Centaur crankarm stiffness?



LewisBricktop

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Sep 10, 2006
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I'm looking at building up a new bike with the '08 Campagnolo Centaur gruppo, and I can't decide which crankset to go with. There is the model with carbon comp crankarms and one with the aluminum crankarms. Other than the weight savings with the carbon version (campa site claims 707g against 828g)and perhaps aesthetics, is there any reason to spend the extra $100 USD, approximately? Stiffness would be a concern with me, but I can't imagine the alu version being bad in that department. Would there be an appreciable difference with the carbon arms? The weight savings alone as an incentive isn't quite enough to make me spend the extra money, although its really close. I think I could stop eating pizza for a week instead.
 

alienator

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Both cranksets will be fine. The difference in weight will make no tangible difference in your performance. As for the stiffness, you won't need to worry about stiffness. In fact, crank stiffness is so far down the list of things to worry about, you'd need a diving bell to find it. Deflections in a crankset are very small, and any energy lost is likewise puny.

Get the crankset that you think looks the best.
 

kdelong

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Dec 14, 2006
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Just one last thought, if you gave up pizza for a week, you just would probably lose more than 121g. Sogo with aluminum, save the extra $100 but give up the pizza anyway, and you win twice:rolleyes:!
 

alienator

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Don't give up the pizza: just pedal more. Or you can switch to veggie pizza. If you've never had Magpie's pizza in Tucson, then you just don't realize how important Magpie's pizza is as a food group.

Give up fast food, burgers.
 

LewisBricktop

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Veggie pizza is definitely not an option, but I am drawn to the carbon version's aesthetical appeal. If I just spend all of my money on better parts then both pizza and fast food are out of the question anyway, although I already don't eat fast food.

On a related topic, how does one check the integrity of a wheel rim. I have some '01 Mavic MA3's laced to 9sp Velcoe hubs that I could re-lace to 10sp and use as beat-up rain and training wheels, but I'm not sure how many miles they have left in them. They seem to stay in true well(32 spoke).
 

kdelong

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Dec 14, 2006
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LewisBricktop said:
Veggie pizza is definitely not an option, but I am drawn to the carbon version's aesthetical appeal. If I just spend all of my money on better parts then both pizza and fast food are out of the question anyway, although I already don't eat fast food.

On a related topic, how does one check the integrity of a wheel rim. I have some '01 Mavic MA3's laced to 9sp Velcoe hubs that I could re-lace to 10sp and use as beat-up rain and training wheels, but I'm not sure how many miles they have left in them. They seem to stay in true well(32 spoke).
I am speaking from total ignorance here as I have replaced my wheel sets before wearing out a rim, but I believe that you would measure the amount of material on the sides where the brake pads contact it. At least that is where the wear indicators are located on all of the rims that I have seen that have them.

Just use a micrometer and measure the thickness. If you check with Mavic, I am sure that they will have a minimum safe thickness standard. And if I am totally off base here, their customer support can tell you the correct way to check if they are worn out.
 

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LewisBricktop said:
I'm looking at building up a new bike with the '08 Campagnolo Centaur gruppo, and I can't decide which crankset to go with. There is the model with carbon comp crankarms and one with the aluminum crankarms. Other than the weight savings with the carbon version (campa site claims 707g against 828g)and perhaps aesthetics, is there any reason to spend the extra $100 USD, approximately? Stiffness would be a concern with me, but I can't imagine the alu version being bad in that department. Would there be an appreciable difference with the carbon arms? The weight savings alone as an incentive isn't quite enough to make me spend the extra money, although its really close. I think I could stop eating pizza for a week instead.

Crank stiffness is often tested by big gorilla machines that exert way more force than any rider and the differences are small. Nobody can really flex carbon or aluminum crank arms to any degree nor twist a aluminum or steel spindle of the diameters of the Campag or others UT system. More often that not stiffness of outbarod bearing systems are because the support is farther outboard and often stiffness of more of a function of the bike frame than the crank.

Remember the Centaur carbon has Veloce chainrings and the Centaur aluminum have better machined, not stamped Centaur/Chorus quality rings.
 

PeterF

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Crank stiffness is often tested by big gorilla machines that exert way more force than any rider and the differences are small. Nobody can really flex carbon or aluminum crank arms to any degree nor twist a aluminum or steel spindle of the diameters of the Campag or others UT system. More often that not stiffness of outbarod bearing systems are because the support is farther outboard and often stiffness of more of a function of the bike frame than the crank.

Remember the Centaur carbon has Veloce chainrings and the Centaur aluminum have better machined, not stamped Centaur/Chorus quality rings.
Good point, but the carbon still is rather sweet. I do think 121 grams of rotational mass is not a bad savings though.
 

alienator

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PeterF said:
Good point, but the carbon still is rather sweet. I do think 121 grams of rotational mass is not a bad savings though.

