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Car Forum / Honda Cars / July 2005Accord 2000 - Question on Brakes wear
I have a 2000-Accord-4DR-EX with ~60,000 miles. I have never changed my brakes - since new. Today, I went for my annual inspection and the mechanic said that my front brakes look like new and the rear are almost gone, but OK until replacement soon. (1) Should I have both the front and rear replaced at the same time? Should I replace the rotors at the same time or not. (2) Are rear ones the first to go, in general? Thanks in advance Shanks don't change both at same time unless they need changing. You obviously have disc brakes on the rear - they IMHO are too small and wear out fast - have my origional shoes on drum brakes at 189K miles - got about 113 on first set of pads and 70K on cheap autozone pads. Have always wondered why auto makers put such small pads on the rear. Also whatever you do do not let the repair guys talk you into turning your rotors - big mistake - every time they turn they get thinner and more of a chance of warping. Also tell them to use torque wrenches not torque sticks and never ever impact wrenches - will bend/warp your rotors. > don't change both at same time unless they need changing. You > obviously have disc brakes on the rear - they IMHO are too small and > wear out fast - have my origional shoes on drum brakes at 189K miles - > got about 113 on first set of pads and 70K on cheap autozone pads. > > Have always wondered why auto makers put such small pads on the rear. Two reasons: 1) To give them a chance of getting even remotely warm in use 2) To make the parking brake bite properly with reasonable effort.  SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > <snip> >>Have always wondered why auto makers put such small pads on the rear. > > Two reasons: > 1) To give them a chance of getting even remotely warm in use > 2) To make the parking brake bite properly with reasonable effort. Why would small pads enable the p-brake to bite any better than large pads? >> <snip> >>>Have always wondered why auto makers put such small pads on the rear. [quoted text clipped - 5 lines] > Why would small pads enable the p-brake to bite any better than large > pads? Small pads concentrate the load over a smaller area, resulting in better "bite" with a lever that's reasonably easy to pull up. If the pads were bigger, the force exerted by the parking brake lever would have to be proportionally greater. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>><snip> >>> [quoted text clipped - 12 lines] > If the pads were bigger, the force exerted by the parking brake lever would > have to be proportionally greater. This doesn't make sense to me: the surfaces are not deforming--at least the rotor shouldn't be or you get a warped rotor, and that pad material is pretty tough. Friction between these two surfaces is therefore essentially independent of contact area (counterintuitive, for sure), so a larger pad wouldn't provide more friction, but whether large or small, the p-brake lever applies the same amount of force between the pad and rotor, and therefore the same amount of contact friction. No more force is required to press a larger pad against the rotor than a smaller pad. > Friction between these two surfaces is therefore > essentially independent of contact area (counterintuitive, for sure), so > a larger pad wouldn't provide more friction, but whether large or small, > the p-brake lever applies the same amount of force between the pad and > rotor, and therefore the same amount of contact friction. No more force > is required to press a larger pad against the rotor than a smaller pad. As I reread this I can't quite believe that a larger pad would not provide more friction--unless the point is to distribute the load over a larger surface area so that wear is also distributed, and the pads thereby last longer. Perhaps I'm missing something basic? My physics is admittedly somewhat rusty. On 7/6/05 12:43 PM, in article ntCdnTPZfpS6hVHfRVn-qQ@rcn.net, "Abeness" <news@nada.x> wrote: >> Friction between these two surfaces is therefore >> essentially independent of contact area (counterintuitive, for sure), so [quoted text clipped - 8 lines] > thereby last longer. Perhaps I'm missing something basic? My physics is > admittedly somewhat rusty. I had the experience of too big rear brakes on an 87 Ford Aerostar. This is totally apples to oranges in that the Ford was rear drive and had drums on the rear, but I think it is pertinent to the discussion. When the car was new, anything beyond light braking caused the rear to lock up. Forget about driving it when there was rain or God forbid, snow. The fix Ford eventually came up with was new rear brakes that had about a third LESS friction area. The problem was that the rear brakes were too strong, causing them to lock up as soon as the weight shifted to the front when braking. I think this is why the rears are smaller. My Hondas that have the little parking brake drum inside the rear disk (a '96 Odyssey and a '00 TL) have the expected longevity on the rear brakes (they last about 2 years longer than the fronts). My one Honda that used the rear disks for the parking brake (a '95 Integra) ate rears about twice as often as the fronts. My suspicion is that the ratcheting piston doesn't retract as much as they do on normal disk brakes, causing more drag on the rear brakes. Interestingly, the Nissans in the immediate family (a '96 and '97 I30 and a 98 Maxima) that use the rear disks for double duty do not eat rear pads like the Hondas do. The '98 Maxima is driven by the same driver as the Integra. > On 7/6/05 12:43 PM, in article ntCdnTPZfpS6hVHfRVn-qQ@rcn.net, "Abeness" > <news@nada.x> wrote: [quoted text clipped - 22 lines] > strong, causing them to lock up as soon as the weight shifted to the front > when braking. I think this is why the rears are smaller. and this was still not a proper fix. ford /always/ knew the issue - but they took the decision