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Plus Bike Q-factors -- what's yours?

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Ptor

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Discussion starter · #1 ·
Q-factor matters to my knees and hips and the wide pedaling stance on fat bikes has kept me from becoming a dedicated snow biker in the winter, despite great snow riding locally. I've gotten excited about the Otso Voyatek as a possible way to double up on a plus bike and fat bike while having a reasonable Q-factor (183 mm). I wanted to know how that compares to a "regular" plus bike, so I started looking for the published Q-factors for dedicated plus bikes and haven't been able to find them -- just statements like that for the Cannondale Beast of the East, "a sensible q-factor", without any numbers. I would very much appreciate the "plus bike community" sharing their Q-factor numbers -- I can't be the only one for who that measurement is critical.

When looking for a a new race carbon hardtail, I was able to eliminate a whole bunch of makes and models based on Q-factor, ultimately settling on a Scott Scale because it could handle a crank with a 156 mm Q-factor. I'd like to be able to do that sort of winnowing in my search for a plus bike (and maybe a fat bike).
 
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#2 ·
When I had a Krampus, and now on my Jones Plus, I can run a regular Shimano two piece crank. The Q is 175mm, give or take. That feels pretty wide to me--I prefer the ~155mm I can get on the old Suntour XC Pro cranks on my Karate Monkey.
 
#3 ·
Just posting to say you're not alone. The massive Q-factor on fat bikes and Super Boost Plus lol are a turn off for me. My plus bike is too much of an outlier to help you with your search but it has a 142 rear and runs 168 no problem (Sram). There are less 142 plus bikes than 148 but, if you find one, that might be a dead give-away as to likely having a q-factor you'd like (and of course bb shell - target 68/73). Maybe check the cranks that come spec'd?
 
#4 ·
That's one of the nice things about the Cannondale Beast of the East. They use an offset rear wheel with a 142-thru axle hub instead of boost-spaced hub, which allows for a standard width bottom bracket/crankset. Other brands may do this or something similar.
 
#6 ·
The Q factor just depends on what cranks the manufacturer spec's. Most Boost cranks have the same Q factor as non-boost, they just push the chainrings 3mm outboard.

I spec'd both of my Plus bikes with an 83mm BB and use SRAM XO DH GXP83 cranksets. Just looked up the Q factor as 181mm. I don't feel any difference between that and my older 73mm bikes, which had a 168mm Q factor SRAM cranks.

Most people don't start having issues until the Q factor gets in the 200mm range.
 
Discussion starter · #7 ·
I'm not arguing that a smaller Q-factor is inherently better -- I'm only stating that I (and probably others) prefer/need smaller Q-factor to prevent knee and hip pain. I was hoping to get real numbers for stock plus bikes or what is the minimum allowable Q-factor for a given frame. I also note that "standard width bottom bracket/crankset" is not so "standard", with the Q-factor of stock cranks on regular "modern" mtbs ranging from 156 to 175mm (or larger). I'll be putting my big mtb miles in on my bike with the 156mm Q-factor, and most miles will be on the cross bike with 145 mm Q-factor, and I expect (hope?) I can tolerate 175 (or 183) mm for the miles I'll put on a plus/fat bike.
 
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#8 ·
After reading this ^ (history and target) - I'd try to find a plus bike that takes a 168 (I think that may exclude almost all 83mm BB?). I'm sensitive to it too and even a 171/173 Q factor is very noticable and unpleasant after some miles. Not everyone has the same physiology and history so you can't accept "works fine for me" esp if you know you are sensitive. 168mm to 183 is a country mile in terms of Q-factor. Good luck - as you know it's not an easy ask.

Edit: re-read original - my focus and drivers were on pedaling factors - if you want a fat bike for true winter riding, I don't think a plus bike is what you want and you'll just have to target a narrower end of fat - it's compromise.
 
#9 ·
The new version of the Krampus (due out in April) has a 73mm bottom bracket shell and will take a 168mm q-factor SRAM crankset. I did confirm that with Surly direct.

