Question About Tire Size.

The 245 is the size of the tire  the 50 is the aspect ratio (height/width)
and the 16 is the wheel diameter.

Only 16 inch tires will fit on 16 inch wheels.  To go to a 15 inch tire you
need to change to a 15 inch wheel.  For the most part that is seen as a
downgrade on the vehicle.  You would need to make sure the wheels you get
are the correct offset and bolt pattern.

Hope this helps

WCV
www.westcoastvintage.com
Over 10,000 vintage car t-shirts, all makes and models.

Not to mention that on some cars it may adversely affect handling, have more
rotations per mile, thus increasing tire wear and throw off the calibration
of the speedometer.

A lot of people use 15" wheels on late model Camaro's and Firebirds because
that's the size slicks come in. One issue that often comes up is the inside
of the wheel rubs against the calipers in the back. Other than drag racing I
can't think of any good reason to run 15's

Gary

Mickey Thompson makes drag slicks in 16".

Brian

" Other than drag racing I

Cause they come stock on my Cutlass?

On Mon, 04 Sep 2006 04:26:03 GMT, "Eightupman"


Why don't you swap the wheels on both cars and see if they will work.
Both wheels should have the same bolt pattern.

                       ...Ron
--
68'RS Camaro
88'Formula
00'GT Mustang

    As long as his "Cutlass" is RWD not FWD the bolt pattern is the same.
The Offset on a 4th Gen is closer to 4WD S-10 wheels. 84 Up Corvette
wheels use roughly that same offset (comparing to regular RWD wheels).
Charles

On Mon, 04 Sep 2006 14:51:35 GMT, Charles Bendig



You're right of course.  Silly me, not remembering that Olds went to a
front drive platform for that model.  I was thinking about the 80's
and prior models.  Once again, your way more on the ball than I am
Charles.

                  ...Ron
--
68'RS Camaro
88'Formula
00'GT Mustang

Winston,

245x50-16's diameter is 25,645669 inch (static diameter),

245x60-15's diameter is 26,5748031 inch (static diameter).

This says the 15" tire is 3,62% larger than the 16". You wont have the same
good acceleration and nearly surely lower milage. Check if the 15" rims fit
with your brakes.

PS: Because of the larger aspect ratio the dynamic diameter of the
245x60-15s will be still larger than 3,62% compared with the 16"s. For
dynamic diameter of a tire you better call the manufacturer of this tire.
There is no formula!

If you want to know more about static / dynamic diameter let me know in this
group.

George

Yes, slightly less acceleration.


Lower miles clocked.  
Corrected fuel mileage may be better due to less RPMs per MPH.

George:
No, I think not, because on computer optimized cars the transmission must
not be "longer" than stock (they are already optimized!). I installed a 6,5%
longer transmission (using larger tires) and this resulted in 15% lower
mileage and bad accelleration. My V6 didnt run into the red rpm sector while
driving floored in 3rd gear (where I often did reach 5500 1/min and 120mph).

    There is no such thing as a 6.5 longer transmission. GM has not made a
CAR transmission since 1986 that comes in more then one case length per
case type (ie: TH350 Short, Mid, or Long Tail shaft).

    Gear ratios go Numerically higher number means a lower ratio. In rear
end gearing for example a 2.73 is a High ratio, a 4.10 is a Low Ratio.

    In automatic transmissions from 1984 all the way to 2002, V6 & V8
F-cars use the same internals in the transmissions. The exception being
1989 Turbo Trans-am's that used a TH200R4, the same transmission used in
the Grand National.

    The 1993 Up cars with a TH4L60 or TH4L60-E use the same gear ratios as
the first TH700R4's.

    When it comes to standard shift from 1985 to 1992 Both V6 and V8
cars used the same T-5 5 speed transmission, with the same gear ratios.
In 1993 the V8 cars got a 6 speed manual, where V6 cars used a 5 speed.

    None of these transmissions has a computer optimized gear ratio.
The only thing the ECM has to do with tire and gear ratios is on 1995 UP
cars with OBDII. The ECM controls the Speedometer readings of the
electronic output from the transmission. Meaning you can have your
Speedometer calibrated for different size tires using a Scan tool such
as a Tech II.

    Assuming you have a Automatic, and 3rd gear being 1:1 ratio, then your
running a 23.69 inch tall or a 23.7 inch tall tire at 5500 RPM's @ 120
MPH. With a 26 inch tall tire, all other factors being the same you
would be traveling 131.7 miles per hour.

    One thing your car probably does have, if not originally equipped with
Z speed rated tires is a 118 or 125 MPH speed limiter.
With that, as soon as your ECM recognizes you have reached the limit, it
shuts down fuel and spark until you lose 1 to 6 MPH, then it returns to
normal again until you hit limit again. You can bounce off the limit all
day long and not go any faster. If you changed tire size on a limited
car, and do not recalibrate the Vehicle Speed Sensor data, when the ECM
thinks you are at the limited speed it will shut down fuel & spark.
Charles

Winston' s question was: "about tire size"



What I said, was:

I installed a 6.5%  longer transmission (using larger tires) and this
resulted in 15% lower mileage and bad accelleration on a V6.

This meant:  The over all transmission ratio became 6,5% longer by using
larger tires. No longer case. No Turbo, No V8. No Grand National. No
calibration mentioned nor any limiter, but simply 6.5% larger tire
installed.

Thank You for the rest of the information.

George

    I would suggest you change your language a bit. You increased your
total 'final drive ratio' to a higher ratio (numerically lower). In the
automotive world a "longer transmission" means psychically longer.

    V6 cars with larger tires almost always need a rear gear ratio change
to compensate for it (if going more then a few sizes up or down).
Just like taking 237/70/R15's off a truck and putting 35x12.50xR15's in
there place.  The change in the total final drive ratio is enough that
you need to change gears.
Charles

yes, you are right. I do not know so much.

You must be the only one here that didn't know what he meant. Terminology
varies all over the country. What's right for you may not be for others.

Dave

    Considering this is cross posted to 3 news groups, define "here"?

    What I posted is Correct for anywhere in the world. Doesn't matter were
you take the books to and open them, the terminaligy doesn't change.
Neither does the Math. RPM,Speed,Final Drive Ratio=will give you tire
diameter. Sure the formulas are a bit different for "English" Vs
"Metric", but the principals and terms don't change.

    The English Language is the standard language for Engineering.
Charles

"Here" would be usenet. Specifically, anyone who read it but you.


~snip~

As I said, you must be the only here that didn't know what he meant.

I installed a 6.5%  longer transmission (using larger tires).
________________________________________________

Charles Bendig"  wrote:

I would suggest you change your language a bit.  In the
automotive world a "longer transmission" means psychically
longer.
_______________________________________________

Usually, longer transmission would mean "physically" longer,
but the OP was using the "psychically" longer definition.

Rodan.