Q-Factor and Bike Fit : The Basics and what you need to know

Q-factor is one of those metrics on the bike that people aren't sure what to do with. It's poorly understood, can be difficult to change, and is dependent on what type of frame, crankset, and pedal you have.

At one time, it was thought that narrower was always better, but it turned out that wider q-factors are fine for many people. Which is good because there are more bikes than ever being made with wider q-factors.

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[dan]

Firstly I am 72 yo and wider than average build and need 46 cm c-c bars, 110 kg, carrying lots of injuries (Rugby and bike crashes) and OA. Suffered lateral patella knee pain, no patella lateral cartilage. Added 20 mm extensions to each pedals and lateral patella pain subsided. Lateral patella pain is also helped by riding more often out of the saddle, which is more difficult due to dropped foot due to ankle surgery. Still occasionally manage 50 km in two hours .

[neTwo]

Fatbikes saved me big time when they came out... I had always struggled with knee and foot issues no matter what bike I had. When I got my first fat bike the wide Q-factor totally solved my issues, now I run pedal extenders on all my other bikes.

[andymcdermott]

Definitely a helpful video for those of us trying to diagnose knee pain; coming from a touring/MTB/flat pedal background and moving in to a new CX/road bike, I've found myself with a lot of inner knee pain on a single side. Trying to address this knee pain without breaking the bank, traveling to find a true bike fitter (vs the classic "fistfull of seat post, and fistfull of stem, ") or putting in undue labor is a tricky. After moving my cleats inboard of the shoes and still finding pain, it sounds like I should look in to pedal extenders next.

Thanks man!

[pumajpuma]

Finally, I understand the variables to the "Q" and how that could affect my cycling over the long ride and performance.

[perestroika]

I am fairly short at 5' 4" and walk slightly duck-footed. I recently bought a fat bike for the winter. I regularly ride road and a summer mountain bike. I can honestly say it's the first time I noticed q factor, with a 100mm bb shell it's quite significant. I initially had strange pains on my back, tops of my knees and ankles. I have ridden spd's for the past 10 years also. Oh a whim, I switched to flats and lowered the seat slightly, and the pain gradually disappeared. I feel great on the bike. I feel like I have greatly changed my pedaling style too, with much more emphasis on my calves. When I got back on my road bike, the saddle seemed way to high. Thanks for the videos, you earned a subscriber today!

[craigwilson]

The step by step history was well done, thanks. It does make sense that ideal Q would be somewhat related to hip width/range of motion so unusual that there isn't much out there on it as an element of bike fit. Will be interesting to know what you find out from that study. Would it stand to reason that it may be more critical for shorter legged riders as any change in Q would result in greater change of lateral angle at the hip?

I was a little worried that putting a MTB double on my do-it-all bike would cause discomfort over longer distances, but it has proved fine even over a hilly 200K. With the right insoles I got great knee tracking in my bike fit, and if anything it has made me realise that my fixed gear having much narrower Q is perhaps the reason for some of the issues I feel riding it for longer distances... especially as it requires more exaggerated out-of-the-saddle riding for steeper climbs.

[edwardleibnitz]

I started riding a recumbent about 2.5 yrs ago which affords me the opportunity to watch my pedaling regardless of whether I want to or not :). When I wanted to go for a low chainring of 22 the only convenient option was a Shimano Mountain triple since I have a older square taper bb - this requires me to have a 180 mm Q-factor. I'm 5' 6" medium build and I said to myself "wow my legs are really wide apart" with no ability to stand out of the saddle. Also I noticed my knees were "popping out" at the top of the stroke. I lied down on my floor one evening and looked at my feet as they were spread to the stance of the pedals and set the cleats "heeled-in" and this fixed EVERYTHING! Even a teeny-tiny sensation in the back of one knee that I often wondered the cause -just completely disappeared.

[Fidasaind]

My LBS fitter has done quite a few small tweaks with me the last couple of years. One that was pretty painful was I'd get inner quad pain on my right leg only on rides at higher intensities (usually while climbing). At first the shop put a couple spacers in my pedal and that helped a bit. Then when Shimano released the wider Ultegra pedals, I switched to those and put the spacers back in my right pedal (my right foot is very toe out and I walk on the inside due to what I can only assume was a very badly healed sprain as a kid). It really has helped relieve that pain. I will still sometimes feel that part of that quad heat up but it settles down after 10-20 minutes.

My wife on the other hand switched to Speedplays and one of the big reason was the narrow spindles. LBS had a pair of short spindle Speedplay Zeros lying around so the owner loaned them to her to try and eventually gave them to her. She is short and petite build and would get knee and hip pain. She's had a lot of issues fitting herself to her bike and both her and I think next time we may look at using a full fitting with one of the fitter bikes to figure out what would be a good setup before buying our next bikes. She's 5'2" and on a 50cm Trek Silque SLX. She's down to a 60cm stem, narrower bars, and shorter cranks. Seems like before looking at something like an Emonda next time, she's going to want to see if the 47cm would've been a better fit and if there are other frames that may make her happier.

