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Discussion Starter · #1 ·
Dear rbr cycling gurus, I'd appreciate a quick answer on this!

A. I need to know if the q factor is any different for 10speed vs 9 speed DA. I am under a strong impression they should be the same, but just visually b/c of the whole 10speed outboard bearings, it just looks slightly wider and does it mean i have to move my cleats in more? I question myself a lot. Same? Not? how many millimeters difference if not?

B. I read a few posts on lockrings but no clear answer as to compatibility. People babble a lot but nobody ever says yes or no and its always this condition or that. So, I have DA wheelset 10speed and a 12-25 cassette (10speed). I have a 9speed DA lockring i want to use on this wheelset. 10speed and 9 speed lockrings are interchangable? Always? Yes or no?

C. What is the advantage of adjustable-float speedplays rather than regular free-floating? We assume normal biomechanics here, no wacky movements etc. I have opinions but looking for others.

Big thanks in advance!

woof the god... no dog.
 

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Virtually identical.

FC-7800 10-speed Q-factor: 73.0 mm left and right = 146.0 mm total
FC-7700 9-speed Q-factor: 72.95 left, 72.45 right = 145.4 mm total
See chart for other 7700 / 7800 crank versions. I don't have the FC-7900 numbers.

The Speedplay adjustable float lets you rotate the centerline of the float range over to the left or the right, allows you to restrict float range and gives you the option of locking float out all together. This is a good thing for those riders whose neutral foot position is not parallel to the top tube and for those who do better with less float or no float at all.
For what it's worth, Speedplay's "free float" refers to the fact that the foot doesn't rotate against increasing pressure from a centering spring, like it does with almost all other pedal systems. This lack of a centering spring makes some who switch to Speedplay from another system feel as if they're "on banana peels" for the few rides it takes to get used to the Speedplays.


Don't know about the lockrings, sorry.
 

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a thorn in RBR's side
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Discussion Starter · #3 ·
re

thanks! I have 7800 by the way, not 7900.

re speedplays, the real question is whether, biomechanically speaking, it is less "efficient" to do a 90 mile road race with unrestricted float, VS using a system that centers your foot back into the position (or worse, no float which is bad for knees). Theoretically, you can do less work and have ALL your energy go into the pedaling force if you have no float, or restricted float that you get limited by every 50th pedal stroke (as an example). Over a course of 4 hours, this could be real savings. I haven't extensively looked into lock-out design of zero pedals, so if there is no centering, it would be the same thing as regular speedplay - and it makes sense, because whats the point of restricted float then? Faster clickout? No wonder I never bought the zero's. See, you gotta learn to trust your previous decisions sometimes!

Woof the dog.
 

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Woof the dog said:
re speedplays, the real question is whether, biomechanically speaking, it is less "efficient" to do a 90 mile road race with unrestricted float, VS using a system that centers your foot back into the position (or worse, no float which is bad for knees).
I've never seen a study on that, but suspect it doesn't really matter.

As for "no float is bad for your knees," that depends entirely on whose knees you're talking about. Some people's knees (like mine, for example) do better with fixed cleats.
 

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a thorn in RBR's side
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Discussion Starter · #5 ·
re

i bet it does.
 

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Discussion Starter · #7 ·
hey man, i am just bettin'

;)

dog
 

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Discussion Starter · #8 ·
I thought more on this, and I realize how much of an unnecessary, smartass thing it is to say to someone, what you just said Kerry. No, i don't have the data, but it is possible until you or someone else disproves it. Its like science - you can't just dismiss things without properly doing an experiment, and a negative result is still a result.

and re: professional cyclists on speedplays, please! - professional riders and their hordes of coaches and exercise physiologists mess things up in major ways. It often takes 20 years worth of back and forth, contradicting studies to completely turn the original theories of training on their heads. I have some examples, but why bother?
 

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Getting the point

Woof the dog said:
No, i don't have the data, but it is possible until you or someone else disproves it. Its like science - you can't just dismiss things without properly doing an experiment, and a negative result is still a result.
But you are ready and willing to suggest that Speedplays DO reduce efficiency. I'm not making a claim either way - you are. It's the "speculation without data" I'm pointing out. Sorry if that offends you.
 
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