Wheel Gun & Wheel Nut


Formula 1 Wheel nut

Throughout Formula 1 pitstop history they’ve always played a direct role in the outcome of races and as such, the speed with which they’re completed is crucial.
1984 refueling was banned after few fires during the pitstop. That was not a surprise because teams try to shove as much fuel into their cars as quickly as possible. And back then it was often a form of highly volatile fuel mix, making it perilously dangerous. This brought the focus away from pitstops and into the ability to conserve fuel and tires during a race.

ichael Schumacher Ferrari pitstop in Sepang 2006

In an effort to spice up the show after a ten year break, 1994 saw the reintroduction of mid-race refueling. Teams very quickly began to look at ways of speeding up their stops once more. Although everyone had to use the same refueling rig, pumping at the same rate of maximum 12 liters per second, the same hose, nozzle and valve in the side of the car, teams tried simple ways to make the operation ultimately faster. Perhaps the most infamous example was the Benetton pitstop fire of the same season. Investigation uncovered that the team had removed a filter in the standard fuel rig, designed to restrict the flow rate of fuel from rig to the car fuel cell. The increased flow rate would mean the required amount of fuel could be pumped into the car faster than their rivals and of course reduce the time spent in pitlane.

Sauber pitstop Infogram, 2013

With refueling gone once more, pitstops became all about replacing four wheels and tires as fast as possible. Before there was no desperate need to change tires in 3 or less seconds when refueling would take at least another 4, 5 or 6. In days gone by, it wasn’t an uncommon occurrence to see wheel nuts spinning off down pitlane during pitstops or pitstop practice as they popped out of the wheel gun when the wheel was removed. Of course it was hardly ever an issue as a spare nut, always on hand, could be picked up and fitted long before the fuel man had finished his part of the job.

Tightening the wheel nut with hammer

Mechanics of the 50’s and 60’s have to use a hammer to tight a wheel to the wheel hub. Thankfully Formula One’s moved on in every area and tire change technology are no exception. Today’s (2014) world record breaking stops to change four wheels in under 2.5 seconds are impressive to say the least, but they’re the culmination of years and years of development, learning, and improvements in technology.

Force India Formula 1 team wheel nutWheel nut may not be the most glamorous part of a Formula One car, but it still needs to be engineered perfectly if costly pit-stop errors are to be avoided. Like the majority of a Formula One car's parts, the manufacturing of the wheel nut became a particularly scientific process. Wheel nuts are unrecognizable compared to just a few years ago. New ones don't tend to look like wheel nuts at all. They've got all these special sockets and odd-looking fins on them, and are supposed to be more efficient for pit stops.

Precisely machined pockets in the wheel nuts ensure the wheel gun positively and fast connects with the nut so that the torque can be transferred reliably to tighten the nut.
Each wheel seats precisely on drive pins on the axle. They are positioned in such way to make the wheel fit at first time, without need to be wiggled on the hub.
Renault F1 R29 and R30 wheel nut
Williams Formula 1 team wheel nut
Williams Formula 1 team 2013 wheel nut, upper image (click on image for bigger resolution), and on the right, two wheel nuts from R29 and R30 Renault Formula 1 car. Advances are visible.

Ferrari wheel nut locking mechanismFIA rules demand the nut is retained on the axle by a locking mechanism. This used to be a plunger that when pulled by the mechanic extended retaining pins from the axle. Today nut retention is a spring activated system which does not demand any action by mechanic. On the picture right you can see Ferrari locking system. The wheel gun socket pushes the pins into the axle to allow the nut to be removed. When refitted the nut passes over the pins and they spring out when the nut is nearly fully seated and gun removed. With this system, it's not until the wheel gun socket is pulled from the axle that the mechanic can visually confirm the nut is on and the retention mechanism is in place. Often we see mechanics signal their job is done and then frantically wave amid the realization that the nut is not in fact fitted correctly.

