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  #21  
Old December 23rd 05, 05:36 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

Grant Edwards wrote:

> You're lucky. I drove a 96M for 6 years and had to have 2 of
> the four wheels repaired. The first time, I remember the bump
> that bent the wheel, and it had to be fixed immediately (the
> tire would no longer seal). The second time I don't know when
> it got bent -- I just noticed that the steering wheel was
> vibrating, and the next time I had tires mounted they mechanic
> showed me that the wheel was noticably out of round.


It was only about 30K miles on the original wheels before I sold them,
and I remember buying a set of two '96M alloys for $40.00 each to keep
as replacements, but they were badly bent when they arrived so I got a
refund on those.


> You must have much better roads that we have here in Minnesota.



Probably so.
I have never been to MN to see the roads. I have a friend who lives in
MN about 60 miles from the Canadian border and he rides his motorcycle
to stay here during the colder part of the winter.
I'll ask him what the comparison is like.

Pat
Ads
  #22  
Old December 23rd 05, 06:02 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

On 2005-12-23, pws > wrote:

>> You must have much better roads that we have here in Minnesota.


Or possibly you're better at avoiding potholes that I am.

> Probably so.
> I have never been to MN to see the roads.


They're not bad most of the time, but in the spring and fall,
repeated freeze/thaw cycles sometimes open up some pretty big
potholes. Once in a while, at the bottom of a pothole, you can
see the trolly tracks that were paved over in the 50's.

--
Grant Edwards grante Yow! .. over in west
at Philadelphia a puppy is
visi.com vomiting...
  #23  
Old December 23rd 05, 07:04 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires


"Lanny Chambers" > wrote in message
...
> In article

. net>,
> "miker" > wrote:
>
> > > The problem is that they weigh 18 pounds

> >
> > I understand the difference between sprung/unsprung

weight for handling, but
> > so far as acceleration and speed I think the difference

between me and a
> > 100-lb 20-something lead-footed babe is going to make

more difference than
> > that few pounds of wheels.

>
> Some have estimated the effect of unsprung mass on

acceleration at 10X
> that of sprung mass. Do you weigh >380 pounds? :-)
>
> [here's the math: 10 x 4(18-11) + 100]
>
> My tires lose about one psi per week. It was the same with

the stock
> wheels, so I assume that's normal for alloys. My Honda's

steel wheels
> might lose one psi per year.
>


I had alloy wheels on my last two Miatas - I might have lost
a pound or two every 6 months with both cars. The same was
true of my ex's Sentra (with alloys).

> --
> Lanny Chambers
> '94C, St. Louis
> http://www.hummingbirds.net/alignment.html



  #24  
Old December 23rd 05, 07:37 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

On Fri, 23 Dec 2005 15:19:12 GMT, Lanny Chambers
> wrote in
:

> In article . net>,
> "miker" > wrote:
>
>> > The problem is that they weigh 18 pounds

>>
>> I understand the difference between sprung/unsprung weight for
>> handling, but so far as acceleration and speed I think the difference
>> between me and a 100-lb 20-something lead-footed babe is going to
>> make more difference than that few pounds of wheels.

>
> Some have estimated the effect of unsprung mass on acceleration at 10X
> that of sprung mass. Do you weigh >380 pounds? :-)
>
> [here's the math: 10 x 4(18-11) + 100]


I have a completely stock '91.
In a pure test of acceleration, I was able to keep up
with an identical year, but heavily modified car which probably
had 10 to 20 hp advantage (and a lighter driver, initials KT) but
16" wheels. I had expected it to pull away, but we were within
an inch or two up to about 80 km/h.

I would guess the equivalent weight penalty to be about more around
200 lbs. In your equation that's about 5 times.

> My tires lose about one psi per week. It was the same with the stock
> wheels, so I assume that's normal for alloys. My Honda's steel wheels
> might lose one psi per year.


I have the original '91 alloys which leaked about 3 lbs/day.
They were then stripped and repainted almost 6 years ago.
New tires were mounted right after and are still on the car.
I use steel wheels in the winter.
When I take the alloy wheels off the shelf in the spring,
they are exactly the pressure they were in the fall, allowing
that it is usually about the same temperature both times.
They remain exactly the same over the summer as well.
I imagine that when the tires are changed, the damage will
cause some corrosion and the leaking will start.
Although without salt exposure, it won't be as much
of a problem.

