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850 magic brake pads[ALL/1998] posted by Robert van Dam on
Tuesday, 18 November 1997, at 8:38 p.m.
Now that I have approximately 50,000 miles on the car it was time to replace the brake pads. There was a good bit of thickness left on the rear ones, approximately 40% of the original. The front ones had only 10-20% left. When changing the front ones, I noticed something peculiar that I wanted to share with the list.
The front brake pads are not rectangular like the rear ones but have a slight curve to them on both the ID and the OD (internal/outside diameter). It looks sort of like a cut from a doughnut. The interesting thing is when the pads wear down, the contact area available for braking increases....
Eyeballing it I would say that my worn out pads had approximately 40% more contact area then the new ones that I put in.
The interesting thing is of course now with the new pads if will I be able to notice a reduced braking capability. Maybe I won't notice it since the force put on the brake is adjusted (in my brain) so that the desired deccelaration is achieved. So maybe you would only notice it with a full emergency stop.
It would be interesting to know how much less braking distance I get with worn out pads compared with new ones.
Like to hear what you guys think of this.
Re: 850 magic brake pads[ALL/1998] posted by Don Willson on
Tuesday, 18 November 1997, at 10:59 p.m.
It makes no difference unless the coefficient of friction changes. The equation is that Force (braking) = Normal force applied x coefficient of friction. The area does not come into the equation. The normal force is the pressure in the brake line x the area of the piston. HOWEVER, with a smaller pad there will be more heat and the coefficient will drop. In normal braking this would not be noticed.
Re: 850 magic brake pads[ALL/1998] posted by Steve Seekins on
Wednesday, 19 November 1997, at 7:10 a.m.
As noted, the total braking force will not change appreciablly. The reason for the beveled edges on the brake pads is to reduce tendency for squeal.
Steve
Volvo Club of America
Re: 850 magic brake pads[ALL/1998] posted by orson on
Sunday, 23 November 1997, at 10:25 a.m.
Just a little perspective: the "bevelling" of pads is a common trick in reducing brake noise among pad manufacturers for all sorts of vehicles, not just Volvos.