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Stop here! Let's talk about brakes

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  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,536
    >so I don't see how a slightly cooler /slightly heavier rotor will stop a car quicker.

    I do not know that the tenet is that a thicker rotor will stop the car quicker. What it will do is stay slightly cooler as the predetermined quantity of heat is transferred into it. Staying slightly cooler may mean better braking, but in my thinking it means the rotor is slightly less likely to suffer distortion at the end of the stop due to the extreme heating during a hard stop or a long braking period such as a long downhill run.

    But I have another observation. That is that the inside fins of most rotors are covered with a rust material. That has to insulate an old rotor from the air going through the fins and somewhat lower the transfer of heat to the air through those openings. That's why if I drive a car hard or I have had brakes that warped slighty I feel it's time for a quality new rotor that has a cleaner surface on the fins with which to transfer heat to the air that's interior to the rotor as well as the external surface air. If it's my 180,000 mile Buick that's driven mostly gently around the suburban and rural region, I think less about new rotors.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,949
    So, if I machine the rotors on one of our CRV's leaving it well within specs and someone with an identical CRV REPLACES his rotors and we both make a panic stop from 60 MPH, are you telling me that there would be a measurable distance in stopping?

    Of course, this assumes identical tires, same road conditions etc?

    I'm not buying that. Sorry.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,990
    I was thinking that there's a certain amount of glazing on pads and burning on old rotors, and some roughness, so all together yeah, you might get a few extra feet out of brand new rotors and pads vs. a set that's been working hard for 25,000 miles. Perhaps it's the overall combination of all the things about a "new brake job" that gives me that confidence.

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  • isellhondasisellhondas Issaquah WashingtonPosts: 17,949
    Well, I was assuming both cars had new pads. One had NEW rotors and the other had freshly resurfaced in tolerance rotors.

    Speaking of which, our 2003 CRV has 53,000 miles on the original brakes. 10,000 miles ago, they still had lots of pad left.

    Time to take another look!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,990
    I drive pretty darn hard, so I'm not comfortable with shaving any appreciable metal off a rotor. I'm okay with cleaning them up but I wouldn't run mine if they are close to minimum tolerance. I'm just too hard on brakes to take a chance.

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  • shiposhipo Posts: 9,152
    Lets say the stop is from 70 to zero; yes, there will be a measurable difference if said stop is at impending lock-up. Now lets say the rotors are already hot from heat yet to be dissipated from previous stops, then the difference stopping distance will be even more pronounced.
  • jipsterjipster Posts: 5,345
    edited December 2010
    Is this fact or theory? Measurable difference? How much is total weight of an average rotor face? How much is machined off? How much heat would need to be dissipated before it would affect performance?

    Sounds like something the auto parts industry would fund if putting on new rotors were noticeably more beneficial than machining. I mean why not put on a new set of tires after every 10,000 miles... same thing.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,990
    Probably the only real advantage of not turning rotors is that, if you are a hard driver, a thinner rotor would probably warp more easily---let's say if you were coming down a long hill and then hit a puddle of water at the bottom.

    It seems that many modern cars, especially entry-level types, are plagued with rotors that warp as easily as the tinfoil in an Italian TV dinner tray.

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  • shiposhipo Posts: 9,152
    edited December 2010
    Sorry guys, the fact is, the thinner the rotor, the lower the thermal mass of said rotor; the lower the thermal mass, the higher the rotor will heat up with the application of any given amount of heat; the higher the heat the lesser the effective braking power. Is it significant? I believe it is and have read plenty of studies published in the SAE archives that back that up with hard numbers.

    That said, you shouldn't believe some dumb [non-permissible content removed] on the internet; if you're interested in this kind of stuff you should do your own research. I've done mine and I change rotors at every brake job. That's my story and I'm sticking to it.
  • srs_49srs_49 Posts: 1,394
    Yes, the temperature rise is directly related to the mass of the rotor. The lighter the rotor, the more the temperature rise for the same amount of energy (heat) input.

    That said, what kind of difference in temperature rise are we talking about for a machined vs a non-machined rotor? Well, we need an estimate of the before and after machining weight of the rotor.

    Assume a stock rotor weighs 15 lbs. Further assume that after using up one set of brake pads (which wear the rotor) and then machining said rotor, it's weight it 14.5 lbs (0.5 lb metal loss seems high to me, but this will give us a worst case estimate or temperature rise).

    Now, assume a braking scenario that raises the temperature of the stock 15.0 lb rotor 100 deg C. Then that same braking scenario, applied to the used, machined 14.5 lb rotor would raise its temperature 103.45 deg C, a 3.45 deg C increase.

    So yes, the used, machined rotor does run hotter, but does the 3.45 deg C increase make that much difference?

    If the rotor was half as heavy as the one I postulated (7.5 lbs from the factory), and the braking scenario twice as hard, the temperature difference between the two rotors would still only be 24.29 deg C.

