Stop here! Let's talk about brakes

bpeebles

All modern disk brake systems are of the "full floating" design.
This means that the caliper itself is free to float or "center itself" over the rotor. In theory this should make the inner and outer pads see EXACTLY the same amount or wear. (Irreguardless of the fact that the piston is on one side or both sides.)

In reality, there are a few factors that can cause uneven pad wear.
1) The pins that the calipers ride on need to be totally free to slide. Some of themmay need "rubber grease" to help this happen.

2)The pads themselves ride on a flange on each side. All of the braking-forces are transferred to this flange from the pads. This flange can get "groved" wheras a pad can then tend to "stick" in a specific spot even if the caliper is free to float.

#1above is relativly easy to check by assembling WITHOUT THE PADS. With bolts at proper torque-spec, the calipers should be VERY easy to slide back and forth on the pins. (The very best design I have seen is Nissan, their calipers ride on a linear bearing!!)

#2above can be checked by assembling WITHOUT THE CALIPERS. Each pad should slide with ease by hand on its flange. On every disk-brake system I have worked on, the flange is groved to some degree. I use a basterd file to smooth all rough areas from the flanges before reassembly.

Also, high-quality pads (Raybestos Ceramic!) come with stainless-steel shims of varing thickness. WIth the proper shims selected, the pads have a slick stainless-steel sliding surface to work against.

The Idea above is to seperate each moving part into its most simple form and then acertain where the problem is. It is possible to get even pad wear. A bonus is that your MPG will go up due to reduced drag from the braking system.

alcan

GM inner pad wear is usually caused by the caliper slide pins binding in their rubber bushings in the calipers. I've just finished a front brake job on a '97 LSS, same thing. Had to drive the pins out of the calipers, but after cleaning them up on a wire wheel and lubing with silicone brake lube they work fine and slide freely.

Pads can not be switched inner to outer. The outer pad is about 2" longer and completely different in design from the inner. Like almost all cars.

bpeebles

I am a big beleiver in Preventive Maintenance. On my 2000 vehicle I have pulled the brakes off, cleaned them up, checked all moving parts, lubed all moving parts and reassembled at least twice.

With a V8 engine, every little bit of MPG helps.... and the brakes last a longer too. A lot of people ignore the automatic adjusters on drum brakes. With proper PMs, I get over 60K miles out of my brake shoes.

ruking1

Ops! I was just reading where on my Z06 that pads can be interchanged outside to inside. So it seemed to me that other GM models might have the same design. It is probably true that you can not swap pads in all vehicles. Normally all my brake pads I swap out at the same time (per axle) due to the fact the wear as almost uniformly been even.

wtd44

For those of us that hate noisy, grinding brakes, the new ceramic pads are very promising. I slapped a set into my Pathfinder and was amazed at the quieting that took place.

bpeebles

There is a reason that Raybestos calls their ceramic pads "Quiet Stop"

Another side benifet to the ceramic pads is the reduction of all that black "brake dust" that make your wheels look like #$##$.

98monte_ls

Has anyone ever replaced their own brake pads on a 4th gen Camaro? How hard is it? Also, would i get better brake performance using delco's durastop pads (ceramic) with the rest of the system stock?

Another question: my OEM pads now are kind of thin and the rotors keep getting warped & pulsate. A mechanic tells me that its useless to turn the rotor because the thin pad will transfer more heat to the rotor & cause it to warp faster. I have no squeals from the brakes but they recommend new pads (together with resurfacing) to cure the pulsating. Does this sound legit?

bleeet

My 1999 Toyota 4-Runner with ABS brakes has experienced 2 instances in the last week where the brake pedal went to the floor with no braking action. Pumping the brakes once worked to stop the vehicle. All fluid levels, brake pads etc. appear to be normal. Is there a sensor, solenoid, or master cylinder failure that can cause this?

bpeebles

What you describe is the classic symptom of master-cylinder failure.
(fluid not going down)

However, a leaking brake-line could do this too. In this case, the brake-fluid in the resivour will slowly gow down. (a small amount is lost every time the pedal is pushed.)

