E28 - steering shimmy (I've replaced EVERYTHING and she still shakes) - Wot now?
Steve Burley
haven't got a clue what they're doing when it comes to this.
Also check the front shocks for leaks etc.
Steve
"DRP535" <drp535...@softhome.net> wrote in message
news:kgccrvgj6203pemje...@4ax.com...
> Here's what I've replaced to date...
>
> 1) Wheels - Had 7-series TRXes, replaced with genuine E28 M5 BMW/BBS
wheels
> second hand - professionally straightened and restored to perfect
condition
> with no buckles or dents
>
> 2) Tyres - brand new Yokohama AVS ES100 match mounted and dynamically
> balanced. Lightest balance weights to front wheels. Wheels fitted to car
> with manual torque wrench - no air guns.
>
> 3) Radius arm bushes - genuine BMW
>
> 4) Centre track rod - genuine BMW
>
> 5) Steering box adjusted to remove backlash at centre
>
> 6) Full front and rear thrust wheel alignment
>
> 7) Complete power steering fluid flush
>
> Total cost so far.... HEAPS
>
> And she still has a steering shimmy at 85-90km/h. My mechanic is now
> talking about replacing the radius arm bushes with Nolathane ones and
> telling me it might work but it'll also make the steering much harsher.
>
> I don't want my steering harsher. Surely this can't be right? These cars
> weren't sold new in this state were they? Surely the car had no steering
> shimmy at some point in its life. Why can't I get it back to that state
> again once I've replaced just about every single component in the front
> end?
Paul Schnettler
struts? what shape are they in?
strut bearings?
tie rods?
the new tire/wheel additions can cause the steering to tramline a bit
due to the wider than normal spec tires. I have poly upper control arm
bushings, steering isn't harsher but you will notice a bit more road
feel transmitted through the suspension.
the shimmy at 95kph is tire/wheel related usually, a shimmy at lower
speeds (45-50 mph) under braking is usually suspension (control arm)
related.
hope that helps.
Paul
84 533i
bfd
Its not clear whether you replaced your "upper" control arm bushings,
if not, you may want to consider replacing them with 750i bushings.
This is the "upgrade" bushing for all E28/24/34, especially if you've
gone to larger wheels/tires, like you appear to have with the 16" E28
M5/BBS wheels. Note, for the E28, you need to have the bushings
correctly milled to fit your control arms. In the US, I'm aware of 2
places that do it right - Dinan, the person who "figured out" this
upgrade here:
http://www.dinanbmw.com
and Steve D'Gerolamo at ultimate garage here:
http://www.ultimategarage.com/special10.html
here's a description from the BMW database:
Date: Thu, 22 Apr 1999
From: "James Moran" <bava...@cambridge.crosswinds.net>
Subject: Re: <E28>Shimmy/Shudder '87 535i
It's the brake thrust arm bushings (lower control arms - the ones
pointing
rearward). Likely the PO had them replaced with original parts, or
worse,
inferior knock-offs. Replace these bushings with 750iL bushings milled
down
to fit. Steve D'G has 'em. They are a press fit, so line up a shop to
swap
them or buy the entire arm with them pressed in.
( Note: See The Ultimate Garage . http://www.ultimategarage.com
Ed. )
Jim Moran
'88 M6
What if there was a flame war and nobody posted?
--------------------------------------------------------------------------------
Date: Tue, 28 Mar 2000
From: "Steve D'Gerolamo" <ste...@idt.net>
Subject: [uuc] 750 Thrust Arm Bushings
You don't need to spend a lot of money on these for your E28 or E24
car.
Pick up a pair of fluid filled 750i bushings (the green ones made by
Boge)
and take the center down equally on both sides so it fits perfectly in
your
subframe. I use a 20hp Leadwell lathe but you can use a few hand tools
around the shop. Now machine a few mm off the steel casing equally on
both
sides so this will not contact the subframe with side deflection of
the
arm.
If your thrust arms are in very good shape except for the bushing, you
can
simply replace the bushings...on the car with an OTC7249 or you can
carefully remove the old arms with the proper ball joint press (you
dont
want to damage the ball joint side) and 5-10 tons with your shop press
and
proper sized arbor.
