Rollcage

Rollcage building

This is a major undertaking and will require careful attention to get it right. First step is to check the rule book, but basically if you follow the FIA rules you will pass with any organization. Try to get in contact early with the scrutineer of the sanctioning body that will inspect your cage and issue a logbook so that your design choices can be valdated along the way.

You can try to do the cage yourself if you have a bender, tube notcher and appropriate welder and skills. It is usually cheaper, faster and safer to let a professional do the work, there is still plenty to do on the car besides the cage. The cost of a cage will vary depending on the complexity of the cage and how much stripping of the car you did (prices range from ~1000$ to 6k+$). Don't expect to go with a cheap bolt on cage, you need a welded in cage. Seam welding the chassis could also be a good option.

The cheapest option is to entirely strip the car yourself (remove all the interior parts, dashboard, wiring, etc... anything that is in the way of building the cage) which also sometimes require removing the front windshield and/or the roof of the car.

Come up with a detailed plan of what you want for a rollcage, provide pictures from existing builds and a copy of the rules to your builder to show exactly what you want. Here are a few examples::

- Corvette rollcage design document (note this is a road racing cage, not compliant for rallying): https://drive.google.com/file/d/0BzRipEXLp5msbG13SUxJdFFmODg/edit?usp=sharing
- Subaru rollcage design example from http://www.hotrodjim.com/service_roll_cage.php (note that the sketch below does not show the required gussets)
- Audi RS4 rollcage design document: https://tinyurl.com/33m7y29u

Once you have come up with a design, consult with the scrutineer who is going to issue the logbook to make sure he is ok with the design. Keep him updated during the build process too so that he can spot any issue before it is too late to fix them.

You can also check the North America Rally Cage Builder Map to find a fabricator near you: https://www.google.com/maps/d/viewer?mid=zP97LPvuElJ4.k55vLkhn6mps&hl=en_US

There are a number of factors to consider when building a cage like weight, clearances with occupants, ease of egress, reinforcement based on original chassis stiffness, etc... Here is an excellent video showing tradeoffs and analysis of the deformation of the cage:

The rules

Reminder this page is about stage rally rollcages, the rules describes here are for competing in North American rallies sanctioned by ARA, CARS or NASA Rallysport (not NASA road racing).

If you are building a new cage the rules have to comply to FIA Appendix J article 253 (the latest version can be found at https://www.fia.com/regulation/category/123. The older version of the rules that included all the schematics in one place is here: http://www.fia.com/sites/default/files/regulation/file/253%20(2015).pdf

The current FIA article 253 (https://www.fia.com/sites/default/files/253_2024_wmsc_2024.02.28_pj.pdf) only refers to FIA homologated cages for new builds and the requirements are specific to each FIA class. For building a cage in North America, use FIA Appendix J article 253-8 2020: https://www.fia.com/sites/default/files/253_2020_chap_8_wmsc_2020.10.09.pdf

If you are buying an already caged car, make sure it passes the minimum requirements (aka grandfathering rules) of the sanctioning body you plan to compete with. Our Scrutineering rules page has the grandfathering rules for all the sanctioning bodies in North America that are currently organizing stage rallies.

Typically rollcages are made of DOM tubing of size 1.75x0.095” for the main elements and as small as 1.5” x 0.095” tubing for optional elements. ARA also allows Docol R8 and FIA homologated cages might be made out of T45. If you want to build a cage that will allow you to also do some road racing or enter some hillclimb series, you might need thicker tubing like 1.75x0.120" depending on the weight of the car. Always check the latest rules of the sanctioning body you are planning to compete with to see what the current requirements are. See the Tubing material section below for more information.

Road racing vs Stage rally rollcages

If you want to use your car for both stage rally and road racing, you will have to check the rules of your road racing sanctioning body. While a rally cage design will usually be accepted for road racing, the tube sizing in road racing depends on the weight of the car. For example below are SCCA road racing cage size requirements based on the weight of the car (production based and GT cars require 1.75x.120 tubing for weights above 4000lbs) but SCCA time trials requirements are in line with rally requirements. While stage rally allows the diagonals in the main hoop to be of a smaller diameter like all optional bars (1.5x0.095), those bars might be required to be the same size and wall thickness as the rest of the cage for road racing. The rules also change over time so make sure you check the latest rules of the sanctioning bodies you are planning to race with.

Tubing material

The FIA requires Cold drawn seamless unalloyed carbon steel (CDS) tubing for rollcage construction (see table below for specs). they also specify 'In selecting the steel, attention must be paid to obtaining good elongation properties and adequate weldability'.

T45 is a very common material used in FIA homologated cages, it is easier to weld than chromoly that requires precise heat control. Note that homologated cages need to be welded by a certified welder in order to validate the homologation paperwork.

Most North American sanctioning bodies allow the use of DOM tubing (see specs below) and more recently Docol R8 that is starting to become more popular as thinner and lighter tubing than DOM can be used. The ARA rules and specs of DOM and Docol R8 are given below

Tube thickness will be checked when the logbook is issued either using an ultrasonic gauge or by drilling a hole and measuring the thickness with a caliper as shown in the video below.

