Looking for full suspension fat bike with integrated Bafang mid drive (and narrow Q-factor)

El_Topo · May 31, 2019

Hello,

this is my first post so please be gentle.

Please excuse if this is in the wrong sub-forum, I wasn't entirely sure where to post this thread.

I've been wanting a fat bike for quite a while but my knees are preventing me from riding one with a large Q-factor (QF).
Having test driven a Rocky Mountain Suzy Q with a QF of 203mm that didn't cause knee pain and Bosch Fat bike with a QF of 230+mm which gave me knee pain after 15mins of just easy pedaling, I can narrow down the acceptable QF for me to around 200mm and under.

It is possible to fit a 4.6" tire in the rear while having a 183mm QF with a derailleur gear system as demonstrated by the Otso Voytek so I am wondering if there are any full suspension fat bike frame designs that come close to this. Besides the Voytek there are many custom hard tails with a "horse shoe" style chainstay that "wrap" around the bulging tire that also allow for narrow QFs like the Travers Fat Bastard.

The Frey and M2S designs seem to be the most appealing over-all, but I can't find the QF for any of those frame designs, based on the photos from the bikes I am afraid neither the the M2S and especially the Frey have a small QF.
The M2S Ultra frame looks to be narrower (4" only) and maybe one could get down to a reasonable QF with narrower cranks than the standard ones?!

Can anyone comment on this? Could one order a custom rear triangle that allows for a smaller QF? I assume that it won't be too easy to make a narrower one without re-engineering half of the bike.
Also, how is the torque sensor on the new Bafang motors? Can the Bafang be programmed to behave similar to a Brose motor?

Let me list the frame designs I have found, leaving aside the QF, I hope this collection might be useful for other forum members who are looking for a full suspension fat bike with a Bafang mid drive.
There may be more but it is hard to determine from the crappy photos on Alibaba if it is the same design or just a very similar one. For example the M2S Ultra und Kush seem to be different frames.

Asian brands:

Western brands:

Haibike Full Fatsix
Bulls Monster E FS
Huradax EL

If you have any other frame designs that I missed, feel free to post them so they can be added to the list (regardless of the QF).

Thanks in advance for your replies as any input on this subject is appreciated!
El Topo

neptronix · May 31, 2019

Q factor on the addon bafangs is atrocious and uneven. Same with the TDZS2. And many other drives.
If it doesn't use a normal bike BB, consider it suspect.
A fat bike is going to have overly wide pedals and there is no getting around it. OTSO has done a good job of minimizing this but it is still going to be a problem.

I know nothing about drives that are built into the frame because i do not play with proprietary parts or bikes whatsoever. I imagine the Q factor is closer to correct on these drives.

I have bad knees from years of walking around with untreated tibial torsion which was only recently corrected after 7 years of arguing with orthopedists and doing my own independent research. Thus i am oversensitive to anything other than regular bicycle pedal geometry. I suspect wide or uneven Q factors are a problem with biomechanically normal people as well.

The BBS02 hurt my knees very much. I developed full blown patellafemoral syndrome for the first time in my life after a month of riding it.

The only mid drive i would consider riding is one i built myself because these commercial mid drives have so many flaws it's not even funny. A Bafang G310 mounted on the downtube with a chain going from the hub to the 2nd largest crank ring would make for a lightly lighter, and just as powerful BBS02 equivalent, but without the Q factor weirdness and also in theory much more reliable over the long run ( BBS02 is chock full of structurally weak reduction gears etc.. )

El_Topo · May 31, 2019

Thanks for the swift reply, neptronix!

neptronix said:
Q factor on the addon bafangs is atrocious and uneven. Same with the TDZS2. And many other drives.
If it doesn't use a normal bike BB, consider it suspect.

neptronix said:
I know nothing about drives that are built into the frame because i do not play with proprietary parts or bikes whatsoever. I imagine the Q factor is closer to correct on these drives.

