I am investigating a possible bike purchase, maybe custom maybe stock since building my own frame is quite a way off still.
So I’m at it again mulling over geometries and recently been “investigating” pannier associated speed wobbles. So one bike I’m looking at is the secan 56T and have found a couple mentions from owners that only using panniers in the back can lead to front wheel wobbles, further searching resulted in a few hits for the same problems with different bikes, the most suggested solution is to shift more weight to the front as weight behind the rear axle was identified as the cause.
So I looked at the different chainstay lengths, the secan comes in at CS 430mm. But, I just took my salsa Warroad on a 3 day trip, rear panniers only and it does have a 415mm CS and no speed wobbles. However I noticed that riding freehandedly was almost impossible as the front wheel had so little weight on it.
Maybe someone here has taken a look at light touring oriented frame geometries and can chime in.
I’m still looking for that perfect crossover of daily bike for grocerie-hauling, to-work-getting and week-long touring. BUT with a lightweight kit, luggage weight is usually around the ~10kg mark and fits in and around two panniers with ~25L of volume.
My guess is the Secan has more lateral flex through the front triangle than the Warbird. That’s probably a bit by design as well as a product of their respective materials. Production carbon bikes are typically very stiff. Rear only loading causes a lot of twisting in a frame as the load sways back and forth which is where any wobble (oscillation of the headtube) will come from.
Have you got anything against more even load distribution? I know rear panniers are easier to shop with but rear only loading with road geo is kinda asking for shitty handling. Below is a pic of a bike (Crust Dreamer) which is very similar to the Secan (more like the Faran actually) that I’ve ridden 40,000+ km on in the last 7 years. Total capacity of the bags as shown is around 25L, enough for a summer tour with full camping gear. Handles great on road and off.
If you want to stick with rear loading only then if I would try and find a stiffer frame with much longer chain-stays. Most traditional road touring bikes will be stiff enough with stays around the 440-450mm mark. I would consider going even longer still. Just don’t expect it to be as fun/responsive to ride! If you still have shimmy issues you can try a dampening headset such as the Cane Creek Viscoset but that’ll be a work around at best.
Dont forget that bikes designed to have load on the front will have a low trail number. They will be quite flighty when there is no weight on the front to slow the steering back to normal. Check head angle and fork offset.
Edit: just had a quick look at the geo chart on the Secan 56t and its definitely not a front load carrying trail.
One thing I was thinking about is the dynamic of having the weight in the rear. Its going to act like ballast and resist moving while the front will swing around it. Something think about, load balance over the whole bike.
Thanks for the insight! Riding the carbon warroad back to back with the steel Vagabond, the steel is indeed a lot smoother ride. And the Vagabond should be pretty stiff to start with at ~4kg frame and fork. Trail between these two is pretty close at 63/59 but the Vagabond does indeed ride a bit less excitingly.
Weight distribution: since I’m a bit of an efficiency nerd it goes like this: in terms of bag weight for volume, packing ease and volume advantage of a large compartment vs several small, panniers have the upper hand. Since aerodynamically small panniers fare a bit better as well and are ultimately cheaper I didn’t have a compelling reason to spread the weight along the bike. (Until now).
The bike I’m imagining uses the main triangle for at least 3 Bottles of Water (950 st/750 dt/750 dt) which would help a bit to shift the weight forwards. Adding a hub dynamo should help as well. Since I did some touring on the Vagabond with 40L of storage in the back I know 445 CS are long enough (with a steel fork). I haven’t gone really far from civilization but having some on-fork backup storage should future proof the rig.
Looking for frames with reach <=375, stack >=600 and CS ~445, choice becomes very limited:-D
No worries. I’ve done well over 100,000km of touring on everything from a fully front loaded cargo bike to full rear loaded long tail fat bike.There are a lot of options that work! Not familiar with the Vagabond but the majority of smoothness in any bike will come from tyre choice/pressure. Extra weight and a longer wheelbase (among other things) will make a bike less playful but more stable. It’s always a trade off and why most of folks will own at least two bikes!
I would say 100% experiment with weight distribution. Bags are cheaper than bikes and it makes a huge difference. One bike that comes to mind that tick a lot of boxes is the the Kona Sutra LTD. It has a long rear end, plenty of mounts on both the frame and fork, a tall stack height and lot’s of tyre clearance if you want to head off-road. The reach might be a bit longer that you like but they come with a short stem (60-70mm) so the position will be relatively upright. The Tumbleweed Stargazer and BMC La Cabra are other bikes that have very similar geo. Beyond that you have full custom bikes. If you’re UK based I love the look of the Clandestine Carrier (pic below). Stays for days and some very smart bag/rack solutions.
