kimosynthesis

First post, and thanks for the feedback. Also, apologies for the lack of links, but I have to post 10 times before adding links, apparently.

I am looking to narrow my stance-width (long story) and I am finding it tricky to go narrower than 146mm, my current cranks: FSA SL-K Modular Adventure BB386EVO Crankset. I have an external BSA type BB (68mm) and one thought was to go back to an ISIS BB and run, say, a 108mm width and a get a new crankset to suit. My frame has about 5mm to play with before the crank arms get too close to the chain stays.

Oh, I should say that I have gone down the route of shorter spindled pedals, but this is not an ideal change. Also, it's not ideal to run my shoes so close to the crank arms because my shoes rub past the crank arms. Not helpful for centred cleat placement either. Anyway, I guess the question is how much can I expect to reduce q-factor by switching out to an ISIS BB? I understand that cranks vary in their q-factor, regardless of other factors. I guess I could take out a second mortgage to get a set of QRC-2's, but let's kick that down the trail for now.

Road Fan

Ok, I think narrowing q-factor is nicer for riding, so I agree with your goal. On older bikes and BB styles (square taper, cartridge or cup and spindle) I've played with this with some good success. In addition to low Q-factor, I like to have the left and right Q-factors equal. It might just be my imagination, but I do like it better when I'm all in balance.

I stick to a few points:
1. keep the front chainline equal to the rear chainline.
2. set the rear chainline based on the distance from center of the cassette gear stack to the center of the bicycle not the distance from stack-center to the dropout inner face. This is adjusted by proper installation of the cassette on the hub and by proper spacers on the left and right stubs of the rear axle. Sounds like you ride carbon or aluminum, so whatever adjusting you do should not involve cold-setting or otherwise re-shaping the frame.
3. Once you have a BB setup that achieves this goal on the drive side, check the clearances of the D/S crank arm, chainring bolts/heads, and chainrings themselves to the D/S chainstay.
4. Once you have the D/S chainstay clearances as small as practical and front chainline matching the rear, compare the distance from the D/S crank arm end to its chainstay to the similar dimension on the non-D/S arm. At least with square taper, you can control this by choice of spindle, either cartridge or not. For some old-school chainsets equal lateral spacing needs spindles which are the same left and right and in some cases not. You just have to measure.

If you have good and matching rotating clearances, the chainlines are close enough to give you consistent shifting without the chain running off the teeth, and with the front mech tracking across the chainrings full-range and stopping where you need it to, that's about as good as I can get it.

For a modern chainset if the bearings are installed correctly, there is not as much freedom to adjust as with the older BB styles.

Best I have made is my Trek 610, on which I put a 1995 or so first-generation Campagnolo Chorus double, 53/39, original chainrings. For this one Campy did their homework, since the recommended Campagnolo 111 mm Asymmetrical BB (the Campy 115.5 mm is for triples) was a perfect fit to the frame and everything I'm talking about lined up perfectly - no rotating interference, Q a little under 140 mm, and excellent shifting with the frame aligned well. The bike came with a 1984 Shimano 600EX 6207, which could not be made better than Q=about 150 mm with the original Shimano BB parts, without compromising the chainlines. The big difference in these is that the curved Shimano arms themselves move the pedals away from the bicycle centerline, and the Campagnolo ones are less-contoured. Also the Campy arm is thinner, and the "socket" into which the Campagnolo square taper "plugs" is deeper relative to the shapes of the crankarms are very different for the two designs, and how deeply the square taper sticks into the crank arms relative to where the pedal seats on the arm.

I'm trying to get around 135 mm on a vintage 1952 Rudge road bike, using an early TA 5-pin chainset with a single chainring.

kimosynthesis

Thanks for all that! Much to consider, for sure. Sounding like you're recommending square taper for the flexiblity. Some great approches in there. It would be great if the industry made some wider range of options for us skinny-hipped folks out there.

Iride01 

I don't know that you ever said what the issue is that you believe you'll solve with less Q.

I'm not sure what skinny-hipped folks are. Nor am I aware of any particular problem related to Q that might be for a group that claims to be skinny-hipped.

Road Fan

Look into more recent Campagnolo chainsets. They have Q-factor specs printed on the crankarms, and they don't all cost kilobucks. Campy at least has grasped the challenge for low Q.

As far as DIY, yes, I think square taper lets you make the most of the available parts. But Campy modern sets may let you find an affordable part which just works. Worth an investigation, in my opinion!

kimosynthesis

Cheers for that. Good thinking. I did some digging, and from what I have found, Campag cranksets all seem to sit at 145.5mm, and my current crankset is 146mm. So, not much gain. I would have loved it if that could have offered options, as I have enjoyed riding Campag drivetrains in the past, cheap ones, mind, but pretty darn solid. The investigations continue...

