Read the sidewall of the tire on your car and you will find something like 235/40R18 95Y. Most people can decode the first part. The 95Y at the end is the service description, and it is the only part of that string that sets a hard limit on what the tire is allowed to carry and how fast it is allowed to go.
It is also the part people quietly downgrade to save eighty dollars, which is the one substitution on a tire that has no upside at all.
The load index
The number is an index, not a weight. It maps to a maximum load per tire:
| Index | Per tire | Index | Per tire |
|---|---|---|---|
| 91 | 615 kg / 1,356 lb | 105 | 925 kg / 2,039 lb |
| 94 | 670 kg / 1,477 lb | 109 | 1,030 kg / 2,271 lb |
| 95 | 690 kg / 1,521 lb | 110 | 1,060 kg / 2,337 lb |
| 97 | 730 kg / 1,609 lb | 112 | 1,120 kg / 2,469 lb |
| 99 | 775 kg / 1,709 lb | 116 | 1,250 kg / 2,756 lb |
| 100 | 800 kg / 1,764 lb | 118 | 1,320 kg / 2,910 lb |
| 103 | 875 kg / 1,929 lb | 121 | 1,450 kg / 3,197 lb |
Two things to notice. The steps are small - 94 to 95 is only 20 kg - which is exactly why dropping "just one" feels harmless. And the index is a maximum at the tire's rated pressure, not at whatever pressure happens to be in it.
The number you need is on the placard in your driver's door jamb, not on the tire currently fitted. Somebody may have already downgraded it.
The speed rating
| Letter | Max speed | Letter | Max speed |
|---|---|---|---|
| Q | 160 km/h | V | 240 km/h |
| R | 170 km/h | W | 270 km/h |
| S | 180 km/h | Y | 300 km/h |
| T | 190 km/h | (Y) / ZR | above 300 km/h |
| H | 210 km/h |
The obvious objection is that the speed limit on the Malahat is 80. The rating still matters, because it is not really a speed number - it is a heat and construction number. A Y-rated tire has a stiffer carcass and a higher sustained-heat tolerance than an S-rated one, and you feel that in steering response and in how the tire behaves on a hot day fully loaded. Dropping several steps changes how the car drives at every speed, not just at 300.
The exception is winter tires, which are commonly sold with a lower speed rating than the car's summer fitment. That is normal and accepted here. Understand that while they are on, the vehicle is rated to the lower number.
SL and XL: not what most people think
A passenger tire is either SL (standard load) or XL / Extra Load. It is tempting to read XL as "stronger," and it is not quite that. An XL tire reaches its higher load index by being rated to a higher maximum inflation pressure - typically around 41 psi against an SL tire's 36.
The practical consequence: if you fit an XL tire and then run it at the pressure printed on the placard for the original SL tire, you have not gained the capacity you paid for. XL tires generally want a few more psi than the SL tire they replaced to deliver their rating. If a shop hands you XL tires and sets them to the placard number without a word, ask.
Load range: C, D, E and what "ply rating" really means
Light-truck (LT) tires use load range letters instead:
- Load Range C - 6-ply rated, 50 psi maximum
- Load Range D - 8-ply rated, 65 psi maximum
- Load Range E - 10-ply rated, 80 psi maximum
- Load Range F - 12-ply rated, 95 psi maximum
"Ply rating" is a historical term. There are not ten plies in a Load Range E tire; there are usually two or three modern belts engineered to carry what ten old cotton plies once did. The letter is really telling you the maximum inflation pressure and therefore the maximum load.
Why an E-rated tire is usually wrong on a half-ton
This is the conversation we have most often with truck owners, and the answer surprises people.
A Load Range E tire is built to carry weight a half-ton cannot legally put on it. To do that it is heavier - often four to six kilos more per tire - with a stiffer sidewall that only reaches its designed shape at high pressure. On a truck that is empty most of the week, that means a harsher ride, more fuel burned turning heavier wheels, more road noise, and a tire that is running at a pressure well below what its construction wants, so the contact patch is not doing what it was designed to do.
Buy Load Range E when: you tow near the truck's capacity regularly, you carry heavy loads as a matter of course, or you run logging roads and gravel where sidewall punctures rather than load are the real risk.
Stay with what the placard says when: the truck is a daily driver that hauls occasionally. Match the placard's load index, buy a better tire in that rating, and spend the difference on something that actually improves the truck.
The P-metric trap on trucks
Here is a genuine catch that is easy to miss. When a P-metric passenger tire is fitted to a light truck or SUV, its load rating is divided by 1.10. That is not a shop convention - it is written into the federal safety standard (FMVSS 571.120).
So a P-metric tire with a load index of 109, nominally 2,271 lb, only counts for 2,065 lb once it is on a truck. A tire that looks like it clears the placard on paper can be short in practice. LT-metric tires are not derated this way, which is part of why truck placards often call for one.
If you are cross-shopping a P-metric against an LT for a truck, do that division before you compare.
Tires worth looking at, by job
- Half-ton daily driver: Michelin Defender LTX M/S 2 - available in both P-metric and LT constructions, so you can match the placard rather than over-buy.
- Gravel and logging roads: BFGoodrich All-Terrain T/A KO3, available in Load Range C, D and E depending on the size. Buy the range you need, not the highest one offered.
- All-terrain without the noise penalty: Yokohama Geolandar A/T G015 or Toyo Open Country A/T III, both in a range of load ranges.
- Work vans: Michelin Agilis CrossClimate - built for the load indices commercial vans actually run, and 3PMSF rated, which matters on the Malahat in January.
The rule we will not bend
We will fit you a tire above your placard's load index. We will not fit you one below it, no matter what it costs. A tire that is one index light is fine right up until the day the truck is loaded, the road is hot, and it is not.
If you are ordering online and want a second opinion before you commit, send us a photo of the placard in your door jamb and the size you are looking at. That check is free and takes us a minute.
What we can actually get you
Our website does not show everything we can order. SHC is an authorised dealer for over three hundred aftermarket brands - Michelin, BFGoodrich, Yokohama and many more on the tire side, plus most of the wheel and suspension names you would want - far more than the website lists. Those lines are missing from the site only because there is no data feed our catalogue can read, not because we cannot get them. If you cannot find a size or a model online, call us.
About SHC Auto
Reading placards and talking people out of the wrong tire is a daily part of the job here, and we have been doing it in Victoria since 1991. SHC Autographx and Tires is a full wheel and tire shop at 474 Bay Street - tires, aftermarket wheels, suspension and parts, vinyl wrap, paint protection film and ceramic coating. We mount and balance in house, we torque to spec rather than to the impact gun's mood, and we will tell you when the tire you found for less is a load index short.
We are an independent shop, not a chain. Shipping is free anywhere on Vancouver Island.
SHC Autographx and Tires
474 Bay Street, Victoria, BC
Monday to Friday, 9:00 am to 5:30 pm
Not sure what your placard says?
Open the driver's door and look at the sticker on the jamb. It lists the original tire size, the load index and speed rating, and the cold inflation pressures front and rear. If any of that does not match what is on the car right now, bring it in - we will work out what changed and whether it matters.