Subject: Performance and speed

From: [email-masked]
Date: 18 May 1995 00:50:48 -0600

I just got home after driving from Baltimore to Philadelphia. Those of 
you who have driven I-95 know that it's literally a speedway through 
parts of Maryland (and further south in Virginia). I thought it was bad 
up here in Philly, but the speeds are nothing compared to what you'll 
find down there. Of course, the traffic volume (read: # of loonies on the 
road) is much lower too. 

   My mom's little 1985 Toyota Camry was doing about 70-80mph in the right 
lane, with rigs passing me on the left. And cars were flying by them, no 
doubt some had to be doing 95-100mph. It was scary, let me tell you!

   Anyway, what I wanted to say... a car's top speed is (IMHO) a pretty 
useless statistic. I don't know what the top speed is on that Camry 
(certainly not the 170 that the speedometer goes up to :) but it's 
certainly not safe at anything more than 80mph, that's for sure. The car 
is in good shape, but at high speeds it vibrates (especially the steering 
wheel) and the suspension gets kind of wobbly. And you really gotta blast 
the radio to hear it over the engine. It's not meant for fast highway 
speeds like what I had to drive tonight, I don't care what Consumer 
Reports had to say. 

   A few months ago there was this commercial advertising "the 140mph 
Cadilliac Seville". It goes 140mph, woop-dee-doo. What speeds were it 
designed to be driven at? Performance of a car is not something that is 
constant at all speeds, at least not in my judgement. Some cars ride as 
well at 100mph as they do at 55. But on other cars there is a big 
difference between 65 and 75mph. Does anybody know-- does this Cadilliac 
handle well at 140mph? Or was it just advertising hype aimed at the ego?

   My questions, which may be kinda stupid: What's different about making 
a car that performs well at high speeds? Are tires really a big factor? 
What extras go into the suspension? What stops the feel that the car just 
wants to pull apart into 1 million peices? Is the size of the car an 
important factor? and on and on...

Just like there's cost depreciation, there's also performance 
depreciation. I'd love to hear from some designers or people in the know 
about how drivability and safety deteriorate at higher speeds on some of 
the real popular cars. And I'd like to know some cars that don't suffer 
such losses at high speeds.

Comments, or whatever would be appreciated.

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From: [email-masked] (Robert King)
Date: 17 May 1995 16:05:59 GMT

In article [email-masked], [email-masked] () writes:

>useless statistic.

   It depends on what you do with the car.  A grocery-getter`s top speed
rating is as useless as tits on a bull, but I RACE my car.  It's top speed
is importane to me (although not as important as handling and acceleration.)

> I don't know what the top speed is on that Camry 
>certainly not safe at anything more than 80mph, that's for sure.

   You are qualified to make this decision?  What are the characteristics
of a safe car at 80+ mph? 

> The car 
>wheel)

   This is an indication that somthing is wrong, probably in the front
suspension since the vibrations are present in the steering wheel.  You
may have a bad alignment, tire out of balance, bent wheel, etc...  The
suspension may be as smooth as glass at 60 mph, but these problems can
manifest themselves in a limited range of speed as the vibrations reach
a resonant frequency in the suspension.

>and the suspension gets kind of wobbly.

   Its probably getting upset by the vibrations mentioned.  Its also
possible that the car tends to "float" a bit because of high-pressure
air developing underneath the car.  This CAN be dangerous at extremely
high speeds as it unloads the suspension.

> And you really gotta blast the radio to hear it over the engine.

   That's not unsafe.

>It's not meant for fast highway 

   I find it difficult to believe *any* US spec'ed car is dangerous at
80.

>designed to be driven at?

   0, 140 and everything in between.

> Performance of a car is not something that is 

   Oh, I'm sure the advertising was aimed at the ego - all advertising is!

>a car that performs well at high speeds?

   A big part of high-speed stability is keeping air out from underneath
the car.  Other aerodynamics come into play also.  Suspension is a different
story at high speeds too.

>Are tires really a big factor? 

   Very big!  All tires have internal rolling resistance which heats up the
tire.  The faster the tire is driven, the more heat it has to absorb or
radiate.  Speed rated tires (H, S, V, Z, etc...) are designed to handle this
heat without blistering or rupturing.  Running a non-speed-rated tire at high
speeds (or a speed-rated tire above its rating,) for extended periods can lead
to tire overheating, blistering, and possible catistrophic failure.

>What extras go into the suspension?

Primarily the car is brought lower to the ground to reduce the air that builds
up underneath the car.  Obviously, the suspension should be able to handle
high G-loads in cornering, but in some cases this may be a secondary concern
(I'm thinking of dragsters here - they don't have to turn at high speeds.)

>What stops the feel that the car just 
>wants to pull apart into 1 million peices?

   Well, the floating feeling is probably due to air trapped underneath the
car.  The vibration is probably somthing amiss in the suspinsion or driveline.
The BIG factor, I feel, is perception.  Things are happening very fast, the
engine is making a lot of noise, there's a lot of wind noise, your adrenaline
is flowing and you're excited!  No wonder the car FEELS like its going to fly
apart!

>Is the size of the car an 

   Frontal area is important in determining aerodynamic drag.  Weight is
important in determining acceleration.

>such losses at high speeds.

   I can't address specific cars, but in general, cars that are designed
for high-speed use won't suffer as much detrement in drivability at high
speeds as cars that arn't.  That's pretty much a no-brainer.

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+-----------------------------------------------------------------------+
| Robert A. King                |                                       |
| Systems Software Engineer     |                                       |
| Kodak Health Imaging Systems  |    "I drank WHAT?!?" -- Socrates      |
|                               |                                       |
| [email-masked]            |                                       |
+-----------------------------------------------------------------------+
| The opinions expressed here arn't even mine, much less my employer's! |
+-----------------------------------------------------------------------+

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From: [email-masked] (Chris T. Papademetrious)
Date: 18 May 1995 10:54:47 -0400

>important factor? and on and on...

 Well, my car may be an interesting comparison.  It's a Dodge Omni (the
econo hatchback car) with a 2.2L turbocharged engine and Shelby
suspension, with 15" wheels (195-50R15).  It's smooth up to 110mph - the
steering wheel can be controlled with one hand, and it doesn't shake.
 
 I attribute the solidity to the stiffness of suspension (the wind and
road shape don't make the car hover or rock on its suspension) and the
fact that the tires are balanced and are low-profile.  The interior still
rattles. :)  It's still an Omni.

-- 
 | Chrispy                       | Dodge Omni GLH Turbo | Amiga Forever!  |
 | School: Drexel University     | 190hp, 2350lbs, 2.2L | (Commo-who?)    |
 | Workplace: Unisys Corporation | 0-60 in 6.2 s, cheap |_________________|
 |  (CMOS Processor Designer)    | to insure, looks like hell :)          |

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From: [email-masked] (Chris Clements)
Date: 18 May 1995 16:45:57 GMT

Are you serious - 0-60 in 6.2 s?  Damn!!  What's the top speed?

Chris Clements
Florida State University
College of Law
(904) 644-0339
[email-masked]