I personally would rather replace the thrust arms with new
Lemforder/oe
components at this time. This way you can use a bit more force and a
separator fork to muscle the old ones out. Pick up a new set of arms
from
your favorite parts supplier and press in your newly machined
bushings. Be
careful using a shop vice and big socket in lieu of a press and
arbor....you may break the handle off the vice or puncture the bushing
(remember, these are fluid filled) with a poor fitting socket. SD (PS-
these bushings work great in E32/E34 cars without the machining)
=========================================
Steve D'Gerolamo - The Ultimate Garage
201-262-0412 / ste...@idt.net / http://www.ultimategarage.com
--------------------------------------------------------------------------------
Date: Tue, 2 Mar 1999
From: "Pete Read" <pete...@boeing.com>
Subject: Re: <E34><E28> Control (Thrust) Arm Bushings
Dave Nelson asks about thrust arm bushings for his E34 M5:
> I can't seem to pin down the digest that may have had info on
> the replaceability of an E34 M5 thrust bushing, with that of a
> 750IL? Is it a perfect fit, if not is there a heavier duty one
> that is? I've seen some chat about "cutting" down the 750IL for
> fit, but is this necessary for my car (E34)?
Dave,
I wrote a couple of notes last year about thrust arm bushings for
the E28 and E34 five series. The first was a warning about
correctly modifying 750i bushings for E28s. Dinan 650.962-9401
and Steve D'Gerolamo 201.262-0412 both do it correctly (see references
below to the first note which includes the correct dimensions). I've
also included the second note with all the part numbers (see below).
The bottom line is that any E34 can use the 750i bushing (31 12 1 136
607) without modification -- E28s need to have the width machined
down.
I also guessed that the 750i bushing would be a suitable, and much
less expensive, replacement for the E34 M5. Since that time, I've
talked
with James Leong at Dinan and he confirmed that they have successfully
used 750i bushings with E34 M5s (James is always extremely helpful as
is
everyone I've talked with at Dinan).
...old post on thrust arm bushings....
Subject: <E24><E28><E31><E32><E34> Thrust Arm Bushings, Additional
Info
Several people have contacted me about my "<E28><E24> 750i Bushing
Warning (Dinan Bushings are fine)" post in bmw-digest v07.n1375
and Mformation #194, so let me add a little more detail.
Bill Shook (owner of Kraftwagen here in Northern Virginia) has
told me more than once that he appreciates BMW's effort to keep
improving parts when they find a problem area. A good example is
the, twice updated, shift detent cover plate Bill told me about
when I was looking for oil leaks at the back of my transmission.
The old part was a pain to keep sealed properly, but the new improved
part has a built in seal that doesn't leak (cover plate 23 31 1 228
470
for E28 M5/535i, E24 M6/635i, E34 M5 and many others).
Looking at the updates to thrust arm bushings, it seems that BMW has
gone through a similar improvement process. However, the process
has created quite a few superceded part numbers which adds to the
confusion. I've tried to sort out the latest part numbers and
update history (see below -- all prices from 1/97 book).
1.) E31, E32, E34 Thrust Arm Bushings (56 mm wide)
- --------------------------------------------------
E32 750i, 740i E31 850i, 840i
31 12 1 136 607 $ 45.75
E34 M5
31 12 2 226 528 $104.75
E34 535i, 540i, 530i
31 12 1 139 456 $ 46.50
31 12 1 136 606 expired 03/91
31 12 1 133 488 expired 12/90
31 12 1 130 587 expired 03/89
E34 525i
31 12 1 136 605 $ 49.83
2.) E24, E28 Thrust Arm Bushings (50 mm wide)
- ----------------------------------------------
E28 M5, 535i (after 9/85), E24 M6, 633i, 635i
31 12 9 058 819 $ 36.43
31 12 1 126 394 expired 11/90
E28 533i, 535i (til 9/85)
31 12 9 058 818 $ 30.98
31 12 1 125 428 expired 01/89
31 12 1 126 302 expired 09/86
E28 528e, 524 TD
31 12 9 058 817 $ 47.28
31 10 1 129 078 expired 11/88
If you look closely, you can usually find the last seven digits of the
part number on the part itself. For example, the 750i/850i bushings
will have "1 136 607" stamped in the green plastic insert which
surrounds the center aluminum piece.
Each of the bushings above should be physically interchangeable
within their group. That is, any of the group #1 bushings will fit
on the E31, E32, and E34 cars, while any group #2 bushing will fit
the E24 and E28 cars without modification.
The bigger engine, heavier cars have the stiffer bushings. So the
stiffest E31, E32, E34 bushing is the 31 12 1 136 607 used on the
750i/850i, while the stiffest standard E28 bushing is the
31 12 9 058 819 used on the M5/M6/535i/635i.
