Q Factor, quack quack..

[lensmansteve]

Now then, I notice there's lots of threads relating to our bikes' drivetrains- mostly bottom bracket lengths and chainlines, but Q factors don't get mentioned much. To clarify, "Q Factor" is a pseudo-tech term apparently coined by Grant Peterson, who worked for Bridgestone. It stands for "Quack Factor", because a duck waddles. Much hilarity. It simply means the distance between the outer crank faces, or more correctly, the planes they rotate in. Pause for breath.
My bikes vary by 20mm or so. Shimano have been steadily increasing the Q, probably in response to wider chainstays- fatter tyres, wider back hubs, etc. When I bought my first 4-arm cranks (Alivio) I was a bit taken aback by their Q. I thought at first they needed a very short bb. But no- get the chainline right and the Q is still big, compared to the 80's cranks I already had.
So, finally, I get to the big questions. Does anyone care about this? Has anyone got a preference for narrow or wide? Has anyone had ankle/knee/hip problems related to this? Would like to know. Birmingham Uni published a paper on this. Inconclusive on several counts, including differences in power output.

 

[onegoodbike]

Re:

I too would be interested in hearing peoples opinions on this subject.

I've recently dithered over buying a new road bike chainset because the q factor was 165mm, which is around 18-20mm wider than my current Shimano and Rotor examples.

When trying to convince myself to pull the trigger on them I read a fair few articles on the interweb, none of which really helped me decide one way or the other, as some say it's an issue and other say you'll not notice it!.


Matt

 

[lensmansteve]

I think it's important to how a bike "fits". But humans are adaptable animals, and within limits think it's a variable. FWIW, my stable's widest Q is 175mm. I prefer narrower generally, but can live with that. Fat bikes are a no-no for me, like pedalling a horse.

 

[Retro Spud]

Never thought about it before, but then this is a retro forum and my newest most modern bike harks from around 1998/99


Phat bikes are just wrong and should be melted down along with their owners

 

[lensmansteve]

Well there you go, Spud- every bike ever built has a Q, and they seem to be getting bigger. Even Matt's road bikes. But is that entirely a good thing?
Don't mind fat bikes, just be glad you don't have to ride one.

 

[mattr]

It sits in exactly the same place as crank length.
Some people are completely unaffected by it and can ride any size, others have very specific needs.

Getting it wrong (for your morphology) could ether be slightly annoying, or leave you off the bike for weeks.....

And as with crank lengths, there are no hard and fast rules, just suck it and see.

 

[lensmansteve]

Fair comment Matt. What I'd add on the Q thing is that the distance your pedals are from the centre line of the bike affects the way the bike feels when you're throwing it into tight turns, or honking, or sprinting. It's all weight transfer. Just watch the sprinters, they're not swaying for the cameras or to baulk other riders (Ahem..) they're laying as much power down through the pedals as they possibly can. Very different cycling to ambling along. Big Q=more sway. That's physics. I wonder if that's why roadies favour low Q's.

 

[mk one]

Personally no, been riding mtb's for 30 years and other bikes for another 20 before that, never had any issues regarding enjoyment from not knowing. Though there lies my reason, enjoyment, i should imagine in a competitive cyclist every possible aspect should be explored.

 

[lensmansteve]

Yeah, I cycle with joy in my heart too- I'm not thinking "Wonder if I've got the Q right on this one" as I pootle along. I've had 60+ years "in the saddle", btw, and the older I get, the more interested I get- in everything, but bikes are special to me. Sorry if you think I'm just trying to complicate things, it's quite the reverse.. Here's a recent (c1957) pic of me on my Prestige- framed trike. I have no clue what the Q was on that.

 

[Splatter Paint]

Re:

I’ve been using a triple on my road bike for the last 12 years. I switched to a double a fortnight ago and instantly noticed the narrower stance. It instantly felt more comfortable.

SP