James A Sousa Posted October 3, 2011 Report Share Posted October 3, 2011 Volvo has two thickness minimums for rotors. One value for brakes in service and another higher value for new pads (the rotors must last until the new pads wear out). Thin rotors will retain more heat and wear pads more quickly. Um - we have driven almost 500k miles in our 7 Volvos (that's a LOT of brake jobs!) and have never experienced one of our cars not stopping well - perhaps you have some other problem other than pad wear. Link to comment Share on other sites More sharing options...
FAST850R Posted October 3, 2011 Author Report Share Posted October 3, 2011 Volvo has two thickness minimums for rotors. One value for brakes in service and another higher value for new pads (the rotors must last until the new pads wear out). Thin rotors will retain more heat and wear pads more quickly. Um - we have driven almost 500k miles in our 7 Volvos (that's a LOT of brake jobs!) and have never experienced one of our cars not stopping well - perhaps you have some other problem other than pad wear. Yes, I agree with you. Something is wrong here. When I bought the volvo first time, it seemed stop better than now, then after I drove my wife's mini for a while, I drove my volvo again. Compare to mini, it doesn't stop well, it feels mush, etc... I am still waiting for the parts to be arrived. When I change the rear rotors and pads, I will bleed all 4 brakes again, and lets see how it stops. Thank you. I Link to comment Share on other sites More sharing options...
OptimusGlen Posted October 4, 2011 Report Share Posted October 4, 2011 are your soft brake lines old/cracked? I would say this is the most likely cause for mushy brakes. That and improper bleeding (air in the lines) Link to comment Share on other sites More sharing options...
Subayai Posted October 5, 2011 Report Share Posted October 5, 2011 Couple of issues here. You cannot compare the braking on the Mini to your 850. The difference will always be night and day. The German philosophy is to use a soft semi-metallic pad that wears out every 10,000-20,000 miles and eats up the rotors. All lighter German cars (like the VW's, Audi TT's, etc.) have amazing stopping feel and control. Hear is an excellent article from StopTech on brake rotor warping: http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml The real bottom line is that in terms of braking, the biggest factors you feel are the pressure you apply to the pedal and the amount of stopping power, how the pads lose friction (requiring more pressure from your foot) as they get hotter, and the tires you are using. Think about the tires for a moment. With an ABS braking system the shortest distance you can stop your car within, is with the ABS system going full tilt. Now as long as you can trigger the ABS, and keeping it running until the car comes to a stop, then the pads, rotor, and brake lines are all fine. They may not be great, but working well enough to stop your Volvo is the shortest possible distance. What is usually complained about, and is what I think you are concerned with, as well as I am, is that the pedal fell during braking is not as nice and controlled as other cars, or as linear as you press the brake pedal further towards the floor. I still haven't found a good normal dollar solution for my 850. I've installed braided lines, run Motul RBF600, and use Endless CCX (carbon ceramic) pads. The braking control is much better than stock, but you still fell the weight of the car on hard braking when cold. The biggest factors that control the brake pedal feel are the condition of the brake fluid, brake pads, and condition of the rotors last. I would do the following in this exact order and note how much it improves the brake feel as you do each.: 1) Replace your brake fluid, but let a shop with a power bleeder do it. 2) Assuming your rotors are not badly grooved and do not feel like they are "warped" (basically have any deposits on them), replace your pads with ideally Hawk HPS (you could use HP Plus, but the noise might drive you crazy) 3) New rotors Since you are in the SF Bay area, remember that brake fluid is hygroscopic (it absorbs water). Water in the brake lines boils, and creates a mushy feeling brake, replacing your brake fluid once a year will make sure you do not build up too much water in your lines. Link to comment Share on other sites More sharing options...
