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 Post subject: Re: Disc Size Advice
PostPosted: Mon Apr 08, 2013 12:11 pm 
retrobike rider
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Location: Nth Somerset, UK
Thanks for all the information.

For now I am going to stick with my original plan.

The frame is at Argos at present, I'm due to take a look at it next week and give the yes / no on the new rear disc mounts, after that I have to wait for the phone call... and the bill :shock:


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 Post subject: Re: Disc Size Advice
PostPosted: Tue Apr 09, 2013 9:32 pm 
Retro Guru
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valve bouncer wrote:
That combo will be fine. Having a 203mm on a 9mm hub is not recommended as it can apparently generate enough torque under braking to rip the wheel out the dropouts.


Nope. All else being equal bigger rotors generate a lower force at the axle, but a higher force on the fork. Not all forks are rated for 203mm rotors, nearly all will take 180 though.

The weight of the bike isn't all that important (assuming that the frame/fork will take your desired rotor sizes), it's the weight of you that you're mainly trying to stop ;)

Or, in a nutshell, 180/160 will be fine.


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 Post subject: Re: Disc Size Advice
PostPosted: Wed Apr 10, 2013 6:32 am 
Old School Hero
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Joined: Sat Feb 02, 2013 1:18 pm
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Location: Japan
MikeD wrote:
valve bouncer wrote:
That combo will be fine. Having a 203mm on a 9mm hub is not recommended as it can apparently generate enough torque under braking to rip the wheel out the dropouts.


Nope. All else being equal bigger rotors generate a lower force at the axle, but a higher force on the fork. Not all forks are rated for 203mm rotors, nearly all will take 180 though.

The weight of the bike isn't all that important (assuming that the frame/fork will take your desired rotor sizes), it's the weight of you that you're mainly trying to stop ;)

Or, in a nutshell, 180/160 will be fine.

That's good to know then, was always told don't run 8" rotors on 9mm quick releases. I'm running my 8" rotors on a double crown (Jr T) so I should be OK. Thanks for setting me straight.


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 Post subject: Re: Disc Size Advice
PostPosted: Fri Apr 12, 2013 3:00 am 
Gold Trader / MacRetro rider
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Joined: Sun May 25, 2008 11:03 am
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Location: Sunny Glasgow
180/160 is perfect.


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 Post subject: Re: Disc Size Advice
PostPosted: Fri Apr 12, 2013 7:56 am 
retrobike rider
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dyna-ti wrote:
180/160 is perfect.



That's what I thought, but as I've never used them on a bike, as opposed to a motorbike, I was just a little unsure.


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 Post subject: Re: Disc Size Advice
PostPosted: Fri Apr 12, 2013 4:50 pm 
Gold Trader
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Location: Odense, Denmark
I use 160/160 on the Pace twins as the forks stipulate rotors of that size. But these bikes never get ridden down mad stuff....
Tried 180/160 on the mad stuff and found that I still needed a bigger rotor at the back.

But 180/160 rides better for most XC. Ignore your offspring. I make a habit of it!


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 Post subject: Re: Disc Size Advice
PostPosted: Fri Apr 12, 2013 4:52 pm 
Gold Trader
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Location: Odense, Denmark
dbmtb wrote:
I use 160/160 on the Pace twins as the forks stipulate rotors of that size. But these bikes never get ridden down mad stuff....
Tried 180/160 on the mad stuff in Germany and France - and found that I still needed a bigger rotor at the back.

But 180/160 rides better for most XC. Ignore your offspring. I make a habit of it!


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 Post subject: Re: Disc Size Advice
PostPosted: Fri Apr 12, 2013 4:56 pm 
retrobike rider
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Location: Nth Somerset, UK
dbmtb wrote:
Ignore your offspring. I make a habit of it!



Sound advice for every occasion.


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