New e34 rotors installed, but...

I just did my own front brake job on a '95 525i. At 105k rotors had to go.
Worst part was breaking the carrier bolts loose. There appears to be some
shimmy in the front end and I can see why - apparently the rotors have to be
centered on the hub. Why would they have so much play? I'll remove the
wheels again and try to reset the hex bolt. Is there a tool that BMW techs
use for this purpose? I tried to get it right, but it must not be exact.
Any advice would be appreciated.

John

> wrote in message
...
>I just did my own front brake job on a '95 525i. At 105k rotors had to go.
> Worst part was breaking the carrier bolts loose. There appears to be some
> shimmy in the front end and I can see why - apparently the rotors have to
> be
> centered on the hub.

The rotor bore is a good fit on the hub, so no centering is possible.
If they don't locate without any play, maybe they're the wrong discs.
Maybe E39 rotors have similar dimensions, apart from the bore which I'm
pretty sure is 1mm larger in diameter.

Why would they have so much play? I'll remove the
> wheels again and try to reset the hex bolt. Is there a tool that BMW
> techs
> use for this purpose? I tried to get it right, but it must not be exact.

There are no special tools needed to replace the rotors. Just spanners and a
7mm hex key.
Mike.

In article >,
> wrote:
> I just did my own front brake job on a '95 525i. At 105k rotors had to
> go. Worst part was breaking the carrier bolts loose. There appears to be
> some shimmy in the front end and I can see why - apparently the rotors
> have to be centered on the hub. Why would they have so much play? I'll
> remove the wheels again and try to reset the hex bolt. Is there a tool
> that BMW techs use for this purpose? I tried to get it right, but it
> must not be exact. Any advice would be appreciated.

The only centring you need to do is to make sure the mating surfaces are
clean.

Usual cause of shimmy is worn suspension bushes.

--
*Sticks and stones may break my bones but whips and chains excite me*

Dave Plowman London SW
To e-mail, change noise into sound.

No, there is no special tool, and that bolt is not entirely necessary. All
it does is hold the rotor on while the tire is removed.

I just installed new rotors (all 4 of them) on my 3 Series, and I have xsome
shimmy as a result also. I'm going to consider two things, 1.) there is dirt
and corrosion on the hub preventing the rotor(s) from laying flat and true
to the hub, and 2.) the rotors are not machined true from the manufacturer,
which is an annoyance.




> wrote in message
...
>I just did my own front brake job on a '95 525i. At 105k rotors had to go.
> Worst part was breaking the carrier bolts loose. There appears to be some
> shimmy in the front end and I can see why - apparently the rotors have to
> be
> centered on the hub. Why would they have so much play? I'll remove the
> wheels again and try to reset the hex bolt. Is there a tool that BMW
> techs
> use for this purpose? I tried to get it right, but it must not be exact.
> Any advice would be appreciated.
>
> John

"Dave Plowman (News)" > wrote in message
...
> In article >,
> > wrote:
>> I just did my own front brake job on a '95 525i. At 105k rotors had to
>> go. Worst part was breaking the carrier bolts loose. There appears to be
>> some shimmy in the front end and I can see why - apparently the rotors
>> have to be centered on the hub. Why would they have so much play? I'll
>> remove the wheels again and try to reset the hex bolt. Is there a tool
>> that BMW techs use for this purpose? I tried to get it right, but it
>> must not be exact. Any advice would be appreciated.
>
> The only centring you need to do is to make sure the mating surfaces are
> clean.
>
> Usual cause of shimmy is worn suspension bushes.
>

While that may be true, the bushings would have been worn before the rotors
were installed, so the shimmy should not be a new symptom after brake work.

"Jeff Strickland" > wrote in message
...
> I just installed new rotors (all 4 of them) on my 3 Series, and I have
xsome
> shimmy as a result also. I'm going to consider two things, 1.) there is
dirt
> and corrosion on the hub preventing the rotor(s) from laying flat and true
> to the hub, and 2.) the rotors are not machined true from the
manufacturer,
> which is an annoyance.

Assuming it's not 2, which would be terrible - I've used cheap discs and
not had problems, but later I found that ATE discs, which are OE, were not
very expensive - you could try lightly sanding the hub face before
re-fitting the disc. As well as that, I lightly wipe the surfaces with
grease and spin the disc on the hub to even it out. Seems to work. But
what I found on my E34 was that little imbalances would make the steering
wheel shake but the root cause was worn suspension bushes. Replacing a
brake disc, or balancing the wheels, would help for a while but it always
came back, until I got bits of the suspension replaced.

In article >,
Jeff Strickland > wrote:
> > The only centring you need to do is to make sure the mating surfaces
> > are clean.
> >
> > Usual cause of shimmy is worn suspension bushes.
> >

> While that may be true, the bushings would have been worn before the
> rotors were installed, so the shimmy should not be a new symptom after
> brake work.

OP didn't make it clear if the symptoms were there before or not. Many
think because the shimmy is only noticeable when braking it must be a
fault with the brakes themselves.

--
*Why are a wise man and a wise guy opposites?

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" > wrote in message
...
> In article >,
> Jeff Strickland > wrote:
>> > The only centring you need to do is to make sure the mating surfaces
>> > are clean.
>> >
>> > Usual cause of shimmy is worn suspension bushes.
>> >
>
>> While that may be true, the bushings would have been worn before the
>> rotors were installed, so the shimmy should not be a new symptom after
>> brake work.
>
> OP didn't make it clear if the symptoms were there before or not. Many
> think because the shimmy is only noticeable when braking it must be a
> fault with the brakes themselves.
>
> --
Another possibility for the OP "shimmy" is whether his wheels are balanced?
On my 90 535i, 5spd, 110K, my original control arm bushings appeared to be
fine. I swapped out the rotors and balanced the wheels and surprise - no
more shimmy!

I knew I'd get some answers here, always a good place to start!

The rotors came from BMW and there was no shimmy before the rotors went
on, control arm bushings have been replaced recently, with new tires all
the way around

The fact is that there is some "play", in fact several millimeters of back and
forth until the hex bolt is tightly fastened. While lining up the new rotor lug
bolt holes with the hub, some movement besides the circular rotation is
there. Maybe the parts monkey sold me the wrong parts. I'm going back to BMW
today.

>
> > wrote in message
> ...
> >I just did my own front brake job on a '95 525i. At 105k rotors had to go.
> > Worst part was breaking the carrier bolts loose. There appears to be some
> > shimmy in the front end and I can see why - apparently the rotors have to
> > be
> > centered on the hub.
>
> The rotor bore is a good fit on the hub, so no centering is possible.
> If they don't locate without any play, maybe they're the wrong discs.
> Maybe E39 rotors have similar dimensions, apart from the bore which I'm
> pretty sure is 1mm larger in diameter.
>
> Why would they have so much play? I'll remove the
> > wheels again and try to reset the hex bolt. Is there a tool that BMW
> > techs
> > use for this purpose? I tried to get it right, but it must not be exact.
>
> There are no special tools needed to replace the rotors. Just spanners and a
> 7mm hex key.
> Mike.
>
>

wrote:
>
> The fact is that there is some "play", in fact several millimeters of back and
> forth until the hex bolt is tightly fastened.

There shouldn't be any. That bolt is superfluous. The disk should be
a snug fit on the hub.

> While lining up the new rotor lug
> bolt holes with the hub, some movement besides the circular rotation is
> there. Maybe the parts monkey sold me the wrong parts.

It begins to sound like it.
--
C.R. Krieger
(Been there; done that)