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 Post subject: Re: Rotors replaced
PostPosted: Fri Oct 12, 2012 7:58 am 
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Joined: Wed Jan 18, 2012 4:23 pm
Posts: 417
Location: Midlands, United Kingdom
Stopping the grinding is precisely what the springs are for, make sure they are fitted correctly and working as intended!

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 Post subject: Re: Rotors replaced
Posted: Fri Oct 12, 2012 7:58 am 


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 Post subject: Re: Rotors replaced
PostPosted: Fri Oct 12, 2012 9:00 am 
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Joined: Tue Oct 02, 2012 8:36 am
Posts: 36
Well after a lot of fiddling around I managed to get the rotor and pads in a good position.
No rubbing when the bike is tilted. But I have no idea what I did to get rid of it.
Just took off the caliper and the rotor and started all over.

Front brake is still not as sharp as the rear. Will see if it gets better, otherwise new pads will be mounted

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Cannondale Bad Boy 4 (2012) Original weight minus 1541 Gram


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 Post subject: Re: Rotors replaced
PostPosted: Sat Oct 13, 2012 8:53 am 
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Joined: Thu Jan 13, 2011 4:04 pm
Posts: 510
Location: Sunny UK
Firstly if those are 160 mm disc, then a pair of KCNC Razor will weigh 150 g - be similar price too.

I'm about to stir up a can of worms but how can the braking with a disc that has more holes then metal be ever be as good as one with more metal? The coefficient of friction between air and brake pad material is pretty much zero - that is the price you pay for losing weight - do not be surprised if your braking does not get anny better.

Also some design of ligtweight disc will cause the forks to judder due to the pad grabbing the metal then releasing as the disc rotates - I had Gator discs fitted and they were unusable with a pair of SIDs so I fitted Hope floaters and they are fine - the Hopes have the holes stagggered so they are not in one place.


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 Post subject: Re: Rotors replaced
PostPosted: Sat Oct 13, 2012 2:22 pm 
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Joined: Thu Jul 31, 2008 12:20 pm
Posts: 162
Location: Hampshire UK
That is true but doesn't account for the front to rear difference.


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 Post subject: Re: Rotors replaced
PostPosted: Sat Oct 13, 2012 2:44 pm 
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Joined: Tue Oct 02, 2012 8:36 am
Posts: 36
Well did a nice 40k through the woods this morning, and seems like theres nothing wrong with the pads now. Maybe a lot of braking did the trick.

As for better braking, it may be so that the old ones are slightly better. And for a downhill bike I would do it. But this bike is for cyclocross and light cross country and they work brilliant for me.

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 Post subject: Re: Rotors replaced
PostPosted: Wed Oct 17, 2012 2:23 pm 
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Joined: Wed Jan 18, 2012 4:23 pm
Posts: 417
Location: Midlands, United Kingdom
02GF74 wrote:
I'm about to stir up a can of worms but how can the braking with a disc that has more holes then metal be ever be as good as one with more metal?


Did you pass physics? Area is not a value in the calculation for friction, (Fr = Mu x m) I notice no difference going from near full discs to alligators, except the 'gaters squeal more.

For a different explanation, if you halve the contact area you double the pressure for that area remaining.....which is why area isn't in the calc.

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 Post subject: Re: Rotors replaced
PostPosted: Fri Oct 19, 2012 12:33 pm 
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Joined: Sat Jan 03, 2009 9:43 pm
Posts: 2893
Location: Canada
how many ride should it take before new rotors are broken-in and start braking correctly?

I have a new 29er, 160/160 with XO brakes and it sometimes lack braking power, a lot, im only 150lbs. Yesterday I went back on my 26er 160/140 with XX brakes and I was shocked at how much braking power the bike had...

I have 5 rides on the new 29er so far.


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 Post subject: Re: Rotors replaced
PostPosted: Fri Oct 19, 2012 2:19 pm 
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Joined: Tue Oct 02, 2012 8:36 am
Posts: 36
I did about 40k on the road and 45k offroad before they were fine and I must say they are superb now.
I tried to get as much of heat as possible in them. Riding 10-15kmh with front or rear brake slightly on.

Thats how I did it, no idea if its correct, but it worked.

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 Post subject: Re: Rotors replaced
PostPosted: Mon Oct 22, 2012 2:28 pm 
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Joined: Wed Jan 18, 2012 4:23 pm
Posts: 417
Location: Midlands, United Kingdom
The Shimano tech doc reckons on 20 medium rate stops in quick succesion, you need to get some heat into the discs, so you caould do 100's of miles under the right (wrong?) circumstances and never bed your brakes in.

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 Post subject: Re: Rotors replaced
PostPosted: Mon Oct 22, 2012 3:41 pm 
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Joined: Mon Oct 22, 2012 5:30 am
Posts: 19
Location: Santa Monica, ca
What do you think is the best value in a light weight rotor? I am looking for something that isn't too expensive.


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 Post subject: Re: Rotors replaced
PostPosted: Tue Oct 23, 2012 8:07 am 
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Joined: Wed Jan 18, 2012 4:23 pm
Posts: 417
Location: Midlands, United Kingdom
Alligator, sub £20 (US $30) each for a 160mm, about 82g each for a 160.

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