How do I calculate the required length of longer wheel bolts?

Add the thickness of the spacer to the original thread length of your current wheel bolt. For example: 28mm original bolt + 15mm spacer = 43mm new wheel bolt length.

Spacers & Wheel Spacers

Q: Why are spacers with double hub-centring mandatory?

Spacers without hub-centring (flat pancakes) mean the wheel no longer rests on the vehicle hub. The wheel then balances solely on the wheel bolts, which causes severe steering vibrations at 90-130 km/h and dangerous peak loads on the bolts.

Spacers & Wheel Spacers (Hub-Centring & Hub Depth)

Give your car the perfect clean stance and optimally fill the wheel arches. High-grade aluminium hub-centric spacers create extra clearance for large brake callipers (Big Brake Kits) and noticeably improve track width and cornering stability.

The Guide to Safe & Vibration-Free Track Widening:
Fitting spacers widens your car’s track by a few millimetres up to several centimetres per side. This delivers a bold, sporty appearance by aligning the wheels more flush with the arches. In addition, spacers solve interference issues with large brake callipers or coilover kits. At **Wheels 'N Customs** we supply only high-quality, CNC-milled aluminium spacers from top brands (Eibach Pro-Spacer, H&R Trak+, ST Suspensions and JR-Wheels) with **double hub-centring** for 100% vibration-free driving.

1. Compare: Through-Bolt Systems vs. Bolt-On Systems

Choose the right spacer system based on the desired thickness and your fastening type:

System Feature	System 1: Through-Bolt System (Bolt-Through)	System 2: Bolt-On System (Bolt-On / DRA / DRM)
Common Thicknesses	3 mm to 20 mm per wheel (6mm - 40mm per axle)	20 mm to 45+ mm per wheel (40mm - 90mm per axle)
Operation & Fastening	Spacer is clamped between hub and wheel with longer bolts.	Spacer bolts to the vehicle hub; wheel bolts to the spacer.
Longer Wheel Bolts Needed?	YES (Extended bolts required)	No (Original bolts are used into the spacer)
Hub-Centring	From 10mm equipped with a centring ring on the spacer	Integrated steel or aluminium centring ring
TÜV Certified	Yes (Eibach, H&R, ST)	Yes (Eibach, H&R, ST)

2. Crucial: Hub Depth & The “Danger Zone” (8mm - 12mm)

What is Hub Depth?

Hub depth (collar height) is the length of the steel centring lip on your wheel hub/brake disc. If this steel lip protrudes 14mm, the internal recess of the spacer must be at least 15mm deep to sit 100% flush.

The “Danger Zone” (8mm - 12mm)

With spacers from 8mm to 12mm, the spacer is often thinner than the length of the vehicle hub. Is the hub too long for the spacer’s recess? Then when tightening, the vehicle hub will immediately press off the spacer’s aluminium centring ring!

Consequences of Incorrect Depth

If the spacer does not sit flush against the brake disc, a gap will form. This leads to extreme vibrations at 90-130 km/h, warped spacers and the dangerous loosening of wheel bolts.

Overview of common hub collar heights by brand (always measure before installation!):

Car Make / Manufacturer	Average Hub Collar Length	Point of Attention with Spacers
Volkswagen, Audi, Seat, Skoda (VAG)	12.0 mm to 15.0 mm	10mm spacers will not fit all rear axles without an extra-deep recess.
BMW (incl. E36, E46, E90, F30)	15.5 mm to 16.0 mm	Very tall hub lip! Prefer 12mm or 15mm spacers with a recessed chamber.
Mercedes-Benz	Up to 18.0 mm (Front axle)	Front axle has a tall grease cap. Special ‘front axle’ spacers are required.
Ford, Volvo, Peugeot, Renault & Japanese	10.0 mm to 14.0 mm	For through-bolt spacers, check that the original studs do not protrude too far.

Step-by-Step: How to Measure Hub Depth Correctly

01.

Remove Wheel

Remove the wheel so the brake disc and the steel hub centring lip are fully exposed.

02.

Remove Rust

Brush the hub and brake disc mating surface completely rust-free with a wire brush (rust can easily add 1 to 2mm of thickness!).

03.

Measure with Vernier Caliper

Place the depth probe of a vernier caliper against the brake disc and measure to the very tip of the hub lip.

04.

Manual Test-Fit

Place the spacer loosely by hand onto the hub. The spacer MUST rest 100% flat against the brake disc with no gap.