Perhaps my phrasing was unclear in my first post but I was NOT looking for add-on drives but frames that have a proprietary Bafang motor mount.

neptronix said:
OTSO has done a good job of minimizing this but it is still going to be a problem.

183mm is about as wide as any regular MTB, isn't it?!
I am not very well versed with bike tech but I don't understand how other frame designers can't do the same as Otso, having a narrower QF should be a win for every rider and it increases your potential customer base, doesn't it?

neptronix said:
Thus i am oversensitive to anything other than regular bicycle pedal geometry. I suspect wide or uneven Q factors are a problem with biomechanically normal people as well.

I second this, that is why I don't understand how frames are designed with QFs of 240+mm like some of the Bosch fat bikes...

neptronix said:
I have bad knees from years of walking around with untreated tibial torsion which was only recently corrected after 7 years of arguing with orthopedists and doing my own independent research.
The BBS02 hurt my knees very much. I developed full blown patellafemoral syndrome for the first time in my life after a month of riding it.

I don't have much cartilage left under my left knee from years of heavy weight training, most times I don't have issues or pain, I can even still squat a fair amount goof weight but riding a bike with a large QF is unfortunately a no-go for me. :-(

neptronix said:
The only mid drive i would consider riding is one i built myself because these commercial mid drives have so many flaws it's not even funny. A Bafang G310 mounted on the downtube with a chain going from the hub to the 2nd largest crank ring would make for a lightly lighter, and just as powerful BBS02 equivalent, but without the Q factor weirdness and also in theory much more reliable over the long run ( BBS02 is chock full of structurally weak reduction gears etc.. )

Thanks for making me aware of this, it makes sense if you think about it but I didn't consider the add-on drives to be worse in terms of QF or not being 100% centred.

neptronix · May 31, 2019

No problem on the swift reply..

El_Topo said:
I don't have much cartilage left under my left knee from years of heavy weight training, most times I don't have issues or pain, I can even still squat a fair amount goof weight but riding a bike with a large QF is unfortunately a no-go for me. :-(

That sucks but it is interesting that one knee has a problem whereas the other does not. You may also have a biomechanical problem that starts at the bone. My tibia was rotated outwards an entire 20 degrees, which is pretty extreme.
Some people have a valgus or varus deformity.. meaning that their tibia is a bit like a leaning tower of pisa and leans left or right, and this causes gradual erosion of one side of the meniscus.

It is actually very difficult to assess this in clinical practice. My 20 degrees of tibial torsion went unnoticed for years until they put my entire body through a CT scanner and created a 3D model of my bone angles.

If you have this going on for you, then a mid drive that puts your foot at a weird angle is going to hurt that knee. Coincidentally, loading it in an opposite diagonal direction will feel quite good.

neptronix said:
The only mid drive i would consider riding is one i built myself because these commercial mid drives have so many flaws it's not even funny. A Bafang G310 mounted on the downtube with a chain going from the hub to the 2nd largest crank ring would make for a lightly lighter, and just as powerful BBS02 equivalent, but without the Q factor weirdness and also in theory much more reliable over the long run ( BBS02 is chock full of structurally weak reduction gears etc.. )

Thanks for making me aware of this, it makes sense if you think about it but I didn't consider the add drives to be worse in terms of QF or not being 100% centred.
[/quote]

Oh yeah, the right pedal on most add on drives usually ends up 10-20mm further out than the left pedal. I was shocked when i measured it.

MadRhino · May 31, 2019

Not sure I would go FS, building a fat bike. Or, I would mod a DH swing arm to 4’’ and use a monster T fork.
.
.
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The Salsa fs frame is good to build IMO, when you don’t want to do any mods. Shifting hub of course, to use single freewheel and build narrow Q-factor. With some dishing and single gear, I believe 165 mm can be done easy. Square taper crank does make it easier because the variety of crank arms available, but a good SQ crank is very expansive, and cheap ones are all crap.

