Your car deserves better.
Whether you’re driving a used $10,000 Toyota or a new $90,000 Porsche, chances are your license plates are attached to your car with the hardware that came with it. In most cases that means cheap zinc-plated steel screws with minimal corrosion resistance, and even less eye-appeal.
This guide attempts to take the mystery out of buying license plate screws and installing front and rear license plates. It also briefly explores current trends in license plate brackets, plate “relocators,” and “tamper-resistant” fasteners.
Much of the information provided here comes from our experience with BMW automobiles, but the same general principles apply to any license plate hardware, for any automotive application.
License Plate Screw Types
BMW Rear License Plate Screw Comparison
Metric vs Standard (Imperial) Measure
The metric system has been officially sanctioned for use in the United States since 1866, but it remains the only industrialized country that has not adopted the metric system as its official system of measurement. Many sources also cite Liberia and Burma as the only other countries not to have done so. Although the United Kingdom uses the metric system for most official purposes, the use of the imperial system of measure, particularly for use at home, is widespread and is permitted by the law.
So, unless you’re driving a car made in Liberia, Burma or the United States, you probably need metric fasteners. The exception might be some British cars which apparently use a mix of metric and standard (go figure).
Metric Machine Screw Specifications
What does “M5x0.8 x 12mm” mean?
- M5 = Metric 5mm screw shaft diameter
- 0.8 = Thread pitch in millimeters (distance between threads)
- 12mm = Screw length (except for flat-head screws, measured from under the screw head)
You can also purchase metric self-tapping (sheet metal) screws. However, since we’re not usually driving this type of screw into a metal nut or threaded insert, the “metric” specification doesn’t mean much when it comes to sheet metal screws.
Is it a “bolt” or a “screw”?
This distinction is more accurately defined by how the fastener is used, not how it looks. If a machine screw requires a nut to secure two or more objects together, it’s typically called a bolt. If there’s no free nut, calling it a screw might make more sense. Self-tapping fasteners are almost always called “screws.”
This low-strength general purpose metal is often plated with zinc to provide a minimum of rust resistance (see below).
Highly hardened and usually coated with black oxide and/or oil. Offers little corrosion resistance.
A low carbon steel for general use. Relatively inexpensive, with the zinc plating providing moderate corrosion resistance suitable for indoors or otherwise dry conditions. Color is either a blueish tint or yellow depending on the exact process.
Chrome and Nickel Plated Steel
Smooth and polished appearance. The plating offers moderate corrosion resistance.
Type 304 Stainless Steel (A2, 18/8)
Has very good corrosion resistance making it suitable for outdoor applications. More expensive than zinc plated steel.
Type 316 Stainless Steel (A4)
More corrosion resistant than 304 stainless steel. Withstands solvents and pitting caused by chloride, sulfur and harsh outdoor environments. Commonly referred to as “marine grade” stainless steel.
Brass and Bronze
Copper alloys with good corrosion resistance. An excellent conductor of electricity, it’s usually softer than steel and stainless steel. More expensive than steel, these materials are typically used for decorative applications.
Offers mild resistance to corrosion. It’s nonmagnetic and one-third the weight of steel.
Resists corrosion from salt water and stands up to more chemicals than stainless steel. Titanium is extremely strong, yet 40% lighter than steel.
Don’t bother. Plastic screws have a certain cosmetic appeal and won’t rust, but the heads break off with the slightest bit of tightening. Nylon is only marginally stronger. If you insist on non-metal screws, use glass-filled nylon, they’re the least evil of the plastic variety.
There are dozens of screw head types that require all sorts of different drivers, both manual and powered. Aside from the basic slotted design, we’re going to focus on Phillips, Hex and Star screw head types.
Crosshead (Phillips) vs Hex (Allen) vs Star (Torx)
As far as I know, no state is suffering from an epidemic of license plate or frame thefts, but some people insist on getting the most exotic “theft-proof” fasteners they can find. The general rules of common sense apply here: If bandits want your plate or frame badly enough, they’ll get it, so why make it any harder on yourself than you have to? If you’re that much into security, use plain steel screws and let them rust in place. Then nobody will get them off.
Think about it. If thieves are stealing your plates on impulse, they might have a Phillips or flathead screwdriver, or maybe a multi-tool handy. But they’re not any more likely to be carrying a size 3 Hex key than they are a T25 pin-in Torx key. And remember, different size screws require different size tools.
