Brakes Rotor replacement question

Discussion in '2005 - 2009 Specific Tech' started by Bikerdrumr, Apr 2, 2013.


  1. Bikerdrumr

    Bikerdrumr Member

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    My '09 GT/CS now has about 82k miles. It's a DD, and I don't beat it. Most of my commute is hwy miles. I have yet to do anything with the brake pads or rotors. They've been great. I'm just now hearing that sound you hear that they need to be replaced.

    #1: What is the sign I look for that the rotors need to be replaced?
    #2: Should I just change them anyway?
    #3: Keeping in mind I'm trying to keep costs down, is it worth it to invest in upgrades for either pads or rotors? I've never been disappointed with the performance of the stock units.

    If this was answered before in another thread, I apologize. I couldn't find anything in the search.

    Thanks!
     
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  2. SpartaPerformance

    SpartaPerformance Site Sponsor

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    At 82K miles replace the rotors too, no need for upgrade just get Motorcraft parts.
     
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  3. gearheadboy

    gearheadboy Mod Dude

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    If they don't vibrate when you brake then you can probably use them without issue. The problem is sometimes when you put new pads on used rotors the initial heat caused by the new pads seating may cause the old rotors to warp and vibrate. Not always. If you are really worried have someone machine them "on the car". It will machine any hub imperfections into the rotors and they won't likely warp ever. And then there is replace them option..I personally see no need to buy Ford rotors. In fact I'd buy a set of cross drilled or slotted rotors off of Ebay for less money and get them with the ceramic pads as a cheap kit. Problem solved. Just my opinion.
     
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  4. Bikerdrumr

    Bikerdrumr Member

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    Thanks! I'll start looking in eBay and see what's there.
     
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  5. djdizzydave

    djdizzydave Active Member

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    THIS.. get pads and rotors with those kind of miles. easy at home job!
     
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  6. Bikerdrumr

    Bikerdrumr Member

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    Just ordered slotted and drilled rotors and pads from Brakemotive on eBay. They were $187 w/ free S&H.

    I hope they are good!

    Thanks!
     
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  7. gearheadboy

    gearheadboy Mod Dude

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    Let me know how you do. I worked at a dealer for 17 yrs. OEM rotors, while of OEM quality are not made of some special material. Anymore a good slotted or drilled rotor is cheaper than OEM and probably are zinc coated and won't rust as fast. Mine have all had a zinc coating. The only exception I've seen is some imports use a really soft rotor and a really hard pad. The rotor and pad wear at about the same rate. You end up needing pads and the rotors are very thin with a huge lip on the outside. These generally do better with OEM stuff to maintain factory stopping force. They do however cause black wheels, rusty wheels, and squealing brakes.
     
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  8. F. Jason Garriott

    F. Jason Garriott Member

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    Brakes're actually the simplest system on the car. If you replace the pads, you should always machine or replace the rotors. They come right off the car when you remove the calipers and caliper/pad frames. 4 bolts...Machining them on the car is retarded. Machining off the car is about $15, in SoCal. If you're saving money, check the front rotors with a tape measure, on the edge, if it's less than 3/4"...about 19 mm, replace them. My '05 GT 5 speed had a 1/16th over 3/4" left at at least 100K miles. I replaced the rotors just to be sure. Buy new ones if you're in doubt. They're about $50-60 each on RockAuto. Good luck.
     
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  9. 805mustang

    805mustang Member

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    Always replace or machine; depending on thickness; rotors when doing a brake job. I agree with both of you but for different reasons. Technically on the car machining is better but also more expensive and not too common so your local mechanic probably won't have the equipment. I would only do it on 4 wheel drive and bearing type rotors, but in that regard its also a good idea to repack wheel bearings and take the slop out of the bearing play! Taking them off allows you to take them anywhere to be machined for about 15 - 20 bucks. While there off its not hard to clean up mating surface, I.e the hub and back of rotor!
    Now and days you can find new pads and rotors for almost any vehicle for under 150 on eBay. That's your best option seeing as when you machine your rotors they will develop hot spots and or warp due to less heat dissipation because the rotor will be quite a bit thinner than new!
    Hey Jason Garrett hit me back I have a question for you, thanks -Mike
     
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  10. F. Jason Garriott

    F. Jason Garriott Member

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    Hey, Mike: Garriott here. Good advice. I wouldn't machine on-the-car unless you don't want to take apart the wheel bearings, like on older cars and 4wds. Most all new cars have detachable rotors. Always-always-always machine the rotors for the reasons above to do a complete brake job.
     