2old · Jun 1, 2019

This won't solve your problem (might make it worse), but even though the "offset" crankarms on the BBS02-equipped bike didn't seem to cause me problems, Lekkie crankarms resolved the situation. Eventually some company will construct a fat bike with a Fazua motor system; can almost guarantee it will be narrow although maybe under-powered for you.

El_Topo · Jun 1, 2019

Thanks for the new replies in this topic!

neptronix said:
That sucks but it is interesting that one knee has a problem whereas the other does not. You may also have a biomechanical problem that starts at the bone. My tibia was rotated outwards an entire 20 degrees, which is pretty extreme.
Some people have a valgus or varus deformity.. meaning that their tibia is a bit like a leaning tower of pisa and leans left or right, and this causes gradual erosion of one side of the meniscus.

It is actually very difficult to assess this in clinical practice. My 20 degrees of tibial torsion went unnoticed for years until they put my entire body through a CT scanner and created a 3D model of my bone angles.

If you have this going on for you, then a mid drive that puts your foot at a weird angle is going to hurt that knee. Coincidentally, loading it in an opposite diagonal direction will feel quite good.

To make it short and since I don't know the medical terms in English, my kneecap is not shaped optimally to run in the groove of the bone below which is obviously very abrasive to the cartilage. My other knee does in fact show the same symptoms but it hasn't been MRI'ed yet as it doesn't cause me problems (so far) - so yes, the the problem is indeed biomechanical.

MadRhino said:
Not sure I would go FS, building a fat bike. Or, I would mod a DH swing arm to 4’’ and use a monster T fork.

The Salsa fs frame is good to build IMO, when you don’t want to do any mods. Shifting hub of course, to use single freewheel and build narrow Q-factor. With some dishing and single gear, I believe 165 mm can be done easy. Square taper crank does make it easier because the variety of crank arms available, but a good SQ crank is very expansive, and cheap ones are all crap.

Thanks for the recommendation. I don't think I would want to retrofit an analogue frame with a motor because I really don't like the retrofit look, especially since it is best to not draw too much attention with the strict 250W laws in Germany.
Also, that frame is quite expensive to get in Europe and rarely available used.

2old said:
This won't solve your problem (might make it worse), but even though the "offset" crankarms on the BBS02-equipped bike didn't seem to cause me problems, Lekkie crankarms resolved the situation. Eventually some company will construct a fat bike with a Fazua motor system; can almost guarantee it will be narrow although maybe under-powered for you.

TBH, I am tempted to go for a G520 motor instead of the G510 just because of the weight savings and since I really don't care about max speed. Running at 35-40 km/h would be enough for me and even that is risky with the strict enforcement of the 25km/h limit one might encounter. On the other hand, having 160 instead of 90Nm of torque surely is nice.

As far as I understand it (and I don't know much about bike tech), the width of the motor housing isn't the problem but the way the frame is designed/constructed. The Otso Voytek has a 170mm hub, uses a few special spacers to get a slightly more outward chain line while keeping the chain stays narrow and pretty much right under the chain line to allow for the cranks to be as close to the tire as possible, while most designs have a lot of empty space between the crank and tire.
The Bafang mid drive doesn't seem to have a QF of wider than a regular MTB (180-ish mm) with the right cranks. The problem seems to be that most frame designers choose a 190/197mm hub that pushes out the chain line, to account for this you need to use a spider that pushes out the chainring a lot and cranks that bend outwards to not hit anything with the crank or your feet. This allows for very wide tires but but means you have a QF that is too wide for those with sensitive knees*.

*Or narrower pelvises as I assume from a layman's understanding of biomechanics. It would be interesting to see if men with a wider pelvis and women don't suffer as much when riding bikes with a larger QF.

2old · Jun 3, 2019

Near as I can determine, the "Q" on my wife's BBS02-equipped with a 68 mm bottom bracket width bike is about 200 mm and the motor housing just clears the chainstays. Doubt that any of Bafang's mid-systems will improve on that.

El_Topo · Jun 4, 2019

2old said:
Near as I can determine, the "Q" on my wife's BBS02-equipped with a 68 mm bottom bracket width bike is about 200 mm and the motor housing just clears the chainstays. Doubt that any of Bafang's mid-systems will improve on that.

