850 shakes badly at high speed

Sort of a duplicate post here but wanted to flesh this issue out.
My car, an '96 850 turbo sedan runs smooth as butter at 100 mph.
Absolutely smooth, you could finish the decorations on a wedding cake in
the back seat.
But at 110 it begins to shake roughly, almost violently.
1. Tires are V rated Michelins, with about 7k on them, almost new.
2. Car has been perfectly maintained. That means fresh fuel filter,
etc,etc,etc, I even put new front ball joint/control arms on at 100k just
for the sake of it. The car has 122k on the clock and runs like new.
3. Stock ECU and exhaust and air intake.
4. Tranny serviced (despite maint recommends) every 20k miles.
5. Tranny shifts like very smooth, kick down prompt and sure. Lock out
good and easy.
6. Never had anything but Mobil 1 5w 30 in it.

Ok Guys, Got any ideas?

PS I don't usually drive that fast but had the occasion to (was passing
about 5 cars at once and went from 60mph to 100 in about 3 seconds, felt
good and with smooth open road for miles ahead I thought I'd air her out a
little, till she got the "shakes", that is.
Thanks in advance.
Hank

 

Check the balance on the tires and driveline components. My dad has had our
965 up to 210kph (with the whole family aboard on an empty highway 400,
heading south to Toronto, when everyone was heading north to cottage
country) when it was new (1993 model, did 210kph in about 1995), and last
year he attempted another high speed run en-route to Ottawa, up to 180 it
was fine, then at 190+ it started to shake (he was trying for 200+ again...
I don't know why he does this, I think he misses the autobahn's)... He said
the tires were slightly out of balance (H rated goodyear Eagle LS). Our new
Michelin MXV4+'s seem to be better balanced, but the car has not been taken
over 160 with them on.

He told me in Germany the tires are balanced on the car, and this can
correct for high speed imbalances... whether this is the case with your
car... who knows

60-100 mph in 3 seconds, no, i'm afraid not.... it just felt like it... I
don't think supercars are that quick.

When we got the Goodyears, they fell slightly out of balance after a few
months, maybe something similar happened to you... Up to 110kph they were
okay, but at 130kph the steering wheel shook in a scary fashion, rebalance
fixed them, but they are still crappy tires, we replaced them with the
Michelins with over 2/3 of the tread left on the Goodyears.

 

I'd bet on a tire or tire balance problem. See if you can get another
set of wheels and tires on it and repeat experiment. My '98 V70 T5 is
dead smooth at 210 km/hr (130 mph) on H rated snows!

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

My bet is tire balance and/or warped wheels. My 850R's 17" rims were warped
and would vibrate only at certain speeds.

 

My bet is tire balance and/or warped wheels. My 850R's 17" rims were warped
and would vibrate only at certain speeds.

 

Thanks guys, I'm thinking tires... will post later with the fix.
H

 

Where do you get it up that fast? You got access to a cheap track, or just a
good smooth empty stretch of one of the 400 series highways?

 

"Where do you get it up that fast? You got access to a cheap track, or
just a good smooth empty stretch of one of the 400 series highways?"

Just call me crazy. I thought about timing the acceleration from 60 to
100mph, and I swear it's not much more than 3 seconds... no more than 4.

Where the 850 is a little weak is if your are going say, 80mph and nail
it. It will go really fast eventually but it doesn't have the
acceleration like going from 30mph to 60mph in
say 2 seconds. If you argue with me I'm going to break out the stop watch!

 

Henry:

I would rotate the tires, and how long since a 4-wheel alignment? These are
easy cheap things to look at first.

As the speed increases, a slight misalignment could cause resonance
vibration like you mention. Are all the tire balance weights still on?
Sometimes one can fall off, and if it was small to begin with, only high
speed could bring the vibration to the point you feel it.

How are the control arms/ball joints? 122,000 could be time for new ones.

Just a few thoughts.

Jeff

 

I'm just going by professional testing done in Car and Driver. They do 0-60,
0-100, 50-80 (passing).... no car does that 50-80 pass in 3 seconds, at
least none I have read about.... So I doubt that your 850 can do a passing
manuver involving higher speeds any faster... Remeber acceleration gets
slower as speed increases. Stop watches, or the internal cronometer aren't
always the most accurate methods... there is the human error involved, alays
a nasty thing.

You said 60-100Mph in 3 seconds, did you not?... this is 95-161 kph. I think
my 960 (201hp) would take around 10-12 seconds to do it.... My turbodiesel
Golf can do it pretty quickly for its power, it's an awesome car on the
highway (mainly for fuel economy ;-)...of course it is all relative, I mean
quickly for its engine specifications: 90hp at 4200rpm, 155lb ft at 1900rpm
with a flat torque curve into the 3000+ range I believe).

