tires park aveneu

[blacksnake]

i have a 99 buick park avenue ultra, presently have 225/60r/16 tires on it, i was thinking of going to a bigger tire as the car is really low to the ground. would anyone advise going to 235/70r/16 or 235/60r/16. would it affect the ride and do you think they would fit?

[HotZ28]

The first number is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4.

The second number is the aspect ratio. This is a ratio of sidewall height to width. Multiply that by the aspect ratio to find the height of one sidewall.

The last number is the diameter of the wheel in inches.

To figure the outside diameter of a tire, take the sidewall height and multiply by 2,(remember that the diameter is made up of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to get your answer.

Listed below are the sizes you listed, along with several critical (but not all) dimensions. Also, notice the following description of what each one means. It looks like the 235/60 HR16 would come closer to fitting and would have less negative effect on your speedometer, than compared to the 235/70 SR16.

Size 225/60 HR16
Meas.RimWidth 7.5"
Sect.Width 9.6"
Overall Diam. 26.6"
Revs Per Mile 779

Size 235/60 HR16
Meas.RimWidth 7"
Sect.Width 10.1 “
Overall Diam. 27.1"
Revs Per Mile 769


Size 235/70 SR16
Meas.RimWidth 7"
Sect.Width 9.5"
Overall Diam. 29.1"
Revs Per Mile 716

Measuring Rim Width
The measuring rim width is the industry standardized rim width upon which the tire must be mounted in order to confirm it meets its dimensional targets. Because the width of the rim will influence the width of the tire, a standard rim width for every tire size is assigned and must be used. This standardized measuring rim width allows all of the tires produced around the world to meet the same dimensional standards and therefore, be equivalent with regards to their physical size. The measuring rim width is sometimes referred to as the tire's "design rim width".
The assigned measuring rim width changes with the tire size's section width and with the tire size's aspect ratio. As tire section width increases, the measuring rim width increases proportionately in 1/2" increments. Therefore, relatively narrow wheel widths are assigned for smaller tires while wider wheel widths are assigned for larger tires.

Section Width
A tire's section width (also called "cross section width") is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any protective ribs, decorations or raised letters) at the widest point. This measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours.
Because a tire's section width is influenced by the width of the rim upon which the tire is mounted, the correct industry assigned measuring rim width for the tire size being measured must be used.
The width of a tire mounted on a narrow rim would be "narrower" than if the same tire was mounted on a wide rim. NOTE: because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.
The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".
For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its approved range, the tire's approximate section width would change as follows:
Because of the different wheel widths used in the above example, there is a 9/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages

Overall Diameter
A tire's overall diameter is the outer diameter of the tire measured in the center of the tread. This measurement is made without any load placed upon the tire and after the tire has been properly mounted on its industry assigned measuring rim and has been inflated and reset to its test pressure after 24 hours.

Revolutions Per Mile
The revolutions per mile indicates the number of times the tire revolves while it covers the distance of one mile. Depending on the tire manufacturer, revolutions per mile may be either measured in a laboratory or derived from a calculation based on previous test experience.

[Bassasasin]

Great info... Thought I would mention.
.
Deviating from tire factory recommendations can effect steering performance and response intentions of the manufacturer.
One example sidewall stiffness may stiffen the steering and change response feedback and rolling caster geometrics, much as air pressure does.