As I described in my earlier post, the 31 12 1 136 607 for the
750i/850i is the high performance bushing of choice for E24/E28 cars,
but it must be properly machined to prevent interference. You won't
find the part number on modified 750i/850i bushings because the
plastic insert with the part number is also machined.
One last note -- if I had an E34 M5 I'd be very tempted to try the
750i/850i parts when it came time to replace my bushings (less than
half the price of the M-parts).
Pete Read
'88 M5
Arlington, VA
--------------------------------------------------------------------------------
Date: Thu, 21 Jan 1999
From: Matthew Yip <mg...@yahoo.com>
Subject: Re: M5 Shimmy
> Date: Thu, 21 Jan 1999
> From: Sk...@WHAD.com
> Subject: M5 Shimmy
>
> ... Is a thrust arm also known as a control arm? Is there an upgrade option?
> Is upgrading necessary? Are the thrust arms/controls for an M5 the same
> for those for other E28s?
Yes, but on the E28 in particular, since the units are separate, it's
called a thrust rod or thrust arm. I don't know of any upgrades.
They are the same unit as on all E28s.
> ... Is a centerlink also known a s a tie rod center?
> Is there an upgrade option? Is upgrading necessary?
> Are the thrust arms/controls for an M5 the same for those for other E28s?
Yes and no. I don't see a need to upgrade. The thrust arms are
standard E28
> ... Isn't there a commonly accepted bushing upgrade for the E28? I have
> heard conflicting reports of using the liquid bushing from the 750 versus using
> them from the 850? Anyone have experience with either of these upgrades?
Don't know about the 850 bushings. I purchased narrowed rubber 750
bushings from Steve D @ the Ultimate Garage - good prices! Standard
750 bushings are too wide so you'll have to either purchased narrowed
ones or have the OE ones machined. I've heard that the liquid bushing
gives a softer ride which I don't want.
> ... What is the difference between a thrust arm bushing and an idler bushing?
> If they differ, should I purchase an idler bushing as well?
There is a difference (besides one being on a thrust arm and one being
on an idler shaft). The bushing sizes are radically different and
their
purposes are very different as well. Purchase a new idler arm (or buy
my
extra), I don't think anyone makes an idler bushing replacement.
> ... Any other differences between the standard E28 front end shimmy fix and
> the fix for an M5?
Nope - the M5 has more "problems" because of the fact that they use a
wider, heavier wheel/tire combo that wears the components faster and
also makes them more susceptible to the infamous shimmy.
> ... Any recommendations for where to purchase?
Have you considered the folks that advertise on the Digest?. I've
almost
exclusively purchased thru the dealer, albeit not at a standard
discount.
> ... What should I reasonably expect by way of labor time for this job?
Dunno - sorry.
Matthew Yip
mg...@wolf-web.com
'87 GTi 11v
'88 M5
'99 F350
--------------------------------------------------------------------------------
Date: Tue, 26 Jan 99
From: Chris Guy <Cg...@diac.com>
Subject: Re: E28 lower conrol arms or thrust arms?
> Date: Fri, 22 Jan 1999
> From: ABAR...@aol.com
> Subject: E28 lower conrol arms or thrust arms?
>
> What is the upgrade for E28 lower control arms or thrust arms or whatever?
> Are they from E32 7's? I know that one of the two between the 2 has the same
> number, but what about the other, is that the upgrade? You have to press the
> 7 bushings in the 7's right? They are sold seperately?
>
> Thanks!
The stock E28 535i bushings do not seem to last too long. The upgrade
to
install 750 bushings. They almost fit.
1) You can bend back the mounting tabs (a pain) and risk cracking them
(E28 front subframe cracks, esp on steering gearbox are not unheard
of)
and trim OD down so they fit in the arms.
2) You can do it right. They must have their OD trimmed to fit in the
arms. Then center of the bushing must be reduced to fit into the
bracket.
And the outside of the bushing length must be trimmed to allow for
proper
arm movement under hard driving. Failure to do so can consiveably lead
to
cracking and failure of the arm.
Steve D (www.ultimategarage.com) offers the properly trimmed bushings
as
does Dinan (www.dinanbmw.com and via www.bavauto.com). I assume others
do
too, but ask if all three machinings are done.
Chris Guy - BMW5...@aol.com
86 535i 5sp
Denver, CO
E28 Home Page - http://members.aol.com/BMW535i86
Steve Burley
chance that is where your problem is, unless the car has under 50,000 miles
on it.
