the Difference Between 35-inch And 315 Tires: Metric vs Standard mm
Are you interested in knowing the difference between 35-inch and 315 tires? 315-wide tires are the same as 35” tires although 315 is the tread width in millimeters and 35″ is the tire diameter. 315/70/17 is usually the accepted metric equivalent size for standard/imperial 35-inch tires.
When comparing a 35-inch tire to a 315-wide tire, you are comparing two completely different measurements.
The 35” is a metric value and refers to the width of the tire multiplied by the aspect ratio, which is the height of the sidewall, x2.
You x2 because there are two sidewalls per tire, divided by the wheel inch, plus the wheel size…
Phew!!! That’s a mouthful and a lot to digest at once so let’s break it down into a simple formula.
Tire Size: 315/70R17 (35”)
- 315 = the metric width of the tire measured in mm
- 70 = the height percentage (Aspect Ratio) of the sidewall
- (315 width x .70 = 220.5mm)
- Divide mm by 25.4 to get inches
- So….. 220.50 x 2 sidewalls = 441mm (divided by 25.4 = 17.36″)
- 17.36″ + 17″ wheel = 34.36″ approximate tire diameter.
The following chart lists common p-metric tire sizes.
The table lists the converted tread width and the actual tire height in inches.
Values shown are calculated measurements based on the p-metric formula.
This chart is for an estimated conversion and the actual advertised tire height and tread width will vary from manufacturer to manufacturer.
Rim Size | P-Metric Size | Tread Width | Actual Tire Height |
16 Inch | 225/75R16 | 8.8 inches | 29.3 inches |
235/85R16 | 9.25 inches | 31.7 inches | |
245/75R16 | 9.6 inches | 30.5 inches | |
265/70R16 | 10.4 inches | 30.6 inches | |
265/75R16 | 10.4 inches | 31.6 inches | |
285/75R16 | 11.2 inches | 32.8 inches | |
305/70R16 | 12.0 inches | 32.8 inches | |
315/75R16 | 12.4 inches | 34.6 inches | |
345/75R16 | 13.6 inches | 36.4 inches | |
17 Inch | 235/65R17 | 9.25 inches | 29.0 inches |
245/70R17 | 9.6 inches | 30.5 inches | |
255/75R17 | 10.0 inches | 32.0 inches | |
255/80R17 | 10.0 inches | 33.0 inches | |
265/70R17 | 10.4 inches | 31.6 inches | |
275/70R17 | 10.8 inches | 32.2 inches | |
285/70R17 | 11.2 inches | 32.7 inches | |
285/75R17 | 11.2 inches | 33.8 inches | |
305/65R17 | 12.0 inches | 32.6 inches | |
315/70R17 | 12.4 inches | 34.4 inches | |
18 Inch | 265/60R18 | 10.4 inches | 30.5 inches |
275/65R18 | 10.8 inches | 32.1 inches | |
275/70R18 | 10.8 inches | 33.2 inches | |
285/75R18 | 11.2 inches | 34.8 inches | |
295/65R18 | 12.6 inches | 33.1 inches | |
305/60R18 | 12.0 inches | 32.4 inches | |
305/70R18 | 12.0 inches | 34.8 inches | |
20 Inch | 275/60R20 | 10.8 inches | 33.0 inches |
275/65R20 | 10.8 inches | 34.0 inches | |
285/60R20 | 11.2 inches | 33.4 inches | |
285/65R20 | 11.2 inches | 34.5 inches | |
295/55R20 | 12.6 inches | 32.8 inches | |
295/60R20 | 11.6 inches | 33.9 inches | |
305/55R20 | 12.0 inches | 33.2 inches | |
325/60R20 | 12.8 inches | 35.3 inches |
Is a 35-inch Tire the same as a 315 (Metric Vs Imperial MM)
Metric tire sizes can be a bit more complicated when it comes to understanding what size they are.
Let’s see what that means.
Difference Between 35-inch And 315 Tires: Metric vs Imperial Millimeters
Understanding the difference between metric and imperial is handy when it comes to tire sizes because you can get specific.
There are so many different tire sizes available today so knowing the difference can mean finding that perfect fit for your truck.
Things to Note:
- Metric is measured in milliliters and imperial/standard is measured in inches.
- When it comes to tire production there’s no official mold
- Each tire manufacturer uses their mold which means there’s no set industry pattern.
- The 315/70/17 is usually the accepted metric size for 35” tires, even though the physical diameter of the tire can vary from manufacturer to manufacturer.