Road Fan

Good question, but I can't answer it, though I like bikes with narrower stances. IMO that is enough reason. With Qfactor too wide I feel like I'm flailing my legs outwards, while with "good" Q I feel like I'm pedaling smoothly up and down. I can't better describe it even in subjective terms. The vew very old bikes I have seem to have very small Q-values. I think it was highly valued from perhaps the 1950s through maybe 1975 (just a guess?) I don't know why it was desired early, nor why it fell out of favor in later years.

Iride01 

When it was one cog on the back and one ring on the front, it was easy to make a low Q bike. With more cogs on the back, rings on the front and wider chain lines then Q has to get wider.

How much room do you currently have between the ends of your crank arms and the chain stays or any thing else on your bike? That's your limit for getting a smaller Q. And how little space do you want left between them?

Q seems to be something that many at some point or another in their learning about all things bicycle will focus on thinking it's a magical thing that must be important. I did that myself briefly when I was looking for my first new crank to install in my bike many years ago. However, without having an issue resulting from Q, I didn't know what I was going to solve. So now it's not a big deal.

I do agree there is a point where there might be too much Q, but I don't seem to have ever found that yet on any bike I've ridden.

79pmooney

Bicycle and parts manufactures have made many decisions that have been driving increasing Q-factors. Less dense frame materials, hence wider chainstays, Likewise fatter tires. BBs getting wider in effect. (Outboard bearings.) Dropout spacing, number of cogs and chainlines. Fatter FDs that require more crank clearance. And for ease of assembly, more generous clearances everywhere, especially curved cranks that miss everything by a cm or more. Symmetrical BBs that put the left crank much further out than it needs to be. (Some with curvature so they sit close to the BB shell so you cannot go to a shorter BB spindle.) These moves allow parts manufacturers to offer fewer options, make designing frames easier and allow features to be marketed. Everybody wins except those of us who have knees that cannot tolerate large Q-factors.

I rode the narrow, straight cranked bikes of the '70s and early '80s for years. Went to a SunTour triple crankset in the '90s. Curved and I didn't really like it but sucked it up. 2000s, had my ti custom built and put on a stock 105 Hollowtech crankset and BB. Beautiful, light ... and wide! Too wide. 5 years later I had a ti ultimate road fix gear built. Put on a straight velodrome drivetrain excerpt smallest 144 BCD chainring and up to the largest 1/8" cog. Knees love that bike! Even climbing on a 42-24; the lowest combo I've ever seen for stock 1/8th" parts. (Yeah I know, there probably is a 41 tooth chainring out there somewhere.)

Now that first ti bike has a mishmash crankset of old (probably SR) cranks, three different brand chainrings and a minimal length Phil Wood BB that knocks the Q down 2 cm. Knees love it. And for a different project, I made an 1/8" speed fix gear with three chainlines, cogs and chainrings that has barely more Q than my regular fix gears. (Set up on an old straight armed double crankset and Phil BB so narrow the inside chainring almost scrapes the chainstay. Third chainring sits outboard between the regular outboard ring and the crank. I can do this because I have no FD to worry about.)

Those projects were a lot of work but my knees love me for it. (40 years ago a doc set me straight on them. He said "Listen to them. If you don't it will be replacement time.")

I've been seeing recently that some of the top end cranksets are now talking low-Q Maybe I'm not the only one. Or maybe there are those who suspect that low-Q can add to performance. Maybe now I can get a modern 10, 11 or more speed bike with cranks my knees can live with.

Iride01 

Well I just checked on my Tarmac and the Ultegra R8000 cranks miss the chain by about 3 mm when it's in the 52-11 combo. Not sure I'd want less than the 146 mm Q that crank gives.

There are ways to get a significantly narrower Q. But not on that bike with that type drivetrain with that many cogs on the rear. At least not easily. Indeed, 12 speed Shimano will now take the cranks to a Q of 148mm.

ofajen

Yeah my main ride in the 70s through the early 90s was a road frame with first gen DA cranks. I think Q might have been as much as 130mm. Never thought about it until the MTB came along and i didn’t like how wide it felt.

At this point there are a lot of bikes I find interesting that I would never bother to ride because I know the Q factor is too wide. I don’t even know that it would cause injury, I simply don’t like it.

So, I’ll stick to frames that keep it reasonable and I set up the BB width to leave only 1 mm clearance on both sides if I can. Sometimes I have to space the BB with the same type of spacers used between cog cassettes.

Otto

Iride01 

I can't imagine not trying something simply because of imagined fear. Especially when so many others have no issue.

ofajen

If you are referring to me, it’s preference, not fear. I know I don’t like pedaling a wide crank. Been there, done that, don’t want to go back.

Otto

79pmooney

My knees tell me quite plainly what they do and do not like. Every bike I've had in the past 45 years (when my CP started) with a large Q has been an issue for them.