    I do not know if a 24.29 deg C difference in rotor temperature is significant or not. For the average driver who maybe needs to do 1 full blown panic stop from highway speeds a year, probably not. For those who like to push the envelope coming down a mountain, :shades: .
  • bpeeblesbpeebles Posts: 4,085
    edited December 2010
    The main reason for NOT turning modern rotors is because many are HARD SURFACED.... not because of loss of braking charictoristics. There is a min. number embossed on the casting to tell you what is safe. Turning them removes the all-important hardend surface whence the pads create friction.

    Todays modern brake-rotor may be made up of several different materials.
    - The hard-surfacing for the pads to bite into.
    - softer material which conducts heat away.
    - tougher material which resists warping near the bolt-holes

    You may not be able to visually *see* these differences. Modern meterallgy tecniques like flame-hardening can make one cast peice have very different charactoristics.

    Of course, you can always buy cheep rotors that will warp the 1st time you do a panic-stop.

    Heck - the brake rotors on my motorcycle are aluminium inner section with fully-floating StainlessSteel outer area for the pads to bite into. (Just like race-cars use.)
  • tedbarttedbart Posts: 1
    edited January 2011
    The brakes on my 2006 Toyota Avalon (46K miles) started to make a grinding noise. Pads were worn to the center groove but still has ~3/16" of friction material. Changed them any way, but the noise is still there. Rotors are smooth and brakes are steady.
  • srs_49srs_49 Posts: 1,394
    1. Is the grinding noise present all the time, or only when you are applying the brakes?

    2. Can you isolate the noise to the front or rear?

    3. Does the noise change if the wheels are being turned?

    4. Maybe the water splash shield is bent and rubbing on the rotor.
  • dtownfbdtownfb Posts: 2,915
    Are you using Toyota pads or aftermarket pads? I had my mechanic change the brakes on my 2006 Camry. Used napa Gold pads like he always uses on any brake job. Brakes started grinding. Replaced pads again and turned the rotors. Still grinding. Finally he just used Toyota pads and rotors. problem solved.

    A cheaper solution would have been to replace the rotors with Napa brand but we both were so frustrated that he just used Toyota parts.
  • bpeeblesbpeebles Posts: 4,085
    Lets be realistic here. Noisy brakes may be an annoyance... but it is is not a "problem".
  • Check these out... Phoenix Systems brake fluid test strips

    measures the level of copper present in the brake fluid. Just tried these out as I had dealers for both my cars push brake fluid changes at 36K miles which seemed very early. Seem to work well and easy to use.

    http://www.brakebleeder.com/index.php?main_page=index&cPath=3
  • jipsterjipster Posts: 5,345
    Thanks. I'll keep those in mind. Had the brake fluid changed out a few months ago as it was noticeably dirty.
  • Hello Friends,
    Recently my brakes started squealing and I took it to a mechanic. He initially said the brake pads would have to be replaced and quoted me around $260 each axle. Then he called me up and said that the front rotors would have to be replaced since they were metal to metal. I was wondering as to why the rotors need to be replaced since they can be resurfaced and I had brake problems for only a couple of days and surely the brake pads would have given some indication that they were wearing out before going metal to metal. He even showed me the place where the metal on the rotor had filed away because of the brake pads being metal to metal. He quoted me $718 + tax. Of which about $315 is labor and $310 is parts and $50 is something like sublet which I think is rotor turning. Is the job too expensive. My car is at 60k miles and this is my first brake job.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,990
    What year make model of car are we talking about?

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  • It's a 2008 Mitsubishi Eclipse Spyder 2-door convertible.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 45,990
    edited September 2012
    Okay....

    rotors are $90 each

    pads for the front are $99 for a set

    Labor should be about 2 hours give or take

    So if the labor rate is $100 an hour (don't know in your area), that's $200 labor and roughly $300 parts I listed---so $500 is about right.

    any additional work or materials would be added on, of course.

    Rear pads would be $75 the set, plus maybe 1.3 hours to replace them in the back.

    So another $200 for rear pads.