Thanks for the reply, 2old!
I assume this is the same or similar for all the add-on kits, I realised my phrasing could have been clearer as I was only looking for frames with integrated mid drive, I just corrected the title.

Thanks nevertheless!

Bigwheel · Jun 4, 2019

Your desire for 4.6 tire width demands a wider bb and rear hub spacing for the chain to clear the tire in the inner most cog of the cassette which results in wide Q factor. I would say if you can find a bike that has that size tire and a Bafang Ultra that would be as good as you’ll get. The manufacturer should be able to provide that info upon request.

El_Topo · Jun 4, 2019

Thanks for your reply, Bigwheel.

Bigwheel said:
Your desire for 4.6 tire width demands a wider bb and rear hub spacing for the chain to clear the tire in the inner most cog of the cassette which results in wide Q factor.

The aforementioned Otso Voytek has a 83mm bottom bracket with a 177mm hub and can accommodate 26x4.6" tires (which should be 4.2" to 4.3" measured) and a Q-factor of 183mm with the right cranks if you use 80mm rims, it does so by flipping the chainring and using cranks that don't have much of an outward curve (as far as I understand it, please correct me if I am wrong). See this quote, (27.5x4.6 also works according to this article):

Technically, the 26 x 4.6″ Dunderbeist on a 76mm inner width HED BAD fat bike rim is considered a ‘yellow’ combination with the middle chip for the Voytek, which means Otso says it “may fit, but is not recommended.”

While being a layman at best regarding bike tech, I did a lot of research on this and as far as I can tell Otso ist just the first manufacture that did put all this together. I found forum posts about custom fat bikes attempting the same dating back to ca. 2013).
I don't understand why a full suspension frame design would be different in terms of maximum tire width (the minimum chain stay length might be higher given the extra mechanics and motor size) if you keep the cranks and chain stays tightly together as the Voytek does (see also this and this).

Bigwheel · Jun 4, 2019

Anything is possible as seen with the Otso, however it is an exercise in futility for your needs as it doesn't come in electric assist. Stay after it and hopefully something will happen for you!

I will say that a 3" tire on an i40 rim setup tubeless will run all day at low 10-15psi psi and give good traction in all but the deepest sand and snow. Your options would vastly improve by going to that width for even a conventional 175mm Q factor as bb width can be 72mm which matches up well to those integrated systems with a low Q factor. You probably have specific needs for the widest tires however.

PS: if you want to geek out on the latest and greatest in fat bike development visit this blog run by an old friend down in CO. http://lacemine29.blogspot.com He is a past record holder for Iditibike and has done alot of thinking and tinkering on fat bike geo over the years. Plus he tells a good tale and takes nice pictures.

formula101 · Jun 5, 2019

I'd neglected to give this issue the consideration it deserves, until spotting this thread that is. This is a topic that Grant Petersen used to harp on all the time back in the day. It's definitely noticeable when switching back and forth between a road and any mountain bike for example.

I'm interested in the Frey AM1000 fat bike but am starting to reconsider given potential issues with Q factor.

Shopping for an e-bike is often very frustrating because so few brands publish geometry charts 95% of the time. When they do post a chart, it's usually laughably incomplete. Finding information on Q factor seems nearly impossible. Very, very few brand owners understand frame design since they're purchasing generic designs out of a catalog. It's sad.

IME, there are multiple factors which can cause knee pain. For one, I find bikes that are extremely upright to be more painful for my knees. It's almost like pedaling while standing. Your knees are bearing more weight when you are sitting straight up, rather than bent forward.

I also find that longer crank arms can cause knee pain. I'm find with crank arm lengths below 175mm, but 175 mm are terrible for me.

I'll ask in the Frey thread if anyone has information on Q factor. I'm sure someone can measure easily if the information isn't published somewhere. Thanks for the thread.