On the other hand, if they’re dedicated professional license plate thieves, they’ll have all the tools they need including spanner, polydrive and tri-wing drivers.
Personally, we like Hex head fasteners. They’re available in a wide variety of metric sizes, head designs and material grades. The interior hex head allows them to be much smaller than comparable Phillips screws, and they won’t get buggered up like the plain slot-head variety.
Plus, Hex screws are simple, elegant and real easy to find drivers (keys) for — Hex (Allen) wrenches are available just about everywhere. If you lose your pin-in T25 Torx bit, are you really going to remember if it was a Torx, Torx Plus, or Torx TR? Or if it had 6 lobes or only 5? Probably not.
Rear License Plate Hardware
Except for a few notable exceptions, such as the Chevrolet Corvette, most American car manufacturers use sheet metal screws and nylon snap-in nuts for both their front a rear license plates. Most European and Asian manufacturers use a metric machine screw with a threaded insert.
The license plate screws for the rear are usually different from the front, since there is frequently some sort of rear plate mounting bracket that is first attached to the car. The license plate is then attached to the bracket with machine screws.
Pay Attention to Screw Length
Always keep in mind that the length of screw required to attach the plate to the bracket depends on the total thickness of your complete license plate mount, which may include:
- Screw covers with a base
- Clear license plate cover (if legal)
- License plate frame
- License plate
- Frame gasket
All of the above can easily add up to over 12mm (1/2″) or more. If your screws are too short, they won’t reach the threaded insert, or engage enough of the thread for a secure fit. If the screws are too long, you risk passing through the bracket and bottoming out against your car before the screws are tight.
Note the built-in foam pads that adhere to the back of the BMW rear plate bracket holes (see photo below). These are there to prevent marring of the body finish from overlong screws.
Common Rear License Plate Screw Sizes
Below are a few typical metric machine screw specifications for rear license plate fasteners. The shortest lengths are usually for a bare license plate, or plate with a thin metal frame with minimal depth.
- Audi: M6x1.0 x 8-16mm
- BMW: M5x0.8 x 8-16mm
- Honda: M6x1.0 x 12-20mm
- Mercedes-Benz: M6x1.0 x 8-16mm or M5x0.8 x 8-16mm
- Porsche: M6x1.0 x 8-16mm
It’s been our experience that dealers aren’t particularly concerned about the quality or size of the fasteners used on license plates. In fact, most original equipment (OEM) or dealer supplied screws are zinc-plated steel and offer only minimal corrosion resistance.
Front License Plate Hardware
Front plates, in particular, can be a real challenge because you’re at the mercy of the individual who installs them. With most European cars, the front plates are optionally installed at the dealer. If they use a power driver and over-tighten the screws, you can actually end up with little “volcano holes” in your front bumper cover.
Since front plates are not required in every state and country, the options for mounting them vary widely. As noted above, the front plates on European cars are usually affixed at the dealership, but you can often ask that they not perform this task, thus saving your front bumper the indignity of unsightly screw holes.
If you’re fortunate enough to live in a country or state that doesn’t require front plates, you can dispense with mounting them altogether. However, if you’ve already got holes in your front bumper, they can easily be made less objectionable by the use of “bumper plugs.” These are small round plastic inserts that fit snugly into the holes. They can be painted to match your car color, or you can custom order them from several online suppliers.
Front License Plate Brackets
Typically, the dealer will install some sort of plastic license plate holder with self-tapping (sheet metal) screws by drilling holes into your front bumper. Your license plate is then affixed to the plastic holder with more sheet metal screws.
Care must be taken to select a screw of the proper length, or you run the danger of scarring the bumper cover underneath (or actually puncturing the bumper cover). The correct hardware varies from manufacturer to manufacturer, and from model to model. Also, repeated removal of these screws will cause the plastic threads to deteriorate, requiring thicker screws for a secure fit.
Some U.S. manufacturers factory install the front plate brackets, not with removable screws, but with plastic rivets. If you’re careful, these rivets can be drilled out and replaced with plugs.
(Note: Even McLaren Automotive instructs their dealers to drill the front license plate holes directly into the front bumper. Ouch.)
BMW Front License Plate Bracket
As an example, I have a 2011 BMW 335i Coupe with the M Sport Package. I chose not to have the front plate installed (I live in California so had to sign a waiver assuming liability for the lack of a front plate). The dealer simply left the front bracket in the trunk when they delivered the car (no screws or instructions).