Also, Sean (@DEVLINCC) makes a good point regarding trail. Would definitely consider a low trail bike for predominantly front loading if riding on road/paved surfaces. Something like an Elephant NFE comes to mind and is definitely getting into custom territory with regards to design/tubing spec. I will say that off-road a mostly front loaded bike is just plain sketchy though. There were a few companies/custom builders experimenting with fat tyre low trail bikes about a decade ago but it remains a very niche area.
Oh yeah Pi’s stuff is great. I feel like there’s a some great experimentation with loaded/touring bikes coming outta the UK/EU at the moment. Judging from the the coverage at Bespoked and events like Concours de Machines anyway.
I pretty much swapped all components from the Warroad to the (Genesis) Vagabond to find out where the ride feel is actually coming from. I also thought the Vagabond would be slower but on my test course it didn’t make a significant difference for the speed I’m riding at.
It probably makes sense for me to have one 80%/20% road/gravel bike for sporty rounds and one 50%/50% road/anything for day to day and touring. However I quite enjoy the pursuit of the n=1 bike as well
Looking at your suggestions they are pretty similar to the Vagabond with their longer CS although with a slacker HT angle. (Vagabond is 71° offset 55) And all else being equal, lower trail.
In my imagination I’d use two different wheelsets. One 32mm GP5000 28" for day to day and something like the Race king 2.2" in 27.5" with hub dynamo for all my touring needs. The 28" wheelset would also be good choice for road-heavy tours like the Eurovelo routes.
Monstercross frames will easily accommodate this, but skinny 32mm tires look really silly in a fork that clears something like 29"x2.6"
I’ll take a look at bags again to what I might like for more even weight distribution but would still like to try to get away with mostly rear loading only. My warm-weather kit puts about 7.5kg on the back of the bike. I guess I’d be pretty happy to set a limit of 10kg in the rear before having to balance towards the front.
Is there a rule of thumb what HT angle you can get away with at which stem length? Considering you use something along a 40-42cm drop bar?
For most people using a slightly heavier (steel) bike will make negligible difference in speed, assuming all else the same. I guess now you have the data to prove it haha.
Funny how more bikes is always the answer. If goin down the “one bike does most” I guess you just have to decide whether you prefer to under-bike (road bike off-road) or over-bike (vice-versa). Sounds like the Vagabond is a good starting point for you either way.
As far as stem length goes there are no set rules as to what length works with what HTA but there are some general principles. The shorter stems are used on long/slack MTB’s to allow for longer reach frames which gets the front wheel further in front of you the more downhill stability. For performance road the opposite is happening. Long stems allow the front wheel to be as close as possible, which gets the riders closer to the person in front for aero gains. Neither case really matters to you, go with whatever works for the fit you want! I run 52cm drops with a 60mm stem on my gravel bike, having upsized the frame (58cm) for a taller fit.
@DEVLINCC I read what you wrote but needed a bit to think about it. For my first ever tour I had quite a bit more weight, and the bike would often flip up at the front wheel when handling/carrying it I looked a bit more into the front-load-low-trail thing as well and can say I’d not design a bike for me that needed a front load to dampen steering. Let’s see if I can get away with this.
So I played around with cad a bit and it seems that with a 445 CS I can get the rear panniers about 40mm in front of the rear axle. Seems a good starting point.
So why not go full design mode:
I’m 172.9cm / 84.2cm inseam.
Fork: I found two forks that match my tire clearance desires that also allow routing dynamo wire into the steerer Tube. Seido RGT/Enve adventure. With the enve having a flip chip allowing to play around with fork offsets a bit.
Seido rgt: 47mm 28"/54mm 27.5" | 400mm AC | 50mm offset
Enve adv.: 53-58mm 28"/61-66mm 27.5" | 398-496 AC | 49-55.5mm offset
I’d guess the seido will look a bit better with the skinnier racier tires. But I can’t find any drawings to check the actual dimensions.
CS: 445, could be interesting to have a flip chip rear and flip chip front to transform the bike.
Stack ~610
Reach ~375 @ 71° HT angle, but this might change
I know what you mean with a rear loaded bike trying to flip over. If you imagine a line from where the rear tire contacts the ground running up to the handlebars you ideally want to have more weight under that line then above it. Otherwise the weight of the panniers causes the bike to rotate about that line.
If you are wanting to only have a rear load I wonder if making a custom rack would be a good option. The old French style touring racks with the pannier mount shifted down do a good job of lowering the pannier weight as much as possible
Maybe something like this, but less quick. Would allow me to keep the top plattform for the tent. (There is also a version without the top platform.) Shouldn’t be too hard to get a rack made
It’s always a compromise unless you know the setup will not change. I think for light to medium touring a front load is not needed and I’d say with modern compact outdoor gear that even a full on tour these days can get away from loading the front up. If you never intended to put panniers on the front then I wouldn’t be designing with low trail either. Will be interesting to see what you end up with and then your thoughts after riding the setup.