Having Record UT cranks, the CF does look nice, but the effect of crank rotational mass is puny. In fact with 172.5mm cranks, the difference in a set of wheels' moment of inertia is 11.2 times greater than that difference in a set of cranks. In terms of energy, that 121g difference in a set of wheels' energy is 123.2 times greater than the difference in a crankset's energy. Since rotational mass of wheels, w.r.t. bikes, means very little and is very small, the effect of differing MOI for cranks is going to be punyscopic.

I ain't sayin' it to start an argument. I'm just sayin' it to add perspective. :D

I'd go for the CF cranks, too.
 

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PeterF said:
Good point, but the carbon still is rather sweet. I do think 121 grams of rotational mass is not a bad savings though.

Well, those 121 grams(about 4 ounces) are so small, they are certainly lost in the noise of any common 90,000+ gram rider and bicycle package.
 

PeterF

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Well, those 121 grams(about 4 ounces) are so small, they are certainly lost in the noise of any common 90,000+ gram rider and bicycle package.
True. but us obsessive types will see it as less than a dollar a gram of weight savings.. :eek:
 

milliedog

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LewisBricktop said:
I have some '01 Mavic MA3's laced to 9sp Velcoe hubs that I could re-lace to 10sp and use as beat-up rain and training wheels, but I'm not sure how many miles they have left in them. They seem to stay in true well(32 spoke).

Umm... why not just put the 10s cassette on the wheels as they are & then ride them into the ground? You don't need to relace a different hub.

Definitely not worth putting the old rim onto a new hub if it means pulling apart a functioning (even if old) wheel.
 

LewisBricktop

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milliedog said:
Umm... why not just put the 10s cassette on the wheels as they are & then ride them into the ground? You don't need to relace a different hub.

Definitely not worth putting the old rim onto a new hub if it means pulling apart a functioning (even if old) wheel.

I didn't even think about that. Does Campagnolo require a spacer or anything to fit the 10sp cassette on the 9sp hub? I know Shimano does, but then again, they are rather inferior to the Italians;)
 

LewisBricktop

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Oh, and I've decided to go with the aluminum cranks. Nothing from either option really screamed at me, but I might take the extra money I save and upgrade to a Chorus rear mech and a spare tire (the kind that goes on the bike:cool: ).
 

sogood

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Remember the Centaur carbon has Veloce chainrings and the Centaur aluminum have better machined, not stamped Centaur/Chorus quality rings.
That's an interesting piece of info. Wondering why Campy did that? But glad that I went with the Centaur alu CT crankset on my 2nd bike. :rolleyes:
 

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LewisBricktop said:
I didn't even think about that. Does Campagnolo require a spacer or anything to fit the 10sp cassette on the 9sp hub? I know Shimano does, but then again, they are rather inferior to the Italians;)

Nope, plug and play.
 

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sogood said:
That's an interesting piece of info. Wondering why Campy did that? But glad that I went with the Centaur alu CT crankset on my 2nd bike. :rolleyes:

Well, for 2008 at least, Centaur crank offerings are aluminum and carbon. In 2007 they 'upgraded' Centaur with carbon cranks, carbon body on the RD, new hubs, new carbon lebers, all based on Veloce/Xenon components. added 'bling' of carbon but reduced the function of the levers. Not a fan of this, wish they would have kept Centaur like Chorus w/o the carbon.
 

BikingBrian

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Well, for 2008 at least, Centaur crank offerings are aluminum and carbon. In 2007 they 'upgraded' Centaur with carbon cranks, carbon body on the RD, new hubs, new carbon lebers, all based on Veloce/Xenon components. added 'bling' of carbon but reduced the function of the levers. Not a fan of this, wish they would have kept Centaur like Chorus w/o the carbon.

Tell me about it! I also, don't like the direction Campy has been heading in the past couple of years. Seems like they are trying to either a) maximize profits a-la Mavic (all bling, no function), and/or b) get deeper market penetration, trying to get specced as more OEM stuff, IOW compete directly with the big S - this could be a fatal mistake for a company like Campy. They should stick with being a niche, well-respected, maker of quality parts. (even if they have to charge more for them)
FWIW: I just bought a set of NOS 2006 Centaur shifters from TotalCycling. Very nice! Excellent value; the right shifter has the old "run-through-all-the-gears-at-once" thumb button, the left lever still has infinite adjust.
 

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BikingBrian said:
Tell me about it! I also, don't like the direction Campy has been heading in the past couple of years. Seems like they are trying to either a) maximize profits a-la Mavic (all bling, no function), and/or b) get deeper market penetration, trying to get specced as more OEM stuff, IOW compete directly with the big S - this could be a fatal mistake for a company like Campy. They should stick with being a niche, well-respected, maker of quality parts. (even if they have to charge more for them)
FWIW: I just bought a set of NOS 2006 Centaur shifters from TotalCycling. Very nice! Excellent value; the right shifter has the old "run-through-all-the-gears-at-once" thumb button, the left lever still has infinite adjust.

Campagnolo's 'situation' is much more favorable than in the dark days of the late 80s and that wasn't 'fatal'. I too wish they would forget about trying to be anything but mid-high end and dump things like Xenon/Mirage. Like Mercedes(baby Benz) and Porsche(914, 924) learned.