Here's Surly's response:

> Greg, first off, thanks for your interest in our steel. I just ran down the hall and checked in with our team of Enginerds, and they told me, on paper, this should work. We've never tested that combo, but the numbers line up.
>
> Hope that clears things up for you, let me know if you have any more questions.
 
#10 ·
I have a Giant XTC Advanced 29er that I put plus wheels on. It uses a standard Eagle XX1 crankset. So I think about a 168mm q-factor? Plenty of clearance for 3.0 tires.

I went this route as I also have problems with the wide q-factor of fat bikes. Ruined my knee for a season. I REALLY prefer 156, but i'm not aware of any boost plus bikes that accommodate that. If there is one, don't tell me. I don't want to know what could have been!
 
#11 ·
To the OP: I feel your pain - literally.

Some people's hips and knees care about Q factor, others don't. When people say things like "Most people don't start having issues until the Q factor gets in the 200mm range," what they're really saying is that *they personally* don't care about it, and that by implication if you do you are defective or inferior; this is not at all helpful. :-(

FYI there are at least two fatbikes that will accept cranks with Q factors around 170mm, this one: https://www.crustbikes.com/products/scapegoat and this one: Bikes - Tumbleweed Bicycle Co. Drivetrain options are limited but suit the intended use; I should have a Scapegoat frameset next week, but both were designed by riders with many years of serious expedition use behind them and should do the job; the Scapegoat geometry fits me better. (The guys at Crust are super helpful too BTW.)

Re 27.5+ bikes: My frame set was built in the very early days of +, before there were (m)any tyre options, and the chainstays are narrow enough to accept 150-155 Q factor cranks, in my case old Ritchey Logic Compacts. Tyres larger than ~2.8" aren't likely to fit on the rear, but that's an acceptable trade off IMO. The bike was intended for use with a Rohloff hub from the start, and has a 68mm Bushnell EBB. If we'd had access to tyres when the frame was being built a bit more manipulation of the chainstays would have allowed a bit more clearance, but I'm not likely to ride in mud so there's enough as is.

Current MTB cranksets are made to make life easier for manufacturers, rather than to be biomechanically correct, IMHO. Offroad this is often okay since one moves around all the time. On the road, not so much.

My next dual suspension bike will accept sub 160mm Q factor cranks or I won't be buying one. As always, YMMV.
 
#12 ·
I sold my Borealis Echo for exactly this reason...Q factor was too wide and I ended up with knee pain.

I bought an Otso Voytek with 120mm Fox 34 as my only bike at moment. (Recently sold my XC full suspension rig as well.)

I'm completely satisfied with for northern NJ riding. It feels like traditional mountain bike.
 
#13 ·
satanas said:
To the OP: I feel your pain - literally.

Some people's hips and knees care about Q factor, others don't. When people say things like "Most people don't start having issues until the Q factor gets in the 200mm range," what they're really saying is that *they personally* don't care about it, and that by implication if you do you are defective or inferior; this is not at all helpful. :-(
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No, I'm saying most people don't have an issue with Q factors under 200mm. Obviously, some people do, but I never implied that those people are defective or inferior. Go look around the Fatbike forum or elsewhere, and the majority of people have no problems, even with huge Q factors of over 220mm on 197mm bikes.

satanas said:
FYI there are at least two fatbikes that will accept cranks with Q factors around 170mm, this one: https://www.crustbikes.com/products/scapegoat and this one: Bikes - Tumbleweed Bicycle Co. Drivetrain options are limited but suit the intended use; I should have a Scapegoat frameset next week, but both were designed by riders with many years of serious expedition use behind them and should do the job; the Scapegoat geometry fits me better. (The guys at Crust are super helpful too BTW.)
Click to expand...
While both bikes are interesting, they make a bunch of other sacrifices in order to use a 73mm BB. Basically, in order to use fatbike tires, you have to run singlespeed or an internal gear hub.

satanas said:
Re 27.5+ bikes: My frame set was built in the very early days of +, before there were (m)any tyre options, and the chainstays are narrow enough to accept 150-155 Q factor cranks, in my case old Ritchey Logic Compacts. Tyres larger than ~2.8" aren't likely to fit on the rear, but that's an acceptable trade off IMO. The bike was intended for use with a Rohloff hub from the start, and has a 68mm Bushnell EBB. If we'd had access to tyres when the frame was being built a bit more manipulation of the chainstays would have allowed a bit more clearance, but I'm not likely to ride in mud so there's enough as is.