[irkone]

i'm building a bike from scratch and actually discovering all those amazing parameters ! i have a BB68 BSA thread and i wonder if it is not more interesting to stay on a square axle instead of a hollowtech, meaning you can choose from 103 to 118 with the square so that it s easier to tune your chainline and q-factor ? any chance to have tuning width option with a hollowtech ?

[charles]

Thanks for the video. Q-factor is extremely important for my Brompton folding bike when I upgrade my crankset.

[thespiritofgrovel]

Another excellent video, thanks.

I've had anterior knee pain for the past two months brought on by riding and think it might be linked to Q factor. I'm fine off the bike including running and hiking with a pack, but riding can make it worse, and I've gone from 600 miles a month to about 100 (commuting only)! A few months ago I got a bike fit on my race bike, rode it for two weeks no problem at all, then started getting the knee pain. So I put it down to that, but the only differences made were very small adjustments to my cleats, wedges to correct valgus foot position, and putting my seat up a bit. I think the seat actually went too high so I've put it down a bit, but I don't think the bike fit is the main culprit, and instead it might be my commuting bike which I fiddled with at a very similar time (a mistake in hindsight). It changed from a 68 mm square taper bb to a Hollowtech II, and my stance width on that bike is now a bit wider, and I noticed my knees tracking inside my feet, which can't be good. This is exacerbated by me commuting in SPDs which offer little way to move the cleat across, while my road shoes on my race bike are set with the cleats (Look Keo) as far to the outside of the shoe as possible resulting in a quite narrow stance. If I measure the distance between the toe of each shoe when clipped into the pedals it's about 226 mm on the race bike, about 258 mm on the Boardman, which sounds like a huge difference. Could this be a factor in the knee pain do you think? Sorry for the essay!

[erklng]

Great topic — thanks for tackling it! I recently had an experience where I purchased a road disc frame with widely-spaced chainstays; I purchased Shimano pedals with +4mm axles to mitigate heel rub and immediately felt my perceived exertion skyrocket. My hips seemed to rest differently through the pedal stroke and I felt different on the same saddle with all contact points duplicated from my prior bike.

I also came from a 1st-gen BB30/Hollowgram system, to BB86+ultegra 6800 road double. I have a sneaky suspicion this added an additional 5-6mm q alongside the pedal spindles but I never took a measurement. (I wish there was a dynamic spreadsheet somewhere that combined popular bottom brackets, cranks and pedals to give you an ultimate stance or q width.)

I'm sure I would have adapted to this setup, especially since people jump between their mtbs and road bikes with varying q all the time. But it made me realize that (at least for me) a moderate change in q can be felt.

[itsallspent]

I added pedal extenders because I am knocked kneed and I have wide feet. the extenders help me keep a pedal stroke that uses the inside of my foot rather than the outside. I also use flat pedals to keep my foot from rotating outwards.

[dan]

I am a wide build 46 cm c-c bars. Lateral patella pain, 20 mm pedal spindle extensions no more patella pain.

[TheNosarajr]

I installed pedal extenders, I feel happy with them so far.

[driver]

Is there a bike fit expert with anywhere near your expertise around Houston you could recommend? Thanks a million, Scott

[feltusfeicit]

Surely the "ideal" Q factor is an anthropometric function based on the median of the hip joint, letting. The foot move perfectly inline with the hip Pivot point, no? I know this is not necessarily how most of us walk, but it is a mechanical option on a bicycle.

I just had a wee hunt, and anthropometric hip joint dimensions are not easy to find.

Incidentally, Issi (via QBP, USA) has 3 spindle lengths for some of their pedals, both 2 and 3 bolt cleat.

[tacituskilgore]

I recently got a Trek gravel bike and developed knee discomfort over time. It wasn’t until I saw this video that I realised the Q factor was 20mm narrower than the two road bikes I’ve ridden for years! I’ve ordered some pedal extenders to see if that will resolve the problem.

[markmiller]

Appreciate the explanations! Thanks so much. So, I kinda think of Q-factor like _stance_ when I am doing squats. Too wide (with feet parallel) is hard on knees and hips...too narrow and its kinda like doing narrow grip press; strength isn't as good and harder to balance. So, I've gotta believe there *is* an optimum in there somewhere but I'd bet its a pretty flat curve pretty tolerant to tens of milimeters variation either direction.

[TheCrawler]

I prefer a narrower Q-factor coming from a road/touring background. When I built my monster cross bike some 8 yrs. ago, this was the first time with a wider frame and with the Hollowtech crank set and external bearings. As designed, that would set me up with about 177.5mm Q-factor. I narrowed the BB down to 170mm and that works much better (triple crank):
For some time, I ran with the cranks slightly offset (left side wider by 2.5mm) and found I was getting some left knee pain after a ride. When I narrowed the crank and got the cranks symmetrical, that left knee pain vanished. So yes, it's well worth experimenting with Q-factor.