Marin San Quentin adventure build

Back in September I bought a new mountain bike. This ended up being of note for a couple reasons, but I should first cover why I bought this bike, and why I almost did not buy a bike at all. While M and I generally feel quite wealthy day to day, this year in particular, abundant toy funds do not count among the reasons why. A thousand dollars is often what I spend on outdoor equipment in an entire year, much of that usually going towards either materials for projects or replacing worn out items (esp shoes). The option to get a new bike was, thus, a weighty one.

The reasons to not get a new bike centered around the expense of mountain biking, which on an entry and rolling basis outstrips everything else I like to do outside, with backcountry skiing and packrafting being the only close competitors. Ski gear can be had much cheaper used than biking stuff, and packrafting gear has less maintenance cost than either. Mountain biking is also, in sharp contrast to either skiing or packrafting, in a profoundly lame period of development, with vastly enhanced technology and cost coming together with significant access issues and a thoroughly prosaic trailbuilding ethos. The result being an outdoor pursuit with an increasingly homogenized, bourgeois edge; with berms, bike parks, ebikes, and excessive travel taking the place of skill and pushing out the influence of the wild, moving mountain biking quite far towards the golf-with-sweat side of the “adventure” pantheon, where it will in the decades to come join resort skiing and whitewater (party) rafting as camp followers of late capitalism, bound for immolation at the hands of history.

Fortunately, the reasons I wanted a new mountain bike were in most cases divorced from most of the above, either by circumstance or choice. Above all else, I wanted a new bike to have something more suitable, than either my 2011 Salsa Mukluk or 2006 Surly Karate Monkey, for some backcountry riding and hellbiking/bikerafting missions I have in mind for the coming years. I had reason to believe advances in bike geometry would prove useful here, and that starting from the ground up I could have something significantly lighter, and thus easier to push and carry, than the Mukluk with a new and lighter wheelset. While there are some access concerns locally, and most of the Helena area trails are exceedingly tame, there is within a few hours a lifetime of obscure backcountry riding, and plenty of fun trails literally half a block from our back door. I also spend a multiple days a week biking with the munchkins, which usually means horsing around at either the school playground down the street or the local pumptrack and dirt jumps. A new bike may or may not have been better suited to those things, but at the very least I’d use it all the time, if not necessarily for the primary purpose.

With all that in mind I had no shortage of options. I knew I didn’t want to spend much. I knew I’d want to heavily customize any stock build (and even so, it didn’t take long to realize a complete bike would be vastly more economical than building from scratch, assuming I could even buy what I wanted frame-only). I knew that due to weight, cost, and slow-mo precision descending concerns, along with my own desire to limit my speed and thus severity of any future crashes, I did not want any suspension. I wanted slack and low geometry, room for fat tires, and at the same time a reasonably compact frame (vertical space being the primary limiter when putting a bike on the front of a packraft). I wanted a light frame, and while it was not a deal breaker, the ability to go singlespeed would be appreciated.

I considered many options, narrowing them down to the Marin San Quentin and Rocky Mountain Growler, and ultimately went with the former due to lower cost (in the base model), 27.5 inch wheels with space for 3″ tires (not claimed, but widely reported), and availability. This last point ended up being key, as the COVID rush saw 2021 bikes snapped up with unprecedented speed. My laxity here almost saw me miss out entirely, and I ended up finding a San Quentin 1, in blue and extra large, from a shop across the country, who was then so overwhelmed with orders that they took a month to assemble box, and ship the bike. It arrived (after the shop kindly bumped it up in the que) 48 hours before we left for Utah in October, barely enough time for me to add pedals, swap contact points and brakes, and convert the wheels to tubeless (which proved highly problematic, more below).

Overall I have been very pleased with the bike. Fortunately snow with staying power has held off for the past two months, as it has taken all that time for riding and tweaking the San Quentin to get the core elements sorted and begin to get a sense of its personality.

As promised, the San Quentin is radically different than any previous mountain bike I’ve owned. Granted, that list is short, but here the head tube angle is 5 degrees slacker, the seat tube 2 degrees steeper, and the top tube nearly 2 inches longer. The San Quentins wheelbase is not quite 4 inches longer than my Mukluk, something immediately apparent both visually and on the bike. Chainstays on the San Quentin are only 6mm short of the Karate Monkey, and the BB height (with the carbon fork on the SQ) is almost identical, testament to how forward thinking Surly was in those respects. The idea with contemporary mountain bike geometry is to make the bike longer, by both pushing the front axle further forward and increasing the share of the cockpit length taken up by the frame, as compared to the stem, while at the same time keeping the rider centered relative to both wheels by making the seat more upright. In my experience this approach fulfills all goals beautifully, and climbing and descending it is notably superior to anything I’ve ridden, with no downsides save a hair more planning required going around switchbacks. The bike feels stable, but never slow, and the whole package is fantastic at pumping through gullies and hitting berms. There is a bit of nervousness descending steep and loose stuff which I out down to the paucity of rubber up front, relative to the Mukluk. I am eager to put 3″ tires on it.

Fit did prove something of a head scratcher due to the relatively low front end. I had the 490mm Carver carbon fork waiting for the frame to arrive, but the stock suspension fork had a straight steerer and a reducer crown race, meaning I needed a new headset for the rigid fork, which was a needed upgrade anyway, as the open bearing stock headset did not inspire confidence. Even with this longer rigid fork, selected for both weight savings (5 pounds lighter than the stock suspension fork) and to preserve the slack head angle, the stack height (e.g. vertical distance from the bottom bracket to the top of the head tube) is on the low side, and with a 65 degree head angle stacking spacers under the stem eats top tube length in a hurry. I liked the steering of the 45mm stock stem, but getting the bars high enough made the bike far too short. A lot of measuring, virtual modeling, and riding the bike with the 85mm stem off the Mukluk had me take a deep breath and order a 60mm, 84 degree stem (which I run flipped on top of a 5mm spacer) and a 60mm rise bar. This gets me the cockpit length I’m used to, and the slicier steering of a shorter stem. Now, of course, I would really like a fat bike with similar handling.