Current MTB cranksets are made to make life easier for manufacturers, rather than to be biomechanically correct, IMHO. Offroad this is often okay since one moves around all the time. On the road, not so much.

My next dual suspension bike will accept sub 160mm Q factor cranks or I won't be buying one. As always, YMMV.
Click to expand...
Yes, there are obviously people are very sensitive to Q factor, and they need to shop more carefully. But my point in my original post was that Plus bikes do not result in any Q factor change. Even the ones using Boost use the same cranksets as normal 135mm/142mm frames, the chainrings are just spaced 3mm outboard. Most SRAM cranks are 169mm I think, which is pretty standard. If you need narrower, you will run into clearance problems with Plus bikes, especially if they are designed to use a full 3" tire.
 
#14 ·
^ I'd suggest that the people in the fatbike forum (and all forums) are self-selected by their enthusiasm for the subject. This strongly implies that those responding in the fatbike forum will be people who do not have biomechanical problems due to high Q - if they did they wouldn't be happily riding fatbikes. This says nothing useful about the rest of the bike riding population; it may be the case that more people don't mind 200mm Q than do not, but there's no useful data either way.

Given the Scapegoat and Prospector are designed primarily for expedition use, the decision to opt for Rohloff/SS is entirely reasonable, IMHO. Rohloff hubs may not be cheap, but they're a lot less annoying than knee or hip problems, and in my case I would never have considered a fatbike with "normal" Q, even 183mm being too much for my liking. (I've been looking at Pugsleys online since they were first announced but the Q was a deal killer for me.)

Plus bikes may not result in a Q factor change assuming typical current cranks (168-175mm), but as I'm used to 150-155mm there's a significant difference. This used to be a pretty common Q factor that most frames would clear. 156-158mm is still available with XX/XX1/XTR, and several European XC cranks come in around 160mm, but it's very hard to find out what frames they will fit as very few manufacturers list this sort of data anywhere.

If you look at XTR cranks, the Boost options have higher Q; 158 for M9000 Race, 168 for M9020 Trail (even the triple), 174 for M9020 Boost. It's true that low Q cranks won't fit most Plus bikes, but this is a chicken and egg thing IMO. Most current cranks (except expensive XC cranks) have 168+mm Q, and since most people won't pay for these it's easier for manufacturers to ignore the option of making them fit. With decent yoke and chainstay design many bikes could potentially accept lower Q cranks. The other issue is chainstay to tyre clearance, largely solved with an IGH, SS or 1x on Plus.

There's no doubt it's easier for manufacturers to use higher Q cranks as these eliminate a lot of clearance issues. Since many people don't notice or care about the higher Q - or have never experienced lower Q - buyer resistance isn't high, more bling or newer being important to many. That doesn't mean Q does not matter to at least some of us.
 
#15 ·
satanas said:
^ I'd suggest that the people in the fatbike forum (and all forums) are self-selected by their enthusiasm for the subject. This strongly implies that those responding in the fatbike forum will be people who do not have biomechanical problems due to high Q - if they did they wouldn't be happily riding fatbikes. This says nothing useful about the rest of the bike riding population; it may be the case that more people don't mind 200mm Q than do not, but there's no useful data either way.
Click to expand...
I usually find the opposite in the forums, people come here to complain about problems, so the problem rate seems higher than it really is. I any case you are correct, there is no real data on the topic, but I suspect that if a large percentage of the population was having problems, we would know about it.

satanas said:
Given the Scapegoat and Prospector are designed primarily for expedition use, the decision to opt for Rohloff/SS is entirely reasonable, IMHO. Rohloff hubs may not be cheap, but they're a lot less annoying than knee or hip problems, and in my case I would never have considered a fatbike with "normal" Q, even 183mm being too much for my liking. (I've been looking at Pugsleys online since they were first announced but the Q was a deal killer for me.)
Click to expand...
Sure, for expedition use those bikes might be great. But most people here are looking for a bike they can ride on their local trails for a few hours of fun. Most people will not be happy with the need to run SS or Rohloff on their trail bike.