Ferrari three thread wheel nut

Ferrari has gone first down the route of less threads of engagement for the wheel nut on the shaft, meaning less rotations of the nut meaning less time lost. They are using only 3 threads. Today stub axles on the every car have from 5 to as little as 3 threads, to minimize the number of revolutions it has to do in tightening or releasing the wheel.

Formula 1 axel tip is roundedAxle tip is rounded to guide the wheel into place. On the picture left you can see rounded axle tip painted red and wheel nut fitted on it.

Ferrari and Mercedes have first adopted a "nut on wheel" solution which means the nut floats within the rim itself, a loose fit inside the wheel. This means that the nut is partially located on the axle as the wheel is slided on the it. This saves time for the tire removers/fitters and gun man as there is physically one less job to do.

Nut on wheel in Formula 1

Wheel nutWheel nuts themselves are retained within the rims with "O" rings or circlips to reduce the opportunity for cross threading and take away the possibility of one falling out of the wheel gun socket. These expensive spline drive type wheel nuts are normally used just once. Like the stub axles, drive pegs on the car’s uprights and the wheels themselves are designed to guide them seamlessly together and avoid ‘pegging’, where the two butt up against each other and fail to engage.


Mercedes AMG F1 team wheel nutBiggest enemy of the wheel nut is the pneumatic air gun used at pit stops. The gun will often bend a nut out of shape or destroy the fins, rendering it useless. On the right picture you can see used Mercedes AMG W02 wheel nut (click for bigger resolution).
Until 2012, helium was used to drive the wheel guns during pitstops. Using helium to power wheel guns is one of a million technical exercises you’ll find only in Formula One. Like mercury-filled inerters or $20,000 per piece rotary dampers, they are a way to shave another few milliseconds between start and the checkered flag. What helium does is make the wheel guns rotate faster due to its extremely low density, which translates into a faster wheel change, which translates into a faster pitstop, which translates into a faster race.

Formula 1 wheel gunFormula One’s wheel guns with a high flow and hammer effect are quite amazing pieces of highly specialized machinery. Made by the "Dino Paoli" company in Italy, they produce over 3,000 Newton-meter of torque. "Dino Paoli" supplies almost all teams, but I believe that McLaren and Ferrari develop their own guns. Wheel gun men now use custom made guns, customized by the team or by "Paoli". ‘High flow’ gun allow greater air flow through the gun itself and effectively spin the socket faster, around 9000 rpm.

Dino Paoli, Italy

Wheel gun in Formula 1Each corner of the car gets two wheel guns, with the second there in case the first one fails.  Although problems such as faulty guns are rehearsed by the pit crew, everyone focuses on their own job. In a two-second pitstop, there is no time to see what everyone else is doing. Guns will have bespoke grips, with abrasive paper or grippy silicone. Strong hands are needed to operate these beasts.

Formula 1 wheel gun inserts - sockets Formula 1 wheel gun socket
Formula 1 wheel gun socket
Front wiew of wheel nut socket

The guns of today have bespoke sockets to match the team’s own nut designs, lights to indicate to the mechanic when the nut’s done up to the correct torque and buttons to signify to the jack man that the operation’s complete. Before the recent focus on pitstop speed, gun men would give a sign when they were done by raising a hand in the air and when the jack men saw the two hands at their end of the car, car would be lowered back onto the floor. When the chief mechanic saw four hands and both jacks out of the way, he would release the car. Now, the action of raising a hand 50cm in the air is considered to take too long, so a button is fitted on the wheel gun. The flick of a switch or button on the side of the gun shaves off valuable hundredths. That’s how thoroughly things are analyzed. A raised hand is still in use as the back-up to this electronic method. Always mechanic first flip the switch and then rise the hand.
Gun is also fitted with a torque sensor. This sensor will record what the tightening torque was. This information can be reviewed later if needed. As the rules currently stand, this sensor cannot be used in real time to confirm to the pit crew that the correct torque was achieved.

