Gear Ratio and Tire Size Chart

This gear ratio and tire diameter chart is meant to give you an approximation of ideal RPMs at highway speed (65 mph) for three situations: fuel economy, every day driving and increased towing power. This chart provides values that represent a 1:1 ratio on a manual transmission. Gear ratio and tire diameter charts are ideal for making your car as efficient as possible.

Note: Automatic transmission RPMs tend to be a little higher and transmissions with an overdrive tend to be a little lower.


gear
3.313.423.553.733.914.114.274.564.885.135.295.385.716.177.17
tire27"267727662872301731633325345436893947415042794352461949915800
28"258226682769290930503206333135573806400141264196445448135593
29"249325762674280929453095321634343675386339844052430046475400
30"241024902584271528462992310933203553373538513917415744925220
31"233224092501262827552896300832133838361437273790402343475051
32"225923342423254626962805291431123331350136103672389742114894
33"219122632349246925882720282630183230339535013561377940934745
34"212621972280239625122640274329293135329533983456366839634606
35"206521342215232824402565266428453045320133013357356338504474
36"200820752154226323722493259027662961311232093264346437434350
37"195420192095220323082426252026922881302831233176337036424243
38"190219662040214422472362245426212805294830403092328235464121
39"185419151988208921902302239125542733287329623013319834554015
40"180718671938203721352244233124902664280128882937311833693915
41"176318221891198720832189227524292599273328182866304232873819
42"172117781846194020332137222023712538266827512798296932083728
43"168117371803189419862087216923162479260626872733290031343642
44"164316981762185119412040211922632422254626262670283430633559


FUEL ECONOMYEVERYDAY DRIVINGINCREASED TOWING POWER


Here's a formula you can use to calculate your vehicle's tire diameter:

(CROSS SECTION WIDTH x 0.ASPECT RATIO x 2 ÷ 25.4) + WHEEL DIAMETER = OVERALL TIRE DIAMETER

For Example:

235/45ZR-17

(235 x 0.45 x 2 ÷ 25.4) + 17 = 25.327"

And here's a formula that you can use to calculate your vehicle's rear axle gear ratio:

RING GEAR TOOTH COUNT ÷ PINION GEAR TOOTH COUNT = GEAR RATIO

For example:

41-tooth ring gear ÷ 10-tooth pinion gear = 4.10

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