Racey for Loose: Mosaic GT-1

Racey for Loose: Mosaic GT-1

There’s a switchback up on the shoulder of Sonoma Mountain that combines a steep approach with a full 180-degree turn and peppers it with a narrow trail with a soft outside shoulder. If ever there was a turn a gravel bike should struggle to round, this is my submission.

Even though I was pretty gassed due to the tall gear on my ride, I got into the turn, threw as much of my weight onto the handlebar as possible and then gutted a few pedal strokes even as I struggled to keep the bike on the trail. For just a moment the front wheel shoveled at the edge of the trail as it slopes away. I thought I would lose it and did my best to keep my weight inside to gradually lean the bike back toward the middle of the trail.

There was also a moment where the sidewall of the tire rubbed the toe of my shoe and that was the moment that most caused me to fear I’d need to put a foot down. But I made it. As the pitch of the trail rolled off into something more manageable I eased off on the power and took a few deep breaths.

That was the moment that caused me to see the Mosaic GT-1 gravel bike in a truly flattering light. Up until this point I’d felt like we destined to date, but not to fall in love.

The GT-1 is meant to be more like a road bike than an all-out-adventure bike. It’s got a short wheelbase (as short as you can allow and still offer clearance for 38mm tires), short chainstays, not much trail and a low-ish bottom bracket. Basically, on asphalt, the GT-1 feels like a proper road bike, just with mad amounts of tire clearance.

Because the GT-1 carries a road bike pedigree but can easily run a 32mm-wide tire, toe overlap is basically a starting condition. Riding switchbacks is a great way to find out just how much of a problem it is. I can say that on bikes that are balanced the way only a custom bike can be balanced, an occasional toe tap or scrape isn’t much of a deal. But when a bike doesn’t offer that instinctive and natural handling, any touching of the toes to the tire can be a recipe for a fall.

Here are the geo numbers:
Top tube: 55cm
Seat tube: 55.5cm (center to top)
Head tube angle: 72.3 degrees
Seat tube angle: 73 degrees
Chainstay length: 42cm
BB drop: 75mm
Fork rake: 47mm
Wheelbase: 99.6cm

Not my build
The big reason I wasn’t sure how I was going to feel about the GT-1 is that it’s not the sort of bike I’d build for riding around here. The head tube was shorter than my son’s attention span; I needed the handlebar to be at least 4cm higher, partly for my fit, but also because on crazy descents (which are the only descents we have here) I want to be sitting up higher so that not all my weight is on the front wheel. As the GT-1 is a custom bike, anyone who buys one won’t have the challenge I did. The 32mm Clement LCV is a pretty dynamite tire. Were I living someplace with miles and miles of hardpack dirt road, I’d buy these tires by the shipping container. However, due to the amount of rock I encounter on my unpaved rides, anything less than 35mm wide leaves me in a semi-mortal panic that I’ll flat every three miles. There was also the 34×28 low gear which I would once have sworn was low enough for anyone, but there are so many cruelly steep roads around here that even a 34×30 feels like a pretty stiff gear.

So road geometry, seemingly generous gearing, 32mm tires and a bar a good 8cm lower than the saddle—I’d love to live someplace where that was a reasonable response to dirt roads. I can say that setup would be fine in the Mid-South and certain parts of New England.

The trick to writing a fair review of any sort is to say something true about the product in such a way that it both illustrates and simultaneously strips away the reviewer’s biases. We all have some bias. Doesn’t matter what realm we discuss, we all have some preferences, and there’s nothing wrong with that.

What I want in a gravel bike is a rig that accepts 40mm-wide tires. Handles with the calm of a mid-crime psychopath as it descends. Turns gears lower than the ethics of a politician. And isn’t stiff as a shot of whiskey. The GT-1 I was sent wasn’t that bike, but as my four year old says, “But that’s okay.”

As the GT-1 is a fully custom bike, you can ask for greater tire clearance, specify a different crank or cassette, a longer head tube, a longer wheelbase or different handling. Knowing that it was possible to purchase the bike I want from Mosaic had a surprising effect on me: It allowed me to relax and consider the GT-1 and what it might say about Aaron Barcheck’s taste in a gravel bike.

What I realized as I rode the bike was that when I found roads that didn’t make the tire selection a liability, I was able to enjoy the bike exactly as it was intended. I’ll admit that most all-surface road bikes lack some of the spunk of racy road bike; the way the geometry and fit evolve for the different use, out-of-the-saddle efforts miss some of that scalded-cat reactivity. The GT-1 kept that character and the upshot was that I found this bike surprisingly easy to thread through minefields of baby heads.