Dino Paoli wheel gun conected to the laptop

Paoli wheel gun
"Dino Paoli" wheel gun, model DP4000MG with Palindrome Sport "NUGUN Back" fitted

The gun is quickly reversible. To change direction of rotation, gun has a switch on the back side, and you can see during the pitstop that mechanic hit his chest with the back side of the gun or a giving a firm punch with the palm of the hand after removing used tire (clockwise rotation). This action change position of the switch and with this direction of rotation, to prepare a gun to fit new tire (counter clockwise rotation of the gun).
One of the very latest developments in wheel gun technology is an automatic direction change. Rhodri Griffiths of Palindrome Sports, the man credited with most advances in F1 wheel gun technology, has devised a new system, the NUGUN quickShift, which switches direction automatically as the gun is removed from the first wheel. This is actually auto-reverse gun back side only, to suit Paoli's high-performance wheel gun range.

NOGUN back by Palindrome Sports NOGUN Quick Shift by Palindrome Sports
NOGUN back is reversing button to fit on the back of the Paoli wheel gun, enabling the user to reverse the gun rotation quicker than the standard manufacturer's shuttle. The gun back is designed to enable quicker direction change by the user, or to automatic change direction in the event that it is placed on the ground during a pitstop – for example in a one-man-one-wheel scenario. The NUGUN Gun Back is currently available for the "Paoli" 2000 and 2000-S, 3000 and 4000 models, the most widely used wheel guns in top-level motorsport. NUGUN is a proven product, as used by teams in Formula One, IndyCar, GP2, World Series by Renault, A1GP, ALMS and Le Mans Series.
NOGUN quickShift is an auto-reverse gun back to suit Paoli's high-performance wheel gun range. The quickShift features an operator-controlled auto-reverse shuttle. The shuttle direction is pre-set by the operator, from either the top or bottom of the gun back, which provides a safe, secure shuttle position. This gun back has proven to be an operator-friendly, reliable solution to enhance the consistency, security and overall speed of wheel gun direction-change during the pit stop This gun back has proven to be an operator-friendly, reliable solution to enhance the consistency, security and overall speed of wheel gun direction-change during the pit stop.


Wheel nut after use


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Books to read

Some useful links:

- f1technical.net, a great site with a lot of technical information’s and explanations. Site is updated daily with news from F1 word.

 - autosport.com, This site is a legend. A bible for racing lovers. News from all around the word. Unfortunately, to get access to all news, interviews and to open the site completely you should be subscribed to Autosport magazine. Anyway, great read.

James Allen on F1
- JA.F1 site (or blog) ovned by ITV Sport’s lead commentator on Formula 1 James Allen

Joe Saward blog
- joesaward is the Joe Saward official blog about Formula 1 world. Joe is an journalist, who write primarily about politics in and around motorsport, specifically on the FIA Formula 1 World Championship

Vital F1
 - vitalf1.com/ is another great site for Motor Sports fan’s like me. Site is relatively new, but great fun, with great discussion forum, Formula 1 news and forum.

 GP update
- f1.gpupdate.net, Site with fresh news from Formula 1

Planet F1
 - planetf1, another site with many different articles, news and statistics. Biased toward British teams, but anyway good read.

Gurney flap
 - gurneyflap.com, Great history site. You can learn a lot from this site. Pictures, cars and many many more. Great.

4ormula1 is a database of Formula 1 history and statistics of drivers, teams, grand prix, and all results since 1950

Racecar engineering
-Racecar Engineering, an online magazine with a lot to learn from, a lot of technical information’s and explanations

 - fia.com, La Fédération Internationale de l'Automobile, representing the interests of motoring organisations and motor car users. Head organisation and ruler in auto sport.

 - wikipedia.org, I don’t believe that I have to tell you anything about this site. It’s not about Formula 1 technology, but you can learn a lot about that too.

Sutton Images

grandprix photo

 - carbibles.com, a great site for normal car users. Here you can find explanations of almost everything about your car and how it works. Technical reviews and explanations of some in-car gadgets.

Dare To Be Different
- Daretobedifferent.org Susie Wolff and UK governing body of UK motorsport have joined forces to launch Dare To Be Different, a high-profile new initiative which is about increasing female participation, not just on the track but in all aspects of the sport.