Jean_TX

This isn't true based on my experience. I have a bad knee and am very sensitive to a bike's Q-factor. Out of necessity, I replaced the longish axle on my 7-speed Klein Pinnacle mountain bike (which has pressed-in sealed cartridge bearings for the "bottom bracket"). I also replaced the bottom bracket on an old 7-speed Diamondback road bike (which has a standard Shimano bottom bracket). In both cases the change brought each crank arm inward and made them symmetric with respect to the bottom bracket, while still clearing the stays with room to spare. Also, in both cases the chainline was improved.

Doge

That is what it says. I did request the article.

Some things like rolling resistance, aero etc there are lots of tests on and when I read them, while the main point, I generally agree with the details are often neglected. There is not enough here to convince me of anything yet. Is this ONE Q test on a UCI moving bike or a stationary one for example? The upper body, rocking, turning, correcting for wind etc. all requires rider energy and affect speed. Power is just one, a major one, of the going fast components, and comes at a cost. I figure cadence and pedaling style have a lot to do with that too. Circle high rev pedaling vs stomping combined with Q affect bike movement. So what else are they looking at, or forgetting? I don't know, which is why I asked for the article.

I pointed out my pet peeve in saying approximately <a range>. As that is an academic paper, not a forum post, it lost some of it credibility right there.

They also compare a range with a range. I'd like to see 130 vs 145. Something real for a road bike that a rider might achieve with standard parts.

Testing 120 too. This would require retooling, that could be achieved using a 1X (track like) and tri-spoke rear and thinner rear spacing.

Doge

Yes. I linked to it.

Doge

I just measured a TT bike (FELT DA2) of mine along the chain stays.
It is 80mm wide. The cranks are 15mm wide.
115mm wide Q is possible on this 11speed bike.
But it measures 145-150. This is a BB30 and the SRAM Red cranks flare out. They clear the chain by 5mm. Unlike chain-stays that flare, the chain is straight.

The MFGs could do 120Q with the chain on the middle/inner cogs. The cassette could be closer on a composite (disc or trispoke) wheel.

Dean V

I know this is vague but I am sure I read something about one of the pros experimenting with a narrow Q and not finding it helpful. Think it was Armstrong.

Kontact

The rear wheel OLD has increased, but the cassette cogs have also been getting closer to hub centerline. That's why chainline hasn't changed on road bikes - the cassette has expanded right and left equally, leaving the same 43.5mm centerline for the cassette regardless of whether there are 6 cogs or 11.


And no one here is suggesting that a certain Q is the right one. All I've been saying is that Q doesn't come from ergonomics, and it is impossible for people to really try different Qs if the minimum Q is already fairly wide compared to other ways we use our feet. It would be a surprising coincidence if the ideal Q just happened to be 147mm or whatever Shimano decided to expand Dura Ace to this year.

Kontact

Posts 59 and 61.

Racing Dan

What Im saying is, the chain line is largely irrelevant. Its the increasing OLD that pushes out the chain stays. Wider chain stays is the likely reason for increasing Q. Im sure Shimano is not widening Q just for the hell of it.

EDIT: Its not true that the cassette is always in the same place. A 135 mm hub has the cassette further out than a 130 mm hub. That is why the newer R8000 cranks have a different chain ring spacing (and a matching FD) than a 6800 crank.

Kontact

No, widening chainstays are not the reason Q is getting wider. Newer bikes do not have less crank clearance. You can mount an old 7400 Dura Ace crank on any new bike that can be made to accept an English BB.


I appreciate you putting the thinking cap on, but the things you are claiming are relatively easy to disprove with a ruler.

Bearing systems have grown wider, pushing out the center of the crank, and hollow or carbon crank arms are thicker than older solid crankarms.

Sy Reene

I assumed he was talking about heel strike clearance to the chainstays

Racing Dan

Im sure you can get it on, but depending on the crank length and your feet size you are more likely the hit the heel on the chain stay. I dont think you disproved anything. You just have a different opinion (and thats fine).

Kontact

My opinion is that frame companies build bikes to the standards set by the large crank manufacturers, not the other way around. The current dropout width of 130mm was set in the skinny tube steel era, and the frame companies have not issued a technical bulletin to SRAM, Campy, Shimano, Stronglight, Ritchey, etc demanding that they increase heel clearance via larger Q. There isn't a "heel clearance standard" - that's up to the frame designer to get right.

And heel clearance is very easy to get right when you are making bikes in a mold. Even fat metal stays are normally bent or dented to produce clearance regardless of dropout width.

Dave Mayer

Q has been increasing - this is obvious. Look at the Dura -Ace numbers posted previously. And this is for a performance-oriented gruppo, where the desired Q is as tight as possible. Higher Q is caused by wider stays, which during my riding days has increased on road bikes from 120mm - to increasingly 135. Preventing heel strike is why higher OLD gets translated into higher Q. The silly trend to external-BB bearings is another driver.

BTW: chainline and Q are not the same; I don't know how this got introduced to unnecessarily clutter this debate.

Frame design drives the trend to higher Q. The component vendors have to follow.

I would be surprised if the performance penalty of a high Q is only a few %, as cited earlier. I assume this from a test with a bike mounted in a trainer. In real life, wide crankarms cause the bike to rock back and forth with each pedal stroke, robbing power.

Kontact

Okay, if you guys are going to keep insisting that chainstays have caused Shimano to make its cranks wider, please cite examples and where the crank makers agreed to a new clearance standard and what organization made this possible.


Chainline and Q aren't the same, but they are certainly related as chainline is a limiting factor in Q. When chainline changed with the introduction of 126 spacing and 135 moutain spacing, minimum Q definitely increased.

Dave Mayer

Sure I just pulled the 'for your eyes only' memo out of my files that specifies new industry-wide standards for bike Q-factors.

I see another memo where component manufacturers agreed to market-specific pricing, where First World customers pay more based on 'an ability to pay'.

Early in my stack here I see a cover letter from the Warren Commission summarising the first draft of their report, which concluded that President Kennedy had been killed by a drunk driver.

Kontact

And all of that came from the same source as your previous assertion.

Doge

See post #79. The cranks have lots of room from the stays. It is the chain that is an issue. Of course the left could be brought in.

Doge

I don't know if I introduced it, but with the chain on the small cog, that is the closest thing to the crank, not the stays. As mentioned I could have 30mm narrower / less Q without the chain/with the chain on the middle cog. Maybe 10mm less with the chain clearance.

Dean V

What evidence do you have that the wider Q factor of a modern road bike is robbing power?

smith931

Hi There, It's a good question.
I also think that Q factor is also important as the other parts and measurement. It plays a massive role in how we try to maintain our chain line so that it’ll work with really short chainstays or something designed for a more stable ride.
If your feet aren’t fit in the right place when pedalling, it’s will be uncomfortable for you. So, if the Q factor of a bike should be able to make some adjustments that will make you more comfortable.

Bah Humbug

I don't think Infiniti got that memo.

Doge

Today I suggested that junior think about using the more narrow pedals to decrease his stance. I cited the Birmingham study. He said - "I'm not like them". So there is that.

As I posted several time in this thread - I don't see any real proof one way or the other. I get the lever arms/moving the bike from side to side more. Just that I don't know that translates to speed.

Kontact

I don't think there is going to be much proof of anything if you don't do a lot of testing with Qs ranging from wide to much narrower than bikes normally allow.

Doge

I think it is too small a difference to test.
My test would be timed event, but what you had for breakfast has a bigger affect.

I'm very old school on some stuff. If the rider thinks it is faster, it likely is.

Kontact

Having a rider on a power metered trainer and measuring their oxygen use would be the usual way.