to save $'s by /not/ fitting a proportioning valve. cutting corners is always ford policy - even at the expense of, well, shall we just mention the word "explorer"? > My Hondas that have the little parking brake drum inside the rear disk (a > '96 Odyssey and a '00 TL) have the expected longevity on the rear brakes [quoted text clipped - 7 lines] > for double duty do not eat rear pads like the Hondas do. The '98 Maxima is > driven by the same driver as the Integra. > The fix Ford eventually came up with was new rear brakes that had about a > third LESS friction area. The problem was that the rear brakes were too > strong, causing them to lock up as soon as the weight shifted to the front > when braking. I think this is why the rears are smaller. Hunh. That certainly seems to indicate that larger pads = more friction, which does seem logical. Sure wish I could get on the phone with a Honda engineer for a professional explanation of how this works. I guess any physicist would be able to explain it too. I may be able to find someone, will post back if I get around to it. >> The fix Ford eventually came up with was new rear brakes that had >> about a third LESS friction area. The problem was that the rear [quoted text clipped - 7 lines] > works. I guess any physicist would be able to explain it too. I may be > able to find someone, will post back if I get around to it. I just had an off-line conversation with somebody who's been following this thread. He has efectively convinced me that parking brake operation is NOT there reason for the small pads. As you suspected, the physics are pretty simple: If you double the pad area, you halve the force per unit, but then double the units, so the end result is the same. However, if the pad area is greater and force per unit is less, the system has less ability to scrape off surface rust, leading to glaze. Also, because the brakes can't heat up as much, moisture is less likely to be dissipated, leading to more rust. And you know how badly rear discs can rust. My conclusion from all of this: Rear pads are tiny so they can heat up properly to dissipate water, and scrape rust off without causing glaze. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > I just had an off-line conversation with somebody who's been following this > thread. He has efectively convinced me that parking brake operation is NOT [quoted text clipped - 12 lines] > My conclusion from all of this: Rear pads are tiny so they can heat up > properly to dissipate water, and scrape rust off without causing glaze. Hmmm--ok. Thanks. >> Friction between these two surfaces is therefore >> essentially independent of contact area (counterintuitive, for sure), [quoted text clipped - 9 lines] > thereby last longer. Perhaps I'm missing something basic? My physics > is admittedly somewhat rusty. I don't understand the physics either, and there may be other factors at work than just the raw physics. All I know is that this is what happens. The explanation I gave is one I read somewhere, but can't remember what publication it was in. Road & Track, maybe? SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > I have a 2000-Accord-4DR-EX with ~60,000 miles. I have never changed my > brakes - since new. Today, I went for my annual inspection and the > mechanic said that my front brakes look like new and the rear are > almost gone, but OK until replacement soon. > > (1) Should I have both the front and rear replaced at the same time? No. Not if the fronts look brand new. Rears-only are fine. BUT: Have the fronts checked to make sure the pins and pads are floating freely with no binding at all. > Should I replace the rotors at the same time or not. Not if they're not warped or badly scored. Turning *can* increase the probability of future warping because it reduces heat-sink mass if taken too deep. A light skim is no problem, though. > (2) Are rear ones the first to go, in general? Yes, on a car with rear discs where the parking brake uses the disc pads. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ <snip> >>(2) Are rear ones the first to go, in general? > > Yes, on a car with rear discs where the parking brake uses the disc pads. Why is that? Without knowing any better I would think that using the rear disks as the parking brake would not put any additional wear on the pads because it's not engaged until the car is stopped, i.e., the disks aren't turning with the parking brake on, therefore no wear on the pads. TeGGeR® wrote :<snip> > Yes, on a car with rear discs where the parking brake uses the disc pads. > Sparky Spartacus wrote: > > Why is that? Brake bias, the front brakes are always larger than the rear brakes. Why? Because more than 70% of braking is done with the front brakes. This guy's rear pad wear, compared to the front, is probably due to his braking habits. I'm guessing this person is an early, easy breaker. That is, he applies the brakes with light pressure, and slows gradually, way in advance of the final stopping mark. The rear brakes are engaged just slightly before the front brakes. So the majority of slowing, in this case, is being done with "just" the rear brakes, thus the wear. The parking brake has little to do with rear pad wear, unless the car is driven with the parking brake left on. -- Tp, -------- __o ----- -\<. -------- __o --- ( )/ ( ) ---- -\<. -------------------- ( )/ ( ) ----------------------------------------- No Lawsuit Ever Fixed A Moron... My friends with cars having pads front and back seem to always wear out their rear pads first - thus my question as to why the rear pads are so small. A design screw up in my opinion. With 189K on my rear shoes and still a lot of miles left on these shoes - shoes it is for me in the rear - if I have a choice. > My friends with cars having pads front and back seem to always wear out > their rear pads first - thus my question as to why the rear pads are so > small. A design screw up in my opinion. No, has to do with ease of application of the parking brake, and heating up of the pads in use. If the pads were larger or harder, either the lever on top of the caliper (or the parking brake lever) would have to be longer to exert more force, or you'd have to haul up a lot harder on the lever to set the brake on hills. This is Honda's compromise. Our old Toyota MR2 was the same way. