Custom shims are precision components that fix tolerance gaps, restore alignment, and prevent progressive wear in suspension, driveline, and bearing assemblies. Investing in the right shim design and material up front often prevents repeated adjustments, component failures, and expensive downstream repairs.
Measurable cost benefits for fleets and shops
- Lower part replacement costs: Custom shims eliminate the need to replace large components by compensating for wear or manufacturing tolerances with an exact fit.
- Reduced labor and rework: A correct custom shim reduces iterative disassembly and trial‑and‑error stacking, saving technician hours and shop bay time.
- Extended service intervals: Precisely sized, properly specified shims maintain preload and geometry longer, reducing unscheduled downtime and warranty claims.
When custom shims are the right call
- Nonstandard repairs: After welding, frame repairs, or aftermarket modifications where OEM stacks no longer seat correctly.
- Repeated failures: When the same bearing, seal, or alignment issue returns after standard shimming.
- Critical load points: High‑compressive or high‑dynamic locations where standard thin plates crush or creep without a load‑spreading design.
- Tight tolerance assemblies: Precision gearsets, pinion depth setups, and valve trains where a fraction of a millimeter changes contact patterns and life.
How to specify a custom shim (technician workflow)
- Measure and document baseline: record existing stack thickness, bearing preload, gear contact pattern, ride height, and take ruler‑inset photos of the seating surfaces.
- Define the requirement: state exact thickness, outer diameter, locating hole geometry, taper degree (if wedge), and material finish needed for corrosion or wear resistance.
- Select material and finish: choose alloys or coatings that resist compression, creep, and corrosion in the application environment; specify load‑spreading plates where necessary.
- Prototype and verify: fit the first custom shim, torque to spec, re‑measure preload/angles, and validate under representative load or road test.
- Document for reuse: save the final shim drawing or part number with the vehicle record and include ruler‑inset photos and measured before/after values.
Quality assurance checklist and failure modes to avoid
- QA checklist
- Visual: flat, clean seating faces with no burrs; check for corrosion.
- Measurement: caliper‑checked thickness and dial indicator confirmation of preload or angle.
- Hardware: confirm lock hardware and load spreaders are specified and installed.
- Documentation: photo evidence and recorded shim part number in service history.
- Common failure modes
- Crushing under point loads when thin shims are used without spreaders; prevent with plates or thicker custom sections.
- Material creep or corrosion from incorrect alloy choice; prevent by specifying corrosion‑resistant materials and finishes.
- Stacking errors when techs mix multiple off‑the‑shelf shims without a documented conversion chart; prevent with a custom single‑piece shim or clear stack instructions.
Quick ROI example and shop best practices
- ROI example: a repeated wheel‑end bearing failure that costs $1,200 in parts and labor per occurrence can often be fixed with a $30–$150 custom shim and one reliable install, delivering immediate savings and fewer comebacks.
- Best practices
- Standardize spec sheets for custom shim orders with exact geometry, material, and finish.
- Keep a short conversion chart at alignment stations and require ruler‑inset photos on every shim change.
- Stock common custom part numbers for repeat fleet models to shave lead time and get the upfront benefit faster.
Treat custom shims as precision repairs, not stopgap hardware: the right specification, material, and installation discipline pay back quickly through fewer failures, less labor, and lower total cost of ownership.
