Going to post some pics of our times we got VIP passes to the various NASCAR races.  On this page I'll post some pics of how they do various tech checks and try to explain what you are seeing.

A quick overview of the Technical Inspection Process:
TEMPLATES - Aluminum templates are fitted over the race vehicle to measure the aerodynamic profile.  A collection of 19 templates are welded together - called "the Claw" - are lowered onto the surface of the vehicle to assure they are all the same.  There are also separate templates that fit the nose, tail section, fenders, etc that are also tested for fit.
SCALES - Each car is rolled onto the scales in race ready condition. This includes gas, oil, and all other fluids in place. The car must weigh 3400 pounds including the driver.  Vehicles are also measured for 'cross weight'.  The right side of the car must weigh at least 1625 pounds.
This rule prevents cars from having too much weight on the left side of the car. Because NASCAR races are with left-hand turns, drivers would want to have more weight on the left side of the car to aid in turning. The right-side rule limits this advantage. Cars are weighed by NASCAR officials before each weekend's race events begin, beginning with a pre-practice weigh-in. Another weigh-in is conducted before qualification, and a third before the actual race. All weigh-ins are performed on NASCAR's official scales.
- The laser platform was introduced in 2013 and is NASCAR's biggest technological leap. about 60 points on the car; such as front and rear wheel cambers, wheel base, and rear axle location are measured. Measurements must be as precise as 1/1,000th of an inch.
Failing ANY of the steps in the inspection process will cause a competitors vehicle to have to go back to the rear of the inspection line and start the inspection process over again after adjustments are made.  Cars may also be fined or points penalties assessed for continued violations, or more sever tech violations.

Basic Specification for a NASCAR CUP car as of 2014.
CHASSIS - steel tube frame with safety roll cage meeting NASCAR requirements
ENGINE - 8560 CC (5.86 L; 357cu in) push rod V8
TRANSMISSION - manual 4 speed
 WEIGHT - 3400 pound minimum including driver in race ready condition
POWER OUTPUT - 865 horse power
FUEL - 98 octane E15 Sunoco race fuel
FUEL CAPACITY - 17.75 US Gallons
FUEL DELIVERY - Port Fuel Injection
ASPIRATION - Naturally aspirated
WHEELBASE - 110 inches
STEERING - power
TIRES - GoodYear 11.5 inch wide racing slicks  - approximate cost of $1,900 per tire.
LENGTH - 208 inches
HEIGHT - 53.5 inches
WIDTH - 76.5 inches

All Photos copyright and are property of their respective owners

As you know the CUP series uses a full body length template they call 'the claw' that fits the entire car at ones.

Here is the template that fits the hood, you'll notice it is fitted for every contour of the hood, and even as it rolls off onto the fenders

They have these templates to check for proper curve of the windshields from side to side.  Check out the 'arm' that sticks up from the template and goes up to the top of the window

Here a crew member takes the cover off of the wheel so they NASCAR Gauge can measure various stages of wheelbase, width, etc

Here is a close-up of the gauge.    You can see the green and red "go / no-go" allowances.  Green and yellow is OK, Red says it fails inspection and has to be changed.  Usually tech inspection station checks two or three different things

They inspect the cars ride height at various points at this station.  You can see the red box I added has the height gauge for the rear of the car.

Here is a better look at the height sticks.  CUP does not check height any more, But Nationwide and Trucks still do. You can see in the rear it sets on top of the spoiler (not the tabs on top)

Here is where the roof height is measured.  The car rolls under the gauge which hangs down (see red arrow).  Like the other gauges it has the go / no-go indicators.

I have to find out what this measures.  There is a hole in the side of the body, and this rod goes in and hits something...  I'll find out and post this then.

 I'll OK - I FOUND OUT - Actually they also changed the process. Here you see some disc attached to the cars wheels. Also you see two pins attached to the same place as in the pic above.  This is NASCAR's new lazer tech scanner.  It measure many different items, and it 'reads' these plates to get the squareness, width, etc etc.

Wish I had a video of this thing in action. Teams just roll the cars up on the pads, and it moves itself to align with all the lasers so it can check the cars the same every time. Pretty cool piece of technology.

Each car comes with a Technical Inspection sheet.  The inspector checks off things that meets requirements, and notes things that need fixed. Contrary to popular belief much of the technical / safety inspection is done in the cars garage stall.  For many of the items, the inspectors come to the race car and inspect such things as safety belt and seat mounting, roll padding, etc.. a very extensive list.

