From mgb-v8-bounces+mharc=autox.team.net@autox.team.net Sun Jul 20 19:42:10 2008 From: "packrat6" To: Date: Sun, 20 Jul 2008 21:42:00 -0400 Subject: [Mgb-v8] disc brakes the disc brakes on my 79B are rubbing all of the time. not making any noise (the pads are relatively new), but they are not releasing completely when the fluid pressure (pedal) is released. both front wheels seem to be affected the same. is there some common cause for this? thanks for the help. robert _______________________________________________ Support Team.Net http://www.team.net/donate.html Mgb-v8 mailing list Mgb-v8@autox.team.net http://autox.team.net/mailman/listinfo/mgb-v8 From mgb-v8-bounces+mharc=autox.team.net@autox.team.net Sun Jul 20 20:15:30 2008 From: "Wayne Kube" To: "packrat6" , Date: Sun, 20 Jul 2008 21:15:42 -0500 Subject: Re: [Mgb-v8] disc brakes Robert - I've seen a couple of things cause this. One is the return orifice in the master cylinder is plugged with rust or some other foreign material. The other (and more common cause) is a misadjustment of the brake light switch. The way the master cylinder works is the fluid from the reservoir goes into the cylinder in front of the rubber seal on the piston, then gets sent out to the calipers and rear wheel cylinders when you press the brake pedal. When you release the pedal, the piston in the master cylinder is returned by an internal spring, and needs to travel backward far enough past the orifice to let the brake fluid return back to the reservoir. If the brake light switch is adjusted too deep, it prevents the brake pedal from returning far enough, and that prevents the piston in the master cylinder from retracting fully. All of this said, the disk brake pads actually never retract fully - they are always in slight contact with the rotor. There is no spring action - only the very slight run-out or wobble of the rotors actually push the pads (and caliper pistons) back a bit. Unlike the rear brake shoes, which are returned by the springs within the rear brake assembly. Are you experiencing binding of the front brakes, or just the slight rubbing? Very slight rubbing/contact is normal, binding isn't. If one of the conditions that I first described happens, usually the brakes start binding the more you drive it. If the fluid can't return to the reservoir, and the pads are rubbing, heat is generated, which expands the brake fluid, which presses the pads tighter against the rotors, which generates more heat, which..... you get the idea. Wayne Kube Plano, TX '79 MGB V8 3.9L "Hobbes" Logan 1925 n5wmk ----- Original Message ----- From: "packrat6" To: Sent: Sunday, July 20, 2008 8:42 PM Subject: [Mgb-v8] disc brakes > the disc brakes on my 79B are rubbing all of the time. not making any > noise > (the pads are relatively new), but they are not releasing completely when > the > fluid pressure (pedal) is > released. both front wheels seem to be affected the same. > is there some common cause for this? > thanks for the help. robert > _______________________________________________ > Support Team.Net http://www.team.net/donate.html > > Mgb-v8 mailing list > > You are subscribed as wkube@augustmail.com > > Mgb-v8@autox.team.net > http://autox.team.net/mailman/listinfo/mgb-v8 _______________________________________________ Support Team.Net http://www.team.net/donate.html Mgb-v8 mailing list Mgb-v8@autox.team.net http://autox.team.net/mailman/listinfo/mgb-v8 From mgb-v8-bounces+mharc=autox.team.net@autox.team.net Mon Jul 21 03:00:38 2008 From: "Paul Hunt" To: "packrat6" , Date: Mon, 21 Jul 2008 09:58:10 +0100 Subject: Re: [Mgb-v8] disc brakes Problems with the bypass hole or *mechanical* brake light switch adjustment causes the brakes to bind on when the fluid heats up and will affect all wheels (if single circuit or brake light switch) or one circuit if bypass hole problem. Other causes can be caliper flex hoses breaking down internally and acting as a check valve, usually affects one caliper but both pads. Both these are revealed by slacking a caliper bleed nipple, if fluid spurts out in a jet i.e. is under pressure one of the above is the cause. Another cause is simply stuck/corroded pistons, which affect just one pad in a caliper, unless both pistons are equally affected of course. As Wayne says unlike the rear brakes there is no pull-off spring, as well as hub-bearing end-float to some extent the springiness of the seals will also pull the pistons back in very slightly. PaulH. ----- Original Message ----- > the disc brakes on my 79B are rubbing all of the time. not making any > noise > (the pads are relatively new), but they are not releasing completely when > the > fluid pressure (pedal) is > released. _______________________________________________ Support Team.Net http://www.team.net/donate.html Mgb-v8 mailing list Mgb-v8@autox.team.net http://autox.team.net/mailman/listinfo/mgb-v8