"Especially when so many others have no issue." I'd love to be one of those who came off the popular cookie cutter. Wouldn't have to seek out 180mm stems. Have access to shirts that fit in department stores. I've been hearing the words to the effect of "Suck it up and be like/do as everybody else" all my life.

ofajen

The good news is that sometimes you can change it. My old RockHopper MTB is set up SS and I installed SR road cranks that give me a Q-factor of 143mm, which feels great.

Otto

Iride01 

If it's strictly a personal preference I don't really have an issue. But if you are imagining bad and irreversible things will happen and were to ever use that as validity to tell someone not to try something, then I'd be against that.

No, I don't have any issue if your knees tell you it's too wide and you have correctly identified the cause. But Q is seldom an issue for most people, IMO.

Obviously if you've tried wider and found it doesn't work for you then my statement doesn't apply to you.

Here we have an OP that seems to be imagining bad things happening from the current Q given by todays cranks and not trying any bikes to see if that will even be an issue for them.

So though there are those people that do suffer from issues of Q, I don't think you are an overwhelming majority. So a person shouldn't just assume because some have an issue that they will too.

Carbonfiberboy 

I don't get it, either. If it were a knee issue, then I would think the ideal would be to have one's legs be either straight or at whatever natural angle they assume when standing on the ground, as seen from the front. That's simple to fix with cleat wedges. .Our hips are ball and socket, so they don't much care how far apart our feet are.

ofajen

There isn’t a lot of research on this, but what there is indicates it does matter.

https://www.tandfonline.com/doi/abs/...4.2020.1845440

This paper compared standard road Q-factor with several wider stances. The conclusion from the abstract:

”However, gross mechanical efficiency, cycling economy, and perceived comfort significantly improved while perceived exertion significantly reduced with the narrowest pedal spacing for the whole population, as well as for the narrow and wide pelvis groups. Therefore, the lowest medio-lateral distance between the feet seems more suitable for comfort and performance improvement, irrespective of the individual’s morphology.”

This older paper found that GME was increased for relatively narrow Qs of 90mm and 120mm compared to wider Qs.

https://onlinelibrary.wiley.com/doi/...8.2012.01479.x

Otto

Iride01 

But none found anything particularly bad for wider Q's.

No one ruined their joints and had life altering permanent pain. None had any harmful findings.

Road Fan

My Rudge is set up narrow with one rear sprocket, so like a track bike except it has its original Sturmey-Archer AW and steel cottered single chainset. I'm looking to match that narrow Q with a TA 5-pin single. I think I need to go to the Blackbirds site to read up about TA track solutions. The 5-pin might not be the best solution for me. I'd love to try a cotter-pin Campagnolo Gran Sport, or maybe a 3 arm TA pista.

Carbonfiberboy 

I've done quite a bit of experimenting with this while doing another activity, backpacking, which puts a much heavier load on everything below the shoulders. I go in with about 60#. I've tried many variations, from Indian fashion, feet right in front of each other, to variations on wider stances. I've concluded that there's no practical difference in performance - it's just what one gets used to doing, training IOW, like most of this sort of position thing in cycling. Note that the pros ride whatever they're given by their sponsor, just fine. There are a few who ride rebranded bikes but the same drivetrain. That's very rare and Q is not an issue. The reason that it's not is that the cranks have to clear the chain stays. Standard road Q is 150mm. 90m and 120mm road Q is non-existent. One can get narrower with SS and fixed. I like cranks which clear my ankle bones - I already wear all the coating off my cranks with my booties in the cold or rain.

unterhausen

I used to think that I wanted low Q, but now I'm not so sure. But I've really never tried to get it, I'm just basing this on the fact that wider Q doesn't seem to slow me down at all. I have a mtb crank on my gravel bike that has been used on some long rides without issue, so I'm starting to think it doesn't really matter to me much.

I thought I had recently seen that older folk do better with wider q. Anyone see that?

ofajen

Some fairly apt discussion of Q factor quoted from the Rivbike website:

”In any case, Q varies from about 135 to 180, with most good road double cranks hovering around 140mm, and most mountain bike cranks around 173mm.With the exception of Ritchey, crank makers do not list Q. Most make high-Q cranks, and would prefer that you not ask. There can be no arguing that a lower Q improves aerodynamics, but a far more compelling and practical reason for attending to your crank's Q is...how it feels.

Some riders are not sensitive to it at all. Others have physiological quirks that make them better off with their feet closer together (low-Q) or farther apart (high-Q) cranks. In general, road riders accustomed to the superb, low-Q professional grade Campy, Zeus, TA, and Stronglight cranks have a harder time adapting to modern cranks with higher Qs. They often hate them, and don't even realize what it is until somebody suggests the Q. On the other hand, riders raised on higher Q cranks often think the whole issue is silly, because they can't tell any difference.

If you're used to a low Q crank and you pedal a bike with a high Q, it's possible that you'll experience pain on the inside of your knees.”

I seem to fall into that category of long-time road riders accustomed over many decades to low-Q cranks who just can’t warm up to wider cranks.

Otto