The base model San Quentin coming with a square taper bb was a plus, as the whole fleet is to this day standardized around that design. I’ve killed a few of the cheaper Shimano cartridge models, but only after years of significant abuse. This allowed for some drivetrain futzing, as the 32:46 low gear which came stock is not quite low enough, and I can’t imagine running a backcountry bike without a bashguard. Bending ring teeth into workable shape with a rock is a field repair I don’t need to do again. Currently, and as pictured above, the SQ has most of the drivetrain the Mukluk has used for years; 26 tooth Surly ring, old XT derailleur, 11-42 cassette, and a Dura-Ace barcon friction shifting on a Paul mount. The stock Microshift drivetrain worked just fine, and reminded me that 9 speed great (and when it comes to performance in the mud, vastly better than 11 speed), so I put on a nice, nicely cheap, all steel Microshift 11-42, 9 speed cassette. This gives me enough granny gear, enough high gear for pavement cruising, and the most frequent ratios right in the middle. I like that the old derailleur is slim and light relative to the big Microshift, but the last few rides have drove home the virtue of having a clutch, so that will, eventually, need to be replaced.

While there is a lot to like about current geometry, there is almost as much to dislike about other trends in bikes. Internal cable routing seems both pointless and annoying (ting), and the level of specialization which means that I (a reasonably competent home mechanic) can’t even begin to figure out the type of headset needed seems excessive. But wide cassettes are cool, as is the clearance that comes with wider hub spacing. Complaints with the bike itself (aside from the cable routing) are minimal, confined to a derailleur hanger which seems a bit soft, and a seat tube that seems needlessly high, especially given modern trends with dropper posts. I’m on the shorter side of folks who will likely buy an XL, and while I have plenty of standover (and framebag space) I’ll max out at a 125mm dropper from any brand save OneUp. There is actually space for two bottles on the downtube, and given Marin’s boss-intensive approach with other frames it would be cool to see more storage tech on the San Quentin. Good bikepacking bikes need to be good mountain bikes first, and the SQ is certainly that.

I’ll keep riding until winter finally comes in earnest and shuts down the trails and pump track (if that ever happens). Priorities for spring and summer outings include a dropper, cushier tires, and a frame bag. When the time comes and I’ve had more than afternoon rides in the bag, I’ll update with a comprehensive breakdown.


13 responses to “Marin San Quentin adventure build”

  1. spring Maah Daah Hey?

    1. I would like to. Depending on conditions it might not mesh with other things on the schedule.

  2. I’ve always seen riding rigid as a necessary self-limiting factor; I don’t need to go faster at this point in my life, I know what would happen if I could.

    1. Been there, had the hospital visit. Not again.

  3. I am curious to read what wheels and tires you’re currently using, especially with the reference to going tubeless

    1. The stock wheels and 2.6 Vee Flow Snap tires. I used Stans valves and the stock taping job. The conversion process was obnoxious, but I’m quite sure that was due to the stock taping being less than ideal, especially around the valve. If I were to redo it I’d pull the tape and do my own, at which point I think it would convert easily.

  4. Holler if you ever want to show a neighbor around some of your spots in the Elkhorns. I’ve not explored there at all.

  5. If the seattube is too tall, cut it down. I have done that twice now, a very easy job. Drill a bottom hole for the new vertical slots, and use the hacksaw to cut down to that. A few seconds with some sandpaper and your ready to go.

    1. I have thought about that. I could trim close to an inch down to the gusset. On this frame especially 5 inches of drop is more than enough, and I actually like the balance between frame bag space and low standover, it just seems oddly out of keeping with current trends to have a seat tube in excess of 500mm.

  6. Avatar

    Hi, Dave…post-merry-Christmas to you! 

    So I read that you’re dedicated to square taper bottom brackets, eh?  Would you like a free zooty piece of history if you can use it?  I have one of the old legit Canadian-made titanium bottom brackets from Syncros that has been sitting here a long time.  I used it only briefly on an old ’95 GT LTS special edition team race bike before switching cranks and…and all that came later.  It’s made for 73mm shell, 122mm spindle length.  This one was the “hardcore” version or whatever with the double-row bearings….double rubber seals, serviceable and theoretically replaceable if you have a press.  English thread, both cups use lock rings so chainline is totally adjustable.  I would estimate it probably only has about fifty-ish hours of riding on it.  I think these were something like 3-4 oz less than similar typical cartridge styles…I never found them flexy (as “they” say…forgetting that most flex is within the frame).  I think it’d hold up to a pack load just fine.  Later on after GT bought Syncros they started making some bum spindles before folding operations, but the originals were great as long as you weren’t ham-fisted with the installation.  (it’s the version lower on the page…this one has the OG hammer sticker on the white dust shield)

    If you can use it I’ll send it your way! 


    1. Hell yes! That spindle length will fit the Marin perfectly. Email sent.

  7. Putting that Microshift drivetrain on the fatbike has been a revelation this winter. Decent, reliable shifting, and cheap to replace the derailleur when I eventually destroy it.

  8. […] building my new bike, and frankly after doing almost everything I ever care to do in backpacking over the past decade, I […]

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