blacks92seAuto

getting some 18"s...what size tire do I need to have so that overall tire size is not different, so my speedo isn't off....

blacks92seAuto

according to this calculator thing i have 205/65/15 now, and I would need to get 235/40/18 tires and it would still make my speedo 0.4% too fast.....

whitemax28

go to whalentire.com
they compare everything for you in detail.
Good Luck

avmaldo

just a general question to anyone who knows.
is there a way to reprogram the speedo?

blacks92seAuto

looked all over in the tire forum....How much do our stock rims/tires weigh?

blacks92seAuto

someone has to know the weight of the stock rim and tire

whitemax28

i think the weight of the tire is 20lbs, not sure

Bman

Not easily, and it's not something that you can "program". It's mechanical.

ElVito1981

iTrader: (4)

225-40-18 tires if you're getting 18's

Loe max

iTrader: (6)

Read Aaron92SE http://forums.maxima.org/showthread....2&page=3&pp=30

DennisMik

iTrader: (2)

Here is a sheet I made up about 30 years ago (and updated since) that tells you how to compare tire sizes. If you want an Excel file that will calculate for you, email me at dennismik@yahoo.com. I'll need an email other than maxima.org, I don't have permissions to do attachments.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

METRIC TIRE ROLLING CIRCUMFERENCE CALCULATION


Explanation of size label:

Example: P 205 / 65 S R - 15 85
1. 2. 3. 4. 5. 6. 7.

1. Class of vehicle intended for. P = passenger car, LT = light truck.
2. Cross section width, sidewall to sidewall, in millimeters .
3. Aspect ratio (height or profile); a percentage of the width, rim seat to tread.
4. Speed rating: M = up to 81 mph; Q = up to 99 mph; S = up to 111 mph
T = up to 118 mph; U = up to 124 mph; H = up to 130 mph
V = 130+ mph; 93V = up to 149 mph; Z = 149+ mph
W = 168 mph.
5. Type of construction: R = radial; B = belted bias ply; D = diagonal bias ply.
6. Wheel rim diameter in inches.
7. Load rating.

Circumference calculation formula: (profile + profile + wheel rim diameter) * pi

Examples:

Tire sized P205/R65-15

Profile = tread width multiplied by the ratio (#2 times #3).
Profile = 205 mm multiplied by 65% (.65).
Profile = 133.25 mm.


(133.25 mm + 133.25 mm + 15 inches) * pi
(133.25 mm + 133.25 mm + 381 mm) * 3.14
647.5 mm * 3.14 = 2033.15 mm.

2033.15 mm converts to 80.045 inches or 6.67 feet


Tire sized P235/R40-18

Profile = tread width multiplied by the ratio (#2 times #3).
Profile = 235 mm multiplied by 40% (.4).
Profile = 94 mm.

(94 mm + 94 mm + 18 inches) * π
(94 mm + 94 mm + 457.2 mm) * 3.14
645.2 mm * 3.14 = 2025.928 mm.

2025.928 mm converts to 79.76 inches or 6.646 feet


These 2 tire sizes turn out to have almost identical rolling circumferences.
If you were to switch from one of these sizes to the other, the geometry of
the wheel alignment would require very little to no modification and speedometer
error would be negligible.