Steel vs Alloy rims

[y_p_w]

You've made this statement twice now without *any* substantiation.

Would you care to tell us *where* you got that info from?

I think in general an equivalent sized aluminum alloy wheel would
be lighter than a stamped steel wheel. It all depends on design.
There are some elaborately designed, ultra-light aluminum wheels.

From a practical point of view, aluminum is a lot easier to cast

and forge than steel. I guess that's why most steel wheels are
stamped. I suppose it might be possible to make some super
lightweight forged steel wheel, but who would go through the effort
when aluminum is easier to work and frankly looks better?

Or are you just repeating your unsubstatiated *opinion* ?


How do you *know* that?

Aluminum definitely conducts heat better than steel. Stainless
steel pots typically have a copper bottom or an aluminum disk
to improve heat flow.

There's also how well the wheels cool the brakes. Most steel
wheels are stamped and cool with stamped holes. Aluminum wheels
are either very open to the air or otherwise channel air to the
brakes.

 

[Jirí Lejsek]

You've made this statement twice now without *any* substantiation.

Sorry - is it so important?

Would you care to tell us *where* you got that info from?

Are you an expert on wheel design? Did you personally weigh 100s
of steel and alloy wheel pairs for the same car? Did you find a web
site that carries both steel and alloy wheels for the same car and
shows their weight?

No I didn't wiegh 100s wheel, but I weigh some of them (I tried to take some
usual, typical), different sizes, all alloys where heavier. Unfortunately I
didn't recorded weights, so I could not provide them.
Did you weigh any one? Did you find anywhere information about weight of
wheels? No, they do not need you know thruth.

Or are you just repeating your unsubstatiated *opinion* ?

What you are repeating here?

How do you *know* that?

With normal driving you do not heat up discs much, so there is little heat
that can be dissipated. If your discs be 10 degrees cooler you think you'll
see any difference? The effect can even be negative, because discs have to
warm for optimal breaking power.

 

[y_p_w]

Sorry - is it so important?


No I didn't wiegh 100s wheel, but I weigh some of them (I tried to take some
usual, typical), different sizes, all alloys where heavier. UnfortunatelyI
didn't recorded weights, so I could not provide them.
Did you weigh any one? Did you find anywhere information about weight of
wheels? No, they do not need you know thruth.

It all depends. Honestly some of the lightweight aluminum wheels
required some exotic alloy that is more expensive and harder to
work with. Often a manufacturer will just settle for a lower cost
alloy and make it heaver for a certain strength.

Here's a list of OEM and aftermarket Mazda Miata wheel weights:

http://www.miata.net/faq/wheel_weights.html

I think this is a fairly good place to start. The 14" stamped steel
wheel weighed 18 lbs, while the same sized aluminum wheel was 12.3
lbs. The BBS aluminum alloy wheel was an incredible 8.5 lbs.
Larger and wider aluminum wheels did weigh more, but I suspect the
same sizes with steel would have been well over 20 lbs.

Even with the larger wheels weighing about as much as the 14"
steel wheel, I suspect they would be used with lower profile tires
that improve handling/response. They probably also weigh less.

 

[y_p_w]

Here's a list of OEM and aftermarket Mazda Miata wheel weights:

http://www.miata.net/faq/wheel_weights.html

And here's another list:

http://www.superhonda.com/tech/wheel_weights.html

Subaru Impreza MY02 WRX Cast 16x6.5 16.5
Subaru Impreza MY02 WRX (BBS) Forged 17x7 16.0
Subaru Legacy Stamped Steel 15x6 19.5

In general, steel wheels weigh more, and can weight more in a
smaller size.

 

[Paul Pluzhnikov]

Sorry - is it so important?

Yes: you've claimed that something is a "common myth", and have
been proven wrong by the 2 references that y_p_w provided.

This certainly tells me something about credibility of any other
statements you make.

With normal driving you do not heat up discs much, so there is little heat
that can be dissipated.

"Normal driving" is not when you need heat dissipation.

When I descend from Cajon pass at 1277m down to the LA basin,
and it is 40C outside, my discs are hot enough to fry eggs on.