I would expect that the redundancy built into all vehicle brake systems would allow some braking action. Also, be prapered to use the emergancy-brake lever at any time.

In any case, get this looked at and resolved.

Mr_Shiftright

Master cylinder can "bleed" internally, so that they can lose pressure but not fluid. If you actually had a bad leak, pumping the brakes wouldn't really help as you'd soon be out of fluid entirely. And the dual braking system wouldn't give you a very good pedal or stopping power on 2 brakes.

So if your pedal goes back to "normal' after pumping, I'd guess an internal defect in the master cylinder.

You could actually test this by disconnecting the brake lines from the master cylinder and putting solid plugs in the holes. If you then lost pressure suddenly with the lines disconnected and the exit holes plugged, you'd be pretty sure you had the problem nailed. A lot of trouble, but some master cylinders aren't very cheap either and they don't like to take them back if you guess wrong.

bleeet

Thanks for your reply. The first time the brakes failed, my wife was pulling into a parking space at a shopping center. She hit the car in front of her doing minor damage but no injuries. We took the vehicle to a brake and tire center that was located in the shopping center. Their visual inspection didn't find anything so a tech took it on a test drive. He was driving when the second failure occurred. He said that he took his foot off the pedal and it came back up. He pushed again and it "caught" this time. He described it as a bypass somewhere. We called Toyota and they told us to take (tow) the vehicle to the nearest dealer. They had the vehicle for a week and claim to have performed several road tests where the brakes worked normally. After a manufacturers field rep from Toyota looked at the vehicle on Friday, they called us to come pick up the vehicle. I was shocked. I picked it up on Saturday but no one was there who could actually tell me what specific tests they did--other than visual and road testing as written on the record.
 
I too was surprised that backup systems didn't work which means that either multiple things failed or there are some single point failures in the system. I'm now looking for a good brake repair garage in San Diego to take the vehicle to.

swschrad

one would have thought the dealer would catch it. not sure how honda handles ABS on that car (either one master pressure valve, or pressure valves for each wheel) ... I would guess one valve system per wheel.

what you describe sure sounds like one part failed and affected all brakes. I see no evidence in the post that you lost your brake fluid. it thus almost by default has to be one of three things... a one-valve ABS modulator... massive failure in a vacuum brake booster (oh, but that would be a rock-hard pedal, wouldn't it?)... or the master cylinder and/or proportioning valve is kaput. with a "no-pedal", on a honda, my gut reaction is the hydraulic cylinder has a problem. even if it's a chunk of crud or rust that jammed the valve, I'd bleed new fluid into the whole system top to bottom, replace the master cylinder after a bench bleed, re-bleed the whole system because it IS a brake issue... and see how things are then. brake fluid is real cheap compared to running down people, things, or cars; you can't bleed brakes enough.

wtd44

Or, you can't bleed them too much...

bleeet

Thanks for your input. A mechanic totally checked everything out and found that the brake pads, shoes, etc were in good shape. The rear brakes were out of adjustment and likely not providing much, if any, braking action. He adjusted the brakes, replaced the master cylinder at my request, added new fluid top to bottom. Essentially exactly what you suggested. However, I'm still not sure that all the bases have been covered. If we assume that the rear brakes were not working because of misadjustment, it would have only required a failure of the front brakes to cause the pedal to go to the floor without braking action. Is there a possible failure mode where the ABS system sticks open so the fluid is temporarily diverted into the ABS reservoir and not to the front discs? Other failure modes? Remember the symptoms were intermittent (only happened twice where the pedal went to the floor). Fluid levels were normal, no leaks, solid brake pedal (other than the failures), no ABS problem indicated by a light or computer code. Since getting the brakes adjusted, the pedal has a somewhat shorter stroke but the Toyota techs who drove the vehicle before the repair didn't note that the pedal was soft or the stroke unusual.