You all have probably saw these on TV - Just thought I explain what they are (things under the wheels). Basically it's a device to have to keep from jacking up the car over and over. Half of the pad is static.  When teams work on the car the roll it onto the static part; make any adjustments, and then roll it back onto the other part.  THAT part is a set of scales. SO they can weigh the car and see how they can maximize things like left side weight, etc. 

This isn't tech, but interesting anyway. This is the set up for the in-car camera system.  On the lower left you'll see the battery supply; in the center of the picture is a set up much like you'd find on the back of your TV set.  You can see the RCA jacks and connections. 

The fuel tanks are inspected also.  This is where the fuel line connects from the fuel filler.  The yellow arrow points to the "check Valve".  You'll see a large stainless steel ball there in the bottom, if the car flips over the ball rolls up to the top, and prevents fuel from spilling out to help prevent a fire.

This is a new inspection item named "the Claw". It sits down over the top of the car, and tests the car all as one unit.  This puts even tighter restrictions on the teams to keep the bodies all the same. Additional templates can be attached so all readings are taken 100% the same.

These are the new style dump cans used to fuel the car.  You can see the clear hose that the fuel backs up into when the car is full.

The Good Year "tire busters" sure earn their money on a race weekend. these guys will remove and mount about 10 sets of tires for each race team. Counting the CUP and Nationwide series they mount tires for about 100 teams.  That's 1000 tires. FYI they tires are not filled with air.  Nitrogen is used to fill the tires because it does not expand when it heats up as much as air does.

Tech inspection (looks like Daytona) Doesn't look like there is any rhyme or reason to who goes next

Here in the Nationwide series they have separate templates.   These two pics show the templates to fit the nose, and rear end.

This is the full length template that runs from the front to rear of the car.  Tolerances are strictly enforced

You'll see the templates have a gauge that makes sure the measure is taken at the exact same place on every car.  It fits right up against the top of the window opening

This checks for overall wheelbase length.  It is attached to a specific place on the rear axle and the reading is taken here on the front axle.

This measures the width of the front wheelbase.  On the opposite side is a stationary rod positioned at exactly the same place as this one. (on the wheel lip).  There is a go / no-go indicator where the arrow I added is

Here you can see the height sticks used to check the front.  You'll see the hood is open so if it needs to be adjusted they can access the jacking bolts

Here is a close up of a height stick.  If you look close you'll see this car fails. The indicator sits JUST in the yellow (you can see all the green). So they'll have to lower the rear of this car..

Here are some of the templates I showed before.  They are color coded, one color for Chevy templates, another for Ford, etc.

This is a newest addition to NASCAR Inspection.  With the laser inspection all the race car chassis have RFID Chips attached, and NASCAR can track all of the cars.  This is also the system mentioned above that checks 60 different spots on the car.

Here you can see the wheel disc again.  They mount over the lugs.  You'll also see there is a bar that hangs down off the center of the disc.  This moves and lines up by gravity. I THINK it checks camber.  ON the picture on the left you'll see two rods inserted into the body with a white disc on the end; this is also parts of checking frame width, etc 

Here is another view of the laser inspection area. Here you can clearly see the wheel disc and also the rods inserted into the car body.

Here is a good look at the inspection sheet the NASCAR officials come by and check out. They either mark an "OK" or note what needs fixed. As you can see there are a TON of things they check

The template sitting in the left side of the picture is the template that fits the nose of the car.  It attaches after the Claw is sat down on the car. NASCAR has went back more to cars looking at show room cars, so each brand of car has a separate template.

In the picture on the left you'll also see a gray cable (with yellow tape) coming from the Video box, attached to the roll bar.  IN this pic you'll see as the gray cable continues on the roll bar; goes up vertically, then loops around and attaches to the camera. (black box mounted on roll bar)

This is "old school".  As you can see even way back "in the day" GoodYear supplied tires to NASCAR

This looks to be 1970 when they had severe tire problems in practice.  The 'big name' driver boycotted the race, but in the race no one had tire issues.  Here is one of the blistered tires.

Darel Dieringer has his 1967 Ford cross the scales. Just noticed as I posted these that they are both the same car make.

Templates for checking the cars aerodynamic shape are nothing new. Here AJ Foyt has his car go threw the inspection process.

More organized modern tech line