Q factor

[stackie]

So, a recent thread brings up the subject of q-factor. Now, it seems to me that the old school thought, before the wisdom of the internet came in play, was that the lower the q the better. So, me, being the good little grasshopper, always slammed my cleats as far lateral on the shoe as possible to bring my feet as close together as possible on any given crankset. Seemed ok.

Well, last summer, I got a bike fit from John Howard. He saw me cleat position and asked, "Why?" Well, I spouted off my old school wisdom of better aerodymanics. He said, that doesn't make much sense if you don't have good power transfer. So, he returned my cleats to midline and tweaked them back a bit also. You know what, I subjectively feel like it's a better "power platform" ( I made that up :)). Sure, half of the stuff John did to my bike I put right back after a couple of rides. But, the cleat position i like.

That little anecdote now on the table, I must ask... Should q-factor be any significant consideration in choosing a crankset? Obvioulsy, there must be some relation to body proportion, in particular, pelvic width. But, assuming you don't have a ridiculoulsy narrow pelvis, why do we care? Should we? At what point should we care? When we get into the triple crankset range?

Jon

[Charles M]

It maters like any other fitting things matter. And like other things in fit it's relative to other things going on.

making generalizations is, eh, generally wrong...

[Ken Robb]

one way to get a quick idea of what Q is best for you is to ride a bike with flat pedals and smooth rubber-soled shoes like Topsiders or tennis shoes that will let your feet move around on the pedals while preventing slipping. You can easily move your feet side to side and up and back while pedaling to see what feels best to you. If you're like me you may prefer one position for climbing/heavy effort and another for spinning. No problem on flat pedals but if you want to clip in a compromise position may be required.

[Marcusaurelius]

I never believed in that nonsense about a crank with low q factor being better. Cranks with a higher or average q factor works well for me. The low q factor cranks never seem to work.

[Tobias]

That little anecdote now on the table, I must ask... Should q-factor be any significant consideration in choosing a crankset? Obvioulsy, there must be some relation to body proportion, in particular, pelvic width. But, assuming you don't have a ridiculoulsy narrow pelvis, why do we care? Should we? At what point should we care? When we get into the triple crankset range?
Jon, unless I’m missing something in translation, what he adjusted didn’t change the Q-factor of the cranks at all. He moved your feet further apart by moving the cleats to the middle, but that’s not the same, is it? To know for sure you'd have to try wide Q cranks with proper cleat location.

What you “subjectively” feel as improved could be mostly the cleats being positioned correctly, and not having your feet further apart. Placing the cleats off-center by a significant amount in order to move feet closer together may produce a rotating moment (depending on cleat type) the legs have to resist. That can’t seem natural if it occurs.

To your direct question, I don’t have a problem with triple Q-factors. I’ve thought of modifying one of my triples to include the shorter BBKT so it will be the same Q as a double, but haven’t gotten around to testing it yet because I probably will need a different front derailleur. It’s also not a high priority because when I switch from a double to triple and back it doesn’t seem to make much difference.

[stackie]

Tobias,

You may be right about the moment arm of moving the cleats far laterally. I presumed that it was all about how far the feet were apart, but certainly there exists the potential for some play in the cleat pedal interface if the power applied to the pedal is not inline with the center of the pedal. That may well have been the difference that I noted. Honestly, it never bothered me before. It was only after it had been changed that I noticed the change was better.

Thanks,

Jon

[Dave]

The most common complaint I've read is folks encountering knee pain when they ride a bike with a wider tread width (I hate the term Q-factor). It does not bother me. I've switched back and forth from a double to a triple with a 10mm wider tread width and had no problems.

Moving the cleats to spread the feet wider apart may not be exactly the same as using a crank with a wider tread width, but is it much the same. I always ask people who whine about needing a narrow tread width if they also have their cleats positioned to place their feet as close to the crankarms as possible, since their complaint is usually that the wider placement of the feet is causing knee pain.

I also suggest that the complaining person check out his foot alignment. I see a lot of people riding with foot alignment so bad that it's obvious after riding behind them for only a minute. Forefoot varus is the most common problem - the outside of the forefoot tilts downward.

As best I can tell, I have the opposite problem (forefoot valgus), but only with my left foot. I use one Lemond wedge with the thick side at the outside of the left cleat. Before I did that, I wore grooves in the spindle of my left speedplay pedal, because that foot was misaligned.

[bzbvh5]

I saw a program where the Lance Armstrong team Discovery did about a million dollars worth of testing and research trying to make the bottom bracket narrower so the cranks could be closer together thus that aero dynamic thing. They found it to be a waste of money because it worked best with the way the frames were made stock from the factory.

[Dave]

I can't imagine why bringing the feet closer together would improve aerodynamics. To do that, the frontal area must be reduced. The feet would not be hiding behind anything; they'd still be fully exposed to the wind.

[MRB]

If I do long rides (100 miles or more) with a "wider" crank, then I generally have a little pain in one of my hips the next day or two. This is probably because I have a little arthritus in my hips for playing Hockey, etc, or perhaps my hips are a little narrow.

When I ride my bike equipped with an Ultegra 6500 Triple crank, which has a large Q factor, on long rides, I feel it in my hips a day or so later. When I ride my bike with my DA 7410 or my Campy Record cranks, which have very low Q factor, I get zero hip pain no matter how long the ride is. I use the same pedals and shoes so the cleat position is consitent.

