels are a no-brainer. Disc R45 to HED Belgiums. Done.

Mosaic GS1 Disc All-Road

Now onto the question I got asked the most: the fork. These are from Colorado, under the name Ethic. They’re the in-house fork for the brand Alchemy. They’re plenty stiff, plenty good lookin and offer plenty of clearance without going full-on disc cross. With a 45mm offset, it matches quiet well with the 72.5º head tube. Painted to match, too!

Mosaic GS1 Disc All-Road

Take Me Away with the Take-Away:

The GS1 is a roadie’s dirtbike. It’s not so overblown with clearances that it looks like a drop bar hard tail. It dances with you on the climbs and rails the descents. It’s got classic panache with a confidence-inspiring build kit. The paint, geometry, silhouette scream road, road, road! in an era that is shouting dirt, dirt, dirt. Yet it can eat its share of the sketchy stuff too.

With a custom geometry, custom paint and built to suit your needs, the GS1 is a worthy bike for consideration.

Make it Rain:

Frameset (Custom Geo Frame, Fork, King headset, choice of paint) – $3,700.00
Estimated full build cost for current baller setup – $6,700.00

Turnover on steel Mosaics is approximately 6-8 weeks, see your Mosaic dealer for more details or give them a shout.