IN BRIEF
Mosaic Cycles has reworked its titanium gravel platform around a single figure: 55 mm of tyre clearance, the equivalent of a 700c in 2.2 inches. To get there, the American workshop redesigned the rear triangle with a 3D-printed chainstay yoke, shortened the chainstays from 435 to 430 mm and offset the seat tube. Unable to find an off-the-shelf fork meeting its requirements, Mosaic also designed its own, in carbon, with fully internal cable routing and mudguard mounts. The two models are called GT-1 i55 and GT-2 i55; custom frame kits are quoted at 8,250 and 5,000 dollars by The Radavist, while the official shop sells the stock-geometry versions for 7,500 and 4,200 dollars.
| Tyre clearance | 700 × 55 mm (700c × 2.2 inches) |
| Frame | Titanium, double butted tubeset |
| Chainstays | 430 mm (against 435 mm previously) |
| Fork | Carbon, designed by Mosaic, suspension-corrected geometry |
| Maximum chainring | 50 teeth |
| GT-1 i55 frame kit | 7,500 US dollars in stock geometry, from 8,250 US dollars custom |
| GT-2 i55 frame kit | 4,200 US dollars in stock geometry, from 5,000 US dollars custom |
Gravel has spent ten years getting bigger, and frames have ended up following. At Mosaic Cycles, the American workshop that specialises in custom titanium, the GT platform has just been overhauled from top to bottom for one simple reason: to take 55 mm tyres. That is to say, in mountain bike terms, a 2.2 inch fitted to a road wheel.
Mosaic GT i55: a completely reworked rear triangle
Widening the rear wheel opening is not something you settle by shaving off a few millimetres. Mosaic puts it in its own words on its product page: “What sets this model apart is 55 mm of tyre clearance. To achieve this modern specification, Mosaic undertook a complete redesign of the frame: a 3D-printed chainstay yoke to shorten the chainstays, 55 mm of tyre clearance and room for a 50-tooth chainring; an offset seat tube to make way for the wider tyre […]”
The Radavist puts a figure on the result: the chainstays go from 435 to 430 mm, at the same time as clearance increases. The rest of the frame relies on what Mosaic describes as its “proven double butted titanium tubeset”.
A fork designed for want of anything better
The most unexpected part of the announcement concerns the front end. A maker of custom titanium frames normally buys its carbon fork from a specialist. According to The Radavist, “unable to find an existing fork meeting all the requirements of the new platform, Mosaic designed its own, developed specifically around this new chassis”. The stated brief: 55 mm of clearance, fully internal cable routing, suspension-corrected geometry and mudguard mounts.
Mosaic justifies the whole thing with a reading of the terrain that many share: since the arrival of the original GT platform, The Radavist sums up, “races have got rougher, adventure rides longer, and riders increasingly expect a single bike to take everything, from fast rolling paths to the muddy back of beyond”. The workshop’s answer therefore comes down to a bigger tyre and a shorter rear end — not to a second bike to keep in the garage.
