If you’re replacing a torsion trailer axle, accurate measurements are extremely important. Unlike spring axles, torsion axles are built to specific dimensions and mounting configurations. A small measuring mistake can lead to fitment issues, improper ride height, poor tire clearance, or alignment problems.
The good news is measuring a torsion axle is straightforward once you know what dimensions matter.
The Most Important Measurements
When measuring a torsion axle, you’ll typically need:
- Hub Face Measurement
- Bracket (Mounting) Center Measurement
- Overall Bracket Dimensions
- Start Angle
- Axle Capacity
- Bolt Pattern & Brake Type
These measurements are critical for getting the correct replacement axle.
1. Hub Face Measurement (HF)
The hub face measurement is the distance from one wheel mounting surface to the other.
This is measured:
From the outside wheel mounting surface on one hub to the outside wheel mounting surface on the opposite hub
This measurement affects:
- Tire spacing
- Fender clearance
- Trailer tracking
- Overall axle width
How to Measure Hub Face
Measure:
Hub face → Hub face
Do not measure the axle tube.
Measure directly from:
Wheel mounting surface to wheel mounting surface
This is one of the most important dimensions when ordering a torsion axle.
2. Bracket Center Measurement (BC)
Unlike spring axles, torsion axles mount directly to the trailer frame using welded brackets.
The bracket center measurement is the distance:
Center of mounting bracket → Center of mounting bracket
This determines how the axle mounts to the trailer frame.
Getting this wrong can prevent proper installation.
How to Measure Bracket Centers
Measure:
Center of one mounting bracket to center of the opposite bracket
If unsure, measure carefully several times.
3. Mounting Bracket Dimensions
You’ll also want to measure:
- Bracket width
- Bracket height
- Bolt hole spacing (if applicable)
Some torsion axles use different bracket styles depending on trailer manufacturer and axle capacity.
4. Determine the Start Angle
One of the biggest differences with torsion axles is the start angle.
The start angle determines ride height and suspension arm position.
Common start angles include:
- Down 22.5°
- Down 10°
- Level (0°)
- Up 10°
- Up 22.5°
Replacing the axle with the wrong start angle can dramatically change trailer height and towing performance.
How to Identify Start Angle
Look at the torsion arm position when the trailer is unloaded.
The spindle arm may point:
- Slightly up
- Level
- Slightly down
A photo can often help identify this.
5. Verify Axle Capacity
Confirm the axle capacity before ordering.
Common torsion axle sizes include:
- 2,000 lb
- 3,500 lb
- 5,200 lb
- 7,000 lb
The axle tag or serial number is usually the best way to verify capacity.
6. Check Bolt Pattern & Brake Type
Before ordering, confirm:
Bolt Pattern
Examples:
- 5 on 4.5"
- 6 on 5.5"
- 8 on 6.5"
Brake Type
Determine whether the axle is:
- Idler (no brakes)
- Electric brakes
- Hydraulic brakes
This affects hub compatibility and wiring.
7. Identify Axle Tube Size
Tube dimensions may also help identify the axle.
Common torsion axle tube styles include:
- Square tube
- Round tube
Tube size can vary by manufacturer and capacity.
Common Measuring Mistakes
Avoid these common errors:
❌ Measuring overall axle length only
❌ Forgetting bracket center measurement
❌ Guessing the start angle
❌ Measuring the axle tube instead of hub face
❌ Forgetting brake type or bolt pattern
Even small differences can prevent proper fitment.
Measure Carefully Before Ordering
For most torsion axles, you’ll want:
✔ Hub face to hub face measurement
✔ Bracket center measurement
✔ Bracket dimensions
✔ Start angle
✔ Capacity rating
✔ Bolt pattern & brake type
Because torsion axles are often custom-built, accurate measurements are extremely important.
At Highway Trailer Company, we help customers measure and match torsion trailer axles every day. If you’re unsure about measurements, send us photos and dimensions and we’ll help make sure you get the right axle the first time.