Why need to turn new brake drums?!
Michael Shell
Ford. After the brake job I noticed a vibration when braking and, sure enough,
the new drums were slightly out of round - turning the new drums cured the
problem.
Recently, I installed a new set of drums (I figured I wanted new drums to go
with my new rear axle). Guess what, these new drums are out of round too -
vibration on the first application of the brakes (20MPH around the block)!
I had them turned and everything is picture perfect now!
I read somewhere that you are supposed to turn new drums prior to their
installation. Why? The inner surface is machined. Surely drum manufacturers
will strive to ensure that the drums are perfectly round and ready for use
right out of the box - right!?
It seems a waste to turn the drums when they are new as this reduces the
amount of metal remaining i.e. the life of the drum.
Anyone have any experiences like this?
Mike
--
Mike Shell
gt1...@prism.gatech.edu
pse...@autobahn.mb.ca
> It seems a waste to turn the drums when they are new as this reduces the
> amount of metal remaining i.e. the life of the drum.
In my service station days we cut new drums as a matter of course. I was told
back then that the drums were probably warped. We only cut enough to see if
the drums were OK - as in round. Someone explained that the steel portion was
doing the warping, although that failed to explain why the warping on an all
cast iron drum or the ones sheathed in aluminum.
I was also told that the engine makers would cast a block and let it 'season'
(like wood) for some time before machining to allow for the stresses to work
out. Maybe this is the same deal with iron drums. I never asked, but I'll be
waiting for a better/logical answer, because now I'm curious again.
Pete
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
c...@mvp.net
>
> Years ago I bought a new set of rear brake drums for my early 1970's
> Ford. After the brake job I noticed a vibration when braking and, sure enough,
> the new drums were slightly out of round - turning the new drums cured the
> problem.
>
> Recently, I installed a new set of drums (I figured I wanted new drums to go
> with my new rear axle). Guess what, these new drums are out of round too -
> vibration on the first application of the brakes (20MPH around the block)!
> I had them turned and everything is picture perfect now!
>
> I read somewhere that you are supposed to turn new drums prior to their
> installation. Why? The inner surface is machined. Surely drum manufacturers
> will strive to ensure that the drums are perfectly round and ready for use
> right out of the box - right!?
>
> amount of metal remaining i.e. the life of the drum.
>
Well, there are drums and there are drums. Properly stored (flat, not
on edge) drums from a major manufacturer (Wagner, Bendix, Raybestos)
should be OK. You can mount on a lathe an scratch test it if you want,
but you probably won't need to turn it.
A Chinese rotor, on the other hand, may require substantial machining to
make round. You have to look close at the label to see where it is made
- it may have an American sounding name, or a parts house name, like
Autozone or NAPA. If you have been buying based on price, you get what
you pay for.
--
"Hokey religions and ancient weapons are no match
for a good blaster at your side, kid." - Han Solo
john gourdier
The reason you needed to is because during shipping, they got dropped, and
knocked out. This doesn't happen often--I must have done hundreds of drums
and rotors and can't remember the last time I had any trouble. Sounds like
you are either unlucky or the parts place you deal with has butterfingers.
John Gourdier
ASE master tech
E. William Lawrence III
Technically the drums should be checked to see if they need machined.
Yes often after they sit on a shelf for a while and get dropped by about 20 guys
along the way they will be out of round and maybe the machining process was bad.
All new Drums and Rotors should be measured for thickness variation and runout
before installation (as applicable).
You don't want to put a vibration on to your car.
The 3 day base brake course at the GM training center taught me that and a few
more
little tidbits of info.
Any protective coatings placed on the surface should also be removed with a
non-petroluim based solvent before installation also.
Clean all metallic parts with some brake clean but don't spray the surfaces of the
pads or shoes if you can help it.
Thanks for the post, good job on nailing your vibrations. Sorry you have parts
problems
like that.
Bill
John Schmidt
>[cut]
>> It seems a waste to turn the drums when they are new as this reduces the
>> amount of metal remaining i.e. the life of the drum.
>[cut]
>
>In my service station days we cut new drums as a matter of course. I was told
>back then that the drums were probably warped. We only cut enough to see if
>the drums were OK - as in round. Someone explained that the steel portion was
>doing the warping, although that failed to explain why the warping on an all
>cast iron drum or the ones sheathed in aluminum.
>
>I was also told that the engine makers would cast a block and let it 'season'
>(like wood) for some time before machining to allow for the stresses to work
>out. Maybe this is the same deal with iron drums. I never asked, but I'll be
>waiting for a better/logical answer, because now I'm curious again.
>
>Pete
Lots of large castings were stored outdoors and "forgot about" for
a few years. That length of time would stress-relieve them. My
understanding is that now, the castings are aged chemically. Don't
know the time limit, but it's way less than years.
I used to do brake work in the late '50s, early '60s. We put the
new drums on the brake lathe, then checked for out-of-round with a
dial indicator. No indicator movement, no lathing. However, if one
new drum was re-cut, the other drum for the other wheel, same axle,
was cut to match.
MikeGladue
>
> Years ago I bought a new set of rear brake drums for my early 1970's
> Ford. After the brake job I noticed a vibration when braking and, sure enough,
> the new drums were slightly out of round - turning the new drums cured the
> problem.
>
> Recently, I installed a new set of drums (I figured I wanted new drums to go
> with my new rear axle). Guess what, these new drums are out of round too -
> vibration on the first application of the brakes (20MPH around the block)!
