How to design a bikepacker

I’m curious to hear about your thought process when designing a dedicated bikepacking bike. I’m interested in the fully-custom perspective but also interested in production runs where certain parameters might need to be adapted to fit more people.

“Bikepacking” is kind of a vague term that will mean different things to different people, depending on where they live and what they like to ride. In the end it always comes down to personal preferences, but that’s what I’m interested to know, what do you prefer and why. To me, a bikepacking bike will see a bit of everything: pavement, gravel, dirt roads, single tracks, unmaintained roads, etc. It is somewhat a tough compromise, because you want it to be stable and capable on technical terrain (I personally enjoy a little underbiking), but also not too overbuilt and slow on long paved sections. I also prefer bikes that can be loaded like a mule over fast and light machines made to carry only the very minimal. So here are a couple of design aspects that I’ve been tinkering about or that I see discussed often. I’d also be curious to hear about anything I missed obviously.

(Sorry for the long thread, these are thoughts and questions I have accumulated over a long period of time and preferred grouping them in the same thread rather than chasing answers through multiple discussions)

Front end geometry

I noticed bikepacking bikes generally tend to fall in two categories: more touring-like or more mtb-like. Touring-like tend to have lower trail numbers (60-80) while mtb-like can have moderate to high numbers (80 and up). For a bikepacking bike, I think it is important to consider the effect of the front load on handling and steering. From what I understand of it, a front load will tend to stabilize the steering when going straight, and requires more input when initiating steering, but will then accentuate the wheel flop effect while steering. Based on that, to me it seems more logical to go with a lower trail measurements since the front load will already help with stability. From my experience, my previous bike had a relatively low trail for that type of bike (low 60’s), and it did feel a little twitchy without a front load, but would feel very stable and nimble when front loaded, even on singletracks. My current bike (that I designed and built during my class with Dave Bohm) is very similar but with a little difference in the front end which results in a 80mm trail measurements, and it might be just a question of habit, but I do find it a bit slow to steer. Nothing drastic, but enough that I notice a difference and a preference for how my old one handled. So, unless you are going for very singletrack-heavy bikepacking, is there any reason to favour longer trail measurements?

Chainstay length

The eternal debate about chainstay length… Just like I mentioned about front-end geometry, some bikes a more touring-like with plenty long chainstays while other are more akin to mtb and keeping the chainstays as short as possible. Most of what I hear about long vs short (in mtb at least) is about climbing, cornering and endo angle. I must say I can’t really figure out how all this ties up with a loaded bikepacking bike. I mostly rode long-chainstays bike and never really noticed any difficulties relating to climbing and cornering. I would tend to think how you load the bike would also play an important part (more front biased vs rear biased).

Chainring/tire clearance

I’ve heard a common design issue that comes up with bikepacking bike is the clearance for the chainring and rear tire, where we often want relatively large tires (at least 2”) but chainring generally bigger than mtb (36t and up), which creates a lot of interference. There are various solutions to this I believe, such as yokes/half-yokes, plates and custom-bent stays. Any advantage or disadvantage to any of these, in terms of stiffness or manufacturing efficiency? I have been told that plates generally have poor property compared to yokes but yokes are generally considerably more expensive. If I’m not mistaken the choice of bottom bracket shell and rear hub spacing will also have an impact, although I can’t say I see how they all play together.

Reach, Flat bar vs drop bar

When it comes to off-road oriented bikes, I think most people will agree that the front-end should be as long as possible for added stability and avoid toe-overlap. In that case, the reach of the frame will likely be based on whether it’s intended for drop bars or flat bars. One thing that I’ve noticed tho, is that many off-the-shelf dropbar bikepacker seem to come stock with a 80mm stem (eyeballing here…), which I would consider to be relatively long, while plenty of options exist in the 35-50mm range. My initial thought is, why base a frame reach around a 80mm stem when you could lengthen the front end and use a 50mm stem? I understand that for a production frame you want to leave some room for people with arms shorter than average, but going from 80 to 35 seems like a lot of wiggle room to me (we even have 30mm and 0mm stems around now thanks to Tanglefoot). Even with a custom made frame, are there any reason not to go with the shortest stem possible when running drop bars? I didn’t mention anything about how stem length affects steering because it is not something that I personally understand and that I know is somewhat of a “controversial” topic that would likely need it’s own thread (but I’m always interested to hear your thoughts).

