wonky disc`s
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Bikerboy09



Joined: 02 Apr 2010
Posts: 69

PostPosted: Thu May 13, 2010 8:56 pm    Post subject: wonky disc`s Reply with quote

i have some qmd-5 disc brakes and i set them up perfect( i think anyway) then when i go for a ride i come back in do the checks you do and notice that the disc sways and cause the disc to rub against the pads.
how do i fix this gettin anoyed.
thanks
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Steve Kish



Joined: 06 Jan 2009
Posts: 8029
Location: Near Heathrow

PostPosted: Thu May 13, 2010 10:27 pm    Post subject: Reply with quote

Buy a brake disc adjustment tool like this:-
http://cgi.ebay.co.uk/Super-B-Disc-Brake-Rotor-Truing-Tool-/3501803292 89?cmd=ViewItem&pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item5188 5fc749

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stu8975



Joined: 20 Mar 2010
Posts: 4854
Location: Sunderland

PostPosted: Fri May 14, 2010 8:14 am    Post subject: Reply with quote

Downside of mechanical disc brakes, only 1 piston moves when you pull the brake which then forces the disc into the other pad, personally always set mech. brakes up from the inside pad first, adjust the pad so it's about 1mm away from the rotor, then do the outer pad (the one that moves when you pull the brake), then set the cable tension. check your rotor bolts as well.
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The Flying Ox



Joined: 28 Mar 2010
Posts: 551
Location: Edinburgh

PostPosted: Fri May 14, 2010 10:47 am    Post subject: Reply with quote

stu8975 wrote:
check your rotor bolts as well.


+1. I nearly drove myself mad looking for the cause of a squeak until I realised that my front disc was slightly loose on its mount.

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Steve Kish



Joined: 06 Jan 2009
Posts: 8029
Location: Near Heathrow

PostPosted: Fri May 14, 2010 8:12 pm    Post subject: Reply with quote

Quote:
Downside of mechanical disc brakes, only 1 piston moves when you pull the brake


On most, but not all. The Kooka and Avid BB7 move both pads. The cheaper and excellent Kooka even has micro-adjustment for the disc-to-pad spacing between both inner and outer contact point. Stupidly easy to adjust and maintain.

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stu8975



Joined: 20 Mar 2010
Posts: 4854
Location: Sunderland

PostPosted: Fri May 14, 2010 8:53 pm    Post subject: Reply with quote

Steve Kish wrote:
Quote:
Downside of mechanical disc brakes, only 1 piston moves when you pull the brake


On most, but not all. The Kooka and Avid BB7 move both pads. The cheaper and excellent Kooka even has micro-adjustment for the disc-to-pad spacing between both inner and outer contact point. Stupidly easy to adjust and maintain.


Not true. When the actuating arm on mech. brakes moves it only moves the outside pad, then inner pad stays put, that's why a lot of them have a grub screw to secure the inner pad once it's in position. The inner pad is simply held in place by the magnet.
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Steve Kish



Joined: 06 Jan 2009
Posts: 8029
Location: Near Heathrow

PostPosted: Sat May 15, 2010 1:19 pm    Post subject: Reply with quote

Quote:
Not true.


Sorry, but not so! I've used these and can vouch for the fact that both pads move.

The Kooka Unitwin has a cam setting that when the cable is pulled, not only does it move the outer pad inwards, it also moves the sprung inner part of the body with the inner pad towards the disc.

I had mine set up with a 1.5mm gap between both the inner and outer pad. When the brake was applied, both pads touched the disc simultaneously and the disc didn't flex sideways at all!

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