If your discs be 10 degrees cooler you think you'll
see any difference?

Yes, if your discs are 10 degrees below brake fluid boiling point,
you will almost certainly see difference if you heat them another
10 degrees.

The effect can even be negative, because discs have to
warm for optimal breaking power.

This (I think) is just another bogus statement.
Where did you get *that* from?

Cheers,

 

[y_p_w]

Yes: you've claimed that something is a "common myth", and have
been proven wrong by the 2 references that y_p_w provided.

This certainly tells me something about credibility of any other
statements you make.

I certainly have made factual mistakes, but I'm willing to
own up to them when proved wrong. I make mistakes and
recall things from memory, but I know I'm not infallible.

"Normal driving" is not when you need heat dissipation.

When I descend from Cajon pass at 1277m down to the LA basin,
and it is 40C outside, my discs are hot enough to fry eggs on.




Yes, if your discs are 10 degrees below brake fluid boiling point,
you will almost certainly see difference if you heat them another
10 degrees.

Nothing quite like brake fluid vapor locking (i.e. boiling
over). Luckily, I've never encountered it, although I hear
it can be quite an experience.

This (I think) is just another bogus statement.
Where did you get *that* from?

Well - certain high performace semi-metallic pads are
alleged to have optimum braking performance once they've
warmed up. However - it's not as if air flow is going to
reduce the pad temps down to ambient temps.

I may be mistaken, but aren't the rotors typically connected
to the bearings? I've done a little bit of reading, and
it's fairly common for wheel bearings to get fried or rotors
warped simply from rotors overheating. There also has to be
some heat transfer from the bearings to the rotors. Some
weekend racers try to cool down their rotors with cooling
ducts and wheels open to the air.

Even on a normal passenger car, I think the risk of brake
fluid boiling is far more serious than a slight amount of
"reduced braking power" in some conditions.

 

[Jirí Lejsek]

Sorry, I have made a general verdict from a little measurement (if I remeber
well, steel wheels I weighed were about 14-15 lbs so they could easily be
lighter than alloy).
At least we have shed some light into this problematics.

 

[Jirí Lejsek]

When I descend from Cajon pass at 1277m down to the LA basin,
and it is 40C outside, my discs are hot enough to fry eggs on.

So your discs probably were only warm; hot discs shine...
If you change breaking fluid as required, you first experience break pads
fading (if you do not have some racing). Smart people use engine for
breaking from long hills. You can always behave so you tamper some part.

Yes, if your discs are 10 degrees below brake fluid boiling point,
you will almost certainly see difference if you heat them another
10 degrees.

Temperature of disc and breaking fluid si tied very freely.

This (I think) is just another bogus statement.
Where did you get *that* from?

Try to read something about breaks, there is lot of information around.

 

[y_p_w]

Sorry, I have made a general verdict from a little measurement (if I remeber
well, steel wheels I weighed were about 14-15 lbs so they could easily be
lighter than alloy).
At least we have shed some light into this problematics.

Could you at least state the year and model of the car,
as well as the size of the rim. I'm highly skeptical
because I've seen the weight lists of specific OEM wheels
(including Subaru) specified by size. That 15" OEM steel
wheel weighed more than the 16" OEM aluminum alloy wheel.
The kicker about the alloy wheel was that it was the
base model WRX wheel, and there were optional ones that
weighed even less. For the most part, manufacturers
aren't going to have more than one steel wheel made for
any one application.

I have no doubt that steel of some kind could be made into
a very strong and lightweight wheel. However, working it
into such a product could be prohibitively expensive.
The typical steel rim is stamped and not cast, forged,
and/or machined like aluuminum alloy. On one list, there
were some wheels made of "spun steel" - whatever that is.

 

[Jirí Lejsek]

Well - certain high performace semi-metallic pads are

alleged to have optimum braking performance once they've
warmed up. However - it's not as if air flow is going to
reduce the pad temps down to ambient temps.

All brake pads need warming, but to different temperatures (racing usually
need higher).

I may be mistaken, but aren't the rotors typically connected
to the bearings?