- Two different 35” tire brands can easily vary in true diameter.
This means certain tires are smaller than 35″ like a 34.6” and some will be slightly larger, depending on the brand and overall construction.
So, this means a particular 35-inch tire can be somewhat wider than another.
Other Points
- They are similar in metric size but there are slight differences in construction, weight, pattern, load rating, ply ratings, tread depth, etc.
- One way to find out the exact diameter of a tire is by going to the tire manufacturer’s website and checking the manufacturing specs on that specific tire and then comparing.
Fitting 35-inch Tires On Your Truck
Bigger tires are the single most effective method of gaining improved ground clearance.
This is especially important for overcoming obstacles in an off-road situation.
There are however a few limitations, especially when it comes to IFS (Independent Front Suspension) 4WD vehicles.
Let’s now look at a few factors to consider when fitting 33” tires on your truck.
Lift Kit
Before you even consider fitting 35” tires on your IFS truck, you’ll need to have a minimum 3-4-inch lift kit installed.
Depending on your truck brand and model, sometimes this isn’t enough, since you’ll still need to make additional modifications to prevent scrubbing at full lock.
- Install a lift to retain full functionality and articulation for off-road use.
- 4” or higher lift has serious implications to any IFS suspension
Wheel Offset
Wheel offset or backspacing is a factor that gets little consideration, and it can create complications if you’re not sure exactly how much brake caliper clearance is required.
The problem here is, that you don’t want to go too negative offset on the wheels else you risk too much wheel “poke”.
- Backspacing is the distance measured from the hub mounting surface to the inside edge of the wheel.
- Decreasing backspacing increases inner wheel clearance.
- There is a fine line between keeping the tires in the guards and preventing scrub on arches, UCA, Brake calipers, etc.
- Offset is measured in mm and generally refers to how your wheels sit inside the wheel wells.
- You get positive and negative offset wheels.
- When it’s positive the imaginary line is more toward the front
- Negative means the mounting surface is more towards the rear of the rim creating a deep dish effect.
Fender & Arch Trimming to fit 35s
Usually, there are a few plastic liners on the inner fender guards that need to be massaged since they will scrub at full articulation.
You might even have to do some arch rolling, depending on which truck you have and how much space you’re working with.
- Be mindful of the inner guard pinch weld and the inside of the fender flare.
- This usually requires some trimming, depending on the tire and vehicle.
- Fender clearance and backspacing go hand-in-hand with tire width.
- A wider and taller tire will require more wheel arch clearance.
- Offroad articulation requires room to move when flexing off-road and when turning at full lock.
- Don’t forget to upgrade your bump stops.
NB: When you squeeze oversized tires into a wheel arch without lifting the truck, you’ll need to do extensive trimming on the inside fender and arch plastic to allow the tire to tuck behind the arch when turning and flexing off-road.
Will The 35s Throw Out Your Speedo?
When you upgrade from a stock tire to one with a taller aspect ratio (Sidewall), increasing the wheel circumference, your speedo can be thrown out.
In the case of 35” tires, the diameter will be larger and have an increase in the aspect ratio.
- Oversized tires throw out your speedometer reading quite a bit.
- The increase in tire circumference means the actual speed you are traveling will be higher than your speed reading and get worse the faster you travel.
The below table will give you an indication of how the speedometer reading is affected from 32” (275/70R17) to 35” (315/70R17).
Speedo reading | 20mph | 30mph | 40mph | 50mph | 60mph | 70mph | 80mph | 90mph |
Actual Speed | 21.4 | 32 | 42.7 | 53.4 | 64.1 | 74.8 | 85.5 | 96.1 |
Below are the actual differences between the stock 32” tire and the upgraded 35”
Measurement | Stock Tire (275/70/17) | Upgrade (315/70/17) | Differences |
Diameter | 32.2″ | 34.4″ (874mm) | +6.8% |
Width | 10.8″ | 12.4″ (315mm) | +14.8% |
Sidewall | 7.6″ | 8.7″ (221mm) | +14.5% |
Circumference | 101″ | 107.9″ (2741mm) | +6.8% |
Revs/Mile | 627 | 587 (365mm) | -25 |
FINAL THOUGHTS
We have mentioned quite a few variables to consider before dropping a load on expensive oversized tires.
You should first determine what the primary application for the upgrade is.
Is your 35-inch tire upgrade purely for aesthetics or will you need maximum practicality, and off-road ability, while maintaining maximum articulation?