I will admit that the 960 has pretty bad gearing (automatic, with an engine
that needs to be revved hard to get full power), once as you go flat out in
a gear, the next gear will come below a strong part in the torque curve, and
you have to wait for the acceleration, tho by no means is it a slow car, no
where near a T5 tho. This gearing problem is most noticeable between gears 1
and 2 tho... then again it could just be that the engine doesn't really
start to get loud until 4000-4500ish rpm, so it could just be really a noise
thing.

 

My "little" brother took the family 850 wagon to driving school .I think this
was the program (
http://www.jimrussellusa.com/drivingcourses/highperformance.php ) Everyone
laughed at the teenage kid with the MX helmet in Mom's wagon until track time
came. Other than IPD anti sway bars and a new set of tires the wagon was stock
and embarrassed just about everything other than the Corvette. The wagon was the
corner workers favorite. For some reason a white station wagon with trailer
hitch screaming around the turn smoking the inside tire made them cheer. My
brother had no complaints about high speed behavior. My Dad did have a few
comments about having to replace tires that were just over a month old when he
got home.

Chris V

 

Sometimes the 404 towards the top has long open stretches. Also, head
west and grab the 402 between London and Sarnia - lightly travelled and
straight. I never pass people at those speeds, only drive on open road.

P.S. Watch out for Cam Wooley, maybe he reads this newsgroup!

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

An 850 Turbo can't do 60-100 at anywhere near 3 seconds. My 850R has the IPD
Motronics ECU upgrade, Borla SS exhaust, etc. and can't do 60-100 at
anywhere near 3 seconds.

Think of it this way... in a vacuum, 60-100 takes the same amount of F
(force) as, say, 0-40. In the real world, 60-100 takes much more force
because air resistence increases with the square of the speed of the
vehicle, and 850's are not exactly aerodynamic vehicles.

In fact, I doubt any production car can do 60-100 in anywhere near 3
seconds. Quite a few production cars can do 0-60 in around 5 seconds. If
they can do 60-100 in 3 seconds, they would have 0-100 speeds of 8 seconds.
The only production cars that have 0-100 speeds in the 8's are the Ferrari
F40 & F50, Dodge Viper, Lambo Diablo, and Porsche 911 GT2, and they all have
0-60 speeds well under 5s.

The 2003 BMW M3 can run circles around an old 850 Turbo and does 0-60 in
5.4s and 0-100 in 12.1, giving a 60-100 speed of 6.7s. If a 333HP 2003 M3
does 60-100 in 6.7, you can bet the farm that a 220HP 850 Turbo does it in
about 11s, which is about right. The 1996 850R was tested to do 0-100 in
17.5s. Let's say it has a 0-60 speed of 6.8s. That would give the unmodified
850R a 60-100 time of 10.7s, which makes the 11s+ 60-100 time for an 850
Turbo about right.

Yet another example why when it comes to performance, reliability, etc. I
never take anecdotal evidence at face value. Now I fully expect someone to
question how I *KNOW* Henry's 850 Turbo can't do 60-100 in 3-4 seconds
without having ever seen his vehicle...

 

Hi Jeff, yea I think it's tires. I put new front control arms/ball joints
on at 100k miles. They were not horrible but had wear.
I just javen't had a chance to get to the tire dealer! Another friend of
mine suggested a weight might have fallen off.
Thanks
Henry

 

You guys got me convinced. The 0 to 60 times added with the 60 to 100
times makes a lot of sense. Yea, that's a whole different ball game.
I am going to stop watch it just for grins... it can't take 11 seconds to
go from 60 to 100!
But if it does and it may well, it feels like a damn fast 11 seconds!
)
Cheers!

 

Plus the 60-100 pass is actually longer then the 0-100 subtract the 0-60
time. This is because you need to factor in all the time needed to downshift
the car and such.

I'd be scared if I owned a car that could accelerate that fast.

 

Well I just escaped a speeding ticket tonight (passed 5 cars in the right
lane of a two lane road, before a lane ending then I had to go around a car
in front of me since I had so much speed ... about 110 in a 70... yah yah I
know, not the safest thing, something I would normally avoid, but I you
know, there are just those days for being a moron, usually involves some
excess emotions.... got off with an improper lane change - no signal)
Anyhow I don't think 400 series speeding is in my budget for a little while
anymore.... I think I need to take my speeding off the public roads for a
bit, even if there is no one around.

 

It does, because you are so focused, that adreniline is just pumping....
Like take for instance, my turbodiesel. It takes like 12-13 seconds to get
to 100kph from a standing start, but because of the initial launch speed
(LOTS of low end torque) and because of the engine growl it feels MUCH
faster.... but I did it with the watch... 11.6,12.4, 12.1 seconds.

 

Maybe this should be printed on the Tach.

Warning:
Any shift in the ambient lighting due to Doppler shift is only transitory. Remove
your foot from gas peddle from the floor and things will revert to normal.

Chris V

 

Excellent point.

60-100 in 3 seconds is really supercar and sport bike territory. My 850R
will really go when I floor it at 60mph and it can get to 100mph very
quickly, but not anywhere near 3s.