There is no direct connection (if rotors = breaking discs). But heat from
them surely go also to bearings.

I've done a little bit of reading, and
it's fairly common for wheel bearings to get fried or rotors
warped simply from rotors overheating. There also has to be
some heat transfer from the bearings to the rotors. Some
weekend racers try to cool down their rotors with cooling
ducts and wheels open to the air.
Even on a normal passenger car, I think the risk of brake
fluid boiling is far more serious than a slight amount of
"reduced braking power" in some conditions.

Yes, you are right, but optimal breaking power you need much more times than
cooling. I only ment that you should look at anything from different angles.

 

[Jirí Lejsek]

I have made it maybe 6 years ago, in some second hand, so I don't know from
what cars they have been.

 

[y_p_w]

Try to read something about breaks, there is lot of
information around.

Honestly I'd be far more worried about brake rotor
warping and brake fluid vapor lock. Usually when
coming down steep passes like Paul mentioned, the
brakes are used to slow down but not come to a dead
stop. Once the brake fluid boils over, one can't do
either. Even using engine braking, the brakes still
need to be used.

Usually it's certain semi-metallic pads that need to
warm up (but not stay ridiculously hot) for maximum
effectiveness. Since we're talking passenger cars
and not racing situations, regular pads/rotors don't
need a whole lot of heat to reach their potential
(racing brakes are a different story).

 

[y_p_w]

I have made it maybe 6 years ago, in some second hand, so I don't know from
what cars they have been.

How about just the size of the wheels. You're not
helping yourself by making these broad generalizations
without being able to give a specific example.

 

[y_p_w]

All brake pads need warming, but to different temperatures (racing usually
need higher).

There is no direct connection (if rotors = breaking discs). But heat from
them surely go also to bearings.

You have several metal parts that sit in close proximity to
each other. You're going to get heat transfer from the rotors
to the bearings and vice versa. Rotors overheating will fry
the bearings, and you'll have far greater problems than
whether or not you stop one meter shorter from a dead
stop from 100 km/h. BTW - I'm only using metric for the
benefit of our Czech friend.

Yes, you are right, but optimal breaking power you need much more times than
cooling. I only ment that you should look at anything from different angles.

However - there's nothing about stamped steel wheels that make
them a better overall choice other than cost. At least in North
America, there are now at least as many aluminum wheels in
service as steel. With our litigious society, if there were any
negative safety consequences to aluminum alloy wheels, you
bet that lawyers would be aching to sue the manufacturers for
producing a "defective product". Helping brake cooling is far
more beneficial than inhibiting cooling.

The fact is, basic aluminum alloy wheels weigh less than their
typical basic stamped steel counterparts. Maybe it's not always
that much, but I don't know of many examples where the stamped
steel weighs less than an equivalent sized aluminum wheel.

 

[Body Roll]

You are right, commonly using aluminium alloys brings less weight.
But I know that usual alloy wheels are heavier than steel (I don't know
about alloy wheel that is lighter than steel - maybe some racing or very
expensive are.)
I think reason is that steel is more elastic, so must not be so tough as
alloy. Steel bends and returns back, but alloy stays bended (which have to
be avoided).
Some of reasons for using alloys is better heat distribution (from breaks) -
but it is important only for sport or racing cars.

Hmm, I experienced brake fade a few times back when I had a Legacy.
It was no fun at all when descending. I think you have some mountains
on the Czech Republic also. Properly designed cars these days have
ducting from the front to the wheel wells to guide the air from the
front to cool the brakes.

As for the aluminum wheel weight you can check on tirerack.com
they have the weight of wheels and tires listed as part of the specs.

Tires all seem to be around 21-23 lbs regarding of the size though.
At least 55 16 205 and 45 17 215s were last time I checked.

Just looking at the solid alloys on the civic hybrid makes me shiver.
Apparently brake performance was not a priority.

Speaking of which:
70-0 breaking
Mazdaspeed 6 165 ft : 6th place in the C&D 10 2007 fastest
LGT 195 ft: 5th place.