El_Topo · Jun 5, 2019

formula101 said:
I'd neglected to give this issue the consideration it deserves, until spotting this thread that is. This is a topic that Grant Petersen used to harp on all the time back in the day. It's definitely noticeable when switching back and forth between a road and any mountain bike for example.

I would be surprised if QF isn't an issue for most if not all but it is probably below the threshold for most that don't have any predispositions like knee or hip problems.

formula101 said:
I'm interested in the Frey AM1000 fat bike but am starting to reconsider given potential issues with Q factor.
...
I'll ask in the Frey thread if anyone has information on Q factor. I'm sure someone can measure easily if the information isn't published somewhere.

I can almost guarantee that it will be around 230mm, have a look at this post and the two that follow. The Frey seems to use the same cranks and spider as offered by Luna Cycles in their Kit which Daxxie used for his build.

formula101 said:
Shopping for an e-bike is often very frustrating because so few brands publish geometry charts 95% of the time. When they do post a chart, it's usually laughably incomplete. Finding information on Q factor seems nearly impossible. Very, very few brand owners understand frame design since they're purchasing generic designs out of a catalog. It's sad.

I share that sentiment, I really don't know much about bike geometry, tech and all the terminology but I don't understand how it isn't common practice to share the QF of a bike on the geometry page - let alone that QF seems to be an afterthought in many designs.
Even if a frame is bought out of a catalogue, one would assume that the design is done by someone competent that knows about geometry and how details like the QF influence the ridability of a frame, especially when you can eliminate a too wide QF as can be seen by the latest frame designs.

formula101 said:
IME, there are multiple factors which can cause knee pain. For one, I find bikes that are extremely upright to be more painful for my knees. It's almost like pedaling while standing. Your knees are bearing more weight when you are sitting straight up, rather than bent forward.

I haven't read about this so far but if you have any sources regarding this I would be interested.

formula101 said:
I also find that longer crank arms can cause knee pain. I'm find with crank arm lengths below 175mm, but 175 mm are terrible for me.

I have a also looked into this and determined that 170mm would be maximum crank length for my height (172cm), 165mm might be even better but they are hard to get - especially if you are also shopping for cranks that allow for a narrow QF.
There are two basic way to calculate the optimal crank length, one is (height in cm)*9.7 and other uses the inseam, see also here (just found this link, there may be better articles on this).
In fact I plan to visit a professional bike fitter before I commit to any new frame to let them measure my whole body, let you test ride different geometries and discuss my specific medical issues (knees and neck) with them so they can give me precise recommendations on how to optimise rider position or even frame dimensions if I go for the custom Titanium hardtail instead of full suspension - which seems more likely given the full suspension fat bike frames with integrated Bafang mount (or any other Brand like Bosch, Yahama, etc.) are lacklustre when it comes to QF).

formula101 said:
Thanks for the thread.

You're welcome, I am glad this thread is of use for someone else too.

2old · Jun 5, 2019

Part of the lack of knowledge regarding "Q" factor may be that many are not aware of or affected by the issue. I was amazed that very few individuals knew there was a difference in distance between the right and left crank arms from their respective chainstays with the BBS02. Seems like the guys that designed the motor weren't bike riders, although to be fair the motor has been dynamite for my wife and me. We ride off road with either no assistance (flat or downhill terrain) or level "1" (of "5") on uphills (mostly 5% - 10%), and are satisfied with the workout as well as the way the power comes on. My Haibike Yamaha, while easier to ascend tortuous trails with since the power is available as long as there is pressure on the cranks, while the BBS02 needs to be spinning, isn't any more fun to ride.

formula101 · Jun 5, 2019

el_topo, I don't have any articles as sources, my comments are based on anecdotal personal experience. The bikes I've ridden with the most upright positioning: the gazelle cityzen (speed), radrover, and my own city bike with a 30degree rise stem, are the ones that have caused knee pain.

Whereas my endurance road bike with drop bars and my mtb with short head tube, long top tube and stem, cause zero knee pain. Also, the road and mtb have 172.5 and 170mm crank arm lengths, respectively.

