New disks old pads
 

I was informed by the local firestone guy who rotated my tires that the front rotors were thin. He showed it to me. In fact, there is an "outer" and "inner" lip on the rotor surface. However, the pads looked brand new.

Question, is it ok to change just the rotors and not the pads? or am I asking for trouble? Any tips are appreciated.

If the wear on the pads is uniform then I would say there is no problem using them with new rotors, in fact I just did that on my 240D. It may take a couple of hundred miles for the rotors and pads to "mate" completely, or to let the minor surface irregularities in the pads wear. But even new pads need to break in so this is nothing special in the case of reusing them.

The rotors cost more and are a little more work - I would replace them all. You might be talking about $100 total. I'm ashamed i let my brakes get as bad as I did before I fixed them, but glad I did - what a difference.

I think the rough surface on new rotors will quickly wear the "not new" pads to their liking.

This is a common part for reuse. Simply rough up the surface of the pads with coarse sandpaper or something before putting them in place to reseat on the new rotors.

That said, except when ABSOLUTELY new or freshly resurfaced there will ALWAYS be a lip on the edge of the rotor. I would NOT replace them on that indication alone. In fact unless you drive very hard in lots of in town driving, I wouldn't replace them at all. If you want to go by the letter of the specs, then put a mic on them and see just how thin they are.

Good luck,

You didn't say that the "mechanic" at Firestone used a micrometer, which is the only way to know for sure if your rotors are out of spec. Even if they are, I would just drive the car until a rotor gets warped and then change the rotors and pads together. One of my front rotors has been out of spec for over a year (I have a mic), and hopefully everything will be fine until it's time to change the pads.

The minimum thickness allowable is stamped on the rotor.

When I put on new rotors I alway put on new pads. Why..just becasue. They aren't that expensive.

i assume that mic means micrometer.

no, a mic was not used. he was trying to sell me a whole brake job based only on the 'lip'. little did he know I have you guys on my side. thanks once again!

the car brakes fine with no shudder or fade. he didn't like it very much when i said i would 'think about it' . dumb blond my a$$.

it is when you're a grad student living your savings.

well my problem is the week or so you are going to have reduced braking capacity till the pad surface wears flat and smooth to match the new rotors...I totaled a car in the rain becasue I hydroplaned in a turn becasue I was driving on bald tires trying to save a buck in college.before I bought new recaps. I tore out 150 feet of metal guard rails...luckily neither me nor my brother were injured.

since then I find other ways to save money when its tight...I never shortcut on safety issues.....or what I percieve as saftey issues anyway.

The Firestone here in dallas in well known for pulling fast ones. One of my idiot friends was taken for over $1000.00 by them.

AutoZone will both turn your rotors and tell you if they are out of specs. Save yourself some green find out for yourself.

very good point. excellent example. thanks for sharing the experience.

He's trying to rip you off. Or he is an ignoramus, possibly both. The lip on the rotor is normal wear. It could also be harmless rust and dirt buildup. It has absolutely nothing to do with needing a brake job.

To answer your question: I always put new pads on a new rotor. Partly because if the rotor needs replacing the pads are pretty well gone. Partly because in my day rotors were very expensive and it did not pay to chance uneven wear to save a cheap set of pads. Partly because I want the job to last as long as possible.

I'll definitely back you on that statement. Used pads are going to take a lot longer to break in compared to new ones, which will break in immediately as they are flat to begin with. It's not a chance I'd take given a new pad set can be had for $20.

I should have said that the rotors should only be replaced if they are below minimum thickness or otherwise unserviceable. Bolting on new rotors is fairly easy when the time comes.

I think I could break the pads in over a very short period of time :D
Its now your call...you know the worst case scenario and the usual case scenario...

Personally? I'd run the old (but good thickness) pads and new rotors and just keep in my mind that my breaks are not optimum (ie...no speeding excessive...follow far...and break them in as fast as possible)

But that is me...Driving is a lot more for some of us than others :)

P.S. And after you have driven a old VW...you know how to drive with "non-optimum" brakes :D

Do not change the rotors, or the pads, unless a micrometer proves that the rotors are below specified thickness.

Even in this condition, you can drive the vehicle for 20K miles if you don't use the brakes hard and heat up the rotors.

old VW?.....did you ever drive a 1954 Willys CJ5? with 4-9" manual drum brakes? I think a Modle T ford with cable brakes on the rear only would stop faster

Scary!

BTW...I forgot to mention for the lady thinking of changing the stuff...I would most defintely check the thickness with a micrometer or something...how thick is the lip on the rotor?

I do bet they aren't bad however....with what these shops charge for brake jobs they certainly have all the incentive to convince everyone they desperately need them............whether they do or not............

Just about everybody who does brakes uses this tactic. They play on the fears of the customer and tell them that "their safety is critical, especially with children in the car".

"You need to replace these rotors right now".

