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PostPosted: Thu Oct 27, 2016 2:43 pm 
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As this is weight weenies and people are supposed to be half crazy when it comes to weight...
I would like to ask.
How many of you guys have been using a dremel, sanding or such to make a crankset lighter?

I have been looking up a few brands and waited for cranks, that i now hear is put on ice.
So i am contemplating if i should buy a new crankset and experiment or just keep sane!?

Worst is i don't know walls thickness on different cranks.
FSA went bonkers when i told them i was reworking a K-Force Light crankset.
I took it easy and i quit when i got 20 grams off.

Hand sanding took hours and i dared not proceed further.
Asking for a blue paper of the drawing is possible, but to get one is another story (ofcourse FSA declined me this :( ).

Tips and ideas are always welcome!

So far i have only sanded 3T Team fork, Easton EC90 Aero handlebar and FSA K-Force BB 386 EVO.
But i am considering Rotor 3D+.

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PostPosted: Fri Oct 28, 2016 11:50 am 
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Image

Apologies for the poor picture. I sanded my Fulcrum cranks down to the carbon primarily to remove the decals. I never weighed them as I was eager to get them back on my bike after how long it took to sand. The paint was very thick though so there could be 20-30g to save between both crank arms?

Hope that gets the ball rolling.

Edit: I think people have discussed removing material from the crank spindle before on here but I remember that being shot down fairly quickly.


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Posted: Fri Oct 28, 2016 11:50 am 


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PostPosted: Fri Oct 28, 2016 12:53 pm 
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A bike wash would drop more than that! :lol:

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PostPosted: Fri Oct 28, 2016 1:20 pm 
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I wouldn't fancy making wall thickness much thinner on a chainset, usually they're optimised pretty well for strength to weight.


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PostPosted: Sun Oct 30, 2016 8:15 am 
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I recommend you start with bottom bracket, bolts, chainrings, chain, pedals (ti spindles etc.) before attacking the marginal grams. Plenty of weight to be saved before firing up the dremel!


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PostPosted: Wed Nov 02, 2016 3:49 pm 
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Broady wrote:
I wouldn't fancy making wall thickness much thinner on a chainset, usually they're optimised pretty well for strength to weight.


I see what you're saying and kind of agree. But most companies does not dare to chance, so they leave some to spare.
Anyway, weight weenism all started like this. People drilling holes in frames aso.

So again, you can't blame me for having the itch :mrgreen:

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PostPosted: Wed Nov 02, 2016 4:05 pm 
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Have seen some of the thin wall shimano cranks actually crack from quite minor heel rub.
If you are on the decent gear, there isn't that much margin!

If you have a search you'll probably find some sectioned D-A crank pictures.


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PostPosted: Wed Nov 02, 2016 9:10 pm 
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Are we talking about carbon cranks
What about drilling holes on a non carbon crank. Anyone tried that?

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PostPosted: Thu Nov 03, 2016 3:14 pm 
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Not seen that mattr, but it had been interesting.

We could discuss this up and down. I agree with you in terms of Extralite and Ax Lightness (aso).
But perhaps not if we look at some other brands (Pinarello for example). But i would not say they are not descent just because of this.

xena, no specific material.

OFF Topic, but I've seen they make a composite of abs plastic and carbon injection, carbon fiber reinforced thermoplastics.
I wonder when this start to appear in shape of stems, handlebars and crankarms.
I saw a video when they hit a component with a hammer... it was hard and stiff. Not a crack or dent even.

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PostPosted: Thu Nov 03, 2016 4:48 pm 
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Image

Just for interest.


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PostPosted: Thu Nov 03, 2016 4:51 pm 
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xena wrote:
What about drilling holes on a non carbon crank. Anyone tried that?
They are pretty dependant on the complete surface to provide stiffness. As soon as you drill a hole you get a massive stress riser (for crack propagation, even if it's perfectly shaped and deburred) and also the cranks torsional stiffness will start to drop off. Unless the hole was tiny, in which case it wouldn't be worth doing for weight saving.

Also, it'd whistle when you were pressing on.

And fill up with water in the rain.


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PostPosted: Thu Nov 03, 2016 5:10 pm 
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Great info ,thanks . mattr
Had no idea that the walls were that thin.
I used have 7800 cranks , so glad I never drilled any holes " so tempted"

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PostPosted: Fri Nov 04, 2016 12:57 am 
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Thanks mattr, in this case i agree.
Totally see your point!

There is nothing i would dare to remove. Wonder how some companies manages to reduce weight from an alu crankset.
The axle in Shimas case, i wonder, is it made out of steel?
Perhaps that's why the weight is not lower!?

Reducing weight in a crankset, would seem most logical to do in the crankarms.
Rotor and FSA have pretty thick axles. But that i guess matters little, if not just to lower all in all weight of the bike.

I pity that FSA have no gravel option chainrings for K-Force Light BB 386 EVO crank. However, when i asked FSA, they told me K-Force Light is not suited to gravel riding.
For that, we should go for SLK.

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PostPosted: Fri Nov 04, 2016 9:46 am 
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It's not all about weight though. You need to keep stiffness up (in all modes) or the crank feels horrible (it'll make little or no difference to actual performance) also need to keep the rings and ring mounting tabs rigidly located so that shifting is good/predictable, especially with EPS/Di2.

Shimanos requirements for a crank focus on this. Others focus on weight. And then there is a trade off with cost.


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Posted: Fri Nov 04, 2016 9:46 am 


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PostPosted: Fri Nov 04, 2016 11:06 am 
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mattr wrote:
It's not all about weight though. You need to keep stiffness up (in all modes) or the crank feels horrible (it'll make little or no difference to actual performance) also need to keep the rings and ring mounting tabs rigidly located so that shifting is good/predictable, especially with EPS/Di2.

Shimanos requirements for a crank focus on this. Others focus on weight. And then there is a trade off with cost.

Looking at the cutaway of the da 9000 crank, the structure looks pretty dang simple. I'm 99% sure there's room for improvement there.


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