D/A 7410 cranks - the all-time narrow champion?

[Xavier]

Those are narrow cranks (and a specially made narrow Comete disc) on that GT. GT made a traditional diamond design narrow frame which fitted the cranks/wheel too.

Xavier

[über-goober]

Some narrow and rare Campy (& Mavic BB?) from the Yamaguchi photo gallery on Flickr:

[Fuchs]

the 7400 cranks are much nicer! and i think they are quite narrow like the 7410

http://www.pedalsandginger.com/wp-conte ... anks/1.jpg

[Xavier]

If people are interested, we've just had a paper published on the topic:

http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract

Loving those hubs in the picture above, brilliant!

Xavier

[j0m]

Cool. Just read the Abstract. Any other tidbits from the study you could share with us?

[Xavier]

The differences found weren't gigantic, but for the population that would be working at that kind of submaximal intensity (stage racer, MTB enduro, Ironman cyclist) it adds up as they're on their bikes for so long, so you're saving minutes in some cases.

In terms of comfort, the participants all (apart from one girl) hated the 180mm Q Factor and didn't like pedalling with it at all. Most preferred either 90 or 120mm. Interesting as 180mm isn't really that wide if you look at standard triple cranks, there are a few MTB cranks that approach 180mm and people don't tend to whinge that much! But it becomes more acute when you're swapping Q Factors on the fly as we did.

The participants were blinded to it by having to face away from the bike as we were changing the Q Factor (the muscular activation [EMG] sensors were still attached so we couldn't get them to leave the room), if they went from something like 180 to 90 they worked out pretty quickly what was going on! It didn't really matter if it was blinded or not though, as you can't subjectively manipulate your GME (efficiency) unless you breathe really weirdly into the equipment (or burp a lot ).

Xavier

[über-goober]

Thank you for posting your research.. very much appreciated.

If there is isn't a significant biomechanical edge from a narrow pedaling stance, how about with aerodynamics? Even your wild guesses would be welcome.

again, thanks..

[Xavier]

Around 5 watts at submaximal intensities will help, that's like having latex tubes in your tyres and we know how people rave about them!

In terms of the aerodynamics, hard to test in the tunnel as you need to build a special rig or bike which will let you go narrow but isn't a gigantic monstrosity that will have interference effects with the rider. But it seems pretty intuitive that a narrow Q Factor would be more aero, yes. The bike would certainly be thinner. What the scale would be I'm not sure though - you're not taking the lower limbs out of the airflow, but by bringing them closer together you're manipulating how the airflow behaves.

Xav

[Ypsylon]

A narrower Q-Factor should also have better cornering clearance, right? Someone who paid better attention in trig 101 could probably calculate how many 10th of a degree that would be for a given frame.

Probably nothing you could really take advantage of through every single turn, but it might be the difference between a light scrape and a lift off.

[über-goober]

Those of you saying the 7400 series of Dura Ace cranks are even narrower, you were right.

Using the same Phil BB, I measured 128mm for a Q factor and 121 for the "U factor".. which is ridiculously narrow.

Mounted on a D/A 7410 bottom bracket (103mm) it is another 2mm wider.

So with about the same heel and ankle clearance as the 7410s, the 7402 are a centimeter narrower at the pedals.

[Cyco]

IIRC, its been a while, a 7402 was designed with a 113mm BB in mind for chainline.

With the wider axle it will be about the same as a 7410

[JLFast]

Very interesting, and I have a set of 7410's on a period correct restoration. I think they're great to look at.... but since I am not technically minded, I have a question about this.

Does all this figuring actually mean that someone would willingly choose to run with 20 year old cranks, instead of new tech? On a new build? I assume the benefits given here, would suggest that?

Thank you

[über-goober]

Does all this figuring actually mean that someone would willingly choose to run with 20 year old cranks, instead of new tech? On a new build?

I use them, but I'm kind of a freak.

I think it's a reminder that new cranks should try and evolve towards widths in the 130s instead of widening up towards the 150s. It's much easier to add width if that's the rider's preference.

[über-goober]

IIRC, its been a while, a 7402 was designed with a 113mm BB in mind for chainline.

With the wider axle it will be about the same as a 7410

That's true, and I don't think the combination I measured would work in the small-to-small gears.

[Ypsylon]

I think it's a reminder that new cranks should try and evolve towards widths in the 130s instead of widening up towards the 150s. It's much easier to add width if that's the rider's preference.

I couldn't agree with you more, but I am under the impression that it's more up to frame manufacturers. It's just a gut feel but I believe right now the system is optimized to allow a low frame weight. IME it would need system integration or a joint effort between a frame and a crank manufacturer to have a low q-factor.