How does is handle if you brake while cornering? You'll get a good shudder
if the front shocks are worn. Run your finger around the shocks to check
for fluid leaks, which aren't always wisible.
If you've checked everything else, it wouldn't hurt to get a second opinion
on the wheel balancing, and much cheaper than replacing new parts or ones
that are ok.
Steve
"DRP535" <drp535...@softhome.net> wrote in message
news:p0pirvcv3d14b31jc...@4ax.com...
> On Mon, 17 Nov 2003 09:57:47 -0600, Paul Schnettler
> <pau...@NOSPAM.ssec.wisc.edu> wrote:
>
> >what about:
> >struts? what shape are they in?
>
> Don't know. They are the original struts with original shocks. Car is
> Australian delivered (probably South African built) April 1986 M535i
>
> >strut bearings?
>
> Where are they?
>
> >tie rods?
>
> These are fine. They were checked out when I had the centre track rod
> replaced.
> >
> >the new tire/wheel additions can cause the steering to tramline a bit
> >due to the wider than normal spec tires.
>
> The wheels and tyres are absolutely correct and to BMW specification for
> the car. I was very careful to ensure that this was the case when I bought
> them. I previously had BMW wheels but not ones that were specifically
> intended for an E28 and was told by everyone that this was the cause of my
> shimmy. So I took their advice and bought wheel/tyres that definitely were
> straight from the E28 parts bin and now apparently this wasn't the problem
> after all.
>
> > I have poly upper control arm
> >bushings, steering isn't harsher but you will notice a bit more road
> >feel transmitted through the suspension.
> >the shimmy at 95kph is tire/wheel related usually
>
> This is what everyone keeps telling me, but it just can't be true in my
> case. The wheels are genuine E28 M5 wheels that have been professionally
> restored by a local rim repairer who took out one very small dent and
> straightened the three that had very slight buckles when I bought them
> second hand. The tyres were match mount fitted and spun on a zero rim
first
> to confirm the position of the high point. The worst wheel has only 25g of
> lead on it. The tyres are brand new Yokohama AVS ES100s which were
> recommended by every man and his dog with an E28 on mye28.com
>
> I don't know what else anyone could do to get the perfect set of
> wheel/tyres anywhere. This just cannot be the problem.
>
>
> >, a shimmy at lower
> >speeds (45-50 mph) under braking is usually suspension (control arm)
> >related.
>
> I have no braking problems. The car is rock solid under brakes and tracks
> dead straight. After I took the shine off the new tyres I stamped the
> brakes as hard as I could from 180km/h to test this very thing.
bfd
> >http://www.ultimategarage.com/special10.html
>
>
> I've had a look at that picture and what you're describing as an "upper"
> control arm is the same thing as what I call a "radius" arm. So, yes,
these
> have already been replaced. They were the very first thing to be replaced
> in fact.
>
> These are what my mechanic now wants to replace with nolathane ones. He
> says doing the 750 bush conversion is out of the question as it requires
> "drug money" to get it done. The bushes themselves are hideously expensive
> and then on top of that is considerable machining costs to make them fit
> the E28.
This doesn't make any sense. Where are you located that makes this
conversion so expensive that it requires "drug money"? The 750i bushings,
p/n 31 12 1 136 607,unmodified retail from BMW for like $45.00US each.
Modifying these bushings cost anywhere from $50.00US each from Dinan
(www.dinanbmw.com) to $65.00 each at www.ultimategarage.com. How much would
it cost to have 2 ship to you? You ought to look into this "upgrade", worth
every penny....
Steve Burley
from US. Total cost was under NZ$250 (around AUD$200) including freight and
they were easy enough to fit myself. Price included the whole arm/ball
joint assembly with the 750i bushes already pressed in. No duty to pay on
parts here but local dealers still charge over 3 times the equivalent US
price for most parts.
Anyway if you've already changed the bushes that's unlikely to be the
problem. For $20 you should be able to get someone else to re-balance the
front wheels and tell you if they were ok. I have had a deep mistrust of
tyre shops myself long before going through a similar experience to yours.
My local shop told me the tyre walls was failing and causing the
vibrations - recommended a new set of tyres. I swapped the two most worn
ones to the front and replaced them but with no difference. Another shop
found a front shock was leaking invisible fluid which was the cause.
Most tyre shops pay their staff crap and they don't always know how to work
the machines properly, that's assuming the machine is properly calibrated.
I reckon at 150,000kms the shocks are due for replacement anyway so if
you're keeping the car it wouldn't be a waste to replace them.
