Mosaic redesigned its titanium gravel race frame. The new GT-1 i55 replaces the outgoing GT-1 i45, and the changes aren't cosmetic — the rear triangle is new, the fork is new and engineered for this frame, and the clearances and drivetrain have moved to commit the bike to a specific kind of riding: gravel racing on rough surfaces, on big tires, with a 1x drivetrain.
If you were riding or watching the i45, this is the version to look at now. If you're new to Mosaic's gravel lineup, the GT-1 is the Boulder-built titanium race frame — made to order to your fit.
What's new in the rear triangle
The clearest change is at the back of the bike. The seat tube is curved to open room around the tire; the chainstay yoke is 3D-printed titanium; the geometry choices that come with those two moves are the reason the redesign exists. The rear triangle is what unlocks the tire clearance and the drivetrain commitment that follow.
Mosaic is doing what titanium builders do well — using the material's forgiveness at the seatstays and its stiffness at the yoke, and letting a printed component solve a shape that a butted tube can't. The result is a frame with more room for tire and more room around the chainring, without the compromises a bolt-on plate or a stretched-tube workaround introduces.
A fork built for this frame
Most gravel frames pair with a fork the frame designer chose from a supplier catalog. The GT-1 i55 doesn't — it pairs with the Mosaic Zero Integrated Gravel Fork, a Mosaic Zero Components part engineered for this frame's headtube standard, routing, and clearance ambition.
That matters in two practical ways. First, the fork's clearance matches the rear — you can run 29x2.2 tires front and back without a mismatch that forces you to size down. Second, the routing is fully integrated through the same IS52/52 tapered headtube and ENVE In-Route system Mosaic uses at the 1-Level spec, so cables and hoses run inside from the cockpit through the frame with no exposed lengths at the head tube.
Frame-fork integration on a stock frame is often "the fork clears the tire and the routing works." Here it's "the fork is a designed part of the same system."
Room for 29x2.2, and only room for 1x
The GT-1 i55 clears 700x55mm — 29x2.2 — front and back. It's 1x-only, up to a 48T chainring, on a gravel wide chainline. There is no 2x provision. That is a design decision, not an omission.
The frame is committing to a use case: gravel racing on chunky surfaces where tire volume is doing real work, where the drivetrain is a single ring with a wide-range cassette, and where the frame is engineered around that setup rather than trying to also serve the rider who wants a 2x road-race spec on gravel wheels. If that's your riding, the commitment is what makes the frame worth choosing. If it isn't — if you're building a fast all-road bike, or a road-first frame with occasional dirt — the i55 isn't the frame in Mosaic's lineup for you, and we'll say so at the fit.
What's in the frameset
The GT-1 i55 is sold as a Mosaic 1-Level Frameset Module. That's the premium-integration spec level, made to order, with rider-specific geometry standard on every Mosaic Made to Order frame.
The Module includes:
- Custom-butted 3/2.5 titanium tubeset, sized and butted to the rider (Mosaic Made to Order, 1-Level)
- Rider-specific geometry from your fit numbers — standard, no upcharge
- Mosaic Zero Integrated Gravel Fork — carbon, engineered for the frame
- IS52/52 tapered headtube with ENVE In-Route integrated cockpit stem and seatpost
- T47x68 threaded bottom bracket
- 27.2mm seatpost
- UDH flat-mount dropouts
- Fully integrated 1x-only routing, 48T max chainring, gravel wide chainline required
Paint at the 1-Level MTO spec includes Tier 1 Matte Knockout or Mosaic Factory Finish; Tier 2 two-tones and fades and Tier 3 Mosaic Artist Series full custom are available as upgrades.
The frame is built in Boulder. The tubes are welded and finished there. Lead time on a Mosaic Made to Order frame runs about six weeks from the order going in to the frame arriving at Alpha; the build at the studio adds one to two weeks after the frame lands, depending on component sourcing.
Pricing and how a build starts
The GT-1 i55 Frameset Module starts at $8,250. That number is the Mosaic MSRP for the frame, fork, headset, and ENVE In-Route cockpit — the parts Mosaic ships. It does not include drivetrain, wheels, tires, saddle, or brakes, and it does not include fit or the labor to build the bike.
Priced honestly, a build starts like this:
- Professional fit at Alpha: $600
- Frameset Module: from $8,250 (paint tier upgrades add from the Mosaic paint program)
- Drivetrain, wheels, tires, saddle, brakes: spec'd to your fit and your riding, priced when we build the spec sheet
- Bike assembly and finishing at the studio: $600
- Sales tax: additional
There is no out-the-door number until the spec is written, and the spec is written after the fit. That's the order.
If you're ready to look at the GT-1 i55, the fit comes first — a professional session at Alpha Bicycle Studio in Denver, on the Front Range about an hour south of where the frame is welded in Boulder.
