Plastic parts · Lighting · Buying in bulk
How to check plastic bike parts before you buy in bulk
In short
Before you order plastic parts in bulk, ask for samples and check four things: fit on the actual bike, clean molding with no bubbles, flash or sink marks, the right material for heat and sunlight, and colour that matches a master sample. Then ask the supplier how they keep every batch the same as the sample.
- Always fit a sample on the real bike before ordering in bulk.
- Bubbles, sharp edges and sink marks are signs of rushed molding.
- Cheap plastic yellows, fades and cracks in the sun within months.
- Ask how every batch is checked against the approved sample.
Why this matters
A plastic part that almost fits, or that fades after one summer, comes back to the dealer. That costs more than the few rupees saved on the purchase price. A few minutes checking samples saves a whole order going bad.
Check the fit on the real bike
Fit the sample on the bike it is made for, not just next to the old part.
- Every mounting hole should line up without forcing.
- Clips should click in and hold firmly.
- There should be no gaps between the part and the panels around it.
- Lenses should sit flush in their housings with no rattles.
Tip: Fit the sample on two or three different bikes of the same model. Small differences between assemblers can show up a part that only just fits.
Look at the molding
Good injection molding leaves a clean part. Hold it up to the light and look for:
| Problem | What it looks like | What it means |
|---|---|---|
| Flash | Thin sharp plastic along the joint lines | Worn mold or too much pressure |
| Sink marks | Small dips on thick areas | Rushed cooling time |
| Bubbles | Tiny air pockets, easy to see in clear lenses | Wet or poor material |
| Short shots | Edges or clips not fully formed | Not enough material or pressure |
| Flow lines | Wavy lines or streaks on the surface | Wrong temperature or speed |
A few of these on a sample usually means many more in the bulk order.
Check the material
Pakistani roads are hard on plastic: heat, sunlight, rain and potholes.
- Lenses should be clear with no yellow tint. Cheap clear plastic yellows and goes cloudy in the sun.
- Red and amber lenses should be deep and even. Thin colour fades to pink or pale yellow.
- Mudguards and covers should flex a little without cracking. Bend a corner gently. Brittle plastic snaps.
- Smell and weight can tell you a lot. Very light parts with a strong smell often use too much recycled material.
Watch out: Some recycled plastic is fine, but too much makes parts brittle. Ask the supplier what material they use and whether it is new or recycled.
Check colour and finish
Keep one approved sample as your master. Compare every delivery against it in daylight.
- Colour should match the master with no streaks.
- Chrome and metallic finishes should be even, with no peeling at the edges.
- Black parts should have the same gloss level across the batch.
Ask the supplier the right questions
- Do you make your own molds, or buy parts from someone else?
- How do you check each batch against the approved sample?
- What happens if part of a delivery does not match?
- Can you mold our brand name into the part?
- What is the lead time for a repeat order?
A supplier who makes its own molds can fix a fit problem at the source and can make parts with your brand on them.
Want samples?
Tell us which parts and which bikes on WhatsApp. We will send samples so you can check them on your own bikes before you order.