I did some more research regarding tire sizes, since I do have a desire for skinnier tires. Evidence suggests that bigger tires don’t actually get any slower. Even as far as 50mm+ go according to Rene Herse and for smaller sizes (26-32ish) also tested by other people.
So I asked myself, what is actually the appeal of thinner tires and in one article “road feel” is mentioned as well as “inertia” which both might be a reason to make them more fun to ride.
Regarding inertia I still have some more research to do and find some actual data on acceleration that shows a significant difference rather than what - lets say 1kg of luggage weight does to avg speed/wattage.
Amongst other things, pneumatic trail is also interesting to me as it slows down steering which would play well into my idea of a two-wheelser bike. Nimbler, quicker wheels for city stop and go and fatter, more stable wheelset for touring.
Pure rolling resistance tests don’t factor in aerodynamics. You can’t roll without displacing air, so rolling resistance and aerodynamics must be examined together. Silca has a good blog series on tire pressure, tire size, and aerodynamics (https://silca.cc/blogs/silca/part-5-tire-pressure-and-aerodynamics)
To me, biking on the road is all about optimization. Why ride a 50mm tire when you don’t need to? It depends on the road surface. A watt here, a watt there, it all adds up to allow you to go further with less energy.
Yep. Bigger tyres are usually only slower for two reasons. Weight and tread pattern. Since most tyres above 32mm are designed for touring (thick walls) or trail (knobs) use.
Rene Herse tyres are one of the few options available with both wide and thin casings. This is changing with the growth of “endurance road” or whatever you want to call long distance event riding. The downside is durability. I’ve ridden them and find the kind of terrain I want to be able to ride with a tyre wider than 35mm means I need more protection. But I also have no interest in riding super fast, doing timed events.
I would say the sweet spot for mixed surface touring is 45-55mm. Lots of great tyres in that size, especially those made by panaracer if you’re looking for relatively light casings (Gravel Kings, Soma Cazaderos, BG Rock n Road, Ultradynamico, etc).
Bigger tires “only” give you more bottom out protection (and maybe a bit more cornering grip independent of the additional corner grip that comes from a lower tire pressure which is possible with more bottoming out protection). By “bottom out” I mean: your rim is hitting a road obstacle which you want to avoid.
Comfort: What increases comfort is low tire pressure. On bigger tires you can decrease tire pressure more without risking bottoming out.
Speed: Bigger tires (cet par) only have lower rolling resistance than skinnier ones if the tire pressure stays the same. If tire pressure is adjusted so that both tires provide the same comfort (same suspension travel) then rolling resistance is roughly the same. Here are a few comparisons that compare the same tire model at different width at tire pressures adjusted so that comfort is the same between tire sizes (defined by the same amount of tire drop / suspension travel):
Other disadvantages of bigger tires are: aerodynamics (not only due to the higher frontal area of the bigger tire but also because of how a bigger tire negatively impacts the aerodynamic interaction of rim and tire which is relevant if you have a deep section rim), weight, lack of availability of high performance road tires.
Conclusion: get a tire that is just wide enough to give you the bottom out protection you need for the tire pressure that is ideal for your terrain. That may still be a tire that is wider than the widest (high performance) road tires available.
@Daniel_Y
The title of this article resonates well with my ambitions theradavist.com/fairlight-secan-review-2/ “Easy Wins and Marginal Gains”. I’d like to take the easy wins and cherry pick some marginal gains that don’t require too much ongoing effort.
The silca article(s) were an interesting read. But those are aero gains I’ll only encounter with a headwind of approximately 30kph
For reference, on my last 3-day trip on the Warroad I’d average ~20kph and going with my partner we meander around at about ~16kph.
Having found no further evidence on inertia being a considerable factor I’m thinking bigger tires don’t feel as zippy due to the lower stiffness/energy stored/lost in deformation of a bigger tire. I’m guessing weaving patterns in the tire will do their best to mitigate this.
@bushtrucker
Hmm width-terrain durability is an interesting factor! And underbiking is more fun. So thinking more about getting a clear definition of my target use cases.
Next year we plan to ride from oslo to bergen via mjolkevejen/rallarvejen which seems to be 70/30 unpaved/paved. Since there is a lot of climbing maybe something wide with shallow knobs would be a good choice for good grip on the unpaved climbs.
@Homo_Birota
While the BRR rankings seem to hold up well in real world testing, they don’t show an increase in RR at higher pressures. Which I think might misrepresent RR for bigger tires when the pressure is adjusted for the same amount of tire drop as the air volume is different and I think will act as a physically different “spring”.
I looked a bit more into the front-load-low-trail thing as well and can say I’d not design a bike for me that needed a front load to dampen steering. Let’s see if I can get away with this.