  #25  
Old December 23rd 05, 09:46 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

> Some have estimated the effect of unsprung mass on acceleration at 10X
> that of sprung mass. Do you weigh >380 pounds? :-)


How fast am I accelerating? :-)

miker



  #26  
Old December 24th 05, 03:48 AM posted to rec.autos.makers.mazda.miata
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Default rims and tires

Lanny Chambers > wrote:

>In article . net>,
> "miker" > wrote:
>
>> > The problem is that they weigh 18 pounds

>>
>> I understand the difference between sprung/unsprung weight for handling, but
>> so far as acceleration and speed I think the difference between me and a
>> 100-lb 20-something lead-footed babe is going to make more difference than
>> that few pounds of wheels.

>
>Some


Who?

> have estimated the effect of unsprung mass on acceleration at 10X
>that of sprung mass.


Are you really seriously believing that complete nonsense or just
baiting me?

> Do you weigh >380 pounds? :-)
>
>[here's the math: 10 x 4(18-11) + 100]


The math is right but the physics is as right as I am 381 lb.

>My tires lose about one psi per week. It was the same with the stock
>wheels, so I assume that's normal for alloys.


Untrue. I lose a couple of lb in a couple of months. The reason I know
is that in an ideal world, I would check my tire pressure every week, but
in real life, I end up checking only at the autocross one or two months
after the last one.

> My Honda's steel wheels
>might lose one psi per year.


Maybe it is just usage. How many miles on the Honda versus the Miata?
Or oxidation.

Leon
--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)
  #28  
Old December 24th 05, 06:08 AM posted to rec.autos.makers.mazda.miata
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Default rims and tires

"miker" > wrote in
ink.net:

> but so far as acceleration and speed I think the difference
> between me and a 100-lb 20-something lead-footed babe is going to
> make more difference than that few pounds of wheels.


That depends entirely on the measurements, particularly bra size.
Better send .jpg of 100-lb 20-something lead-footed babe and we'll make
an assessment.

  #29  
Old December 24th 05, 06:32 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

Lanny Chambers > wrote:

>In article >,
> (Leon van Dommelen) wrote:
>
>> > have estimated the effect of unsprung mass on acceleration at 10X
>> >that of sprung mass.

>>
>> Are you really seriously believing that complete nonsense or just
>> baiting me?

>
>Baiting, of course. Feel free to come up with a more supportable number.


The maximum possible is 2 times, or a 100% increase in effective mass.
However, only the tires can approach that number. (Another benefit of
light tires. A 2 lb heavier tire adds an additional 15 lb or so to be
accelerated.)

For stock 14" wheels, the maximum increase is only 40%, rather than 100%,
and the true number is more likely to be about 20%, assuming the wheel
is attached to the axis. For the 205/45 R17 tires coming with my new
Miata, the maximum increase is 50%, and the likely one 25%.

For example, for stock 11 pound 94-97 alloys with 16 pound Toyo T1-R
195/55 R14 tires, the effective wheel and tire mass to be accelerated
is about 161 lb, not 1080 lb as by your formula. Switching to
19 lb 205/45 R16 Toyos mounted on 21 lb TSW blades, this increases
to 236 lb. But if you dump the blades for 11 lb alloys (lowest
weight I could find on miata.net, corresponding to Mugen MF-10,
Racing Hart CP-035, Sparco Viper R, Volk TE-37), your mass to
accelerate is only 187. The 26 lb increase compared to stock
is mainly due to tires; the 11 lb wheels account for only 4
of the increase. Note: low price and effect of potholes on wheels
not guaranteed.

If you decide you may as well go for 30 lb Momo Arrows, with
24 lb Michelin Pilot MXX3 tires, the mass to accelerate becomes
317 lb, or almost 10% of the mass of the car, something that
should be noticeable.

Also, I may be underestimating the effect of the tires in
the above. Masses could approach 181 lb for stock, 256
for TSW Blades, 206 lb for racing alloys. At 343 lb for
your nice Momo wheels, your cool could suffer if you cannot
keep up with a Miata fitted with wheels that look like teddy
bears. The bears have 130 lb less to drag along and should
keep up quite well with the racing alloys.

Other suspension elements' effective mass is not mentionably
increased above true.

Leon
--
Leon van Dommelen Bozo, the White 96 Sebring Miata .)
http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)
  #30  
Old December 26th 05, 04:44 PM posted to rec.autos.makers.mazda.miata
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Default rims and tires

XS11E: Good call!

Chris
99BBB
92BB&T SOLD!

"XS11E" > wrote in message
...
> "miker" > wrote in
> ink.net:
>
>> but so far as acceleration and speed I think the difference
>> between me and a 100-lb 20-something lead-footed babe is going to
>> make more difference than that few pounds of wheels.

>
> That depends entirely on the measurements, particularly bra size.
> Better send .jpg of 100-lb 20-something lead-footed babe and we'll make
> an assessment.
>



 




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