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > TomP wrote: > This guy's rear pad wear, compared to the front, is probably due to his [quoted text clipped - 3 lines] > the front brakes. So the majority of slowing, in this case, is being done > with "just" the rear brakes, thus the wear. TomP, WOW! You just described my braking habits, which is exactly the way I brake. Now back to basics. Can someone tell me the right way to apply brakes? > The parking brake has little to do with rear pad wear, unless the car is > driven with the parking brake left on. This is also very much true! I start driving and suddenly I notice that there is a red-light on the indicator panel, which says brake, then I realize that the parking brake is still on, and then I disengage it. It happened several times. Maybe whenever I park, I should apply parking brake hard -- so that my car wouldn't move when I am driving, then I remember to release the parking brake, for sure. >>TomP wrote: >> This guy's rear pad wear, compared to the front, is probably due to his [quoted text clipped - 7 lines] > way I brake. Now back to basics. Can someone tell me the right way to > apply brakes? I don't think it's wrong to apply brakes as you do--TomP is saying that it just results in a certain kind of pad wear. Pads aren't expensive, really, and aren't difficult to replace--and you got 2 years/60,000 miles out of those pads, even with a few times of leaving the p-brake on while driving, which will burn them up fast. If you're comfortable braking as you do, i.e., gently, that's just the way you brake. Don't feel a need to change it. > This is also very much true! I start driving and suddenly I notice that > there is a red-light on the indicator panel, which says brake, then I > realize that the parking brake is still on, and then I disengage it. It > happened several times. Maybe whenever I park, I should apply parking > brake hard -- so that my car wouldn't move when I am driving, then I > remember to release the parking brake, for sure. Absolutely. The p-brake is there to keep your car from moving while parked. Engage it fully, with some strength: the service manual says 200 N/20 kg/44 pounds of force. The proper adjustment for my 94 Civic--may be different for yours--is full engagement within 6-10 clicks, and I'd have to be completely oblivious to not realize that it's on when it's fully engaged, not that I've repaired the rear brakes and properly adjusted the p-brake. Get in the habit of releasing the p-brake before you put it in gear, and you won't have a problem. Abe > have to be completely oblivious to not realize that it's on when it's > fully engaged, not that I've repaired the rear brakes and properly > adjusted the p-brake. Oops: "NOW that I've repaired..." > > TomP wrote: > > This guy's rear pad wear, compared to the front, is probably due to his [quoted text clipped - 17 lines] > brake hard -- so that my car wouldn't move when I am driving, then I > remember to release the parking brake, for sure. There is nothing wrong with your driving/braking habits, and they do not need to be altered. Just drive and enjoy. Brake pad "life" expectations, should be considered more by driving conditions, rather than raw mileage accumulated. -- Tp, -------- __o ----- -\<. -------- __o --- ( )/ ( ) ---- -\<. -------------------- ( )/ ( ) ----------------------------------------- No Lawsuit Ever Fixed A Moron... > TeGGeR® wrote >:<snip> [quoted text clipped - 16 lines] > slowing, in this case, is being done with "just" the rear brakes, > thus the wear. I brake hard and late. My rears always wear first. It has nothing to do with the parking brake itself, but the way the rear brakes have been designed so that the parking brake will operate correctly, and so the brakes will heat up in use the way they should to burn off moisture and rust. It's a compromise that must be made in all FWD cars that have rear discs which double as a parking brake. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > <snip> > [quoted text clipped - 10 lines] > aren't turning with the parking brake on, therefore no wear on the > pads. See my response to Abeness. It has to do with the size and softness of the pads, and with the leverage necessary to apply the parking brake. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>I have a 2000-Accord-4DR-EX with ~60,000 miles. I have never changed my >>brakes - since new. Today, I went for my annual inspection and the [quoted text clipped - 18 lines] > > Yes, on a car with rear discs where the parking brake uses the disc pads. as a side note- my local dealer, norm reeves honda of cerritos, CA sent me a flyer with their service specials in it. they want $165 to do the front brakes... damn. $165, and thats a "special"? and that doesnt include turning the rotors, which would be extra, if needed. but it does include a complete inspection of the brake system! something i can do in 10 minutes myself. id change front pads all day for $165 a pop. hell, id even drive to someones home or place of business and do it there! <snip> > Yes, on a car with rear discs where the parking brake uses the disc pads. true. interestingly, not all cars with rear disks use them as parking brakes. the subaru legacy has a drum/disk combo. drum is inside & operated by the hand lever, disk on the outside of the same piece of cast iron, used for a disk. very good idea as there's always a completely independant [cool] emergency brake. >From the shop manual: BRAKES Front Pad thickness: Standard: 0.41 - 0.45 in Service Limit: 0.06in Rear Pad thickness: Standard: 0.33 - 0.37 in Service Limit: 0.06in |
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