Thanks

wtd44

What comments did the mechanics have concerning your rear brake adjusters? They are supposed to work automatically: They take up slack when backing and braking. That could be a problem on your car, from the symptoms you note.

bleeet

No specific comments about the rear brake adjusters but they were obviously not working to keep the rear brakes adjusted to the proper level. However, that had been the case over a longer period and would have been the same every time the brakes were applied. Even if the rear brakes weren't working at all, a failure in the front brake system is still required to produce the results--complicated by the fact that it's intermittent. Since no problems were identified in the front hydraulic system, I'm wondering if an intermittent erroneous signal from the computer or a sensor or a sticky solenoid in the ABS system could have provided a path for hydraulic fluid to pass? I haven't had access to a detailed shop manual for the system to determine if this is even remotely possible but one book that I bought describes the ABS system as temporarily allowing a small amount of fluid to pass into an ABS reservoir which is pumped back to the master cylinder reservoir.

wtd44

How about a faulty proportioning valve between the front and rear brakes?

probe94

I have a '94 Ford Probe GT with ABS. My insurance company claims my car doesn't have 4-wheel ABS. They claim it either has NO ABS, or only TWO-WHEEL ABS, in which case they don't offer the discount, which is only for cars with four-wheel ABS!! I can't find anywhere online that says if those things are even possible for my model car, or if the insurance reps are lying through their teeth. I called the local ford dealer, who claimed they would have to take all the wheels off to find out! I feel like I'm being lied to from all sides. Where can I learn the truth?!

alcan

Look under it. If the front halfshafts have toothed rings on the outer CV joint housings, they're the reluctor rings for the wheel speed sensors and it has 4 wheel ABS. My database shows that 94 Probe/Mazda MX6 didn't come with 2 wheel ABS.

probe94

Thanks for the tip! So, my probe either has 4-wheel ABS or no ABS?

I'm not sure I'd know what I was looking for... but maybe I can find someone local who can interpret your advice for me.

Thanks again!

swschrad

all around an outer edge of the halfshafts out by the wheels. every wheel hub that has these teeth has an ABS sensor nearby. you got 'em on all four wheels, it's 4-wheel ABS. two, two. none, it's no BS. or something like that

beernut

I had the brakes replaced by a Joe Schmoe shop three months ago which may or may not be related to my problem. The left rear wheel started clunking with brake application on Tuesday. On Wednesday, same thing but also a rattle sound all the time. The Ford dealer drove it and said it was definitely not brakes. I disagreed. Last night I took the wheel off and found that you could fry eggs on the drum and not turn it by hand. The adjuster had to be turned completely in just to turn the drum let alone get it off. I found the upper long spring (return spring?) to be off at the top with the top hook looking like it had been straightened out to a 90 degree bend and the small cable and spring doo-dad that hooks to the adjuster hanging loose at the adjuster.

With my limited knowledge of brake systems, it seems that not only were the shoes not returning, the adjuster might have been firing every time I applied the brakes pushing the shoes out hard.

Questions: a) Could my initial clunking have been the adjuster working when driving forward? b) How could those springs have just come off? Its not easy to straighten that hook and I don't think it just happened by itself. I suspect the Schmoe did it but if so, why did it take three months to show itself? c) What's the cable and spring doo-dad going to the adjuster for and how is it it could come off?

Any comment would be useful. Thanks.

geauxnow

There is a noise coming from the rear. It happens when the brake pedal is applied, but not always. It's a swish-swish noise like something may be rubbing. I thought the intermittentency was possibly due to warm-up, but I'm not sold on that. The car has about 18000 miles.
GM said there was nothing they could do about it, because they have no history on it. Has anyone had this problem yet?

joe3891

tank shifting,the sound come and goes with changes in fuel level.The Cav has little sound deading installed as you already know. I bet you won't hear it with a full tank.

geauxnow

Nah, sounds like somethings rubbing under there. Apply the brake, you get a swish-swish. Let off the brake and it goes away. I'll try the full tank test though.

newbie_buyer

I've read a number of comments about ABS systems and problems people have had with them here. But I have a more basic question: is this something that I need? Will it save my life? I haven't yet found anything that really recommends them over traditional systems, so I am wondering why would I buy them in that case?

bpeebles

ABS, by itslef is not a big deal and actually may get in the way of a good drivers skills. (Who, in their right mind would try to steer while the front wheels were locked up?)

