An Interview with Tyler of BTCHN’ Bikes About His New Raw Mullet Gravel Prototype

 Most of you know I’m attracted to weirdos and eccentric people, so of course I love stopping by the BTCHN Bikes shop here in Chico to see what Tyler is welding on. He’s spent most of his life racing all types of motorcycles at insane speeds, and has been adapting the hyper-analytical engineering he’s learned in the motorized world into pedal-powered machines he pushes to equally scary speeds. He’s also one of the most enthusiastic people I’ve ever met, so imagine that he’s yelling and gesturing wildly with his hands as you read this interview about his latest prototype.

The first thing that jumped out at me when I saw this as a raw frame hanging on the wall were these big beautiful brass welds. What do you call this technique? Why did you use this method? Why didn’t you also use it on the bottom bracket? Why do you think we don’t see more framebuilders using this method?

   “Oh man, I have such an infatuation with the great British framebuilders of the past (and present!) I grew up around welder guys and fabricators and all of them held the Brits in the highest esteem in regards to their craftsmanship and skill in joining tubes, specifically with gas-brazing. The most iconic method of brazing is the stop-and-start technique, creating a wonderful and pronounced “stack of dimes”. This is a technique I had to spend some time practicing before throwing down on a bike frame. This style isn’t like fillet-brazing where the one crucial factor is to get a solid and reliable joint, then you can proceed to file the fillet until it’s pretty and perfect. This is more like welding, where what you lay down is what will be seen. I wanted this bike to be completely naked and untouched, a time stamp in my level of craftsmanship, raw and exposed. And it’s certainly that. When I look at this bike, I don’t so much see a badass rig with big beautiful welds, I see it through a lens of harsh criticism. Out there lie all of my inadequacies, mistakes, bobbles, learning… and lots of room for improvement. Every frame is a struggle because you know this one will never be as good as the next. The builder’s conundrum, I guess.

   I got a TIG welder over the winter and have logged a bunch of hours with it and am stoked to now be offering TIG-welded frames if you’re looking to save a little money or weight. I’ve played around on a couple of frames now by brazing most of the joints except for the chainstays and BB junction. This does two things: saves me a shitload of time and abuse on my hands, but also it saves a bit of weight if you’re concerned about that kind of thing.

   Right now I’m really stoked on the hybrid TIG/fillet-brazed frames, it just seems to make sense. Filing the BB area is by far the hardest junction to finish. I can whip out headtube/downtube/seat tube fillets pretty quickly these days, and fortunately, the BB is an area mostly hidden behind chainrings and underneath mud. I wish I had the guts (and skill) of Cjell Mone of Mone Bikes to produce endless amazing raw fillets… but alas I currently have neither, so I will continue doing my one-off raw prototypes (for myself), and filed fillets and TIG welds for customers.”

The finish on this bike is tuff and beautiful at the same time. But wait, it’s raw? You blued it or waxed it or something? Will it rust or corrode eventually? 

   “Yes yes! It was an experiment for sure! Once the frame was completed, I polished the shit out of it in preparation to apply a gun bluing solution. The gun bluing I used (Perma Blue if ya really wanna know) is essentially an acid that oxidizes the surface of the steel, which is basically a way of beating the bad oxidation (RUST!) to the punch. It also makes for a really cool gray/blue hue that shines almost pearlescent when applied over a polished surface. But that alone isn’t really enough to create a stable and protected surface. I then applied some high-tech metal oil that takes 4 days to cure. Yeah, the stuff is awesome and kinda gnarly. After the metal oil had hardened, I began applying coats of equally fancy metal wax. I applied a coat of wax every day I came to the shop for a few weeks until I was satisfied with the depth of the finish and the level of protection from sweat, water, and the various corrosive elements (cow shit, berries, rocks, etc.) while “Just Riding Along”.

  This finish was ridiculously labor-intensive and I am definitely not doing it again. I do assume it will require a lot of attention to keep the frame from corroding too quickly. That’s all okay though, it’s a prototype and with any luck, I’ll crash into a tree at Mach speed or slide off the edge of a trail sending the bike to a spectacular death tumble at the same time I’m ready to build myself another prototype.”

You look really good with a mullet, and we live in NorCal so it makes sense. But why did you choose mullet wheel sizes for this bike? Beyond the ride characteristics of the wheels themselves, how does this affect geometry?

   “Mullets for the win! I mean, how else do you expect to capture the essence of fashion and function all in one fell swoop? Okay, for real though, mullet wheel sizes have a ton of potential advantages especially when designed to be swapped around to achieve different geometry or handling characteristics. For example, this bike in its current state with a 27.5×2.3 rear and 29×2.3 front is at its most aggressive. It’s in its slackest configuration with the maximum amount of tire volume and wheel size that will fit into this frame while also capitalizing on the added gyroscopic stability of that front wheel/tire for high-speed stability. Now, say you aren’t riding very much trail and want to lighten up your tire choice. Okay great; just throw on a 650×48 rear and a 700×45 upfront. This should give you an equivalently plush ride front to back, but still retaining the shreddy geometry. Okay, so now you want to go on a ride with monster climbs but the descents are really chill/smooth. Then throw on a matched 700×42 wheelset, which would increase the BB height slightly, and simultaneously steepening the head angle, making the bike handle quicker which is advantageous for riding up a wall at 2mph. You can literally go crazy thinking of combinations and their uses… trust me, I already lost my mind a couple of times over this topic.”

What do you call this bike, a drop-bar mountain bike? A monster-gravel bike? You told me you had a very specific local loop in mind when you built this bike?