So, a comfortable ride position for me seems to require either shorter crank arms or a more stretched out aero ride position. A shorter crank arm also brings the feet a little bit closer together.

It's tough to say whether the Frey AM1000 fat bike will work for me or not. It has an admirably long top tube (61.5mm) and short crank arms (170mm). Will those two factors be enough to offset the 230mm Q factor? Tough to say without a test ride.

formula101 · Jun 6, 2019

Q factors of various motors, with sources listed below. The bafang M600, with 500 watts and a top speed of 28 mph, has a q of 177mm. I may be a lot better off with the M600. It can achieve a top speed of near 28 mph. Or, I'll go with a hub motor if I can get a Q factor similar to the m600. The Surface604 Rush and JuicedBikes Cross Current S and X both have top speeds of approximately 30 mph.

Shimano Tiagra 4700 (road group): 150 mm
Shimano XTR (mtb group): 158, 168 mm, two previous revs.

Yamaha PW-X Q Factor Length: 168 mm
Shimano E8000 Q Factor Length: 175 mm

Bafang M600 Q factor: 177 mm

Brose Drive T, TF, S Q Factor Length: 179 mm
Bosch Performance Line Q Factor Length: 180 mm

https://electricbikereview.com/forum/threads/bicycle-q-factor-definition-ebike-mid-drive-motor-q-factor-list.23133/

[youtube]https://www.youtube.com/watch?v=ZR0gFy1xIGQ[/youtube]

El_Topo · Jun 7, 2019

2old said:
Part of the lack of knowledge regarding "Q" factor may be that many are not aware of or affected by the issue.

Sure but wouldn't you expect a full time (professional) frame/bike designer to be aware of this? As can be seen from the Voytek and other frames it is possible to have clearance for big tires with a reasonable QF, it is beyond me why not everyone is doing it. Designing such a frame costs the same and if you don't want to spend the extra money on the offset spider and cranks you can just use a 100 BB to get the same chainline for cheaper.

formula101 said:
el_topo, I don't have any articles as sources, my comments are based on anecdotal personal experience. The bikes I've ridden with the most upright positioning: the gazelle cityzen (speed), radrover, and my own city bike with a 30degree rise stem, are the ones that have caused knee pain.

Thinking about it, an analogy to this would be doing a 45 degree leg press vs hack squat machine, most if not all people don't have problems with the former while many have problems with doing the latter (assuming good technique for both). The leg press is equivalent to a racing position in terms of angles and the hack squat machine to riding upright as you can see in the videos.

formula101 said:
It's tough to say whether the Frey AM1000 fat bike will work for me or not. It has an admirably long top tube (61.5mm) and short crank arms (170mm). Will those two factors be enough to offset the 230mm Q factor?

Based on my experience test riding a 230mm QF bike I doubt it but I would be happy for you to prove me wrong.

formula101 said:
Q factors of various motors, with sources listed below. The bafang M600, with 500 watts and a top speed of 28 mph, has a q of 177mm. I may be a lot better off with the M600. It can achieve a top speed of near 28 mph.
...
https://electricbikereview.com/forum/threads/bicycle-q-factor-definition-ebike-mid-drive-motor-q-factor-list.23133/
https://www.youtube.com/watch?v=ZR0gFy1xIGQ

The M600 indeed looks interesting, another option would be the G520 motor but I assume they all have different motor mounts? The M600 seems to be name for the system with battery, display and controller, the name of the motorseems to be G.521 - what is the difference between the G.520 and G.521? Finding out these details is very hard for me.
I think the better approach would be to look at the spindle length of each motor as that is the fixed part in that setup. You can always choose different kinds of cranks for your setup (given they are available with the particular mounting system) but the spindle length you can't change on any motor if I am not mistaken.
The Bafang Ultra has a spindle length of 150mm (according to this post) with ISIS mounts if I am not mistaken so a QF of 183mm might be achievable if the motor bulge on the non-drive side isn't in the way of cranks with minimal offset (see my post behind the previous link). If it is, choosing cranks with a bit more offset should result in a QF or around 190-195mm which should be acceptable for most. As mentioned in my opening post, I once test rode a bike with a QF of 203mm where I was one the fence, it work for me but I would have to ride it for a few hours consecutively to be sure.