I bought the triple for comfort on long rides, but do not use it on long rides, because of the lingering discomfort. This is just my experience.

[RPS]

I can't imagine why bringing the feet closer together would improve aerodynamics. To do that, the frontal area must be reduced. The feet would not be hiding behind anything; they'd still be fully exposed to the wind.
That is not correct Dave; to improve aerodynamics frontal area does not have to be reduced.

While bringing the feet closer together probably doesn’t reduce frontal area, nor does it reduce dynamic pressure for a given bike speed, it “can” decrease the coefficient of drag. In theory anyway. ;)

In that sense I can easily see how bringing the feet (and more importantly the lower legs) closer together could indeed reduce overall drag, and hence reduce power requirement. Granted it would be by an incredibly small amount if at all.

[bironi]

It depends on your body. I like a very tight q-factor. My buddy who is about my size, but much more muscular likes a wide q-factor. We swap bikes occasionally, and we both feel uncomfortable. I find that I get better climbing power with my knees very close to the top tube, and I spin better in the same position. It's all personal preference for your body configuration. We're all different. :beer:

I ride an old pro strada, a pista, and a Mavic starfish crank. All of these have low q-factors, but the Mavic is the lowest.

[Dave]

Granted it would be by an incredibly small amount if at all.

So, a post about nothing.

[Tobias]

So, a post about nothing.
This is not Seinfeld. Getting fundamental principles correct is quite important in my opinion; particularly when we have non-technical guys reading this forum. Frontal area is just one of many parameters that influence aerodynamic drag.

Otherwise it would be easy to mislead some non-tech guy and have him not understand how placing a bottle on the seat tube, which normally adds frontal area, can reduce overall drag.

Lighten up guys. I for one don’t mind when someone corrects me when I make a mistake …. not that I ever do. :rolleyes:

[Mike748]

And don't forget that drag increases with the square of velocity. My solution is to go slower.

[Sheldon4209]

My last two mountain bikes (wider Q) always gave me some left knee pain. I thought that it was the 175 mm cranks so I replaced the 175 cranks with 170 mm cranks. The knee pain is still there and it must be the wider Q. I found the same think when riding a tandem with a wider Q because of a 160 mm rear drop out spacing as compared to a narrower Q with a 145 mm spacing.

[RPS]

My last two mountain bikes (wider Q) always gave me some left knee pain. I thought that it was the 175 mm cranks so I replaced the 175 cranks with 170 mm cranks. The knee pain is still there and it must be the wider Q. I found the same think when riding a tandem with a wider Q because of a 160 mm rear drop out spacing as compared to a narrower Q with a 145 mm spacing.
When the OP asked whether Q-factor should influence consideration for cranksets, it reminded me that it can also affect consideration for the bike itself if taken to an extreme.

It’s interesting you mention a tandem with 160 MM rear wheel spacing because that influenced my decision away from buying a Santana and going with a custom Co-Motion years ago. As I recall the 160 MM rear spacing required a custom extra-wide bottom bracket to correct the chainline, which when combined with a triple crankset (common on tandems) made for an unusually wide Q. By going custom I used standard components instead to keep function within normal range.

The biggest problem for me is not giving myself enough time to adapt to change. I expect that’s also the case for many riders. I can imagine that if a rider mainly rides a double for years and suddenly jumps on a tandem or other bike with an extra wide setup it could cause problems; particularly if ridden on a long ride and/or at high intensity. I also think the opposite may be true. It would not surprise me if some stokers who only ride wide Santanas may suffer hip or knee discomfort if they suddenly start riding narrow cranks on long rides. I’ve noticed that as I get older I need a little extra time to adapt to significant change, but fortunately the difference between double and triple cranks isn’t one yet.

[Charles M]

It depends on your body

it can also affect consideration for the bike itself if taken to an extreme.

:hello:

Right back to the start.

Q factor is a fit thing...



Suggesting narrower is better for Q factor is the same as suggesting narrower bars are "better" or a longer stem is "better" or cleats for or aft or saddle should be set back further are "better".


Different people will attach to different bikes in different ways.

[Sheldon4209]

The biggest problem for me is not giving myself enough time to adapt to change. I expect that’s also the case for many riders. I can imagine that if a rider mainly rides a double for years and suddenly jumps on a tandem or other bike with an extra wide setup it could cause problems; particularly if ridden on a long ride and/or at high intensity. I also think the opposite may be true. It would not surprise me if some stokers who only ride wide Santanas may suffer hip or knee discomfort if they suddenly start riding narrow cranks on long rides. I’ve noticed that as I get older I need a little extra time to adapt to significant change, but fortunately the difference between double and triple cranks isn’t one yet.[/QUOTE]

Last winter I bought an 08 closeout Santana and put 1100 miles on it this spring. I normally ride a Co-Motion 4 - 5 K a year. As I rode the Santana my left knee started bothering me and got worse with more miles. For this reason and a couple of other reasons I sold the Santana this fall.

I have wondered if there would be any stretches that I could do to ride the wider Q bikes.

[Mike748]

To reinforce what Pez said, everyone is different, or at least I am. I prefer a wider Q. It took me a while to figure out that was why I was more comfortable in the knees on my MTB and with a triple. The 160ish of a Campy triple is much better for me than the 140ish of a double.