The followon to ABS which uses the existing ABS sensors and some additonal sensors has been PROVEN to be a lifesaver. It is sorta like "active ABS". Is knows which direction the vehicle is moving and where the wheels are pointed... it instantly applies the brakes at the proper wheels to correct any skidding.

It has several names (European vehicles call it ESP for "Electronic Stabilization Program")

I can attest that with the ESP turned on, my Volkswagen is virtually impossible to put into a skid even in the snow. It is almost UNCANNY how it works.

Several indipendant tests have shown that ESP (and its counterparts) is much safer than not having it. One test on a snow-covered track with cones was very convincing. The test drivers were over 60% better at manuvering around the cones without hitting them when ESP was turned on.

I can tell you that this next generation of ABS technology was well worth the xtra $350 pricetag when I orderd my vehicle.

stubborn1

Having ABS is kinda like having a parachute on a plane. Chances are you will never need it, but it can save your behind if you ever do.

I've avoided one accident with ABS. I had to make a panic stop in rain when someone pulled out in front of me. I was able to steer around them while standing on the brake.

My collision deductible is $500. ABS tends to be a $400-$500 option on most vehicles where it isn't standard. I'd rather pay for the ABS than an insurance deductible.

wtd44

Some newer brake materials (unfortunately) are very noisy. If everything about your brake system seems to be in proper order and condition, and your only complaint is the noise you hear when you engage the brakes, you may need to "just get used to it." I went through this fiasco with a Pathfinder. I paid a non-dealership shop to do a brake job. It didn't get quiet until the front pads were changed over to Raybestos Quiet Stop.

bpeebles

Another bonus from "Raybestos Quiet Stop" pads is that they are CERAMIC-based. They do not enerate nearly as much black dust and thus, your wheels will stay cleaner.

I actually replaced the perfectly good, hardly-warn OEM pads on my vehicle over to "Raybestos Quiet Stop" to gain the benifets of cleaner wheels.

rae52

geauxnow, I had a similar problem w/ the brakes on my Cav; Mine is a 2002.

The dealer cleaned out the rear drums of brake material and adjusted them (the rear brakes). Also, the dealer cut the (front) rotors; was experiencing steering wheel and brake pedal vibration when applying the brakes.

Hope this info helps you...Richard

foraza

I would like to buy a brake pedal cover for my car.

Any recommendations?

Should the pedal cover surface be smooth or somewhat rough (to avoid slip off)?

Mr_Shiftright

The previous post is a duplicate and has been addressed in our "Technical Questions" forum.

Host

dudebloke

Hi guys,

Need some help. Recently, some chick banged into the rear side of my passenger side. I was parked and she was getting out of her parking spot. Aside from some bumps, I didnt notice anything.

Almost around the same time (some 4 weeks ago), I was hearing scratching sounds everytime I brake, or even when Im rolling forward!

A body shop guy looking at the bumps said he didnt think the impact caused anything, and the scratchy noice was coming probably from my rear brakes, He said the brake discs looking from the outside seem to have darker concentric circles on both the rear wheels. The front tire discs both look pretty clean

First, I thought the front brakes give in first, but they look ok (I have about 56k on my 97 lude)

Second, could the impact have anything to do with it, beacause i hear the sound mostly from my right rear side where the impact took place, although the concentric circles appear on both rear tires

Third, do I have to change the discs, pads and how much would it cost me??

Thanks so much in advance!

dudebloke

Thanks Isell.

sensei1

I'm thinking of upgrading to slotted rotors (fronts only). Anyone with firsthand experience to share? pros and cons?