El_Topo · Jun 7, 2019

Bigwheel said:
Anything is possible as seen with the Otso, however it is an exercise in futility for your needs as it doesn't come in electric assist. Stay after it and hopefully something will happen for you!

As I mentioned I feel that there is little advantage in having a larger QF than necessary, so I am hopeful other frame manufacturers will follow the route Otso has paved with the Voytek.

Bigwheel said:
I will say that a 3" tire on an i40 rim setup tubeless will run all day at low 10-15psi psi and give good traction in all but the deepest sand and snow. ... You probably have specific needs for the widest tires however.

I rode a 3" tire and 3.8 and larger tires and I feel an appreciable difference. I am not an experienced rider but I just like the way those wider tires ride and I don't mind the speed penalty the introduce (which can be more than offset with a motor anyways).

Bigwheel said:
PS: if you want to geek out on the latest and greatest in fat bike development visit this blog run by an old friend down in CO. http://lacemine29.blogspot.com

Thanks for the link, I read a lot of what he writes on the mtbr forums.

formula101 · Jun 7, 2019

That's a good point el_topo: with an upright riding position, almost all of your body weight is directly above your knees, forcing them to do more work. When you are leaning forward, this reduces the weight above your knees. In addition, you are in a more aero riding position, reducing drag. Third, you can leverage your upper body strength a bit to generate a little bit of power by pulling on the bars, especially when climbing. Overall, a very upright riding position is disadvantageous unless mobility issues forces one to adopt it for lack of other options.

I can also say I strongly dislike a very upright riding position when descending. I feel like I have more control when my weight is distributed over a larger percentage of the bike front to back. Perhaps it's easier to steer the bike just by leaning when in a more aerodynamic position as well.

Everyone has their sweet spot though. My road bike has a 165 mm head tube, so it's pretty upright by road bike standards. But a fully upright riding position doesn't work (well) for me. Neither does an extreme aero position with say a 135 mm head tube on a road bike.

I'll keep looking for that unicorn (big tires with low Q factor): if there is enough "demand" perhaps even just a detailed email or a few phone calls to brands like Frey that are very open to listening to their customers could do the trick. Functionality wise, I would be completely fine with a plus sized tire rather than a fat tire. The novelty and comfort of a fat tire are appealing, but not what I'd consider to be an absolutely necessity. Not by a long shot.

El_Topo · Jun 9, 2019

formula101 said:
...
I can also say I strongly dislike a very upright riding position when descending.
...
Everyone has their sweet spot though. My road bike has a 165 mm head tube, so it's pretty upright by road bike standards. But a fully upright riding position doesn't work (well) for me. Neither does an extreme aero position with say a 135 mm head tube on a road bike.

Unfortunately I can't go too low with my upper body because I also have problems with my neck (same reason as why the knees aren't in top shape anymore...) because obviously you have to compensate for low upper body by over-stretching your neck to look forward instead of down.

formula101 said:
I'll keep looking for that unicorn (big tires with low Q factor): if there is enough "demand" perhaps even just a detailed email or a few phone calls to brands like Frey that are very open to listening to their customers could do the trick. Functionality wise, I would be completely fine with a plus sized tire rather than a fat tire. The novelty and comfort of a fat tire are appealing, but not what I'd consider to be an absolutely necessity. Not by a long shot.