Have you tried bouncing the car and listening for knocks, squeaks or clunks?
Steve
">
> I'm keen, but I'm in Perth, Western Australia, so Dinan and other US shops
> and suppliers are out of the question I'm afraid. Here, we have one BMW
> dealer in a state which makes Texas look positively tiny. Run a line from
> Houston up to Winnipeg in Canada, then everything in the USA west of that
> line is about the size of Western Australia. In that area there is one BMW
> dealer. They can pretty well sell for whatever price they want.
>
> 750/850 bushings here are A$240/pair (US$ 85 each) plus an estimated $250
> each for the machining (major set-up costs for a one-off job), plus labour
> to have them fitted to the arms and to the car.
>
> At the end of it all, I'd be very lucky to get away for less than $1,000
> (the same as what I paid for the M5 wheels FFS!!) with no guarantee that
it
> would work and no chance of returning anything if it doesn't because of
the
> machining.
Dan Buchan
> On Mon, 17 Nov 2003 09:57:47 -0600, Paul Schnettler
> <pau...@NOSPAM.ssec.wisc.edu> wrote:
>> struts? what shape are they in?
> Australian delivered (probably South African built) April 1986 M535i
They must be fairly stuffed by now.
>> strut bearings?
> Where are they?
He might mean the strut top bearings. Either side of the engine
compartment at the top of the struts.
>> I have poly upper control arm
>> bushings, steering isn't harsher but you will notice a bit more road
>> feel transmitted through the suspension.
>> the shimmy at 95kph is tire/wheel related usually
> This is what everyone keeps telling me, but it just can't be true in my
> case. The wheels are genuine E28 M5 wheels that have been professionally
> restored by a local rim repairer who took out one very small dent and
> straightened the three that had very slight buckles when I bought them
> second hand.
Personally I wouldn't be using wheels that had needed straightening, not in
a million years. But that's just me.
bfd
"Steve Burley" <sjbu...@paradise.net.nz> wrote in message
news:OIjub.7946$ws.7...@news02.tsnz.net...
> Anyway if you've already changed the bushes that's unlikely to be the
> problem.
I disagree. IF he changed the control or as you call it radius bushings, and
he used the standard E28 version, p/n 31 12 9 058 819, for cars after 9/85,
then he needs to have this bushing reinspected to see if its still valid. If
not, the 750i bushings, p/n 31 12 1 136 607 , milled to fit the E28
control/radius arm is the upgrade. However, since you're in Australia, and
"the only BMW dealer" gouches you on parts AND you have no aftermarket
source who can get the fluid filled green 750i bushings manufactured by
Boge, then maybe the poly urethane bushings may the a "cheaper" upgrade and
the way to go. In any event, it and every other suspension component should
be reinspected for wear, no matter how "new" it may be.
As for tire balancing, I agree, that should be the first, and cheapest,
thing to inspect. If you're comfortable that both the tire and rim are
round, true and balanced, then have a competent independent shop look at the
rest of your front suspension. Good Luck....
C.R. Krieger
> "Steve Burley" <sjbu...@paradise.net.nz> wrote in message
> news:OIjub.7946$ws.7...@news02.tsnz.net...
> > Anyway if you've already changed the bushes that's unlikely to be the
> > problem.
IME, it's a good idea to replace *all four* of the control arms in the
E28 front suspension. Each and every one of them has a nonreplaceable
ball joint in it that's (obviously) as old and worn as the replaceable
(WHY?) bushing at the other end. The smaller (upper?) arms are
selling for only ~$75/pair on eBay these days, so why not?
As for the lower thrust arms into which everyone wants to stuff the 7
Series bushings, your car will do fine for some 50-60K miles on the
stock ones that sell (same vendor) for ~$150/pair. If you want to
upgrade for more expected miles, I personally like the
polyurethane-bushed arms sold by Bavarian Autosport (www.bavauto.com)
for about twice that price, although they offer the 7 Series-bushed
arms as well. In either case, there's little sense in mucking about
with a press either fixing up your old arms (and *old* ball joints!)
or screwing with new stock arms and new stock bushings you'll end up
throwing away in the process. BavAuto sells them assembled and ready
to bolt in. Yeah; there's more 'feedback' through the wheel with the
polyurethane, but it's not unpleasant. Certainly no more so than the
Eibach sport springs introduce.
While you've got it apart, it's a very good time to change the old
strut inserts *and* the upper strut bearings (whether they seem to
'need' it or not).