   “It’s a rigid mountain bike that happens to be built around drop bars. So ummm… this is what I’d call a gravel bike. It has a 68º head angle, 35mm stem, dropper post, 27.5×2.3 tires out back and a 29×2.3 up front. It gets down!! The fit was optimized for my hood-centric riding position and with emphasis on being in a commanding position for descending proper MTB trail.

   I live in a pretty neat area geographically, nestled in a canyon that leads straight into the foothills of the Sierra Nevada mountain range. I’m also pretty hardcore about riding from door to door. Now, I totally understand this just simply isn’t feasible for some folks, so no judgment there. But damn, here in Chico there are no excuses! Just a couple miles up the road are the beginnings of a literal unending network of dirt and gravel roads. Within that are smatterings of jeep trails, moto trails, and a good little network of secret MTB trails. The ride to the top of those trails has about 20 minutes of pavement and then a 2000ft gravel road climb that pretty much sucks to do on a burly Mountain Bike. BUT, it doesn’t suck to do on a 20-pound bike with wide ass drop bars, and tires that are 2.3″ wide. Once you get to the top of the trail network, it’s not so much a chill descent to the bottom. In reality, it’s a maze of tight and rugged trail with countless sharp techy corners leading into wall-like climbs which only last a moment or two before forcing you to walk or crest and then plunge straight into another full focus narrow trail rail session. There are no wicked high-speed sections, so the 68º headtube angle is perfect for navigating the tight switchbacks and keeping the tires on that 8″ patch of trail.

   If I’m not riding this loop, I’m usually doing a slightly longer 5+ hour gravel ride with a ton of climbing, which should be a pleasure on this same rig with the same setup or even slightly narrower tires.”

Whoa, those seatstays are PINNER, dude! What’s up with those?

   “SUPER PINNER!! Yeah, they are pretty tiny, and so is the top tube. But you’ll also notice that the chainstays and downtube are monstrous! I’ve been bending up my own chainstays lately, which has given me a ton of freedom to build rear ends stiffer and with more clearance. 19mm (3/4″) chainstays appear to be more than adequate for most applications, but I wanted to experiment, and that’s exactly what prototypes are for. These chainstays are 22.2 (7/8″) and a super-thin wall. The oversized yet super-light chainstays are paired with a svelte 35mm downtube that is radically ovalized in order to further increase lateral stiffness while keeping the chassis plush while upright. Furthering down this path is the ultra-light 11mm (7/16”) seatstays paired up with classic and super thin wall 25.4 top tube that has also been aggressively rolled and ovalized.

   My attempt with this bike was to create a “bottom end” that was planted enough to bury into a hard, fast corner without the latency of a more flexible frame that takes a second to calm down and settle into the corner. I wanted a bike that could be slammed into a corner without unnerving the handling or giving a sensation of hesitance in the front end (which is mostly caused by a swaying BB, thus a moving Center of Gravity). But at the same time, I wanted something that wouldn’t be jarring while descending a fast and washboard descent. This is why the downtube is so heavily ovalized, the chainstays are massive, but the seat stays and top tube are equally ovalized/shaped but just adequate in size. So far, the bike appears to ride as intended. With only a couple of short shakedown rides, many more are in order to truly understand all the nuances of a new and experimental frame.”

Did you machine those dropouts yourself? They’re eccentric so you can adjust the chain tension? How does it work with the White Industries DOS freewheel?

   “I machine all of my dropouts myself. They are pretty labor-intensive to make but are totally worth it. Their main design concept is to be able to use a lightweight aluminum insert to support the thru-axle and hub while integrating the dropout clamp into the seatstay. It’s pretty slick and ends up being significantly lighter than an off-the-shelf steel dropout system. Since I made the first version of this design, I realized I had just enough room to make an eccentric insert that could be used for a single-speed setup.

   80% of my miles are on a SS, so I have a very good grasp of what my preferred gearing is for the riding I do locally. My previous SS was a double dingle setup. It had 36/38 chainrings with a White Industries DOS 16/18t freewheel. Technically I had four available gear options, but I really only ever used the 36/18 for climbing and 38/16 for cruising around in the valley, 54 and 64 gear inches respectively. Both of those options require essentially the exact same chainstay length, which is awesome and super convenient. Undoubtedly, I was going to build this bike around those gear combos. Now, I happened to have this carbon 1x crankset lying around the shop with a 36t, so I threw it on instead of installing my old polished XT crankset I previously ran with the 36/38 combo. Oh well, guess I have an excuse for not doing a boring valley ride now!

   The eccentric dropout solves only half of the problem though. The other (and more challenging) problem is to figure out how to keep the disc rotor from interfering with the caliper body, or being too far back and not getting enough brake pad contact as the axle moves fore/aft. My dropout inserts are 25.4mm (1″) in diameter, which when you squeeze in a 19mm hub, that only leaves you with barely 3mm of room to offset the thru-axle. That 3mm offset gives you a total of 6mm of travel, which actually is pretty dang adequate if you plan on running certain gear combos while accommodating chain wear and other factors. Now, the thing I’m most stoked on is my sliding flat-mount brake setup. It’s almost too simple, but also works too good! Instead of having the normal slot in the brake post that allows the caliper to only move inboard or outboard, I simply opened that slot into a hole so the caliper could now also move fore/aft. This of course created an issue with supporting the relatively small base of the caliper body on the larger hole, so I machined an aluminum foot that presses onto the bottom of the caliper base which gives it a much wider support area than before. I then had to lower the flat mounts by the thickness of the caliper foot so everything stays at its relative “home”. That’s really hard to explain in just words, I normally use lots of hand gestures when I speak, so look carefully at the photos.”

Have questions? Drop them here in the comments and Tyler will do his best to answer them!