> If the struts have substantial wear either in the shock-absorbing part or
in
> the ram-bush your car will start to get unstable. Often the strut shock
can
> be deteriorated but not be obvious to the driver. There is a test rig
which
> involves a chart graph which records how many rebounds or ocillations the
> strut shock allows. This a test for damping. >

The "test rig" that Jason refers to is known as a shock absorber
dynamometer…..and I own one.

Basically, it gives you a graph of the pressures produced as compared to
the shaft velocities at which they are produced when the shock is moved at
different speeds – ranging from a shaft velocity of one-inch-per-second to
20 i.p.s.

Basically, a shock that creates 200 pounds of resistance pressure while
moving at a shaft velocity of five i.p.s will  better control a car than a
shock that only produces 100 pounds of resistance pressure at the same
shaft velocity.

We use these graphs a bit differently in racing applications to "fine-tune"
the suspension with shocks, but the above information is pretty much all
you need to know for standard passenger automobiles….more shock pressure
at a given shaft  velocity controls better than less pressure at the same
velocity.

When internal valves and springs weaken and wear out (imagine how many
cycles a shock valve control spring experiences in 50,000 miles of
compressing to open and close the valving each time the shaft moves in or
out) , they allow fluid to pass more easily at lower pressures – usually
with no external leakage to suggest that any sort of problem exists.

The so-called "bounce test" only tells you if a shock will control a car
while negotiating "Mickey D" parking lot speed bumps at less than five mph
with a carload of rug rats and Happy Meals.

"Hand-testing" a shock off the car moves the shaft at a velocity of
approximately one-half i.p.s.

A shock can "feel" good at slow "bounce-test" or "hand-test" speeds of one
i.p.s. or less because it is only passing fluid through its designed,
low-speed, bleed orifices and/or bypassing the seals, but be a complete
failure at higher shaft velocities once it gets up onto the
valving….sometimes, actually providing less resistance at five i.p.s.
then at "bounce-test" velocities once the valves open up.

On a smooth road, the shocks will likely be working in the 2-6 i.p.s. shaft
velocity range….which simply cannot be duplicated by bouncing on the
bumper of the car.

Best test for a shock (short of dyno-testing) is to drive it fairly
aggressively – but carefully – over rough road. If the car remains under
control, then the shocks are, likely, okay.

If one end or the other tends to "wash out", then new shocks (or struts)
are indicated.

> > How much do they affect your wheel alignment?
>In severe cases the road wheel
> will have ‘cupping or scalloping" wear points on the tire concerned.

A shock that doesn’t help control the unsprung weight (basically,
everything that moves up and down with the wheel) will allow more than
anticipated suspension movement at the extremes, which allows excessive
camber/caster, gain/loss and bump steer….in addition to allowing the
wheels to bounce and create the cupping pattern.

It CAN contribute to tire wear.

–
Bob Paulin – R.A.C.E.   <><
Race Car Chassis Analysis & Setup Services
Chassis Blueprinting Services (as in engine blueprinting)

Eight years and 129k is getting up there for struts, though I
personally replace them on a functional rather than a schedule basis.

The do-it-yourselfer can replace them (observe safety precautions for
the spring/strut compressor as well as those generic to lifting a car
and working underneath it).  However, I’ve done enough struts to file
this job under "dirty laborious chores that somebody who’s set up for
it, and who does more in a month than I would in ten years, will take
on for a modest amount of money."  It’s quite a bit harder than
changing conventional shocks, which used to be one of the classic
beginner exercises for the budding shade-tree mechanic.

> What differences should I feel in the handling
> after replacing them?  If any?
> Do struts wear out like brakes and tires, or
> do they just work, or not, like an electrical part?

They wear out gradually but can also suddenly lose it.  Have you ever
seen (and dropped back from or very quickly passed) a car with one
wheel juddering up and down like a jackhammer?  That’s a car that has
blown a shock or strut (whichever it has) and no longer has a damping
function to control that tire.   Think of a shock as a time-release
anti-spring.  A strut has more functions than a shock but damping is
usually the one that goes.

A symptom of gradual loss of damping function is best felt on
long-period undulating pavement.   If you feel like a little kid in one
of those inflatable bouncy houses at a place and speed that your car
once would’ve taken in stride, that means  your shocks or struts are
putting in their retirement papers.  A lot more than the usual swaying
and jouncing through a series of lateral transitions is another.

A "cupped" wear pattern on the tires is another symptom, but by the
time you see *that*, things are pretty far gone.

> How much do they affect your wheel alignment?

Get an alignment afterwards.  The strut directly affects some
parameters.  In theory, I guess that if  Scotty beamed the old one out
and the new one in without disturbing its surroundings, you could do
the job without affecting alignment, but in the real world it isn’t
quite that simple (besides which other things that affect alignment
might’ve gotten a bit out of place over the years).

 If it’s been a while since your last wheel balancing and rotation,
might as well get that done too.

For more information, see
http://www.carcarecouncil.org/Steering_Suspension/struts.shtml
http://autorepair.about.com/cs/generalinfo/a/aa012201a_3.htm

Cheers,
–Joe

>Dear experts,
>I have a 97 Camry XLE with 125K miles on it.
>I’m told that I should now change the front and
>rear Macpherson struts.
>Is it time to change them?  Or, how can I tell
>if the struts need changing?

