CheckFitment

Use for "what is 5x114.3 in inches", "is 5x114.3 the same as 5x115", "will 6x135 wheels fit 6x139.7", or which vehicles use a pattern. Converts mm and inch notation, lists look-alike patterns that do not interchange, the vehicles in the dataset with that pattern, the lug tightening order and typical torque ranges by stud size (guidance only).

bolt_pattern_facts

Use for "what does my 3.73 axle behave like on 35s", "what ratio do I need to regear for 33s", RPM at highway speed after a tire change, or the crawl ratio (with transfer-case low ratio and first gear). Returns the effective ratio, RPM before and after in a 1:1 gear, the ratio that restores stock feel, the nearest gear set actually sold and how serious the change is.

gear_ratio_calculator

Use for "what changes if I go from 265/70R17 to 285/75R17", "how far off is my speedometer with 33s", or odometer error after a tire change. Returns diameter, width, sidewall and ride-height change, the true speed when the speedometer shows a given value, the odometer error and how serious it is.

tire_size_compare

Use for "what is the bolt pattern on a 2019 Ford F-150", lug torque, center bore, thread size, OEM wheel size, offset or tire size of a vehicle, or "will these wheels fit my car" when the vehicle is named. Looks the vehicle up in the CheckFitment dataset (a fixed set of vehicles, each spec cited to manufacturer documents and marked verified or unverified). If the vehicle or year is not in the dataset the tool says so (not_in_database / year_covered false) and gives no figures; never fill them in from memory. Optional wheel_center_bore_mm runs the hub-centric check.

bolt_pattern_lookup

Use for "do I need spacers", "what spacer gets +35 wheels to +20", "is a 10 mm slip-on spacer safe". A spacer lowers the effective offset by its thickness. Returns the spacer needed for a target offset (and the nearest common size), the effective offset, track change, whether it is slip-on or bolt-on territory, and, with stud, stud_protrusion_mm and wheel_pad_thickness_mm, the slip-on thread-engagement check (≥ 1 × stud diameter and ≥ 6.5 turns).

wheel_spacer_calculator

Use to compare a current wheel (and tire) with a new one: how far the outer edge pokes toward the fender and the inner edge toward the suspension, the diameter and ride-height change, speedometer effect, backspacing, and whether the new tire width suits the new rim width. With measured clearances (outer: tire edge to fender lip; inner: to the nearest suspension part, both on the current setup) it returns fits / tight / rub. Leave the tire fields out for a wheel-only offset comparison.

wheel_fitment_check