On this particular model, the plastic bracket has two tabs on the bottom that fit into two pre-existing slots on the underside of the bumper (see photo at right).
To install the front bracket:
- Hold the bracket upright and, with your fingers, locate the two pre-existing slots on the underside of your bumper.
- Insert the bracket tabs into the bumper slots and gently pull the bracket up, and hold it snug against the bumper. Be sure the tabs are fully inserted into the slots.
- While holding the bracket in place, mark the bumper through the appropriate two holes.
- Release the bracket and carefully drill the bumper cover.
- Attach the bracket with suitable self-tapping screws.
You would then attach your license plate using the proper existing holes in the plastic bracket. But this gets tricky. On my M Sport bumper, the depth of the plate mounting holes is only 3/8″ before you hit the bumper. Yikes. If you’re not paying attention and use a 1″ sheet metal screw, you will bottom-out and damage your bumper.
So, as noted above, measure your total plate/frame mount thickness carefully and choose the proper length screws accordingly. Oh, and ALWAYS measure the depth of your bracket holes before you blindly attempt to screw on your plate.
Using Washers and Spacers
Proper synthetic washers between the screw head and plate (or frame) can help reduce rattling and prevent damage to paint and reflective license plate coatings.
Sizes are available for both machine screws and sheet metal screws. When using non-metal washers, be sure to choose a material like nylon, that can endure a reasonable temperature range.
Some rubber washers especially, are prone to rapid deterioration in hot and cold climates and can actually crumble and disintegrate within a couple of extreme seasons. Another nasty side effect of rubber washers is that over time they tend to discolor whatever they come in contact with. Nylon 6/6 washers are usually a good choice and come in a wide range of sizes, plus black or white color choice.
Don’t Over-Tighten License Plate Screws
Be careful not to over-tighten license plate screws. Especially the ones that attach the OEM plate bracket (if available) to the rear of your car. Doing so could cause the plastic nut inserts to pull out, necessitating a trip to the dealer for a fix.
Also, over-tightening the front bracket screws increases the risk of deforming your bumper cover or even stripping the holes (necessitating larger screws).
Screw Caps and Covers
License plate screw caps, covers and “hiders” come in a wide range of materials, designs, finishes and colors. They’re primarily intended to cover unattractive screw heads, so if you’re sporting some nice low-profile stainless socket head screws, you most likely won’t want to hide them with plastic caps.
European Screw Caps
Many European OEM factory “covers” are designed specifically for long narrow European style plates, and require special screws with unique head flanges that the covers snap over (see photo above right). Check your screw size and design before purchasing.
2-Piece Screw Caps
The most common license plate screw cover design is the 2-piece “snap-cap.” It consists of a cup-like base (washer), through which your screws are inserted. Once tightened, you simply snap the top cover (cap) in place over the base.
The tight fit between cap and base helps prevent corrosion and deter theft. Snap-caps are made from high-impact UV stabilized plastic and are suitable for extreme outdoor use (see photo below).
Hinged Screw Caps
Another popular design is the hinged caps which are commonly included with some high-end marque plates (see bottom-left photo below). In many cases, these hiders are actually necessary since many of these plates don’t have round screw holes; they’ve got rather large slots or square “holes”. The included covers would actually be required to hide the oversized holes (see photo below right).
What type and size screws do I need?
That depends on your car. As noted above, if it’s an American car, you’re probably looking for standard measure (not metric) hardware for both the front and rear plates.
Also, screws for American cars are typically self-threading (sheet metal) and are fastened to some sort of bracket or plastic anchor nut that snaps into the car body (sometimes called license plate nuts, license plate inserts, or push-in nuts). Keep in mind that the “metric” specification doesn’t mean much when it comes to sheet metal screws.
For imported cars, depending on your state’s front plate requirements, you may need a combination of both metric machine screws and self-threading screws. The former for the rear plate, and the latter for the front plate.
If you’re looking strictly for original equipment (OEM) replacement screws, the quickest way to identify them is to call the parts department of your car dealership. However, dealers are often reluctant to provide part numbers for fear the customer will buy someplace else.
If you’d rather not buy from a dealer, and don’t mind doing a bit of research, try one of the many online OEM parts suppliers. For example, the Real OEM BMW Parts Catalog is fairly easy to use and has a comprehensive database that generally returns accurate results with correct OEM part numbers (see photo below).
