Re: brake runout specs

["jtrealtywebspannet" <jtrealty@xxxx>]

There are no published specs for the runout of the rotors. There is 
also no published spec on parellelism. In general the runout should be 
kept below .0025" and parelleism .0005". (Parden my speeling). 
The only effect these specs have is on preventing pulsation of the 
brake pedal. This is important not only for the improvement in feel of 
the brake pedal but to prevent premature lock-up of the brakes in 
partial application situations and cross control effects in steering.
To measure run-out it is best done on a brake lathe to remove the 
measuring of the play in the wheel bearings. Parelleism or thickness 
variation is easily done at several points around the rotor with a 
micrometer. These specs have very little bearing on brake pad life. To 
fix these variations rotors are cut on brake lathes. At this time most 
Delorean venders don't recomend this. Causes for needing to cut rotors 
are the following, wearing the pads out and the backing plate contacts 
the rotors, excessive braking manuvers, unequal and or improper 
torquing of the lug nuts, excessive rust. Although the rotors are 
considered to be a wearable item, with proper care and inspections 
they can last a very long time. Excessive runout will eventually cause 
wear on the retaining pins that hold the calipers in. This should not 
cause any damage to the calipers but it is not good to drive a car 
with excessive brake pedal pulsation as it is very annoying. Any 1 
rotor could cause this including the rears so measure them all and you 
may only have 1 bad one. All of this is assuming there is only 
steering wheel shake when you apply the brakes.
David Teitelbaum
vin 10757

--- In dmcnews@xxxx, "Walter Coe" <Whalt@xxxx> wrote:
> Question 1: What is the maximum allowable brake runout on the 
rotors? I'm
> almost to the point of putting the car back on the ground, but I've 
noticed
> that both my new rear rotors appear to have around 1mm wobble inside 
the
> calipers. This seems to be excessive to me, but I would like to 
know anyone
> else's opinion.
> 
> Question 2: Will moderate rotor runout cause premature wear to the 
calipers?
> Before I took the system apart, I had an annoying amount of steering 
wheel
> shake as I applied the brakes. I figured that the calipers were 
toast
> anyway with the sludge I had for brake fluid. But with new calipers 
all
> around, I don't want to mess them up.
> 
> Walt Tampa, FL