This will seem completely devolutionary, but it occurred to me that if it’s not okay to go over the rocks, going around them might be an option. A quick flick of the bar from the hoods and a briefly elevated bum were all it took to snake through stuff that could have pinch flatted some mountain bike tires.

For the most part, gravel bikes as a category tend to be longer, lower and have more trail than your standard road bike. This is a fairly broad generalization, but it’s a theme that recurs often enough. There are, however, a few examples out there where gravel bikes hew closer to traditional road geometry, just with more tire clearance. The Allied Alfa All Road is one of those bikes. The GT-1 is as well.

I’ll admit that when I first saw geo charts that took this approach I was a bit dismissive. I concluded that I just didn’t want anything that nervous on loose roads. Now that I’ve ridden a few bikes with this sort of geometry I’ve really come to love them. That said, a piece of what makes these bikes work is the fact that there’s a big drop between the saddle and the bar. When you adopt a road geo for a gravel bike, you need a fair amount of weight on the front wheel or the bike will become rather skittish.

The GT-1 frameset goes for $5650. That includes the frame, the Enve GRD fork, a King headset and a choice of three different raw finishes they offer. The paint seen on this bike is their “Alpine” scheme and adds another $1800.

Of the many companies building custom titanium bikes, Mosaic is among the most interesting. They have a clear vision of what their bikes are meant to do and they work with first-rate retailers. Add to that they are doing some of the best work in ti frame finishing out there and it’s no wonder they have made the inroads they have.

The GT-1 made me long for a place I’ve never lived: a land with long stretches of hard-packed dirt, roads devoid of cars, where you can sprint, head down, for seconds at a time and blister the earth under your tires.

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7 comments

  1. GC

    Hi Padraig, I noticed that generally you place your saddle far up on the rails (or farther up). We are of similar sizes – I saw you at NAHBS, motioned to come your way to shake your hand, got distracted by the candy apple enigma, then you were gone. I ask this because I too ride on the farther up side of things. I wonder if you ever had the chance to ride one of those stubby saddles, namely the Specialized Power. It blew my mind; I know you test and try and review parts for a living. Am sure you have your favorites, of course, and that your undercarriage is made of leathery steel. Regardless, I’d like to hear your impressions about this saddle. It’s worth a try.


    1. Author
      Padraig

      Sorry we missed each other at NAHBS. And yes, that Enigma was very distracting.

      Regarding the position of the rails in the seatpost, I have, proportionally speaking, rather short femurs. They are 50% of the overall length of my leg, which many fitters will tell you is on the short side. The upshot is that in custom bikes I need a steeper seat tube angle to get my knee over the pedal spindle at its most forward position; seat tubes on custom bikes for me are generally 73.5 or 74 degrees. That keeps the saddle centered on the rails.

      I haven’t tried the new Specialized saddle. That said, I’m riding the Shimano PRO Stealth, which has a similar shape. And you know what? I like it a lot.


    1. Author
      Padraig

      I don’t have those numbers on this bike. However, it being a custom bike, even if I did, they wouldn’t matter. The reach was good but I needed more stack. For anyone else buying this bike, those numbers will be whatever they need.

    2. souleur

      well, that being said, sounds like what I am looking for
      I like lower stack height, slightly more reach
      basically looking toward a road bike race geometry with fat tyres, and this is making me salivate a bit
      Love mosaic, classy and I suppose I will have to make a call on it soon
      thanks padraig!

  2. TiConf

    I have a GT-1 which was recently built by Mosaic to my specs. Coming from a road disc Ti frame with 30c clearance, i needed something with 38c but with the same handling of a good road bike. As you very rightly pointed out the GT-1 is truly that.
    A bike which can take you to gravel roads, yet doest leave you behind in spirited rides with with your roadies friends.

    I was very adamant in having a short chain stay for acceleration and lively power transmission. I previously had a gravel bike with longer chain stay and it was too lethargic for my tastes. 38c is the max you can achieve given the CS length constraints and no risk in incurring in chainrings or crank arm interferences.

    As far as toe lap, that was another big no go for me. And Mosaic was v good twitching the design of HT angle and and TT length to address that. I have a 13 size feet on a 58.5 frame and I have zero toe overlap. Thats why you go custom 🙂

    What strikes me the most about this bike is also the weight. With etap i am just at 7.95kg with 35c tire tubeless and 36mm carbon rims. For a 59cm frame this is at par with a carbon bike. This is also why this bike for me is all I need. I used to have 2-3 bikes. Now i sold em all and just left with my GT-1 which i used to train on roads, enjoy gravel and do some single trails.

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