Find a thread checker.
If you’re looking for screws to replace the OEM screws, the you’ll have to look elsewhere. The most foolproof way to get replacement screws is to begin with an original equipment (OEM) part.
Take it to any hardware or building supply store (Ace, Lowe’s, OSH, Home Depot, etc) and get it sized using a “thread checker.” This is a collection of metric and standard bolts, nuts and screw holes mounted on a vertical board of some sort (see photo at right). If you can’t find a thread checker, ask a clerk.
If you don’t have an OEM screw to use as a guide and removing one of your existing screws isn’t practical, then finding the correct size may take a bit of investigative work. As noted above, you can try an online OEM parts supplier. Their part descriptions sometimes give enough detail to find a suitable replacement.
I’ve found online auto forums, Amazon and eBay to be helpful in this regard also, but be forewarned — The Internet is a swamp of misinformation and bad advice, so make sure you confirm any recommendations with alternate sources.
Stick with stainless steel.
Knowing the best fastener material is easy. Get stainless steel. Everything else is a waste of money and time. 316 stainless is preferable over 18-8, but not absolutely essential in most environments. Also, finding 316 stainless fasteners anywhere locally can be difficult.
Know your length.
As discussed earlier, determining the best screw length is mandatory. So, before buying anything, be sure to measure the thickness (depth) of your plate/frame configuration. And also note the distance between the back of your plate bracket (if there is one) and your car body/bumper.
Where can I buy license plate screws?
Now comes the legwork — Actually finding the screws that you need. You could easily spend your entire Saturday searching for the perfect 12mm stainless steel M5x0.8 button-head cap screws and wind up with $40 worth of junk (ask me how I know this).
The practical issue, of course, is that no hardware store or building supply could possibly carry every conceivable screw size; and then triple their inventory with metric and stainless steel varieties.
The photo above right illustrates this challenge. This fellow “wasn’t feeling” the stock license plate screws so he visited his local building supply emporium and bought the ones in the photo. He was so pleased with his purchase that he also installed them on his wife’s BMW. Unfortunately, those screws aren’t metric (they’re standard 10-32 machine screws) and they probably stripped the threaded inserts that they were forced into.
Another option is to try an online industrial supply company. The problem with this alternative is that, even if you found what you’re looking for, you may have to buy 200 screws to get the 8 you need. Not terribly efficient.
eBay and Amazon
Then of course, there’s eBay and Amazon. Both marketplaces have some great stuff, and both have a lot of junk. To weed through the crap, always look for the following information in the seller’s product description:
- What are the screws made of? “Rust proof metal” is not helpful. Look for specifics like “18/8 stainless.”
- What type of screws are they? Metric or standard? Machine or sheet metal?
- What is the exact size of the screws? This is a frequent problem. “Should fit most European cars” is not a size. “A little bit longer than the factory screws” is not a size. You’re looking for descriptions like #12 x 3/4″ long sheet metal screws (standard) or M6x1.0 x 16mm long machine screws (metric).
- What type of head/drive do the screws have? Phillips, Allen (Hex), Torx, whatever. And what size is the drive?
- If it’s a non-standard drive (not flat or Phillips screwdriver) does the vendor include the proper tool?
- Does the seller have an easy return policy in case the screws don’t fit.
“No Holes” Front License Plate Relocators
License plate “relocators” are primarily intended for folks who don’t want to drill holes into their front bumper. The most common alternate mounting style makes use of the existing front tow hook receptacle to attach a removable plate bracket. Other bracket designs allow you to drill holes underneath the bumper, or fasten the bracket to existing front grill-work.
Depending on how your vehicle is equipped, and the position of the relocated plate, keep a few things in mind:
- Relocated plates can block needed airflow into the engine compartment.
- Relocated plates can trigger proximity (parking) sensors in your front bumper, if your car is so equipped.
- Relocated plates may be more susceptible to automatic carwash damage.
- Relocated plates that use the tow hook receptacle can actually be easier to steal than conventionally mounted plates (just grab and twist).
License plate relocators are now available in dozens of designs, in a wide range of applications and prices. Some of the most popular suppliers are:
- Bavarian Auto
- Custom Performance Engineering (CPE)
- Go Mini Go
- Hide The Plate
- Perrin Performance
- Skene Design
- Turner Motorsport
- US Mill Works
Or, just do a Google search on “no holes license plate holder.”