Even though the suspension links most likely won't allow for it but 4" tires would be easily possible with the Bafang Ultra's 150mm spindle which might allow for a 183 QF :

El_Topo said:
The Bafang Ultra has a spindle length of 150mm (according to this post) with ISIS mounts if I am not mistaken so a QF of 183mm might be achievable if the motor bulge on the non-drive side isn't in the way of cranks with minimal offset (see my post behind the previous link). If it is, choosing cranks with a bit more offset should result in a QF or around 190-195mm which should be acceptable for most. As mentioned in my opening post, I once test rode a bike with a QF of 203mm where I was one the fence, it work for me but I would have to ride it for a few hours consecutively to be sure.

formula101 · Jun 12, 2019

As a bit of a sidebar, it got me thinking about my city bike, which has been shall we say, far from optimal for my knees. It came stock with a ridiculous 30 degree stem. I swapped it out for a 7 degree stem, also 90mm. Voila knees feel a whole lot better. Another benefit of a lower, more aero position is that I am feeling less shock through the saddle. When you are seated in an upright position, shock is transmitted straight up the seat tube to your butt and back. However when you are leaning forward, your hips and back have a chance to bend and give a little, dissipating shock. Third of course, you are more aero and therefore at least theoretically faster. Fourth, as discussed, leaning forward a bit more gives your knees a break. You can pull the bike with your torso a little bit so your legs (and knees) aren't burdened with the entire load. You can pull with your upper body a bit as well as push with each pedal stroke.

I really don't know why so many people love an upright riding. There are too many cons for me to believe that this type of riding position is optimal. Then again, all three of my current bikes have relatively skinny tires so that is a consideration as well. If anyone is riding with narrow(er) tires, I don't think an upright riding position makes much sense.

Even on e-bikes with much fatter tires, I still think an upright riding position is not great for the knees, although the fat tires could save your back. Just a bit of extra "data" to consider.

A lot of these finer points may be lost on a general audience but for those who had knee issues in the past, it's best to think through the various aspects of fit that can get you riding at your best, with I think the very real possibility of zero pain.

2old · Jun 13, 2019

FME (and others that I ride with), switch the pain from knees to the neck area and you'll see why some individuals prefer a more upright stance.

formula101 · Jun 14, 2019

The ideal handlebar/stem height is anywhere from level with the saddle to about 1 to 1.5" above. Higher than that, and the position is too upright for me. Lower than that can lead to neck strain. Proper fit definitely requires a bit of fine tuning. Most go about it through trial and error. Ideally, a bike fit can save you a lot of time (and pain and frustration), assuming you work with a highly qualified fitter.

The fitter can assess your level of flexibility, and sometimes can find out how much power. you can generate based upon riding position. I highly recommend it. You can save the data and use it in the future. I know alot of people are turned off by the price, but the $150 to $300 asking price can be well worth it long term.

A fitting is absolutely critical if you are going to be using clipless pedals, which usually require careful alignment. But it's useful for just about anyone, especially if you plan on logging heavy miles.

A lot of these fine points of bike fit are totally lost these days as LBS's become less popular as consumers increasingly turn to online shopping.

El_Topo · Jun 14, 2019

2old said:
FME (and others that I ride with), switch the pain from knees to the neck area and you'll see why some individuals prefer a more upright stance.

Please excuse my question but what does the acronym "FME" stand for in this case (google didn't help)?

formula101 said:
...a bike fit can save you a lot of time (and pain and frustration), assuming you work with a highly qualified fitter.
The fitter can assess your level of flexibility, and sometimes can find out how much power. you can generate based upon riding position. I highly recommend it. You can save the data and use it in the future. I know alot of people are turned off by the price, but the $150 to $300 asking price can be well worth it long term.
...
A lot of these fine points of bike fit are totally lost these days as LBS's become less popular as consumers increasingly turn to online shopping.

This is the way I see it:
A bike fit will cost me not a even a tenth of the (hypothetical) bike discussed in this topic but I get a (supposedly) perfect fit for all bikes I own now and future bikes assuming I don't grow anymore (that is highly unlikely given my age) or become more restricted in my riding position due to knee, neck or anything else that might break (knock on wood!).

Is there some literature or a good website that covers the difference aspects of bike fitting in more detail you can recommend?

Looking for full suspension fat bike with integrated Bafang mid drive (and narrow Q-factor)

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