850 shakes badly at high speed

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.

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!

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?"

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).

My "little" brother took the family 850 wagon to driving school .I think this was the program (

) Everyonelaughed at the teenage kid with the MX helmet in Mom's wagon until track timecame. Other than IPD anti sway bars and a new set of tires the wagon was stockand embarrassed just about everything other than the Corvette. The wagon was thecorner workers favorite. For some reason a white station wagon with trailerhitch screaming around the turn smoking the inside tire made them cheer. Mybrother had no complaints about high speed behavior. My Dad did have a fewcomments about having to replace tires that were just over a month old when hegot home.

Chris V

Rob Guenther wrote:

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!

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

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.

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

Henry wrote:

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.