satanas said:
Plus bikes may not result in a Q factor change assuming typical current cranks (168-175mm), but as I'm used to 150-155mm there's a significant difference. This used to be a pretty common Q factor that most frames would clear. 156-158mm is still available with XX/XX1/XTR, and several European XC cranks come in around 160mm, but it's very hard to find out what frames they will fit as very few manufacturers list this sort of data anywhere.

If you look at XTR cranks, the Boost options have higher Q; 158 for M9000 Race, 168 for M9020 Trail (even the triple), 174 for M9020 Boost. It's true that low Q cranks won't fit most Plus bikes, but this is a chicken and egg thing IMO. Most current cranks (except expensive XC cranks) have 168+mm Q, and since most people won't pay for these it's easier for manufacturers to ignore the option of making them fit. With decent yoke and chainstay design many bikes could potentially accept lower Q cranks. The other issue is chainstay to tyre clearance, largely solved with an IGH, SS or 1x on Plus.

There's no doubt it's easier for manufacturers to use higher Q cranks as these eliminate a lot of clearance issues. Since many people don't notice or care about the higher Q - or have never experienced lower Q - buyer resistance isn't high, more bling or newer being important to many. That doesn't mean Q does not matter to at least some of us.
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Again, I'm saying for most people it doesn't matter. I've even read about people having the opposite problem, knee pain from cranks that are too narrow! For some people, it matters, and they need to choose wisely and decide what their priorities are. There is just no way to fit narrow Q cranks, wide tires, short chainstays and 11/12 speeds into the space available. For me, I choose to use wider Q cranks in order to fit big tires, short chainstays and 11 speeds on my bikes. Others will make different choices, and it's great that there are at least some options out there.
 
#16 ·
The limiting factor is the chain.

With a 73mm BB (Q factors vary a bit, obviously), the widest available chainline (assuming a single ring drivetrain) is about 58mm. That works pretty well with a 157x12 rear end, or an offset 148, assuming you want to run gears. For IGH or SS, you can do a narrower/non-offset rear.

Max tire size ends up around 90mm assuming you want at least 2-3mm of space for the chain when in your lowest gear. You could push that a tiny bit with a SS or IGH setup, but not a lot.

As you might expect, if you go to an 83mm BB, you gain (wait for it!) about 10mm of space for a bigger tire, and you add about 10mm to the Q factor.

If you just want "plus" (~3") tires, you should not have any problems finding normal Q factor mountain bike cranks that will work. If you are pushing into the big plus/small fatbike sizes, things get tricky.

-Walt
 
#17 ·
Walt said:
The limiting factor is the chain.

With a 73mm BB (Q factors vary a bit, obviously), the widest available chainline (assuming a single ring drivetrain) is about 58mm. That works pretty well with a 157x12 rear end, or an offset 148, assuming you want to run gears. For IGH or SS, you can do a narrower/non-offset rear.
Click to expand...
With the new splined driver the standard chainline for Rohloff is now 57mm. There is a narrower splined driver available which gives 55mm, but is limited to cogs with 15+ teeth. Older cogs were 54mm. Shimano chainline is somewhat narrower, IIRC about 42 or 48mm depending on which way the cog faces.

Max tire size ends up around 90mm assuming you want at least 2-3mm of space for the chain when in your lowest gear. You could push that a tiny bit with a SS or IGH setup, but not a lot.

As you might expect, if you go to an 83mm BB, you gain (wait for it!) about 10mm of space for a bigger tire, and you add about 10mm to the Q factor.

If you just want "plus" (~3") tires, you should not have any problems finding normal Q factor mountain bike cranks that will work. If you are pushing into the big plus/small fatbike sizes, things get tricky.
Click to expand...
Unfortunately that's the area I'm about to occupy... :madman:
 
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