Makes me wonder how did Mazda make the heavier car to accomplish this
feat.
Anyhow, C&D staff apparently was not impressed. Maybe that had
something to do
with suck-out-of-our-asses mazda design versus the very distant rally
heritage for LGT?

 

[y_p_w]

Yes, you are right, but optimal breaking power you need much
more times than cooling. I only ment that you should look at
anything from different angles.

Perhaps I'm having a hard time understanding you; I'm guessing
your native language is not English. Just to rephrase, are you
trying to say that you feel that brake parts being maintained at
a certain temperature ("optimal breaking") is needed more often
than cooling the brake system to prevent vapor lock?

If that's it, then you seem to be sorely mistaken about the relative
consequences of having slightly less efficient braking versus the
total loss of braking from vapor lock. Fortunately I've never gone
through this, but people who have lived to tell their experiences
say it's terrifying to have the brakes pedal all the way down with
absolutely no braking. In addition, I think you overestimate how
warm a typical passenger car's braking system needs to be to perform
at optimal levels. Racing pads might need to be hot, but the
average Subaru with aluminum alloy wheels should have brakes that
are plenty warm for an emergency stop at highway speeds.

BTW - I did find a company that makes spun steel wheels. They
primarily make wheels that are not street legal, and the wheels
that are street legal are extremely heavy. I'm guessing products
like these are around because steel wheels are a requirement for
certain racing categories. For the most part, their wheels have
large openings designed to provide brake system cooling. I
suspect that the lightweight steel racing wheels don't last that
long, but they're not terribly expensive either.

 

[y_p_w]

Hmm, I experienced brake fade a few times back when I had a Legacy.
It was no fun at all when descending. I think you have some mountains
on the Czech Republic also. Properly designed cars these days have
ducting from the front to the wheel wells to guide the air from the
front to cool the brakes.

I think using a lower gear for "engine braking" was mentioned. For
some of those passes (Cajon Pass or Tejon Pass) where you're traveling
at highway speeds, I wouldn't drop more than one gear down because I
wouldn't want to over-rev my engine at 65 mph either. I typically go
in 2nd gear at 25-20 mph down a 20% grade where I live. I wouldn't
be in 2nd gear going down the Tejon Pass, because that might destroy
my engine if I kept it up for long.

Just looking at the solid alloys on the civic hybrid makes me shiver.
Apparently brake performance was not a priority.

Well - I think the regenerative braking system helps. They're pretty
much magnetic braking systems channeled to a generator. I've trusted
my life to the magnetic braking systems in amusement park rides. The
claim is that they still work even with a total loss of electrical
power.

I mentioned a steel wheel company earlier, but forgot to add a link.

<http://www.bassettwheel.com/steel.html>

 

[Jirí Lejsek]

BTW - I did find a company that makes spun steel wheels. They

primarily make wheels that are not street legal, and the wheels
that are street legal are extremely heavy. I'm guessing products
like these are around because steel wheels are a requirement for
certain racing categories. For the most part, their wheels have
large openings designed to provide brake system cooling. I
suspect that the lightweight steel racing wheels don't last that
long, but they're not terribly expensive either.

Did you thought about what you just said? Steel wheels are _required_ for
some racing cat.?
This means that all the advantages are unimportant against something more
important.
So I have to again say that using alloy wheels is just a fashion.
(There are many things much more important which make car controllable like
tyres, suspension, brakes, .... But it would be another discussion.)

 

[Mark T.B. Carroll]

Did you thought about what you just said? Steel wheels are _required_ for
some racing cat.?
This means that all the advantages are unimportant against something more
important.

On the other hand, Formula 1 cars pretty much all use forged alloy
wheels, don't they? Maybe you know something they don't?

(Hmmm, I wonder if they'd use carbon fiber ones if the regulations
didn't require them to be all-metal.)

So I have to again say that using alloy wheels is just a fashion.

(snip)

http://www.grmotorsports.com/news/012005/picking-the-right-wheels-for-you.php
makes interesting reading.

-- Mark

 

[CompUser]

(snip)

Bear in mind that where he lives, the available
alloy wheels may well be functionally-inferior
fashion statements. Time and capitalism will
change that. ;-)