3. How to Calculate the Correct Wheel Bolt Length

A. Original Thread Length

Measure the thread length (shank length) of your current wheel bolt. At most European cars the standard bolt length is approximately 27mm to 28mm.

B. Add Spacer Thickness

Add the thickness of the chosen through-bolt spacer to the original length. For example: 28mm (bolt) + 15mm (spacer) = 43mm new bolt length.

C. Seat Type (Conical vs. Ball Seat)

When ordering extended wheel bolts, ensure you choose the correct seat: Conical (60°) for aftermarket wheels or Ball Seat for original factory wheels.

▵ IMPORTANT: Always Choose Hub-Centric Spacers!

Cheap flat universal rings (“pancakes”) without a centring lip cover the original hub-centre of your car. The wheel then balances solely on the wheel bolts. This will **inevitably cause severe steering and chassis vibrations at speeds between 90 and 130 km/h**. On driven and steering axles use only hub-centric spacers!

▵ Binding Installation Instructions & Liability Disclaimer

To guarantee a 100% flush fit of the spacer against the brake disc and prevent loosening, the installation instructions below must be strictly followed:

Thoroughly De-Rust the Hub: Brush the mating surfaces of the brake disc and wheel hub completely free of rust, dirt and paint residues with a wire brush before fitting the spacer.
Manual Flush Test-Fit (Without Bolts): First press the spacer by hand onto the hub. Is there a gap between the spacer and the brake disc? Then the hub depth is too long. Forcing the spacer into place by tightening bolts is strictly prohibited!
Manual Installation Only: Tighten all wheel bolts fully by hand, turn by turn. The use of a pneumatic or electric impact wrench is strictly prohibited during the entire installation process.
Cross-Pattern Tightening with Torque Wrench: Tighten all bolts/nuts in a criss-cross pattern to the torque specified by the vehicle manufacturer (usually 110-140 Nm) with a calibrated hand torque wrench.
Mandatory Re-Torque after 100 km: After driving the first 50 to 100 kilometres, the torque of all wheel bolts/nuts must be checked and re-tightened by hand.
Exclusion of Warranty: Damage resulting from a non-flush fit due to excessive hub depth, a dirty hub, bolts that are too short (less than 6-7 full turns of thread engagement) or the use of an impact wrench falls entirely outside the warranty and liability of Wheels 'N Customs.

4. Our Premium Spacer Brands

Eibach Pro-Spacer

Manufactured from high-quality anodised aluminium alloys. Offers extreme corrosion protection and maximum weight savings. Supplied with TÜV certificate.

H&R Trak+ Wheel Spacers

German precision with the patented DRA and DRM bolt-on systems. Extremely strong and perfectly suited to performance cars and heavy SUVs.

ST Suspensions Spacers

Powered by KW Automotive. ST DZX and AZX spacers offer an innovative through-bolt system with adapters for virtually all imaginable PCDs.

JR-Wheels Aluminium Spacers

Lightweight and affordable aluminium hub-centric spacers. Ideal to combine with Japan Racing and Concaver alloy wheels.

5. Frequently Asked Questions about Spacers & Wheel Spacers

What is hub depth and why can a spacer break?

Hub depth is the length of the steel centring lip on the vehicle’s wheel hub. If this lip is longer than the internal recess of the spacer, the spacer will not sit flush. When you then tighten the wheel bolts, the steel hub will immediately press off the spacer’s aluminium centring ring.

Are spacers legal for the APK inspection in the Netherlands and Belgium?

In the Netherlands, the vehicle’s track width may not be more than 2% greater than the value stated on the registration certificate. In addition, the tyres must be within the legal arch coverage (not protruding too far). In Belgium, spacers must have a valid Goca/TÜV certificate per vehicle type.

How many turns must a wheel bolt be tightened at minimum?

For secure retention, a wheel bolt must be able to screw into the hub by at least 6 to 7 full turns (approximately 10mm of thread). Is it less due to fitting a spacer? Then extended wheel bolts are absolutely mandatory for safety!

Do spacers cause extra wear on wheel bearings?

Fitting quality spacers of 10mm to 20mm has a negligible effect on wheel bearings, comparable to fitting a wheel with a slightly lower ET value. As long as you choose hub-centric spacers, the load distribution over the hub remains optimal.

100% Hub-Centring Guaranteed vibration-free driving

Eibach, H&R, ST & JR All top brands from our own stock

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Order Spacers or Wheel Spacers?

Unsure about the maximum thickness or hub depth for your wheel arches, or want advice on the correct extended wheel bolts? Feel free to contact the experts at Wheels 'N Customs!

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