FAST850R Posted October 9, 2011 Author Report Share Posted October 9, 2011 Couple of issues here. You cannot compare the braking on the Mini to your 850. The difference will always be night and day. The German philosophy is to use a soft semi-metallic pad that wears out every 10,000-20,000 miles and eats up the rotors. All lighter German cars (like the VW's, Audi TT's, etc.) have amazing stopping feel and control. Hear is an excellent article from StopTech on brake rotor warping: http://www.stoptech....brakedisk.shtml The real bottom line is that in terms of braking, the biggest factors you feel are the pressure you apply to the pedal and the amount of stopping power, how the pads lose friction (requiring more pressure from your foot) as they get hotter, and the tires you are using. Think about the tires for a moment. With an ABS braking system the shortest distance you can stop your car within, is with the ABS system going full tilt. Now as long as you can trigger the ABS, and keeping it running until the car comes to a stop, then the pads, rotor, and brake lines are all fine. They may not be great, but working well enough to stop your Volvo is the shortest possible distance. What is usually complained about, and is what I think you are concerned with, as well as I am, is that the pedal fell during braking is not as nice and controlled as other cars, or as linear as you press the brake pedal further towards the floor. I still haven't found a good normal dollar solution for my 850. I've installed braided lines, run Motul RBF600, and use Endless CCX (carbon ceramic) pads. The braking control is much better than stock, but you still fell the weight of the car on hard braking when cold. The biggest factors that control the brake pedal feel are the condition of the brake fluid, brake pads, and condition of the rotors last. I would do the following in this exact order and note how much it improves the brake feel as you do each.: 1) Replace your brake fluid, but let a shop with a power bleeder do it. 2) Assuming your rotors are not badly grooved and do not feel like they are "warped" (basically have any deposits on them), replace your pads with ideally Hawk HPS (you could use HP Plus, but the noise might drive you crazy) 3) New rotors Since you are in the SF Bay area, remember that brake fluid is hygroscopic (it absorbs water). Water in the brake lines boils, and creates a mushy feeling brake, replacing your brake fluid once a year will make sure you do not build up too much water in your lines. Thank you for the good info! I am going to replace rear rotors and pads. I was going to bleed it myself, but I guess I will take it to a shop and let a mechanic power bleed it. Is power bleed different from regular bleed? Link to comment Share on other sites More sharing options...
Gilhuly Posted October 9, 2011 Report Share Posted October 9, 2011 I usually just look at my rotors. If they are seriously grooved out I buy new ones. This is usually the case after one set of pads on the front. Recently I warped my first set of rotors on the 850 ever and cut them myself at work and it worked out great. Took of a little more than 1/10th of an inch off each side. Correction: I took 1/100th of an inch off each side (10/1000ths) Link to comment Share on other sites More sharing options...
Fudge_Brownie Posted October 10, 2011 Report Share Posted October 10, 2011 Is power bleed different from regular bleed? You can buy a power bleeder... It's a tool used for one-man bleeding. Link to comment Share on other sites More sharing options...
Subayai Posted October 10, 2011 Report Share Posted October 10, 2011 I know of four different ways to bleed brakes: 1) Manually (2 man operation), by pumping the brakes, etc.. 2) Vacuum hand pump (sucks the fluid out at the bleed nipple, so you do not need someone to pump the brakes). 3) Compressed air "power" bleeding (http://www.motiveproducts.com/) 4) Airless "power" bleeding (http://www.flodynamics.com/section_BrakeSystem/BrakeMateJr.shtml) There is mention that the compressed air power bleeding introduces air into the fluid, at the microscopic level, which makes sense, but how much air, who knows. The airless (or air is prevented from contacting the brake fluid) type units are the best and usually found at auto repair shops & dealers. They require quite a bit more brake fluid than what will go into your brake system which means you usually have to live with what ever fluid they are using (you should ask). Link to comment Share on other sites More sharing options...
FAST850R Posted October 11, 2011 Author Report Share Posted October 11, 2011 I ordered motive power bleed tool. Thanks for all the good info. Link to comment Share on other sites More sharing options...
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