The Best Instructions in Aero

Every Street Aero part ships with a written installation manual for the exact part you ordered, and all 80 of them are downloadable free before you spend a dollar. Seventy-five are vehicle-specific. If you want to read the instructions for your car before you buy, you can, right now, without asking us for anything.

That sounds like a low bar. It is not. Plenty of aftermarket aero arrives in a box with no paperwork at all, or with one generic sheet showing a diagram of a car that is not yours. We write a manual per application, because a front splitter for a 2016 Mustang does not mount the same way as one for a Civic, and pretending otherwise is how people end up drilling in the wrong place.

Browse the full manual library, sorted by product line and make, or read on for what makes them different and why our front splitters ship without pre-drilled holes.

What makes our instructions better

Four things, and they are all decisions that cost us time rather than clever writing.

  • One manual per application, not per category. 75 of our 80 manuals are written for a specific year, make, model and trim. When your car's bumper geometry differs from the car next to it, the document differs too.
  • They are public before purchase. Every manual is a free PDF on our site. We would rather you read the job and decide it is not for you than buy a part and discover that afterwards, especially on something final sale.
  • They tell you what the part does not include. Splitter rods and brackets are not in the box. The manual says so, up front, instead of letting you find out halfway under the car.
  • They cover the part you actually ordered. A splitter ordered with fins has a different manual from the same splitter without them, because the mounting sequence changes.

See for yourself

These are the general manuals for each product family. They cover the mounting method, tools, sequence, and what to check before you commit to a hole. Open the one for the part you are considering and you will know exactly what the job involves.

Looking for the manual for your specific car? All 75 vehicle-specific manuals are on the instruction manual page, organised by product line and then by make. Find your SKU and download the exact document that ships with your part.

Why our front splitters do not come with pre-drilled holes

This is the question we get most, usually phrased as though it were an oversight. It is the opposite. It is the single most deliberate decision in how we build front splitters, and once you understand what a splitter actually hangs from, it stops being a question.

A front splitter does not bolt to your bumper cover

It cannot. A bumper cover is a flexible plastic skin. Hang a rigid panel off the front of it at highway speed and the cover flexes, the fasteners work loose, and eventually something tears.

A front splitter has to be carried by structure. The bumper, undershroud and valence assembly has to be properly mounted to the chassis, and the splitter fastened into that assembly so the load ends up in the under-frame. Every one of our 118 front splitter applications carries the same requirements on its product page, because they are not negotiable:

  • Designed to fit the OEM undershroud
  • The bumper, undershroud and valence must be mounted to the chassis to support the splitter's weight
  • The assembled front splitter and bumper must be bolted to the under-frame
  • Use brackets (not included) if your bumper is not bolted to the under-frame
  • Mount as close to the front of the bumper as possible
  • If the OEM undershroud has been removed, additional mounting may be required
  • Removing splash guards is recommended for better fitment
  • Splitter rods (not included) are recommended for high-speed use

And no two undershrouds are the same

The undershroud, or undertray, is the panel closing off the underside of the front bumper area. It is where most of your mounting happens, and it is the single most variable part of the front of a car.

Across the cars we build for, we see all of this:

  • Different shapes on the same model. Trim levels and appearance packages change the undershroud, so two cars of the same year can have different panels with fasteners in different places.
  • Cars that never had one. Some models simply do not come with a full undertray from the factory.
  • Cars that had one and lost it. Undershrouds are the first thing destroyed by a speed bump or a curb, and plenty of used cars are running without one, or with a replacement that is not the original shape.
  • Cars where somebody removed it on purpose. Track cars, project cars, anything that has had the bumper off more than once.
  • Cars with an aftermarket bumper or lip. Now the whole mounting surface is different from anything the factory ever built.

A pre-drilled hole is a permanent guess

Here is what happens if we drill the holes at the shop. We would be picking one specific configuration, one undershroud in factory condition with everything where the drawing says it should be, and stamping that assumption into the panel forever.

For the customer whose car matches exactly, it saves ten minutes. For everyone else, the holes land somewhere that is not structure. And you cannot un-drill a panel. The best case is a hole in the wrong place that you work around. The worst case is a splitter mounted into flexible plastic that lets go on the freeway.

So we leave the panel solid and tell you how to find your own mounting points. You test fit the complete splitter on your car, in your car's condition, confirm the position, mark where the structure actually is, and drill there. It takes longer. It is right for every car instead of one of them.

That is also why the instructions matter more to us than a hole pattern would. A hole pattern is a guess we make on your behalf. Instructions are how you get it right on the car you actually own.

What every manual covers

  • What is in the box, so you can confirm the shipment is complete before starting
  • Tools you need. For most parts that is a drill, a screwdriver, a 1/4 inch wrench, a 10 mm wrench, and a properly rated jack with stands
  • How to test fit before anything permanent happens
  • Where to mount, and how to tell whether what you are drilling into will actually hold
  • Fastener sequence, so the panel ends up straight instead of pulled to one side
  • What to check afterwards, including retorquing after the first few drives

Common questions

Do Street Aero parts come with instructions?

Yes. Every part ships with the installation guide for that application, and the same document is downloadable free from our manual library. You can read it before you order.

Why are there no pre-drilled holes in the front splitter?

Because a front splitter mounts into the undershroud and bumper structure, and that structure differs from car to car. Trim levels change it, some cars never had a full undertray, and plenty of used cars are missing theirs or running a replacement. A pre-drilled hole would be correct for one configuration and permanently wrong for the rest. Leaving the panel solid means you drill into whatever your car actually has.

Can I install a front splitter if my undershroud is missing or damaged?

Often yes, but expect additional mounting work. Our splitters are designed around the OEM undershroud, so if yours has been removed or replaced you will likely need brackets to get the load into the under-frame properly. Brackets are not included. Email us photos of your underside before ordering and we will tell you what you are looking at.

Do I need splitter rods?

They are not included and they are not a substitute for mounting the splitter to the under-frame correctly. They are recommended for high-speed use as additional support. If the car sees track time or sustained highway speed, add them. Do the primary mounting properly either way.

Do I have to remove my splash guards?

It is recommended on most applications because it gives a cleaner fit, but splash guard designs vary. Test fit with them in place first and see how it sits before removing anything.

Can I install this myself, or do I need a shop?

Plenty of owners do it at home with the tools listed above and an afternoon. Professional installation is recommended if you are not comfortable lifting the car, drilling, or judging whether a mounting point is solid. Read the manual for your part first and decide honestly.

My manual is not in the library. What now?

Use the general manual for that product family as a reference, then email info@streetaero.com with your SKU or order number and we will send the specific document.

Before you start

Three things worth saying plainly. Installation involves drilling, on front splitters, side splitters and most rear diffusers. We do not describe our parts as bolt-on, because they are not. Aero sits lower than the bodywork it mounts to, so you will be planning for driveways and parking stops afterwards. And test fit everything before you drill anything, because that is the step that separates a part that looks factory from one that looks like it was fought onto the car.

Ready to order? Browse front splitters, side splitters, rear diffusers or a complete full kit. Or read every manual first on the instruction manual page.