I just bought a late '91 900i(s) with 220,000km. It is in great
condition, but only has winter tires on steel rims.

Background: I am in Germany. Aluminum rims are considered a luxury,
and fetch a premium price even used. Also, my driving habits are
divided between very high speeds on the Autobahn, and very tight turns
in the Hartz mountains (but that involves some dirt, so I can't go too
low).

I've got an extra set of steel rims from my last car. The question is:
How much do aluminum rims affect the performance of this car? I've
driven Saab 900s with both types, but not in a way to objectively
compare.

I'm looking at either buying new mid-level summer tires and sticking
them on the steel rims, or shopping used, where for similar money I
could get aluminum rims already mounted with slightly used P6's and
the like. Whatever I do, it is only for summer, so I want to go on the
wide side, like 205/60. I have noticed a huge performance difference
from aluminum wheels on other cars, like VW's, but my last (poor
persecuted...blast the bloody a§$holes at the inspection...) Saab ('92
390kKm) did really well on humble steel. Everything from Stuttgart to
Munich at 180km/h to muddy cow paths in Latvia. There never was or
will be be another car like this.
Opinions?
Robobass

robanzellotti (AT) googlemail (DOT) com wrote:
I can't see why there should be any difference in performance. But
changing the wheel diameter for e.g. low profile might change the
gearing and the perceived performance on the speedo. It will of
course also improve the handling. Performance drivers usually
like a lower gearing. (though I prefer relaxed long gearing)

With your fast driving style, you're more likely to hit a stone or
a kerb, or even a pothole in the road. That usually puts a big dent
in alloy wheels. Steel wheels are much more durable.

in article 1177717409.114121.130300 (AT) q75g20...oglegroups.com,
robanzellotti (AT) googlemail (DOT) com at robanzellotti (AT) googlemail (DOT) com wrote on
28/04/2007 00:43:

I would go for alloy wheels, rather than steel, but can't cite any
"scientific" reason for that - perhaps weight?

The correct ratio would be 205/55 for 15" (standard C900 wheels). On normal
5.5" wide they would be a bit too "fat". On 6" wheels off a 9000 they would
suit a little better but the track would not be any wider - in fact it would
be 2mm narrow, but who's counting

There is a wheel you can get, which is an official SAAB wheel and 7" wide -
the offset gives you an extra 3" width in the track and is perfect for
205/55 tyres. IMO, this is a better solution for the C900 than 16" with low
profile tyres.

The wheel in question is:
<http://www.pjgh.pwp.blueyonder.co.uk...0%20Wheel%20St
yles/Five-Spoke%20(15x7).jpg>
<http://www.pjgh.pwp.blueyonder.co.uk...0%20Wheel%20St
yles/Five-Spoke%20Dark-Inset%20(15x7).jpg>

I have seen a few of these wheels come up on eBay in Europe - Belgium and
France, particularly, but also Estonia. I was looking for a set myself
recently.

Paul

1989 900 Turbo S
http://saab.go.dyndns.org/

Expect a rougher ride with low-profile tires. Higher-profile tires have
much more "give" and a smoother ride. The advantage of low-profile tires
is that there is less "roll" in hard cornering. You're giving up comfort
for performance.

My 9-5 Aero has low-profile 17" tires in addition to stiffer suspension.
It's definitely a harder ride.

In article <4632E20B.6FEC3026 (AT) siz-nospam-efitter (DOT) com>, johs@siz-nospam-
efitter.com says...
body kit) made a difference to top speed because of aerodynamics (not
weight), compared to a steel or standard alloy shod car with no kit.

I would suggest looking for a set of 16" 9000 Aero 3 spokes for the
summer on a later 900, with decent tires on, and fit winter tyres to a
set of 15" steels for when the weather is less clement (and/or if they
salt the roads locally to you). Depending on the weather extremes where
you plan to travel, you might find two sets of all season tyres in the
different sizes/profiles/widths might be better than a set of wide
sticky summer and narrow soft winter tyres
--
Carl Robson
Audio stream: http://www.bouncing-czechs.com:8000/samtest
Homepage: http://www.bouncing-czechs.com
Now Playing at home:Front Line Assembly-A Decade
http://www.myspace.com/theelderuk

Elder wrote:

I have the 16" 3 spoke aero wheels on my 9000 and they do look bloody
nice. I jumped on the opportunity to buy them when a saab dealer cleared
out some stock. They don't fit on newer saabs as they switched from 4
nuts to 5.

However, about the science, I still think it is mostly marketing speak.
The 3 spoke wheel was obviously a convenient symbol of the turbo. There
was marketing talk that they helped cooling the disc brakes. But wait a
minute here:

Suppose that a 'turbo' wheel on the right side is blowing into the disc
when the car is moving forward. Then imagine taking off the wheel, while
still spinning and blowing air towards the back side of the wheel. Then
take the same wheel to the left side of the car (wheel still spinning).
Mount the wheel on the left side (wheel still spinning). Which direction
will it now roll on the car? To perform the disc cooling function, it
will obviously have to roll backwards on the left :-) Hence right and
left side 3 spoke alloys would have to be mirrors of each other.

And they are... AFAIK

--
MH
'72 97 '77 96 '78 95 '79 96
'91 900i
'95 900SE

Most of the used stuff I'm looking at is Alu 15"x6" with 205/60. This
profile is plenty tall to deal with the smooth roads here (there ain't
no Major Deagan Expressway in Deutschland!). The 185/65's I have now
are a bit squirrelly up in the 100mph+ range.

Conceptually I figure that aluminum rims not only allow faster
accelleration and braking, as since being lighter, there is less
rotational inertia, but also, a lighter wheel can move up and down
faster, allowing the suspension to react faster to bumps and dips. As
I said, the effect probably depends on a lot of factors. I haven't
really noticed it with this car, but I'm probably gonna do it anyway
to get a bit wider, and also to indulge myself a little. I work hard!

Robobass

robanzellotti (AT) googlemail (DOT) com wrote:
I don't believe that this has any significant effect at speeds eh.. under
100mph or so, but I'll have to get my calculator out.

Yes, this is perhaps more like it. The weight of the wheels doesn't depend
on speed (unless close to speed of light :-), so lighter 'un-sprung' weight
is an advantage for handling and ride.

in article 4633871F.2BA6F692 (AT) siz-nospam-efitter (DOT) com, johannes at
johs (AT) siz-nospam-efitter (DOT) com wrote on 28/04/2007 18:40:

If you're referring to the curly Aero wheels, then they are - the wheels are
rotational.

When I had a new set of tyres fitted to my set, I drove around for a day, or
two, before noticing that they had the sides wrong on the front. I duly went
about swapping them over and realised that my rotational tyres would then be
the wrong way around. I returned to the tyre fitter and pointed out their
error, the fitter pointer to the rotation lines and assured me it was okay.
I tried to explain again, but the fitter kind of sniggered and went to find
his Manager. They could clearly be seem laughing about it in the office and
then the Manager came out to see me. He also pointed to the rotation arrows
and assured me that the tyres were on the correct sides. I pointed to the
rotation arrows and the wheel and he went white, then red, then yelled the
at the fitter who swapped them over

Paul

1989 900 Turbo S
http://saab.go.dyndns.org/