What Size Snow Chains Do I Need? Tire Size and Class S
2 lessons in this series, 6 min in total
- What Size Snow Chains Do I Need? Tire Size and Class S 3 min read
- Do Snow Chains Go on the Front or Rear Wheels? 3 min read
This lesson draws on Peerless and Security Chain Company (SCC) product pages and instructions, König’s XG-12 Pro page and Toyota’s 2025 4Runner owner’s manual. How we research explains the method.
Step 1: read the size on your sidewall
The size is molded into the tire’s sidewall. In 225/50R17, 225 is the section width in millimeters, 50 is the aspect ratio (sidewall height as a percentage of width), R means radial construction and 17 is the wheel diameter in inches. Toyota’s manual uses the same legend and defines an LT tire as one made for light trucks.
The door-jamb placard also lists your car’s factory tire sizes, as explained in what PSI your tires should be. Use the tires actually on the car, though. SCC notes that carmakers set chain clearance with the original tires, so a different size can change what fits.
Step 2: match it on the maker’s fit chart
Every chain line comes in many part numbers. Peerless lists 16 Super Z6 sizes, from SZ115 to SZ451, and 7 Auto-Trac LT sizes. Each part number covers a list of tire sizes, and the maker’s chart or online chain finder tells you which one is yours.
Match all three numbers: width, aspect ratio and wheel diameter. Peerless says tire size must be known to pick a product of correct fit. SCC adds that real tire sizes vary by age, brand and tread, so it strongly recommends fitting the chains to the tire before you need them.
Step 3: check your manual for Class S or “no chains”
SAE classes set the minimum space around a drive tire. Peerless says most of today’s vehicles have tight wheel wells that call for Class S products. Here is the space each type needs, in Peerless’s own inch and millimeter figures:
| Chain type | Tread face | Inner sidewall | Peerless examples |
|---|---|---|---|
| Regular link chain | 1.97 in (50 mm) | 0.91 in (23 mm) | Quik Grip Type P |
| SAE Class S | 1.46 in (37 mm) | 0.59 in (15 mm) | Z-Chain, Auto-Trac |
| Exceeds Class S | 1.20 in (31 mm) | 0.25 in (6.3 mm) | Super Z6, SuperSox |
Some manuals go further and rule out chains on a given tire size. Toyota’s 2025 4Runner manual says chains cannot be mounted on 265/70R18 tires because the space between tire and body is too narrow, and says to use snow tires instead. Peerless says carmakers often write this when a car has less space than Class S, and that many such cars can still take one of its products. That is the chain maker’s view, not the carmaker’s, so ask your dealer first.
For any tight fit, Peerless says to fit the chains, drive a short distance slowly, and stop and remove them at once if you hear contact (a ticking sound).
Which chains for low clearance, SUVs and trucks
Tight wheel wells (most cars, many crossovers). Peerless says the Super Z6 needs only 0.25 in (6.3 mm) of space at the inner sidewall, where typical Class S products need 0.59 in (15 mm). Built-in rubber tensioners mean no stop to retighten. On alloy wheels that stick out past the sidewall, SCC says to use a product without rubber tensioners instead.
Security Chain Company Super Z6
Low-profile cable chain for cars, pickups and SUVs with tight wheel wells. Sold by tire size: pick the part number (SZ115 to SZ451) that lists your exact tire size.
Key specs
- Needs 0.25 in (6.3 mm) of sidewall space
- Exceeds SAE Class S clearance
- Max 30 mph (50 km/h) per SCC
- Rubber tensioners, no retightening stop
Paid link
View on Amazon (opens in a new tab)Pickups and SUVs with Class S space. Peerless says Auto-Trac meets Class S on SUVs and pickups and goes on without moving the vehicle. Ratchets tighten it as you drive, and Peerless says not to add extra tensioners.
Peerless Auto-Trac LT
Self-tightening link chain for pickups and SUVs. Ratchets tighten it while driving. Sold by tire size: choose the part number (for example 0232105) that lists your tire.
Key specs
- Meets SAE Class S on SUVs and pickups
- Self-tightening ratchets, no tensioners
- Installs without moving the vehicle
Paid link
View on Amazon (opens in a new tab)Large SUVs, vans and motorhomes. König says its XG-12 Pro, with links at most 0.47 in (12 mm) thick, suits vehicles that lack the clearance for traditional 0.63 in (16 mm) chains. It tensions and centers itself while you drive.
König XG-12 Pro
Self-tensioning, self-centering chain for midsize to full-size SUVs, vans and motorhomes too tight for traditional chains. Some listings use the older Thule name. Pick the size for your tire.
Key specs
- Links at most 0.47 in (12 mm) thick
- For vehicles too tight for 0.63 in (16 mm) chains
- Self-centering and self-tensioning
Paid link
View on Amazon (opens in a new tab)Whichever line you pick, choose the part number for your exact tire size. If you only need traction now and then, compare snow socks vs snow chains and check where socks count as chains. Next, learn which wheels the chains go on.
