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PostPosted: Mon Aug 29, 2011 12:10 pm 
retrobike rider
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Russell wrote:
You guys make me laugh. Discs using up the weight savings? You are aware that a decent modern disc set up is comparable in weight to a set of xtr v brakes?


I could really do with seeing a source on that one

Well lets just say I cannot see how the presence of all that extra material fits within the weight of a set of XTR brakes, but I'd like to be shown if it is the case


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PostPosted: Mon Aug 29, 2011 12:27 pm 
retrobike rider
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Lets use facts!

XTR Vs:

Arms 200g a pair

http://www.merlincycles.co.uk/Bike+Shop ... es_453.htm

Lever 166g

http://www.dotbike.com/p/8602?utm_sourc ... mpaign=FGL

XTR Disks:

Caliper 108g

Lever 194g

Disk weight not specified(!)

http://www.merlincycles.co.uk/Bike+Shop ... KE-SET.htm

But after much digging

Disk @ 160mm 126g

http://www.leisurelakesbikes.com/produc ... ?&id=16861

So yeah...

Even without accounting for fluids, hoses and unions compared to cables the Vs win the weight arguement. And this is XTR vs XTR


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PostPosted: Mon Aug 29, 2011 12:33 pm 
SotS Winner
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And you can treble the weight of the rotor whilst the bike is in motion. Basic physics.

Of course disc-specific rims can be machined in ways rim-brake rims cannot to reduce rotational weight.

And discs save a riders energy by stopping faster with less lever effort, more modulation and less inclination to wheel lock and skidding.


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PostPosted: Mon Aug 29, 2011 1:02 pm 
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Location: No brakes? Way to commit soldier.
hydorah wrote:
Lets use facts!

XTR Vs:

Arms 200g a pair

http://www.merlincycles.co.ukok/Bike+Sh ... es_453.htm

Lever 166g

http://www.dotbike.com/p/8602?utm_sourc ... mpaign=FGL

XTR Disks:

Caliper 108g

Lever 194g

Disk weight not specified(!)

http://www.merlincycles.co.uk/Bike+Shop ... KE-SET.htm

But after much digging

Disk @ 160mm 126g

http://www.leisurelakesbikes.com/produc ... ?&id=16861

So yeah...

Even without accounting for fluids, hoses and unions compared to cables the Vs win the weight arguement. And this is XTR vs XTR


I'm on a mobile now but will give you proper figures, including cables and rim weight later.


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PostPosted: Mon Aug 29, 2011 1:14 pm 
retrobike rider
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Cool... I would also mention hubs, as there seems to be a good bit of material neeed to provide a good mounting surface for a rotor

Although non disk hubs my not have benefitted from the same development effort that disk ones haves...

This is interesting stuff and using verifiable sources we'll come up with actual answers 8)

Of course there's always these:

http://www.readytoridecycles.co.uk/kcnc ... -196-p.asp

A WHOLE BIKE full is is 248g


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PostPosted: Mon Aug 29, 2011 1:33 pm 
Old School Grand Master
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Location: No brakes? Way to commit soldier.
Weight weenies has real world data.

I remember working out that there was only about 20g in it between decent v brakes and a good disc set up.


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PostPosted: Mon Aug 29, 2011 1:46 pm 
retrobike rider
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The number are true regarding the KCNC stuff, a few guys on here have bought them...

http://dirt-boy.blogspot.com/2007/05/kc ... pdate.html

But it'll be cool to see you get your numbers together


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PostPosted: Mon Aug 29, 2011 3:29 pm 
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mechagouki wrote:
And you can treble the weight of the rotor whilst the bike is in motion. Basic physics.

I'd love to see a derivation of that. Are you talking about relativistic effects?

:lol:


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PostPosted: Mon Aug 29, 2011 4:06 pm 
MacRetro rider
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gm1230126 wrote:
The Ken wrote:
I've recently switched to lightweight rotors should I be worried? :)

From this...

to this...


Yes you should be worried. You've got a clamp on a cast magnesium fork leg that wasn't engineered to have one on it. This and just welding disc tabs to any old seat stays that don;t have the engineered thickness to handle it are two reasons that failure will happen. Have seen it posted more than once. I think this is one of the biggest dangers in retroland....personal engineering of newer parts onto older frames and forks that weren't designed to have it in the first place.


Don't worry GM, I've been using that front disk for almost 18 years now with no ill effects on both those Mag 21s and the original rigids. The hub uses a 9mm through axle which I think helps. And the discs I use are older than my frame and forks.


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PostPosted: Mon Aug 29, 2011 5:38 pm 
SotS Winner
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one-eyed_jim wrote:
mechagouki wrote:
And you can treble the weight of the rotor whilst the bike is in motion. Basic physics.

I'd love to see a derivation of that. Are you talking about relativistic effects?

:lol:


http://easycalculation.com/physics/classical-physics/moment-of-inertia.php :wink:


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