I would not be caught dead in a Firestone dealer. :pukeface:

Off the top of my head I think my front rotors are 15k miles old. I just checked them last week and they do have a lip on them already. Have the rotors checked for their thickness and see how close it is to the min MB specs.

"did you ever drive a 1954 Willys CJ5? with 4-9" manual drum brakes"

No but I drove a late 60's six cylinder Chevy Nova with the same size brakes. Not very far or very fast, but I drove it.

The scary part is these were the standard brakes used on EVERY Nova up to and including the 396 V8.

well the Nova had better brakes...take my word on it...

the Jeep top ended at about 55 mph....in fact it should have been lower becasue I blew the engine driving it 55mph....you could put it in neutral...put both feet on the brake..grab the wheel in both hands stand on the brakes and not come close to locking the wheels up on the asphault.

If you will rough up the old pads with 36 grit you will have no longer break in period than new pads.

If new rotors were put on every car on the road that showed a lip on the edge of the rotor then there would be no traffic problem at all because the vast majority of cars in the world would be in the shop.

You can buy a 0-1" micrometer for probably less than $20 unless you want a high quality one that will last the career of a machinist. Measure the thickness in several locations around the rotor.

I will say again, unless you drive hard in stop and go traffic, even thin rotors will get the job done just fine. A rotor that is too thin, simply lacks the mass to sink all the heat during breaking. The heat is then hopefully dissipated before the brake is used again. Think of the rotor as a heat bucket. When you stop, you put heat in the bucket, then while going down the road without the brakes on, the bucket empties. If you have a bigger bucket (thicker rotor) it can hold more heat.

If you are braking hard from stop sign to stop sign there is not much time for the heat bucket to be emptied before it needs to be filled up again.

As long as the rotors are not warped and have not had metal to metal contact, and are showing smooth scores or no scores, and you're not driving hard in stop and go, then don't worry about them.

Have a great day,

Pads
 

I have replaced the rotors and used the old pads. As the gentleman said ...
just sand them down on a flat surface. They sand real easy....
If the rotors are within spec.....just drive it...The rotors wear with pads.
If you replace the rotors you will soon notice the "ridge" reappear.
I have used 2 sets of pads without cutting the rotors…….at the third interval I replaced the rotors and the pads. At that point the rotors had worn down to their limit.
The ideal thing may be to resurface the rotors at each brake job. If the rotors are very shiny that may indicate the calipers may be dragging overheating the rotor. If that’s the case replace the rotor and the caliper and possibly the flex line.
So ….what I saying is, don’t spend the money if you don’t need to. On the other hand, if you have some extra cash……..did you say cross drilled……
:D

Well Bonehead you had a problem. Those brakes were not working correctly. I had a 1951 Willys Overland 2 wheel drive panel truck at one time, in which I installed a 371 cu in Olds V8. It went like hell and I never had trouble stopping, but I rebuilt the original Bendix brakes on the front and the Ford brakes in the 9" rear end. Mind you I knew better than to go barrelling around depending on the brakes to get me out of trouble.

Jen,

My rotors had ~200,000 miles on them and I got a beater MB with new rotors on it. So I reversed the rotors between the 2 cars and left the same pads on each car. No problems and those pads now have 150,000 miles on them and are only about 1/2 worn out.

Motto of the story: If it ain't broke don't fix it.

If you brakes work fine, leave them alone. The usual catastropic falure for brakes is a broken hose. Thehoses can easily be tested every so often by stomping on the brake pedal. Better the blow a hose out when not moving.

Brake places always to scare people that there brakes aren't safe to get you to spend a lot of money replacing them. Ignore those idiots and avoid being riped-off.

P E H

The truck had larger brakes than the CJ5 did.....as you had the Spicer axels adn the CJ had the Dana axels.

oh the jeep did stop...it gust didn't do it in any real hurry...sort of like how it accelerated with the L head engine....


If I had not taken that engine apart for a post mortum...(rear piston braoke in half at the oil ring land.) I would not have believe someone built a motor with the intake valve in the head (and a big one too) and had the exhaust valve in the block.............

When I worked for Chrysler, I remember the Dodge Omni/Plymouth Horizon as having non-power brakes. I believe that it did have discs in the front, but, it stopped like it had all drums. Just slows the vehicle to a stop. Not a chance of locking up the wheels. :(

Bonehead,

It was called an "F" head engine. My FC 150 has one in it.

P E H

Jen Tay, as we can see from BHD, or in his case, we cannot see, any savings. Sometimes it is better to save $100 by spending $20 rather than to save the $20 now and risk losing several hundred. In BHD's case, he got off cheap. Totaled car. That can be replaced. Totaled BHD, well, you get the picture.

Gilly and other MB Techs used to tell me that the brakes were set up so that you changed brake pads then you changed both rotors and pads and then back to just pads, etc, etc. Now, I had another car where the rotors were not changed because it was a junker. Well one day, the rotors cracked when I was applying the brakes at 50 mph. I had fresh underwear at home and it was needed.

