What Does 108S Mean On A Tire? | Load And Speed Decoded

A 108S tire can carry 2,205 pounds at its rated pressure, and its S speed symbol is rated for up to 112 mph.

That little code on the sidewall is doing a lot of work. If you spotted 108S while shopping for tires, checking your current set, or trying to match a replacement, you’re reading the tire’s service description. It tells you how much weight one tire is built to carry and the top speed category tied to that tire.

The short version is simple: 108 is the load index, and S is the speed symbol. Those two marks matter more than many drivers think. Get them wrong, and you can end up with a tire that doesn’t match your vehicle’s needs, your payload, or the maker’s spec.

This is where the code starts to make sense. Once you know how to read it, you can compare tires with a lot more confidence and skip the guesswork.

What Does 108S Mean On A Tire? Load And Speed Codes

You’ll usually see 108S after the tire size. A sidewall may read something like 235/65R17 108S. Everything before 108S describes the size and build. The 108S part tells you the service description.

What The 108 Load Index Tells You

The number 108 is the tire’s load index. That index matches a set weight from an industry chart. In plain English, load index 108 means one tire can carry up to 2,205 pounds when it’s inflated to the proper pressure for that rating.

That does not mean your vehicle should be loaded right up to that number on a whim. Your door-jamb placard, the owner’s manual, axle ratings, and the tire’s pressure all still matter. The load index tells you the tire’s ceiling under the right conditions, not a blank check for extra cargo.

What The S Speed Symbol Tells You

The letter S is the speed symbol. In this case, S means the tire is rated for speeds up to 112 mph. That figure comes from a controlled test standard. It is not a green light to drive at that speed on public roads.

Speed symbols also tie into heat control and stability under load. So even if you never get near 112 mph, the symbol still matters when you replace a tire. It helps match the tire to the vehicle’s original spec and intended use.

Where 108S Sits On The Sidewall

Most drivers notice the size first and stop there. But the service description sits right beside it, and that’s where the useful detail lives. On a tire marked 235/65R17 108S, here’s the breakdown:

• 235 = section width in millimeters
• 65 = aspect ratio, or sidewall height as a share of width
• R = radial construction
• 17 = wheel diameter in inches
• 108 = load index
• S = speed symbol

According to Goodyear’s tire load index chart, load index 108 equals 2,205 pounds per tire. That number gives you a clean way to compare one option against another when two tires share the same size but not the same service description.

Sidewall Mark	What It Means	Why It Matters
235	Tire width in millimeters	Affects fit, contact patch, and wheel match
65	Aspect ratio	Shapes ride height and sidewall depth
R	Radial construction	Standard build for modern road tires
17	Wheel diameter in inches	Must match the wheel exactly
108	Load index	Sets how much weight one tire can carry
S	Speed symbol	Sets the tire’s tested top speed category
XL	Extra Load	Shows a tire built for higher inflation and load
M+S or 3PMSF	Snow or all-weather marking	Tells you about cold-weather intent, not load or speed

108S Tire Meaning When You Replace Tires

This is where many people slip. They match the size and forget the service description. A tire can be the right size and still be the wrong fit for the vehicle if its load index or speed symbol falls below the maker’s requirement.

Say your current tire is 108S and you’re staring at a cheaper 104T. The 104T tire has a higher speed symbol than S, but its load index is lower. That lower load rating can make it a poor substitute if your vehicle was built around 108.

Goodyear’s speed rating chart lists S at 112 mph and notes that replacing with an equal or greater speed rating is the usual move. The same common-sense rule applies to load index: do not drop below the spec tied to your vehicle.

What To Match Before You Buy

• Check the driver’s door placard for the factory tire spec.
• Match the size first.
• Match the load index, or go higher if the tire maker and vehicle spec allow it.
• Match the speed symbol, or go higher if the replacement tire is approved for that use.
• Keep the same type across an axle.

If you tow, haul gear, or drive a loaded SUV or van, the load index deserves close attention. That number is not decoration. It’s part of the tire’s working limit.

Code	Meaning	Plain-English Readout
108S	Load index 108, speed S	2,205 lb per tire, up to 112 mph category
108T	Load index 108, speed T	Same load, higher speed category than S
104S	Load index 104, speed S	Same speed category, lower load capacity
108H	Load index 108, speed H	Same load, higher speed category than S
108S XL	108S with Extra Load build	May carry more at higher pressure, based on tire design
120/116R	Dual load indexes on light-truck tire	One rating for single use, one for dual-wheel use

What 108S Does Not Tell You

108S gives you two pieces of data. It does not tell you everything about the tire. It does not tell you tread life, wet grip, snow grip, ride comfort, noise, or puncture resistance. It also does not tell you the proper inflation pressure for your vehicle.

Pressure still comes from the vehicle maker’s placard, not from guesswork and not from the biggest number printed on the sidewall. A tire only reaches its rated load under the pressure tied to that rating. Underinflation cuts into that margin and builds heat fast.

Common Mix-Ups With 108S

Thinking S Means The Tire Is Slow

Not at all. An S-rated tire still sits at 112 mph. For many family cars, crossovers, vans, and small SUVs, that’s a normal fit.

Thinking The Load Index Is For The Whole Vehicle

It’s per tire. To get a rough four-tire total, multiply by four. Even then, the vehicle’s own gross weight rating still rules.

Thinking A Higher Letter Is Always Better

Not always. A higher speed symbol can bring a firmer ride, a different tread design, or a different price point. The right match is the one that fits the vehicle spec and the way the vehicle is used.

Thinking Any Tire In The Same Size Will Work

Size alone is not enough. Two tires can share the same size and still differ in load index, speed symbol, load range, and build.

When 108S Is A Good Fit

108S is common on heavier passenger vehicles that need a healthy load rating but do not call for a high-speed performance tire. You’ll often see service descriptions in this range on crossovers, vans, and some SUVs.

If your placard calls for 108S, sticking with 108S keeps things easy. If you move to 108T or 108H, that may still be fine if the tire matches the vehicle maker’s requirements and all four tires are chosen with care. Dropping to a lower load index is the move to avoid.

So when someone asks, “What does 108S mean on a tire?” the clean answer is this: it tells you how much weight that tire can carry and the speed category it was built to meet. Once you know that, you can read the sidewall like a spec sheet instead of a code puzzle.