Frequently Asked Questions
Q: Do I need a front license plate?
That depends on where you live. Currently 31 of the states in the U.S. require a front license plate. You should consult your specific state’s motor vehicle department for additional rules and regulations regarding plate display.
Q: What is rust?
Rust is another name for iron oxide, which occurs when iron or an alloy that contains iron, like steel, is exposed to oxygen and moisture for an extended period. Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an “oxide” and weakening the bonds of the metal itself. Only iron or alloys that contain iron can rust, but other metals can corrode in similar ways.
If salt is present, for example in seawater, salt spray or salted winter roads, the iron tends to rust more quickly, as a result of electrochemical reactions. Given sufficient time, oxygen, and water, any iron mass will eventually convert entirely to rust and disintegrate. Surface rust is flaky and crumbly, and it provides no protection to the underlying iron.
Q: What is type 316 stainless steel?
By far the most common stainless steel is type 304, most often referred to as simply “18/8” for its composition of 18% chromium and 8% nickel. While most 300 series stainless steels share this 18/8 mix, slight differences in chemical composition between the different grades of the 300 series make certain types more resistant than others to particular types of corrosion.
The second most common 300 series stainless steel is the 316 grade. In type 316 stainless, the chromium content is lowered from 18% to 16%, and the nickel content is raised to 10%. In addition, 2% molybdenum is added to the mixture. This change in the alloy ratio increases the resistance to corrosion. Type 316 is often referred to as “marine grade” stainless because of its frequent use in marine construction.
Q: Do I really need marine grade license plate hardware?
That depends. If you live in a warm, dry climate where it rarely rains or snows, and they never salt the roads, probably not. However, if you live near the coast, or in areas with frequent snowfall it might be a good choice.
Also, the use of 316 stainless can help eliminate the pitting and spotting that can occur with lesser grades of stainless such as 304 (18/8). And, you’ll never be surprised by the inability to remove a license plate that’s permanently rusted to your car.
Q: How can I be sure that my hardware is stainless steel?
Most 300 series stainless steel is not magnetic unless it has been “cold worked” (the strengthening of a metal by plastic deformation at room temperature). Obviously, it’s unlikely that your license plate screws have been cold worked, so they should not be magnetic. If you’ve safely ruled out aluminum (and exotic metals like titanium), and it’s not magnetic, it’s probably stainless steel.
Also, some stainless hardware is actually marked with a grade (A2, A4, etc) or other distinguishing mark, such as a tiny bump or indentation on the head. However, these methods are unreliable for 100% positive identification because they differ by manufacturer.
Q: How can I tell the difference between 304 (A2, 18/8) stainless steel and 316 (A4) “marine grade” stainless?
The 2% of molybdenum which is added to the basic 304 composition to turn it into 316, can only be reliably differentiated by chemical analysis or some similar technique. This addition is done to improve pitting resistance, important for stainlesses in wet corrosive environments which tends to result in crevice corrosion.
Q: What is Nylon 6/6?
Nylon is one of the most widely used engineering thermoplastics and offers an excellent combination of mechanical performance and cost. Of the many nylon grades available today, nylon 6/6 and nylon 6 are the most widely used. The properties of both types of nylon are very similar and can frequently be used interchangeably. Nylon 6/6 is frequently used when high mechanical strength, great rigidity, and good stability under heat are required.
Q: What does “OEM” mean?
The initials OEM mean Original Equipment Manufacturer. When referring to automotive parts, OEM designates a replacement part made by the manufacturer of the original part. It typically means that the part was made by a company that is a subcontractor to a vehicle manufacturer. It does NOT mean — and this is important — that the part was necessarily made by the vehicle manufacturer.
It is a common myth that only a vehicle dealership is “authorized” to sell OEM parts. Nonsense. Most, if not all, of the OEM parts you get from a dealership can also be purchased elsewhere for less money.
Many items at national auto parts retailers will have OEM prominently printed on the package, but followed by a qualifier such as “meets OEM standards.” These parts are not OEM — They are simply claiming to have been manufactured to the same specifications (whatever those are).
Also, when buying auto parts, remember that the label OEM does not necessarily make the part better; only “the same as” the original part that came with the car. Many aftermarket parts are actually better than the original part.
- BMW USA
- Real OEM BMW Parts Catalog
- Pro-Dec Products
- Turner Motorsport
- Wikipedia: Metric System / Stainless Steel / Nylon / Rust