Can they be turned like an OEM plain rotor? Can I get away with 2 fronts instead of all 4? Thanks.

burdawg

I used Powerstop drilled and slotted rotors in the past on Pontiac cars due to the problem with the rotors warping. My experience has been as follows:
Wear rate is about the same as good aftermarket (Raybestos) rotors.
Braking action is the same as long as real hard (i.e. "long life", "severe service") pads aren't used.
Machine shops will charge more to turn these since the cutters on the lathe get worn faster by machining these.
I've seen some close up pictures lately of stress cracks that form around the holes after long use in some cases. Not all performance rotors have holes, some just have slots.
When you brake you may notice more noise coming from the brakes. I think it's due to the edge of the pad slightly hitting the edge of the slot, but i'm not totally sure.
In my own opinion, for most of us, the cost outweighs the benefit and I won't be using them anymore. I will stick to good aftermarket rotors and do my best to be easy on the brakes. I think the way we drive today (always in a hurry to get to the next red light, rush here, rush there, heavier traffic for most of us, etc) is the root cause of premature brake wear.

wtd44

Another cause of fast brake wear is ABS.

sensei1

Thanks for your FYI. Yeah, I'm looking at the Power Slots and braided brake lines too. Maybe just front rotors first.

Mr_Shiftright

I think basic rotor design and quality has a lot more to do with good braking and preventing warpage than mere slots or drilling.

If your car is basically "underbraked" to begin with, by factory design (not uncommon) adding slotted or drilled rotors of the same size and quality (that is, sand-cast with the rotor and hub as one piece---typical low cost factory stuff), is only going to make your rotors wear even faster.

So you need to thinking about a better quality rotor, perhaps runing on a separate hub, and also perhaps, depending on how hard a driver you are, about cooling your rotors with special wheels or ducting.

If you can't duct away the heat and you can't put on a high quality rotor with great high-temp metallurgy, then slots and drilling won't help you much if at all.

Don't be fooled either by a rotor that looks thick and heavy. If it's the same low quality cast iron that the factory gives you, all you are getting is heaviness to compensate for poor heat dissipation and all kinds of casting defects.

wtd44

Are Raybestos or Bendix disks a good bet?

snowman

Either I got a bad batch or Reybestos are not up to par.
I did my front brakes on 00 Taurus last year June. Everything was smooth and perfect. I used Quit Stop pads as well. I put 12K within a year and now I've got vibrating pedal and steering when breaks are applied @ around 70-80 mph.
City traffic is fine though. I believe slight imperfections occured on the rotors.

I've read some discussions that some blame calippers for reoccuring rotor warpage. They say pistons are not moving freely in the bores and not giving equal pressure to rotor surface.

Whay you guys say about this?

Mr_Shiftright

Well it's possible I guess in some cases but really I think so many modern cars are "underbraked" and using inferior metallurgy for their rotors.

I think if you're shopping for rotors you need to look at manufacturers claims on metalllurgy (what process is used for casting) and engineering (is the rotor cast with the hub or is the hub a separate "hat" as they call it that might be welded on.

Basically you get what you pay for. The rotors on my car are pretty expensive but you know they are beautifully built, they don't warp and they suck your eyeballs out. But, yes, they will wear and are not turn-able.

You can feel bad for the owner of a Porsche GT2--he's going to pay $8,000 apiece for his new rotors (yeah, no kiddin'). Of course at an MSRP of $180K he can probably afford them.

bpeebles

I agree that most new cars are under-braked when compared to vehicles built in the past. The designers, have the pressures to improve MPG, ride-qualitiy and other design-goals. At the same time, the bean-counters demand low cost to manufacture. These 2 ideals have competed for many years.

 I fear that the the brakes have lost the battle in this case. The rotor-size has become smaller, the pad-area has shrunk and the calipers have become lightweight devices. Even the material the pads are made of must meet strict emmissions laws. (brake dust can lead to health problems)

In the end, the brake components are running closer to the limits of failure. My 2000 Dodge Dakota original rotors were made of such cheep material that they were totally rusted beyond use within a year....even while stored in my basement for several months, they shedded about a cup full of rust!!

I now am running "powerslot" rotots, even after many salty winters, they are essentually rust-free.

