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Porsche Part Numbers, Decoded

The fastest way to buy the right race part is to speak part number

Porsche's part numbering system is one of the most disciplined in motorsport — and once you can read it, a string like 991.631.141.82 stops being a serial number and starts being a sentence. This guide decodes the structure using real numbers from real Cup parts, so you can verify fitment yourself before you spend money. It's the same system we use to verify every listing in our catalog against the factory parts books.

The anatomy: three groups and a suffix

A Porsche part number reads as three groups of three, plus a two-character suffix:

991 . 631 . 141 . 82

  • First group — the platform. The model type the part was cataloged under: 991 here. You'll see 996, 997, 991 for the GT3 Cup generations, 981 and 982 for the Cayman GT4 Clubsport cars, and 992 for the current Cup car.
  • Second group — the subsystem. Porsche organizes its catalogs by functional group and exploded diagram, and this group encodes it. From our own shelves: 631 numbers are lighting (tail light assemblies), 333 lands in rear suspension (support bearings, catalog section 5.5), 505 covers front/rear-end covering hardware like retaining frames (section 8.x), and 575 underbody panelling such as brake-air ducts (section 8.6).
  • Third group — the part itself within that subsystem, with one convention worth memorizing (next section).
  • Suffix — revision or variant. The same physical location on the car, in a different version.

Odd/even endings: the left/right convention

Paired parts usually differ only in the last digit of the third group — odd for left, even for right. Two live pairs from our inventory:

  • 991.631.141.82 tail light, LH → 991.631.142.82 tail light, RH
  • 991.505.875.80 retaining frame, exhaust air, LH → 991.505.876.80 RH

It's a convention, not a law — always confirm against the catalog (every listing of ours states the verified side). But when you're staring at a label in the pits, odd/even is the right first guess.

The suffix: variants and revisions

The trailing characters do double duty, and this is where most ordering mistakes happen:

  • Variants. 991.631.141.14 and 991.631.141.82 are both the left tail lamp in the same position on a 991-generation car — but they are different parts. The factory books make the split clear: the .14 lamp is printed in the 991.1 Cup catalogues, while the .82 lamp appears in the 911 GT3 R parts manual. Same corner of the car, different specification. We stock both, which is exactly why a listing has to carry the complete number rather than "991 tail light."
  • Revisions. When Porsche updates a part, the suffix moves (.00 → .01 → .02 …). A later revision often supersedes an earlier one — sometimes interchangeably, sometimes not. Where the factory catalog supports interchange, our listings say so; where it doesn't, we don't guess.

Families that cross generations

Because the middle groups describe function, the same part family recurs across platforms with the platform prefix and suffix changed. A real example from our shelves: the rear suspension support bearing family xxx.333.061.xx appears as 991.333.061.8C on the 991.2 GT3 Cup and 981.333.061.81 on the 981 Cayman GT4 Clubsport — same functional part, two platforms, two revisions. Reading the family out of the number is how experienced Cup mechanics spot cross-generation candidates before opening a catalog. It's also how we build the interchange notes on our listings: family first, then verification against each platform's factory pages.

Dots, spaces, and how to search

You'll see the same number written 991.631.141.82, 991 631 141 82, or 99163114182 depending on the label, invoice, or forum post. They're identical. Our search normalizes all three — type the number with or without dots and you'll land on the same part. Every product page also displays the canonical dotted form, so what you verify is what you order.

A worked example, start to finish

Your left tail lamp is broken, its label reads 991.631.141.82, and you need the one for the other side:

  1. 991 — 991-platform part. 631 — lighting. 141 — odd ending, so this is the LEFT lamp and the right one should end 142. Suffix .82 — carry it across unchanged, or you'll end up with the .14 lamp, which is a different specification.
  2. Search 99163114282 (dots optional) in our catalog. The factory manual confirms that number as the right-hand tail lamp — the exact mate of the one in your hand.
  3. Check the listing's stated fitment against your chassis and the grade, and you're done — no cross-referencing forum threads at midnight.

Part-number questions we actually get

My number's suffix doesn't match yours. Will the part fit?

Maybe — that's a revision-or-variant question. Check whether the listing notes catalog-supported interchange for your suffix; if it doesn't, send us both numbers and we'll check the factory pages before you buy.

Is a road-car part number the same part?

Sometimes the catalogs do share numbers between road and Cup cars, but never assume it from the number alone — Cup catalogs frequently specify motorsport-only hardware in the same subsystem. Verify against the Cup catalog fitment, which is what our listings state.

Are these genuine Porsche parts?

We sell used and NOS parts identified by their factory part numbers for fitment purposes; where a part is from another manufacturer (a Manthey kit component, for instance), the listing says so and carries that maker's number instead. Race Parts Depot is not affiliated with Dr. Ing. h.c. F. Porsche AG.

What if the number I need isn't in your catalog?

Ask. Inventory arrives in batches from one Cup program, and we track requested numbers against what's coming in.