Looking forward to hear anything I’m missing!

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I don’t bikepack, but I will answer some of the specific bicycle engineering questions:

IMO, trail is more of an identity debate among road/gravel and mountain bikers. Mountain bikers don’t even talk about trail and are perfectly fine with floppy steering. They also have upper bodies and are used to riding with a different body position (elbows up and out).

If offroad riding is the dominant terrain, 2.4’s and above are the way to go. All the data points to those being faster. Luckily, if you go with longer chainstays >440 and mountain bike drivetrain, you can easily fit the tire and chainring

The shorter the stem, the more steering input you have into the bike. This makes the steering feel twitchier. People pair the short stem with longer trail to slow down the steering response. How twichy is acceptable depends on personal preference.

I made this chart a while back:

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A lot of the extreme geometry differences in modern MTB have to do with long travel suspension forks and all the interesting things that happen when you add them to a bike.
If you thinking fully rigid, then super long front centers and 30mm stems aren’t necessary or even preferred.
On the other hand if you are planning to make a 2.4 tyred bike with suspension that can accept enough load for touring err bikepacking, you have a different series of problems.
I really recommend riding a similar bike on the intended terrain if at all possible. I think an hour banging around will tell you more than endless calculations and expert opinions.
Hahn"one good test is better than a billion ipinions"Rossman

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I have been arguing with my neighbor about this for years!! Thanks for this. He is adamant that short stems are better and I’ve challenged him to put a 50mm stem on his road bike and see how he likes it. Well articulated. Thanks.

I like Daniel’s chart. The spectrum of what’s acceptable is large and based mostly on personal preference.

My current bikepacky gravel bike is running a 35mm stem and 44cm wide bars, 71º HTA, 55mm fork offset, 29x2.25 tires, and 520mm chainstays. On paper that sounds like an abomination. But it rides fine.

You can also look at the bike of Kasia Niewiadoma, who just won the lady’s TdF.

Screenshot 2024-08-21 at 12.09.20 PM

That looks like a 70mmish stem on probably an XS race bike. Many would consider the handling too twitchy with such a short stem. But she seems to be doing a fine job piloting the bike.

All I’m saying is there’s no magic formula. I’d encourage you as a frame builder to get a little weird sometimes. Try something that Trek or Spesh aren’t doing. The weird bikes can help inform future design decisions.

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I’m not a framebuilder but I’ve toured a lot over the past decade and even finished first in a few bikepacking type events back before they became so serious (and popular haha). I also went as far as having a custom touring MTB made a few years back. My thoughts on a few things mentioned so far are:

Handlebars

Bikepacking means predominately off-road riding (I still call it off-road touring). For me that means flat bars only. I’ve ridden drops enough off-road to know I don’t ever want to again haha. I prefer an alt/comfort flat bar with around 15-25 deg sweep. That gives enough comfort without compromising control on technical sections. I also prefer a slightly higher stack than typical. This reduces pressure on my hands and also open up the frame a bit, allowing for a bigger framebag. I usually average about 8hrs pedalling a day on solo trips. Up to 12-14 hrs during events. I’m now at the point where I can do this amount of riding without any lingering hand soreness.

Packing / Weight Distribution

Centralise your weight as much as possible and keep it low. A framebag works wonders for heavy things like tools and water. The rougher the terrain is the less you want to have additional weight over the front wheel. I try to only pack light layers and snacks in my fork/handlebar bags. I find a small rear rack and panniers work better than saddle bags which tend to sway a lot. Panniers are far easier to pack and they also allow you to run a dropper post if you want.

Front End Geo

I like my MTB’s slack so I’m used to high trail handling. For a rigid bike I think 69ish degrees is about right. For a hardtail I’d go at least a couple degrees slacker. Low trail bikes suck off-road.

Rear End Geo / Chainstay Length / BB Height

Long stays are better loaded, especially when using rear racks. If ya building yourself a bike I’d defo go longer as a bit of an experiment as @manzanitacycles suggested. I think many brands are scared of going long and looking weird. My current touring MTB has 450mm stays which provide just enough heel clearance for a rear rack but keep the handling fairly familiar. I’ve also done a 11,000km trip through remote Australia on a Surly Big Fat Dummy which has 875mm(!) stays. That bike handled surprisingly well once fully loaded with 5 days food and water (25L!). A slightly higher BB allows for easier pedaling. I find a lot of off-road stuff here is actually rougher than MTB trail but also flatter which means a lot of pedaling though chunk/wheel ruts. Nice not to worry about pedal strikes.