HOWEVER: I used Raybestos "QS" (Ceramic Based) pads and have experienced a pad-failue. One of the pads started to xferr itself to the rotor. until virtually all of the pad material was gone from the pad and now the rotor has a thick layer of pad-material on it.

I changed to the CERAMIC-based pads so the wheels would not get so BLACK with brakedust....now I am not so sure that brakedust is a bad thing. (considering the pad failure.)

bpeebles

I also want to address your concern about the calipers not sliding properly.

This is actually 3 seperate issues.
1)The piston itself sticking
2)the Caliper housing not SLIDING freely
3)the PADS not sliding where the braking-forces are xferred.

#1 Above should NEVER happen if the brake-fluid is changed according to specs.

#2 Above is VERY COMMON and is often fixable WITHOUT REPLACING THE CALIPERS.

#3 Above has nothing to do with the calipers. The HUGE braking forces are directed from the pads to the suspension system thru a critical sliding area. This is the MOST COMMON location for disk brake problems to occor. One should install ONLY the pads (no caliper) and be able to slide them freely on the wear-surfaces. All burrs have to be filed out by hand. The pads need to slide while the weight of the vehicle is applied by the rotor under heavy braking.

BTW: For the record, I have been replacing brakes on vehicles for at least 20 years. The VERY BEST brake design I have ever worked on has been NISSAN. They use linear-bearigs for the caliper sliders...The worst was AMC Eagle.

soccerpws

Is there any safety difference between Disc and Drum brakes? What about between front disc / rear drum?

Thanks,
soccerpws

Mr_Shiftright

Well sure.

Let's use the old "quarter" demonstration.

Take a US quarter, pick it up and hold with TWO fingers only by the EDGES of the coin. That is, your index finger is wrapped around the top edge and your thumb is holding the bottom edge. Now pull it out of your right hand with your left hand.

Easy to pull out, huh? Even if you squeeze the edges very tightly, it's pretty easy.

That's DRUM BRAKES

Now grab the coin with two fingers, but this time put your thumb and index finger on the SURFACE of the coin, thumb on one side and index finger on the reverse side.

Not so easy to pull out!! That's DISC brakes.

Disc/Drum is a cost-cutting compromise that works pretty well on lighter vehicles, because most of the weight shifts to the front of the car when you brake anyway.

soccerpws

So on a Civic with front disc/rear drum shouldn't be a safety issue? I'm assuming since there are hundreds of thousands (millions perhaps) on the road with that configuration they must stop pretty well on dry pavement.

Thanks.

ruking1

I would probably agree with that. Stock brakes are usually a compromise of a lot of factors. However, the Edmunds.com economy car shoot out, lists the Honda Civic 60-0 stopping distance at 129.3 ft.

The range for the eight tested cars was 121.8 to 135.9 ft

bpeebles

The "quarter demonstration" is leaving out some important details.

First off, it is the SURFACE AREA of the wear materal that determine the braking 'power'. Most DRUM brakes have MUCH MORE surface area. (the shoes are much larger than any disk pads)

If disk brakes REALLY were better for braking, then big trucks would use them..... but they DONT. This is because drum braks have MORE BRAKING POWER than disk brakes.

The big difference between disk and drum design is the ability to SHED HEAT. Disk brakes excell in this area. Also, disk brakes are LIGHTER than drum so there is a benift in other areas such as unsprung weight (ride quality), and MPG.

A drawback of Disk brakes is that they inherantly have DRAG (never fully disengauge) which can reduce MPG. Drum brakes -on the other hand- have springs to pull the shoes away from the braking surface, so there is NO DRAG.

Another drawback to disk brakes is that they are very suseptable to getting water, salt and other contaminants on the rotor surface. After going thru a water puddle, Disk brakes will be useless for about 2 revolutions of the wheels.

I have even had a layer of ICE build up on brake disks, If it were not for my rear drums, I would not have been able to stop.

So, in the end, the question should not be "which is best". It really does not matter as long as the design is not compromized.

Having disk brakes just for the sake of having disk brakes serves no purpose and may even be a compromize in braking abilities.