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  • So you are basically saying that $718 seems right for front rotors and all brake pads.
  • jipsterjipster Posts: 5,345
    edited September 2012
    Look/call around and you can find it a lot cheaper than that. Brakeway will do a 4 wheel brake job with "quality" ceramic pads and turn your rotors for $139. Most shops though you'd be looking at between $400-$700 for that work. A dealership will be at the high end of the price scale.
  • srs_49srs_49 Posts: 1,394
    I had the front brakes done on my Dodge Dakota truck a couple of months ago. Bill came to $750. This included:
    1. Front pads and rotors
    2. One front caliper assembly
    3. New hardware (caliper bolts, spring clips, etc)
    4. Brake fluid flush/changeout
    5. Rear brake inspection and adjustment(?).
  • I'm sure this has been covered but I am patting myself on the back for changing my own pads this weekend. :D If you don't need things like the rotors turned changing your own brakepads is surprisingly easy (and pretty inexpensive). On my car (2004 Honda CR-V) literally, jack the car up and use a second jack to support the wheel (not sure if necessary but I had it so I did it). Remove the tire. Find the two bolts on the back side of the caliper (they have rubber boots connected to them). Undo one and rotate the caliper out of the way. Replace pads and other needed parts. Check the rubber boots for cracking and make sure the pins move properly. Depress the caliper, this is the hard part as it takes strength (I'm not the strongest person in the world) and some patience to do it by hand but I did it. They likely make tools for this but it can be done by hand, just remember that you are forcing liquid back out through a tiny hose so it will move VERY slowly and you just can't speed it up.

    All in all, to replace the front pads it took me 20-30min tops for both sides combined and $50 for some Wagner Thermoquiet ceramic pads. No clue if there are better deals on pads but I've been very happy with them on the rear and I decided to put them on the front as well.
  • bpeeblesbpeebles Posts: 4,085
    Woo Hoo - Congratulations for replacing your own brake pads. I have been doing this since I was about 15 years old and have learned a "trick or two" along the way.

    *) An inexpensive clamp or even a large pair of waterpump-pliers can be used to compress the caliper. (plus you get to own a cool new tool!)
    *) Have the cap off of the master-cylinder and WATCH THE FLUID LEVEL as you compress a caliper.... the level WILL go up and you may need to remove some fluid before it overflows and makes the paint come off your car.
    *) REAR calipers which have integrated parking-brake *MUST* be compressed and rotated at the same time. (An opportunity to own a real caliper-compressor)
    *) File smooth all the pad-slider surfaces before applying the hi-temp grease.
    *) Apply a thin layer of antisease grease to inside of wheel so it does not get stuck to the rotor.
    *) Use torque-wrench on lugnuts and RETORQUE a few days later if you have aluminum wheels. (another opportunity to own a new tool)
  • I own a 2008 Lexus IS 250. I've owned it since late 2009. Just brought my car in for an oil change and they said I need new front brakes. They showed me the pads and I guess they looked low compared to a model they had of new pads. I had my front pads replaced 6/12/11 and it's now Oct 2012. It looks like they wrote my mileage on the receipt, but I'm not positive (it's listed under license No, but it's obv not my license #)...40,815...my mileage now is a little over 50k...I thought brake pads should last closer to 30,000 miles?? I found it interesting when I first was told I needed new brakes that I got, not only different price quotes for the repairs, but that each shop (local mechanics, midas, etc) told me that I needed different things. Some said just front brakes, some said front and back. Some said new rotors or rotor resurfacing, some just pads...Called the dealer who put the pads on in 2011 and said it seems kinda soon to need new pads and he said to bring it in and he'd take a look at it. Any advice?
    Also, after reading the tips on brakes on this website, one article said you can wait until you hear a squeeking noise from the metal in the pads, which is there to tell you it's time to replace. Another article said you should try to time it before that happens...any suggestions?
  • bpeeblesbpeebles Posts: 4,085
    edited October 2012
    Is this the first time you have ever taken a car in for service? Unfortunately, this happens ALL THE TIME. Some places are worse than others. (For example Midas mechanics get a 'kickback' when they sell more stuff to a customer)

    As for waiting for a "squeeking sound" This is only true if the pads have "wear sensors" attached to them. Some better-designed cars actually have an electrical sensor which lite up an indicator on the dash (Volkswagen, Audi and other German makes.)

    If your last "barke job" was done on the cheap... then you may not have any wear-sensors at all.

    On to your underlying question.... "is this "too soon" to be needing new pads" ABSOLUTELY!! (I get 60-80 thousand miles on brakepads)

    However, your driving-habits may wear the brakes faster. (Do you completely release the brake pedal when not using brakes?)

    Pads which are sticking in the guides may wear faster... but a properly executed "brake job" should have filed the rust off of the guides and lubed them.

    A problem with the hydrolic-system could also cause premature brake-wear. (very VERY unlikely)

    "Do you need rotors" Usually NO... If they are still servicable, they can be used for a very long time.

    Your *real* problem?.... you seem to be having troubles finding a reputable service mechanic that you can trust with your car.
  • Thanks for the info! I am trying to find a trustworthy mechanic, but it seems like you can't trust any of them! And yes, I know all about the mechanics and tire guys trying to get you to buy extra things you don;t need! Thanks again!
  • jipsterjipster Posts: 5,345
    This happens occasionally. A medium to harder stop resulting in a popping sound, then what feels like a split second loss of braking force before reengaging. New pads, rotors turned. Dealership says can't find or duplicate.
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