Tyres

Size up from what you’d typically ride unloaded. Like if you’d ride 2.2’s unloaded then go for 2.4’s. Not only are fatter tyres more comfortable they are also more forgiving for line choice. Don’t expect to be able to ride the cleanest lines after a long day in the saddle. Also allow for extra tyre clearance for mud!

Gearing

Go low. 34t is as high as I’ll go up front, usually sticking to 30t with 10-42 out back. I find 11-speed stuff is super reliable and lasts ages and has the cheapest spares. On trips longer than 1-month I always carry a full spare chain.

The below pic I shared in another thread but I didn’t give much detail. The bike was built in 2020 by Darren Larkin of Larkin Cycles. It’s a 130mm single speed touring hartail. Clearance for 29 2.6" tyres. Sagged angles are 67/73 and it has 660mm of stack which is a lot more than other MTB’s with similar reach (450mm). Aside from finding the STA a little slack and maybe not having enough mud clearance with 2.6" tyres it’s pretty much been the perfect bikepacking bike. As shown I’m carrying enough gear for a 1 month trip, camping down to 0°C and resupply every 2-3 days.

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In my experience the best “bikepacking” bike is just a bike that you like to ride all day with ways to mount a lot of stuff. Every time I’ve built a bike that I catered the geometry to touring I.e. long chain stays, weird front end geo, I just end up riding my regular bikes instead.

I agree with what @bushtrucker room for a bigger tire just incase or mud clearance, maybe a handlebar with more sweep, lower gearing.

For singletrack bike touring on longer trips I end up ditching my dropper post a lot of times. Unless you are doing a cool credit card tour or going ultra, ultra lightweight a bike just ends up too heavy to do “real mountain biking” so I enjoy the unique experience of a loaded bike on trail and lean into that.

So all that to say, just design it like the bike you’d want to ride and put some rack mounts on there.

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I’ve seen many people say that although there is a difference in handling between long and short stem, it is somewhat negligible or easily fixed with, say, a wider handlebar. Would you agree with that statement? I can’t say I’ve tried swapping stems with a great difference in length

But thanks everyone for the great responses, it does help me confirm some of the choices I made for the frame I’m currently designing!

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I personally wouldn’t say stem length is negligible or fixed with bar width. That being said, what is long or short vs twitchy or stable is subjective… That is why I turn to engineering first principles, because it gives me an unbiased framework to make decisions. To me, stem length is about tuning the steering input and the weight distribution between the wheels.

^ all opinions

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I wish that were the case. I don’t consider myself some finely honed machine of precision and skill, but bars only get so wide or narrow until they are unusable.

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I built a bike packing bike for a specific 400 mile self supported event. In rough order, my goals were:

  1. Comfort - fairly upright position with aero bars. I wanted to be able to ride about 100-150 miles a day several days in a row. I didn’t anticipate just how valuable the aero bars would be - not only to change position, but to deal with significant head winds some times
  2. Ability to carry gear - I went with a frame bag, handlebar roll top bag and rear rack. The rear rack was designed to carry a couple of 1 liter water bottles and a roll bag on top. I was also able to strap as much food on top of the rack as I wanted. I encountered riders that had no room for extra food and water at resupply stations just using frame bags. I really benefited from my ability to strap whatever extra supplies I wanted on top of the rear rack
  3. Performance - I went oversize on tires (soft sand was involved) and never regretted it. I used some tires that were on the light side and rolled pretty well. I went mechanical shifting and mechanical disc brakes - this was not a heavy climbing/descending event, so the cable brakes worked fine for me. External cable routing for simplicity.
  4. In general, I felt I was riding an old school compact truck - four cylinder engine, four wheel drive, cranks to roll down the windows, etc. Economical, capable (I wasn’t pulling a boat or camper), safe, comfortable with more than enough performance potential to get me in/out/through all manner of terrain that I anticipated while carrying everything I needed to eat, drink, camp and enjoy all that I encountered.
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