Q Factor, quack quack..

[lensmansteve]

There ya go then. It ain't all in the clouds of theory, is it? But we do adapt to things, even if they're a bit wrong for us. But when we put them right..
Like the Terry Pratchett quote, btw.

 

[lensmansteve]

Hmm, thought there'd be a few more responses. Strange how some people ate very fussy about handlebar width, but don't know/don't care about how far apart their feet are positioned. Maybe it's because they just accept what they've got. Changing bars is really easy and relatively cheap compared to changing cranks and bb's and keeping a decent chainline.
The anklebone's connected to the shinbone, shinbone's connected to the kneebone, etc. We owe it to our legs to have them working at their best. Especially when they're old.

 

[2manyoranges]

Re:

LMS - you are right on the button.

I care a lot about Q. And I got shouted at a bit here for going on a bit about it. But it's neglected, and can have a big (positive or negative) impact on your body. If you relax, and sit with your legs hanging naturally from a chair, that gives a rough idea of the best Q. Anything else loads your knees up with odd forces when you pedal. This can damage cartilage and 'set' your knees in the wrong position over time as the body adapts - something which also is affected by saddle height, of course. But get the height bang on, and Q can still be a problem. Many bikes with square taper BBS had the wrong length axle installed - usually too wide. This gives a Q which is too big, and you can tell by there being a silly amounts of crank arm clearance either side re the chain stays. I have gone down as far as 104 on a single speed, in a 68 BB. And this was for a very young rider, who needed a low Q, and needed his growing knees looked after. Worked brilliantly.

It's neglected.
There's not much to do about it now we have HollowTech.
It's not trivial.
Getting it wrong can have long term health effects.
Pedal design can affect practical Q.
Crank arm design can affect Q.

Alongside Q...
Crank length is important - we run much shorter cranks than we did a decade ago. !65 on my Sentinel 29er.
Saddle height is important.

 

[lensmansteve]

Music to these lugholes, Not Enough Oranges.. I can only add that the more you cycle, the more important Q is. Anyone can get a fat bike with a Q of 200mm+ down to the corner shop (and probably back again), but even moderate hundred milers are something else. (I used to do the CTC Standard Rides with the Burnley group when I lived up there).
Pedal long and prosper.

 

[hamster]

I agree, it's not something I bothered with in the past. Having swapped to Campag Chorus cranks a few years ago on the road bike and instantly things felt more 'right' : it was down to narrow Q cranks. Since then I've gone as close as possible on my tourer and even the singlespeed (using square taper allows much more choice of Q).

I am absolutely a believer in getting the right crank length. While the leg length part is clear, there is a second factor of shin/thigh length ratio which I have never seen covered. My wife has short shins and seems quite comfortable on relatively long cranks. As it's all about knee flexion that would make sense.

 

[Woz]

Well here goes....

The only reason I'm a BB Nazi is actually Q-factor. Honestly, in the most part sod the worry about the chain-line being bang on to the Shimano ever changing bull-shit specifications - chains are flexible!.

Even for SS / Fixed the same applies for me, I will re-dish the rear wheel and play with the axle. etc.

What I am particular about is not only the Q-factor, but also equidistant spacing. ie. the cranks are centered. Here you are at the mercy of all sorts of crank types and profiles. There really is some utter dross out there and manufacturers and even so called qualified bike mechanics can produce some abhorrent set-ups.

You only need to look into some Shimano specs. to realise they actually don't care about it much, unless you do your research and go up to at least LX, XT, XTR level. After years of fiddling, I've pretty much settled on one BB width and one crank, and one crank length and a Q-factor of 160 - 165mm on all bikes road, MTB, errand bike you name it.

Going from one bike to another never feels weird, and it leaves you to concentrate on feeling other aspects of the
bike and riding. I'm also careful about buying frames with too wide chain stays - not only where the crank arms
could potentially touch, but also the shoe heels towards the rear.

Pretty much anything pre-Octalink times I reckon is still the best period to find something suitable. I'll dig in my
archives to find some Q-factor specs. - I have my own cribsheet with a number of suitable cranks with actual values.

Finally, it is an individual thing, and it's no use preaching what you perceive is right and wrong to others - some people are simply not sensitive (or believe so at least) to the bio-mechanics of cycling.

 

[legrandefromage]

I think you lot would weep quality machine oil over my bikes.

I didnt give a stuff about Q factor but I may have inadvertently done so by making sure my chainline is near perfect and arms are equidistant from the stays.

 

[lensmansteve]

Well thanks all, you've made this happy man very old, or vice versa, or something.
Careful LGF, I started out like you before falling into a heavy Q habit. It's noticing how nice to pedal one bike feels compared to others that did it. Not to worry, you turn over so many bikes you're sure to own a few that are just perfect for you. Without extra work.
Anyway, right at the start I confessed my wacky collection of velocipedes range over about 20mm in the Q dept. So much for perfect..

 

[lensmansteve]

Well here goes....

The only reason I'm a BB Nazi is actually Q-factor. Honestly, in the most part sod the worry about the chain-line being bang on to the Shimano ever changing bull-shit specifications - chains are flexible!.

Even for SS / Fixed the same applies for me, I will re-dish the rear wheel and play with the axle. etc.

What I am particular about is not only the Q-factor, but also equidistant spacing. ie. the cranks are centered. Here you are at the mercy of all sorts of crank types and profiles. There really is some utter dross out there and manufacturers and even so called qualified bike mechanics can produce some abhorrent set-ups.

You only need to look into some Shimano specs. to realise they actually don't care about it much, unless you do your research and go up to at least LX, XT, XTR level. After years of fiddling, I've pretty much settled on one BB width and one crank, and one crank length and a Q-factor of 160 - 165mm..

Yes, there's much here that I agree with. About standardising on the bb, for starters. 110mm is mine. Thing is, my cranks are mostly early 90's, M550 etc, and they had 122mm fitted from new. Yes, chainline moves "in", ie towards the low gears- but that's win-win for me, because I'd rather line up my middle ring with a 21 or 24, because they're the gears I use most, and also push the hardest. This may not work for everyone, but it sure works for me. The granny (grandad?) ring also gets closer to the big sprockets, that's ideal.
And I'm disappointed that the newer cheaper Shimano cranks have such a big Q. And I don't think they care much either. Why should they, they're the one big pike left in the pond.

 

[bjellys]

Sorry lads but I think you all have locked in syndrome. My heads hurting just reading this I'm going to lay down in a dakened room now!
Only joking I can only wait with anticipation for the next episode in this saga I'll get the wife to order more paracetamol I think I might need it.