Re: how fast on a spare??

[Alex Kowalski <akowalsk@shrike.depaul.edu>]

BTW, how fast can you really go on a spare (it
> > says max of 50 MPH)?
> I was heading home from work on Interstate 495, happily
> cruising at 75mph when a Taurus blows past in the fast lane with at
> least a 15 mph speed differential. Lady driver, baby belted securely
> into car seat, donut spare on right front!!!!
> 
> --
> Chris Palmer (1995 S6 Wagon)                "Ashes to ashes,
> Data General Corporation                     dust to dust,
> Enterprise Solutions Engineering Division    If Lillee don't get yer,
> chris_palmer@dg.com                          Thommo must!"

Well, my own experience with these tiny spares has taught me to respect 
their limits.  Maybe I drive harder than some, but I blew one of those 
spares quite easily (it was Goodyear construction, as I remember) after 
about 100 miles of driving at no more (I can guarantee) than 65 mph in a 
Chevrolet Chevette Diesel.

Side Note Here:

(Oh My God, DID I actually drive it? (I describe this only because I 
think with the new Audi and VW Diesels, anyone should only remember the 
lowly Chevette Diesel enough to realize how much better the options are 
now, or could be, if you aren't so much into pavement-wrinkling 
accelleration and you like this engine.)  The engine (Isuzu) was 
indestructible.  It wouldn't rev high enough to break, and didn't develop 
enough power to hurt the transmission, no matter WHAT you did to it, 
trust me (170K+miles).  The rest of the car was another story: gronking, 
clacking, creaking and twitching just like the rest of them (UNbelievably 
soft and uncomfortable seats, worse aesthetics, that got no better as the 
miles accumulated). It did get tremendous mileage, and was very slow, but 
still fun in a bumper-car kind of way (momentum is your friend).  It made 
lots of clatter before it was rear-ended at a deserted NJ stoplight, late 
at night, by a nice drunken lady in a Cutlass Supreme, and almost totally 
destroyed, with my Dad at the wheel.  

He survived by virtue of the 1,000 pounds of loosely-stacked Green-Bar 
computer paper and biiiig Systems 370-era IBM disk spindles he was 
hauling at the time that helped absorb the shock (they never made much of 
an impact on the Chev' Diesel's 0-20mph times, and you just whistled in 
the wind afterward anyway). Have you ever seen a ticker-tape parade?  I 
think modern VWs and Audis wouldn't need the printouts to keep someone 
safe.)

Anyway, to return to the Tiny Spare, I was running errand duty for my 
Dad, one left front tire blew out, and I replaced it with the spare.  Got 
home, thought to myself that it could survive another day before 
replacement, drove it (during summer) and blew it. This happened in New 
Jersey, driving over the unimproved RT-9 towards NYC, near the Pulaski 
Skyway, several years ago. The spare had never touched ground before 
that. 

It seems to me that no matter what kind of driver you are, anyone with 
any kind of scientific education woud FEEL the forebodance in such a 
small tire, and think twice twice before driving much above its 
recommended speed/load (I ignored things much more then):  more of the 
weight of the car winds up there because of its small size, at least as a 
fraction of its contact area (yeah, maybe the car shouldn't lean because 
of the outsize rim, but I've never seen a car that didn't also look like 
it was leaning); it has a smaller air and rubber volume to absorb heat; 
it has a smaller surface area to discharge heat; it is already at a high 
pressure to sustain its load; it will wind up being the first tire to be 
pushed across the tarmac in any cornering situation because of its small 
tread, generating more friction and heat; the belts/rubber in the tire 
are already stressed, so if it hits something sharp, its work of fracture 
might not be able to cope (boom!); try transmitting the same power to the 
ground through a much smaller amount of flexing rubber.  Finally, are 
they really made as well as bought tires?  Go lightly on them from my 
experience.  Whomever was taking her kids for a ride was doing just that. 
Hopefully they made it.  

Best Wishes, 
Alex Kowalski
'84 4KQ (so far, pristine spare)