> I had them turned and everything is picture perfect now!
>
> I read somewhere that you are supposed to turn new drums prior to their
> installation. Why? The inner surface is machined. Surely drum manufacturers
> will strive to ensure that the drums are perfectly round and ready for use
> right out of the box - right!?
>
> amount of metal remaining i.e. the life of the drum.
>
At my shop we turn the new drums because its the only
way to know for sure they are round. You might notice
on the box of a new drum the words "stock flat, not on edge".
If the parts company leaves the drums placed on their sides
for a long while the drum can become out of round.
In order to avoid complants and wasted time, always turn
drums before instalation. On a new drum if we have to cut more than
.010" we return the drum as defective.
Hugh
P. J. Remner
In a previous article, gt1...@prism.gatech.edu (Michael Shell) says:
> Years ago I bought a new set of rear brake drums for my early 1970's
>Ford. After the brake job I noticed a vibration when braking and, sure enough,
>the new drums were slightly out of round - turning the new drums cured the
>problem.
In the company I work for, I've worked at several different locations.
The first location would cut all new drums and all rear rotors. The
next location would cut all drums and *all* rotors. The third location
doesn't touch new drums or rotors.
My theory is that the parts drivers/parts warehouses aren't all "up to
snuff" when it comes to handling these parts. At the second location,
just as I was pondering why they insisted I cut brand-new parts, the
main driver came up and *dropped* a few drums from appx. knee height!
I've also seen rotors stacked on edge in the trucks and soemtimes on
the back shelves.
At the location I'm at now, we've not had any problems with brake
puslations on non-turned new rotors or drums except for one car
where both rear drums turned out to be nearly octagonal! Obviously
not a handling problem, but a manufacturing/heat defect. Brakes
were properly adjusted but the drums were both blued from overheat.
--
"Okay, how long has the band been together, as Metallica?"
"Well, since we started."
Pete '88 Subaru GL 4WD '72 Ford Thunderbird Schwinn s[9six].40 and more..
C E White
materials have a tendency to get transferred to the rotor when new (the lining being
new). This is most likely to happen during the early life of the pads/shoes. It can
cause the pulsing or surging sensation we all hate, even though the rotors are not
warped.
Another common cause of "warpped" rotors is uneven and/or over-tightening of lug
nuts. If I see a shop where the tire installer only uses an air wrench to tighten the
lug nuts, I go somewhere else. I don't mind the air wrench being used to "snug-up"
the nuts, I just want the final tightening done with a torque wrench. My 1986 Sable
suddendly developed warped rotors after I bought new tires at a "national brand tire
store". Naturally, the tire store had nothing to do with it. I replaced the rotors
and never bought any more tires at that store. The rotors never warped again (after
100,000 miles). The next two times I bought tires I made a point of telling the
person who took the order that they had better use a torque wrench when they
installed my wheels.
I had no luck having the rotors from a front wheel drive car turned. I understand
that there are special grinders for this, but the one time I needed the rotor
re-surfaced, new ones were only slightly more expensive than having the old ones
re-surfaced.
Ed
"Mr. Fun" wrote:
> I bought my rotors from Autozone and they were perfect when installed.
> And they have held up as well or better then the two sets Ford put on
> ... which is to say they have slight warpage after 10,000 miles... but
> the OEMs warped after 3000.
P. J. Remner
In a previous article, cewh...@interpath.com (C E White) says:
>You should read the TSBs on why brakes pulsate. Apparently the modern brake lining
>materials have a tendency to get transferred to the rotor when new (the lining being
>new). This is most likely to happen during the early life of the pads/shoes. It can
>cause the pulsing or surging sensation we all hate, even though the rotors are not
>warped.
Actually, the break-in process of new pad material *is* the transference
of lining to the rotor/drum surface. It's sort of like how they have to
use diamond dust to cut diamonds.
bri...@voyager.net
The pros run into this all the time. The answer is simple. Quality
parts are hard to
find because of the competition between after market auto parts
manufactures. Make
it as cheaply as possible to increase marketing and profit. New rotors
have the same
problem.
Brian
vseb...@sasktel.net
> Years ago I bought a new set of rear brake drums for my early 1970's
> Ford. After the brake job I noticed a vibration when braking and, sure enough,
> the new drums were slightly out of round - turning the new drums cured the
> problem.
>
> with my new rear axle). Guess what, these new drums are out of round too -
> vibration on the first application of the brakes (20MPH around the block)!
> I had them turned and everything is picture perfect now!
>
> I read somewhere that you are supposed to turn new drums prior to their
> installation. Why? The inner surface is machined. Surely drum manufacturers
> will strive to ensure that the drums are perfectly round and ready for use
> right out of the box - right!?
>
> It seems a waste to turn the drums when they are new as this reduces the
> amount of metal remaining i.e. the life of the drum.
>
> Anyone have any experiences like this?
>
> Mike
>
> --
> Mike Shell
> gt1...@prism.gatech.edu
Scott Dorsey
>On Friday, March 5, 1999 at 2:00:00 AM UTC-6, Michael Shell wrote:
>> Years ago I bought a new set of rear brake drums for my early 1970's
>> Ford. After the brake job I noticed a vibration when braking and, sure enough,
>> the new drums were slightly out of round - turning the new drums cured the
>> problem.
>a while back I put new drums on my 1964 Valiant, now I have discovered that they need to be turned, brake pedal pulsates while braking,
the tire shop use an impact wrench on them?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."