Tunk sizing guide
All bike brands size their bikes a little differently. Here is our guide on how to choose the correct size Tunk bicycle. This is based on the PBH-method, as promoted by Rivendell Bicycle Works, and noted to be effective.
Short version:
If you already know your inseam (or Pubic Bone Height to be more exact) and are confident that it is correct, refer to the table above for choosing a size. If not, read the Long Version below. We’d recommend reading it and re-measuring everything just in case.
The table is quite conservative and should be thought as MAXIMUM frame size for your PBH, and presumes you will ride the “recommended fit” with 42mm tires, very little seatpost showing, minimal standover clearance (0–10mm) and the handlebar more or less level with the saddle. You can size down if you are concerned about standover clearance or want to have your handlebar lower. If you are not at all concerned about standover clearance, and want your handlebar even higher, or for any other reason would like the bigger size, you can also size up. If you are going to run bigger tires than 42mm (frame&fork clearance is up to 48mm with fenders, or about 52mm without fenders), do notice that this will reduce standover clearance by an extra 6–10mm.
The Long version
for those who don’t know their inseam or are unsure about correct saddle height and fit.
The best place to start is to measure your PBH, or Pubic Bone Height. This is your leg length with NO SHOES on, measured from the floor to the pubic bone (if you put something between your legs and pull up, it will be the only bone you will encounter so no knowledge of anatomy is needed.)
Have a friend help you. Stand against a wall with your feet apart, press a hardcover book or similar item firmly to the bone, and have your friend measure the height. It is easy to get a too low number, almost impossible to get a too high number. Do a few repeats and take the highest number. This is your PBH. Your minimum standover is PBH+shoe sole thickness, so probably around 15mm more than what you just measured. Most people will want their standover to be the same or higher than the frame’s standover, to be able to straddle the bike with feet on the ground.
Your saddle height, measured from the middle of the bottom bracket axle to the top of the saddle where your sitbones sit, will usually be about 11cm less than your PBH. You should also measure the saddle height from your existing bike(s) to figure out whether this is true for you.
Our thoughts on bike fit and the finer points of Tunk sizing
Our idea of fitting differs from many other brands in that we presume a rather high handlebar position. The starting point is the top of the handlebar being level with the top of the saddle. The goal is to be able to ride with full comfort even after multiple weeks on tour or even when you are very tired after work et cetera.
If you prefer a lower handlebar position, you can size down and use a longer stem, or use a radical negative angle stem. On the other hand, a drop bar with a deep-ish drop will make it possible to have a relaxed touring position on the ramps&hoods, and a more inclined position for spirited riding in the drops.
The usual mainstream recommendation for standover clearance is about one inch, or 25,4mm, but our recommendation is more like 0–10mm (with shoes on). This piece of math reduces the amount of spacers needed under the stem by about 15mm, which we think looks cleaner.
The top tube and the horizontal reach are not especially long, but not especially short either. We recommend a short-ish 60–80mm stem if you’re using a long-reach drop handlebar, or 80-100mm if you want a longer position or use a short reach dropbar. With back-sweeping “alt-bars”, the stem should be even longer, around 120mm. This is all very personal of course, so trial and error is probably the best way to go.
As an example, Aki is 178cm tall with a 84cm PBH and a 73cm saddle height. They ride a “59” Tunk, with a few millimeters of standover clearance with shoes on, with 48mm tires. Their handlebar is about 1cm higher than the saddle, even though they are quite fit and young and flexible. The bike has a 0-degree 90mm stem with no spacers to achieve this position. The handlebars have a long 115mm reach and a deep 140mm drop. Aki uses the ‘drops’ or the ‘hoods’ position when wanting to ride hard, but mostly cruises with their hands on the ‘ramps’ or the ‘corners’ of the bars, and rests and sometimes climbs in the ‘tops’ position.
Frame stiffness and wheel size
As our frames also change wheel sizes, and have progressively heavier frame tubes, people who are between sizes can sometimes choose the frame size that suits their riding preference better. The major changes are between 53 and 55, where the wheel size changes from 26” (559) to 650B (584). The fork and frame stiffness stays about the same. The even bigger change is between 59 and 61, where the wheels go from 650B(584) to 28” (622), and also the frame and fork change to heavier and stronger tubes. As an example, a person 180cm tall, with a 86cm PBH can choose either of these sizes. The 59 will be lighter and softer, more suited to lightweight riders, light touring and general sportive riding. The 61 will suit better loaded touring or heavier riders. These differences are naturally due to the restrictive nature of series production.
The full geometries can also be found at Bike Insights, where you can compare easily to other bikes.
You can of course contact us by email with any sizing questions, we are happy to help. If in doubt, always ask us first. hello@tunkbicycles.com