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  11. 805mustang

    805mustang Member

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    Garrett I have 3 questions for you, 1 about my cars issue, 2 a favor if you will and 3 a trivial question as your the man who knows all the trivia......so your profile says!
    1. You said you had to replace a var cam sensor? Was that just the sensor or the phaser as well?

    2. Do you have a scantool or do you remember any values? I think I finally found my problem ....not sure but I tested every sensor cleaned all connections ran all the tests I could think of but the problem still remains. With only one bad sensor would the car run a little rough when cold and or under 3000rpm? If you viewed live data on a scantool would u remember some values? Ok that was 2 questions?
    3. Without looking it up first are you familiar with the gulp effect??? I'll tell u if you reply!


    To me this looks like i have something wrong with one or both sensors, do u see a problem?
    Thanks -Mike
     

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  12. F. Jason Garriott

    F. Jason Garriott Member

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    #1Throbbing on the pedal when you apply the brakes.
    #2Probably. rotors're cheap.
    #3 depends on how much you want to spend. Drilled and slotted rotors, and fixed piston calipers are always better.
     
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  13. F. Jason Garriott

    F. Jason Garriott Member

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    Hey Mike:
    #1 Just replaced the Cam Position Sensor, didn't mess with the variable cam timing.
    #2 Just a code reader. P 0340. no other diagnostic equipment used.
    #3 I know nothing about the "gulp effect".
    I'd replace the vct sensors, if you're at high mileage, they're relatively cheap, and reread the trouble codes.
    Good luck.
     
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  14. 805mustang

    805mustang Member

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    Aaaaaaaa.....the gulp effect; it's very interesting knowledge about camshaft and volumetric efficiency....love that phrase....do you know what volumetric efficiency is? I will educate you on both if you would like to know? If your looking for trivia Ill educate you....most techs, even the good ones have not heard of the gulp effect!
    As for the cam issue I know the sensor is good, well 90 percent sure. The car would throw a code if it was bad I'm just confused because of the live data readings I'm getting; I may be looking for a problem that does not exist. If you look at the picture of my scan tool you'll see var cam time 1 advance and error and var cam time 2 adv and error. I'm only getting readings from var cam time 2 and vct 1 stays at 0.00. To me this indicated the vct servo is stuck or not working but I get no codes. Also my fuel trim is equal, bank 1 and 2 at any rpm. I'm wondering if my scantool should read a value or not.....silly question I know, why wouldn't it? I'm going to try swapping cam sensors and see if bank 2 goes out and bank 1 starts reading values. If it does cam sensor is bad, if it doesn't then I'm going to focus on the servo. Any input on that? Get back to me and I will tell u about the gulp effect and volumetric efficiency!
     
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  15. F. Jason Garriott

    F. Jason Garriott Member

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    Cool:
    The vct uses a solenoid to control oil pressure to the sprocket-advance mechanism. Maybe one of the solenoids is sticky.
     
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  16. 805mustang

    805mustang Member

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    I agree, I think they share an oil passage so if it was plugged neither would be working. I have not done my research on removal of the solenoid, I hope it comes out through the top and I don't have to remove the valve cover. If I do I will dvom them while driving (long leads and back probe one at a time) I can check at idle.....I believe it's 5-7 % or hz for the cam sensor not the var cam timing solenoid which I'm not exactly sure but I believe it's a voltage change batt volt at idle and will decrease as u increase speed. I will have to double check that but I will probably just compair the 2 since I know one is working. I will reply again with volumetric efficiency and gulp effect....too hard and too much to do on my phone.
     
