Load Index and Speed Rating: The Two Numbers You Must Not Downgrade

July 7, 2026 · ExtraBrake

Most of the tire size gets the attention — 205/55R16 — but the suffix, 91V, is where safety lives. It defines how much weight the tire carries and how fast it can safely sustain. One rule covers everything: match or exceed what your vehicle came with; never go lower.

Load index: the weight contract

The number maps to a per-tire weight capacity: 87 = 1,201 lbs, 91 = 1,356 lbs, 95 = 1,521 lbs, 100 = 1,764 lbs. Multiply by four and compare with your loaded vehicle weight — the margin is smaller than most drivers assume, especially on family SUVs loaded for a trip. Fitting a lower index than the door-jamb sticker specifies overloads the casing at every mile, builds heat, and is the classic cause of high-speed blowouts. Light trucks add load ranges (C, D, E) — stiffer casings for towing and payload; if your truck came with load range E, replace with E.

Speed rating: more than top speed

T = 118 mph, H = 130, V = 149, W = 168, Y = 186. No one commutes at 149 mph — but the rating also correlates with the tire's heat tolerance, casing stiffness and steering precision. Your car's suspension was tuned around its factory rating; dropping from V to T saves a few dollars and dulls the handling the engineers designed. Insurers in some regions also take note when fitted tires are below spec.

Where to check

Your required ratings are on the driver's door jamb sticker. Every tire at ExtraBrake lists its load index and speed rating in the specs table, and you can filter by speed rating in the catalog. When in doubt between two ratings, the higher one is never wrong — it's just more tire than you strictly need.