You can do a visual inspection to see if any of the struts are leaking.

>What differences should I feel in the handling
>after replacing them?  If any?

You should end up with a smoother more controlled ride.

>Do struts wear out like brakes and tires, or
>do they just work, or not, like an electrical part?

They slowly wear out.  Sometimes they do completely fail if
you blow a seal.  The wear is gradual so chances are you may not
notice the difference until you put new ones in.

>How much do they affect your wheel alignment?

Not sure what you mean.  When you change them, you should get the cars
alignment checked.
—————
Alex

On Sat, 19 Feb 2005 12:31:43 -0800, "Billy Bad Assr©"

- Hide quoted text — Show quoted text -

<billybadausSOCKS@comcastSOC|KS.net> wrote:

><condor_…@yahoo.com> wrote in message
>news:1108837006.908608.214680@z14g2000cwz.googlegroups.com…

>> Dear experts,

>> I have a 97 Camry XLE with 125K miles on it.

>> I’m told that I should now change the front and
>> rear Macpherson struts.

>Are they leaking?

>> Is it time to change them?  Or, how can I tell
>> if the struts need changing?

>Are they faulty >> do this — use your knee or knees, push the front or rear
>bumper down abruptly!!! The chassis as it returns to resting position – Bounces
>one time!!! Chassis bounces more than once– r/r struts!

>> What differences should I feel in the handling
>> after replacing them?  If any?

>If they’re faulty — you feel a tremendous difference!!!

>> Do struts wear out like brakes and tires, or
>> do they just work, or not, like an electrical part?

>They are wear items, so yes they wear out.

>> How much do they affect your wheel alignment?

>?? Don’t know (tech explained this as work?) what you mean — r/r struts and do
>a >wheel alignment< as a requirement!!!!

Oil leaking from the shock/strut?

Loss of stability over a bump?

At 125,000 miles they have cycled up and down millions of times, a
shock absorber (strut)  takes the impact off of important items like
ball joints, frame mounts, things that matter.

Depending on where the car was driven during it’s lifetime plays a
large part on comparing mileage wearout  to equate worn shocks.

A constant smooth road surface, I would imagine shocks would go double
the distance than constantly being made to perform over rough uneven
bumpy surfaces.

I know I personally have felt the difference before and after many
times as I have owned my own Auto Service for over 29 years now and we
never have sold something someone didn’t need but a new set of shocks
make the rest of the car live longer, ride smoother, less tire wear,
and better handling.

All a matter of personal choice ….unless of course they are leaking
or are so soft that the car bounces more than twice when someone (large
person) moves the front bumper up and down hard then lets go….and
counts.  1    2      3      4    …

 stayp"@notsuoh.rr.moc> wrote:
>> Do struts wear out like brakes and tires, or
>> do they just work, or not, like an electrical part?

>> How much do they affect your wheel alignment?

>> Thanks a lot

>Depends on how you drive and what the road surface is like.
>Struts have parts that move.  Moving parts wear out.
>The more they move, the faster the parts wear out.

Right.  Many people don’t replace their struts when they should, since
the degradation in performance is so gradual.  This is one of the
reasons that old cars drive like old cars.

<condor_…@yahoo.com> wrote in message

news:1108837006.908608.214680@z14g2000cwz.googlegroups.com…

- Hide quoted text — Show quoted text -

> Dear experts,

> I have a 97 Camry XLE with 125K miles on it.

> I’m told that I should now change the front and
> rear Macpherson struts.

> Is it time to change them?  Or, how can I tell
> if the struts need changing?

> What differences should I feel in the handling
> after replacing them?  If any?

> Do struts wear out like brakes and tires, or
> do they just work, or not, like an electrical part?

> How much do they affect your wheel alignment?

> Thanks a lot

news:1108837006.908608.214680@z14g2000cwz.googlegroups.com…

> Dear experts,

> I have a 97 Camry XLE with 125K miles on it.

> I’m told that I should now change the front and
> rear Macpherson struts.

Are they leaking?

> Is it time to change them?  Or, how can I tell
> if the struts need changing?

Are they faulty >> do this — use your knee or knees, push the front or rear
bumper down abruptly!!! The chassis as it returns to resting position – Bounces
one time!!! Chassis bounces more than once– r/r struts!

> What differences should I feel in the handling
> after replacing them?  If any?

If they’re faulty — you feel a tremendous difference!!!

> Do struts wear out like brakes and tires, or
> do they just work, or not, like an electrical part?

They are wear items, so yes they wear out.

> How much do they affect your wheel alignment?

?? Don’t know (tech explained this as work?) what you mean — r/r struts and do
a >wheel alignment< as a requirement!!!!
—
BBA
°?°
When Privacy Matters — http://www.epic.org

If they aren’t leaking and the car isn’t bouncing when you go over
bumps, don’t worry about them.

If you want a second opinion, try a local reputable Toyota dealer.
Unlike Sears, they haven’t been accused of selling hundreds of millions
of dollars in unnecessary auto repairs.