This week we unveil a bike that is particularly special to us at AC. Derek, our marketing manager and photographer, worked with Mosaic Cycles to create his dream gravel race bike with any eye focused on events like the Lost & Found, a 106 mile gravel grinder in the Sierra mountains. We'll let him take it over from here and give an in-depth rundown on his thought process for piecing the build together:
A few years back, I raced with frame builder Aaron Barcheck and the crew at Mosaic Cycles at the Rouge Roubaix. A 100 mile "gravel grinder" out in Louisiana. Gravel grinder in quotes as the dirt was pretty light weight and road bikes were more than capable. I raced it on my then brand new RT-1 road bike, a bike you've seen in a number of our blog and Instagram posts. It was my first taste of riding a titanium bike and what a great riding material it can be, and I've been lovingly riding the piss out of it ever since.
My adoration for that bike has long left me dreaming of a proper dirt counterpart. Earlier this year I caught up with Aaron while checking out the Mosaic booth at the NAHB show. We got to talking, one thing led to another, and the next thing I knew I had a gravel bike on order to go race with him out at Lost and Found.
There are quite a few iterations of the GT-1, ranging from touring configurations with full fender and rack mounts to monster-cross adventure bikes that are basically a drop bar 29er MTB. I decided to go more of a race route than do-all adventure bike, and we essentially copied over my fit from my road bike. A slightly taller headtube for less fatigue on rough descents and slight geo tweaks to make it well mannered in the dirt. No fender or rack mounts, just a straight forward, fast bike.
When the frame showed up, it was a sight to behold. We do a lot of raw Ti Mosaics but their paint paint program is exceptional and only getting better. I worked with Aaron on the paint scheme and we wanted to do something that would really grab attention out on the race course. My initial inspiration for the colors came from a Heath Ceramics collection
. Aaron reinterpreted it into something more along the lines of a 90's Klein mtb. Definitely a different vibe but I was stoked all the same.
The drivetrain was something I contemplated for quite a while. We've been pretty impressed with the Sram AXS stuff and I was eager to ride it on a bike of my own, but after growing accustomed to 1x systems for off-road riding, I was a little hesitant to go back to a front derailleur. Sure, the option was there to go with the 10-50 Eagle cassette, but for a race bike I wanted tighter gaps between shifts and the Eagle range is bigger than what I'd need. I could have gone with a tried and true mechanical set up with a 10-42 cassette but when building a new bike, it's hard to not spec with all the new-new. With the new AXS group having a hydraulic clutch in the rear derailleur and improved front derailleur tire clearance, I decided to give 2x another go. Red AXS it was.
Low end is important when keeping traction while climbing loose and steep fire roads, so I went with the 44/33 chainrings and 10-33 cassette to get that 1x1. Obviously, I went disc brake, and the rotors are 160mm front and rear for maximum control.
One thing I've come to really appreciate about the newest Sram levers is the pad contact adjustment. Out of the box with a good bleed, the lever only travels a couple millimeters before the brakes are fully locked up. Backing that off, I was able to get a bigger lever throw which not only helps with modulation, but having the engagement point come closer to the bar really helps reduce hand fatigue on particularly bumpy descents.
The only non Sram bit of the drivetrain is the bottom bracket. Nothing against stock Sram bottom brackets, but in my mind a handbuilt bike is always deserving of a little bling, and the White Industries DUB bb nicely fit the bill. Polished silver to match the hubs and tie in the shiny bits of the Sram Red.
With any bike, the cockpit is a very subjective choice. Comfort is king, but performance and durability need to be there to. For the majority of the ensemble, I went with Zipp.
Handlebars are a Zipp SL-70. Some people question using a carbon bar on an off-road bike due to the higher crash risk when riding in the dirt, but in my experience the vibration damping over an alloy counterpart is huge and well worth the upgrade. I really like the shape of the latest Zipp bars and especially while in the drops, they have a very nice level of forgiveness when plowing the rough stuff. On the flip side, they still feel plenty solid when sprinting hard. I appreciate the extra stability of a wider bar when going full speed in the dirt so I went with a 44cm width. I considered a gravel specific bar with flared drops for even more comfort and single-track prowess, but for a gravel grinder race bike, the road shape ultimately made more sense. If I was going for more of an all terrain adventure bike, I would for sure rock the flares.
The stem is the alloy Zipp SC SL. 11cm in length and custom painted to match the frame. The carbon stem is really nice, but for me and my budget, the alloy was a perfectly good choice.
The seat post however, was worth the splurge to go carbon. There's definitely a noticeable improvement in vibration damping over aluminum, and when racing 5+ hours off road that compliance is your friend. Beneath the metallic purple paint is a Zipp SL Speed post, 27.2 and zero offset for my fit preferences. Mounted atop is a WTB Silverado saddle. Not the sexiest saddle out there, but for me the shape just works.
Wheels, wheels, wheels. Once again, a decision I debated on for a while. Initially I thought I'd use the HED Vanquish 4s like I've been riding on my road bike but after building a recent mountain bike on the Santa Cruz Reserve rims, I looked into their gravel specific Reserve 22 version. They're light, designed with compliance to smooth out rough terrain, and they have an unbeatable lifetime warranty.
They offer them as complete wheelsets but I wanted to build them custom so I had Robert lace them to silver White Industries CLD hubs and silver Sapim CX-Ray spokes. For just a little additional color pop, he used purple nipples on either side of the valve stems. Aero wheels can have an advantage in a long gravel race, but I think comfort plays an equal part, as does weight. 1,410g is pretty light for a dirt specific wheel.
The race promoters of Lost and Found have been saying that the course features smoother, better groomed tracks than in years past. I figured a WTB Riddler would be a good choice as it's got a fast centerline for the flats but good side knobs for going fast through loose corners. As a 37c tire, they're a little less volume than others, but still reasonable and they're pretty light.
All that said, we've gotten some unusually wet weather this past month here in Norther California, especially in the Sierras where the Lost and Found happens. That's having me second guess tire choice and I may end up picking something with a little more volume and tread.
As you see it here, the bike weighs in at 18.3 lbs. Not bad at all for a metal bike with gravel tires. I've gotten a few solid rides on it now and I can safely say the bike captures everything I love in my RT-1 but with the rad level turned up a couple notches. I'm incredibly psyched to get it on the race course next week at Lost & Found!
That wraps up this inside look on dialing in a purpose built gravel race bike. As good as it looks in photos, it's even better in person, so be sure to stop by the shop if your in the area or if you're heading to Lost and Found keep an eye out for it there. The GT-1 is one hands down one of our favorite platforms and we're excited to see how this one performs on race day. If a bike like this looks like something up your alley, give us a shout to get a build going of your own.
Mosaic is partaking in the Sierra Buttes Builders for Builders custom bike giveaway. From now until June 7th, you can enter the raffle online for a chance to win a custom Mosaic of your own. All raffle entries go to benefitting the Sierra Buttes Trail Stewardship, the organization building and maintaining all the incredible trails in the Pulmas and Sierra County area. Head to the link here to support the stewardship and enter to win!