> As for tire balancing, I agree, that should be the first, and cheapest,
> thing to inspect.
And, y'know, I hate to repeat this, but it also pays to rotate *each*
front wheel on its bolt circle (one side at a time, followed by test
driving) to see if that helps. As any theoretical purist will tell
you (and I will agree), it *shouldn't* make any difference - but it
can.
--
C.R. Krieger
(Beent here; fixed that)
Trevor Morris
I had the same on my 150k mile '87 525e last year: did Nos. 2 (went back for
re-balancing twice - the guy thought I was nuts, so took pity & didn't
charge me), 3 (waste of time - old ones were fine), and 5 (easy!) as above
plus new strut inserts (the old ones were soggy & about due anyway) and new
wheel bearings (the old ones were grumbling a bit anyway) plus new brake
calipers / pads and discs (also due) - but it still wobbled like buggery at
55-60 mph!
Eventually, I realised that the brakes seemed to be holding on a bit and
needed the help of a foot *under* the pedal to free them. Also, when
"freed" like that, there was no wobble!
Turns out it is a known problem *confined to right-hand drive cars* (Hurrah
for the British Empire!) and occurs because the brake servo/cylinder stays
on the left, and so needs a mechanical link across to it from the pedal.
There are a couple of pivots in the linkage, which after archaeological time
like 15+ years need some oiling. The one on the left side is a bit awkward
to get at, and that seemed to be the main culprit on mine (naturally) but
WD-40 did the trick, after a bit of easy dismantling to get at the pivot.
After that, no wobbles at any speed.
Trevor Morris
P.S. Another problem with pedal linkages on this wagon is corrosion of the
pivot rod in the nylon bush where the accelerator linkage goes through the
bulkhead, which leads to a "sticky" throttle control. The Haynes manual
advises oiling: DON'T! That will swell the nylon and make it even more
sticky. Take it apart and use dry graphite powder on reassembly - some
shavings from a soft pencil lead will do - and clean up any corrosion /
roughness on the pivot rod itself.
Trevor Morris
My
> car is RHD obviously, so this could well be it I guess. I have always
> noticed that my LF brake seems to drag a bit whenever I've had that wheel
> off the ground and spun it by hand. Compared to the RF wheel, it has never
> spun particularly freely. It doesn't require superhuman strength to turn
> it, but it does stop spinning pretty much immediately when you take your
> hand off it. The RF wheel by comparison will continue to spin at least one
> turn under it's own rotational inertia.
>
> I've mentioned this to a few people more qualified to work on cars than me
> over the years, but the response has always been that it isn't bad enough
> to be worrying about and won't cause any problems at all.
>
> Thanks again,
>
> Dean Parker
No problem. The sticky wheel could be the wheel cylinder itself binding,
instead of or as well as a sticky linkage problem, and the latter may affect
the wheels differently if one cylinder is less free than the others, so it's
hard to tell what is happening that way. A couple of other thoughts that
might help the diagnosis.
1) Do you find the braking effect builds up progressively, like a delayed
servo action, so that you have to ease off the pedal pressure to get a
smooth effect as you come to a stop? If yes, that points to sticky brakes.
2) Is the wobble problem always exactly the same, or is it much worse
sometimes than others, e.g. just after you've had to use the brakes? Wheel
balance & soggy dampers always give the same amount of wobble at exactly the
same speed, and you can usually accelerate through it by a few mph and get
smooth running again. My sticky pedal linkage, on the other hand, gave
different effects every day over a few months, seemingly dependent on how
many passengers or how full the boot was, and was sometimes hardly there at
all. In the end, on the last outing, when the penny dropped, joining a fast
road after having to brake to ease in with the other traffic, the wobble got
even worse when I tried to accelerate through: I thought the whole car was
coming apart!
The best test is to hook your foot under the brake pedal and yank it sharply
upwards: if it's a sticky linkage the problem should disappear, or at least
get better, depending on how much slack there is. There is a very strong
external return spring on the master cylinder itself, accessible from inside
the car, and if oiling the cross-car linkage pivots doesn't work it might be
worth looking at that spring, as a long shot, but it's very tough and well
protected from corrosion, so it's unlikely to be the problem, though there
are some more secret levers and pivots around there that it wouldn't hurt to
lubricate - I bet garages never do them.
Finally, slightly sloppy wheel bearings or warped discs can actually help to
free sticky brakes (from whatever cause) by knocking the pistons back in the
cylinders. So renewing bearings and discs, like I did, can actually make
the wobbling worse - another clue!
TM