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  17. 805mustang

    805mustang Member

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    Here's a little info on volumetric efficiency and the gulp effect. I do not have my notes so all the info is not the full definition .....just what I remember from school.
    Volumetric efficiency- is the amount (volume) of fuel (air and gas) that can be drawn in to cylinder during its intake stroke. No naturally aspirated engine can have 100% volumetric efficiency. Standard engines have about 60% v.e. Sports cars have closer to 75%. NASCAR engines have about 90-95%. At higher rpm v.e. will drop off due to valve float; (valves will not shut completely when rpm are higher than valve springs are strong). The only way to have over 100% v.e. is with forced induction I.e turbo or supercharger. This is a basic term not the complete definition.
    Gulp effect- the volume of air being sucked into a cylinder is not equal through out the pistons travel. At approx. 75% of the cylinders intake stroke the amount of air being introduced into the cylinder is considerably more than any other point of piston travel. This is caused by a continuous flow of air that will start to pull the air behind it. This is a very basic term, when I was in school I was given a 3 page report on the gulp effect. To this day I do not know another person that has heard of this, it is not typically taught in auto class.
    If I find my old text books and notes I will add more accurate info. This is accurate but not complete.
     
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  18. timjimmy

    timjimmy Active Member

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    I don't think I've ever heard another person even mention volumetric efficiency before. I got kinda excited until I continued reading and saw that you had it all covered. Can't say I've ever heard of the "gulp effect" before, but to me, it sounds a lot like the principle behind venturis on a carburetor...as the air the moves from the plenum through the intake runner and into the cylinder, the overall diameter of the "tunnel", or path the air follows, goes from large to small to large, causing the air to rush through the intake runner into the cylinder at a rate greater than the engine vacuum sucks it in. If I'm not mistaken, I believe a few exhaust manufacturers are now producing headers with collectors that utilize a similar technique, actually helping to pull the exhaust gases from the primaries and into the mid-pipe. It's really amazing when you step back and really take a close look at the amount of engineering that goes into pieces of equipment that we all think are relatively simple.
     
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  19. 805mustang

    805mustang Member

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    And valve float..... Have you heard that before? When an engine is at such a high rpm that the valves try and open and close so fast that they are not actually closing all the way before they are commanded open again. This is always due to the springs not having enough tension or pressure to close the valves fast enough. Compression is lost and so is power.....a way to fix this is to obviously put stiffer springs in but by doing that you lose power by trying to compress stiffer springs or another method that I like is to put a smaller spring inside the larger spring! I agree that engines are much more complex than we make them out to be! A technician is like a dr. only cars are always changing and evolving and people are not, well not at a rate we notice! What you mentioned about the carbs and exhaust was also interesting to me! Keep the trivia going, did you know top fuel dragsters have no cooling system and need 2 distributors at 45 amps each to fire a almost hydro locked cylinder? Don't know what the air fuel ratio is but I would guess close to 75% fuel and 25% air! Here's one more, do you know the term for the perfect air fuel ratio of 14.7 to 1?
     
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  20. timjimmy

    timjimmy Active Member

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    Yup, I'm familiar with valve float. I've had good results with small block Chevy engines using beehive shaped valve springs. They're lighter weight and have a lighter tension, but due to their unique shape, the spring's harmonics change slightly as engine rpm rises, leading to a spring rate that is more or less proportionate to the engine load. I'm not sure what they're air/fuel is either, but I do know that they use a one gallon fuel tank, which is nearly empty after a single, 3.4 (or so) second pull. Also, Top Fuel dragsters use 7,000 horsepower engines, but under load, their superchargers require 1,000 horsepower just to spin, so before parasitic loss they actually produce 8,000 horsepower. I do believe 14.7:1 is called stoichometric, because it's the optimum ratio for combustion.
     
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