And that thing has a stoke about as long as your forearm right........and a bore about the size of a soda can...

I keep confusing the "F" head engine with the "L" head engine....I guess the "L" head was the flathead......

What kind of car was this? Was it an older (probably American) car with cast iron rotors? Those things were tough, but didn't dissipate heat very well. With the soft metal alloys that MB uses I don't think the rotors would be as likely to crack...but stranger things have happened.

Not sure what they were. it was a 89 Merkur Scorpio. German Ford.

"The truck had larger brakes than the CJ5 did.....as you had the Spicer axels adn the CJ had the Dana axels."

It was the 2WD version with Willys' own design of independent suspension. The lower control arms were the spring, a transverse leaf spring like an old flathead Ford. It was similar to the Planar independent used by Studebaker in the 30's.

"I would not have believe someone built a motor with the intake valve in the head (and a big one too) and had the exhaust valve in the block............."

This was a very sophisticated design for the time. As you noticed, it allowed for a much bigger set of valves than you could fit in an OHV head over such a narrow bore. And it gave a better combustion chamber shape than a flathead. Rolls Royce featured an F head design for years and so did several other high grade cars of the classic era. It only became obsolete when the short stroke, big bore type motor allowed larger valves in an OHV engine.

In the old long stroke engine days an OHV was inferior to a good flathead because it was restricted to such small valves. The F head combined the good points of the flathead and OHV designs.

Even new pads will take 0.020" metal off rotors until they are broken in. The ONLY ways to tell you need rotors is with a micrometer and dial gauge w/magnetic base (Unless there is visible damage such as cracks or heat checks). If they are below minimum thickness or have 0.003"+ run-out, then you should replace them. I WILL NEVER MACHINE ROTORS. Why? Even rotors with captive bearing races are not very expensive. If you machine 0.030"+ off your rotors, I'd bet you money that you will be back within 2 months for "vibrations between 40 and 60mph."

I've even had a come-back on a Mitsubishi Montero LS where I did only the front brakes. Turns out she had the rears done at a "quick-brakes" type place after I serviced her SUV and they sold her a "new" rotor that had been cut 0.050" BELOW the scrap specs! :eek: Needless to asy, I called them and had a few choice words with their boss....

I'll bet you money that you will be back within 5 minutes for the very same vibration. The chance of machining the rotor and maintaining a runout of less than .001 with respect to the bearing race is just about zero. On a fixed caliper, any runout above this level will be felt as vibration through the steering.

My ex-girlfriend has a 325i Convertiable (1989) and her steering wheel used to shake about 20 degrees off of straight ahead when you braked hard at like 55MPH....very scary.

I machined the rotors for her and they have worked great ever since...usually they are replaced on a BMW obviously but she didn't have the money to replace them so I just visited a friends shop and did the work (for free :P)

The german steel is good stuff to machine. Not sure how her brakes got warped so bad but I taught her a good lesson on how not to warp them again...

ill second that. i work there and we can make them look like new.

Jen,

Bonehead's example is comparing apples to oranges. Maybe that's why he is called bonehead, LOL.

If the brakes work well and they pass the "stomp the pedal test" I explained earlier, you have no problems.

P E H

he says there are brake problems....if you do anything short of fixing them correctly then you are playing russian roulette....


there is no apple and oranges thing.

running on shot brakes untill they fail is exactly like driving on bald tires a few thousand miles more to save spending a few bucks......

Both cases you never really know when the devil is going to jump up and bite you for doing it. You might get away with it...or you might not....you never know now do you.

the "its fine if you stomp and they stop" argument works righ tup until the rotor seperates during a panic stop..then what?

Have you seen his car..or for that matter have any of us.

Saftey issues are more important the this weeks date hopeing for a chance to get laid......

If the devil jumps up and bites you then you will be out a car (like I was) or far worse.

and by the way...all brakes usually work right up to the point they stop working. There isn't always a lot of warning that Joe average might notice.

I never said to blindly trust the shop either......

...........ROTF..............Jen is going to love this. I don't think she is in the category of "hoping for a chance to get laid"......................ROTF.................you really are a Bonehead sometimes. :D

... :eek: never looked at "her" profile before to realise Jentay was a she.....that would change things a lot...

Like my wife says....women don't only have the keys to the Vault...they own the bank.

Jennifer
1981 240Diesel
1990 350sdl turbo

That is her sig. Know of a guy name Jennifer? Wait. Don't answer. We might not want to know how you know of this individual. :eek: :D

Firestone, Goodyear, etc, etc, tend to have sleezy mechanics that will take advantage of a girl. When the car needs work, the wife will drop it off and pick it up. No conversations. I tell them what to do. She is the medical person. When I go to the doctor, she discusses with the doc what to do and I rubber stamp it.

Never looked at the sig either...