Tube bending

Cage tubing can only be bent using a cold process. Some benders tend to stretch and ovalize the tubing at the bend. The rule is that the diameter of the thinner part of the bend has to be at least 90% of the size of the tubing. If you are using a 1.5" tubing, the diameter of the tube in the bend must be 1.5*0.9=1.35", similarly an 1-3/4" tubing must be at least 1.75*0.9=1.575" tubing.

The tube in the picture has a minor diameter that is 94% of the major diameter and is therefore within spec.

The rules are pretty specific if bends are allowed or how many bends are allowed for the different elements of the cage.

For example: 'The near-vertical part of the main rollbar (or the rear pillar of the lateral rollbar) must be as close as possible to the inner side panels of the bodyshell and must have no more than one bend'. If you look at the picture of the main rollbar below, the bend at number 2 in red is not allowed, you can only have 1 bend in the vertical part (like the 1 in yellow).
While the rules say to follow the diagrams, it does not explicitely say that you cannot have a bend on the rear 253-22 bars like in the picture below. Note that in case of an impact in the center of the main hoop or at the front of the windshied, the rear bars would likely bend or shear at the weld. The minimum would be to add a gusset as represented by the red triangle but ideally those bars should be straight without any bend.

Tube junctions

The FIA sets 100mm (3.94") as the maximum distance between bars at a junction. Having all bars joined together at a node properly transfers the forces instead of acting as a lever on the bar they are connected to. You can see the footage of the crash test in the tutorial video at the top of this page.

Welding

Check every weld for completion with an inspection camera (aka boroscope), you can also find very inexpensive versions on Amazon that will connect to your phone. I recommend you inspect welds especially in the roof and hard to weld areas like near the foot at the bottom of the A pillar.

You will see below a collection of welds or tube fitment that are subpar at best. This is your safety, make sure the build quality is acceptable. Once again a logbook does not guarantee anything as unfortunately not all inspectors take the time to verify all the welds and FIA homologations are only based on a few samples and pictures.

Depending on the material you are welding, make sure you control your temperatures and perform any post-treatment necessary to ensure the robustness of the welds and avoid the brittleness of the tubes.

Typical cage design for a new build

Base structure

The base structure of the cage has to follow one of the 3 basic structure designs with 253-3 usually being the preferred design (see picture below). The cage is fixed to the chassis to 6 mounting feet, a main rollbar, a main rollbar (in red), 2 lateral half-rollbars (in blue), a transverse member over the windshield (in yellow) and 2 backstays (in green).

Main rollbar constraints

The design of the main rollbar has to be as straights as possible but it can lean up to 10 degrees of the vertical in any direction. 'The near-vertical part of the main rollbar (or the rear pillar of the lateral rollbar) must be as close as possible to the inner side panels of the bodyshell and must have no more than one bend'.

If you look at the picture of this main rollbar, the bend at number 2 in red is not allowed, you can only have 1 bend in the vertical part (like the 1 in yellow).

Rear backstay

The backstays have to be at angle of at least 30 degrees, if they are too vertical they won't be able to push back forces that would be applied in case of a frontal impact.

Support diagonals

The next step are the diagonals in the main rollbar which are mandatory for all new builds and most grandfathering rules, The FIA regulation is confusing because the rules are also provided for series that don't use a codriver. The mandatory 253-20 bar is mandatory if you don't have a codriver but for stage rally with a codriver you will need either 253-21 or 253-22 which will pair with roof bar designs 253-12 and 253-14 respectively. See in the next section why we think no one should build a cage with a 253-13 design.

Single or no diagonal in the main hoop

The lack of a diagonal in the main hoop will cause the main rollbar to bend and collapse as shown on these pictures. On modern constructions, it is mandatory to have a 253-7 diagonal support. The old style V brace does not offer any support either for impacts to the upper corners of the main rollbar.

Roof bars

Why you should not consider 253-13

The 253-13 roof bar design does not offer any support in the front roof corners where impacts are most like to happen in case of a rollover or impact with a leaning tree. Here is an example of an incident at a US event (100 Acre Woods) where a relatively low speed impact with a tree caused the cage to collapse. Despite the windshield support bar, the lack of a roof bar in the corner to counteract the forces applied to that corner of the cage compromises the cage integrity immediately. Also note that in this case, the front lateral was not gusseted to the A pillar.

We think that this roof design should be banned and if you buy an already caged car with that design, think about upgrading it with a 253-12 or 253-14 design (see also our Buying a used rally car page).

253-14 roof bars without 253-22 rear bars

As it was always mentioned in the FIA rules, the 253-14 roof bars have always required the 253-22 rear bats so that the forces can be transferred to the rear mounting points. There are unfortunately a number of cars that have been logbooked without the mandatory 253-22 rear bars.

As illustrated below the lack of rear bars mean that any forces applied to the roof bar will be transferred to the center of the main hoop. This in turn will pull the corners of the lateral towards the occupants collapsing the cage down on the occupant. This will be even more problematic if the main hoop does have diagonals or just lower half bars (like the bars in green in the drawing below)

Single roof diagonal

Another problem with an asymmetric design is that the cage is going to collapse only on one side as in this famous crash with Peter Solberg in Germany. The original cage only had 1 bar in the roof and no diagonal support in the main hoop causing the cage to collapse on the codriver side.

Doorbars

The door bars must be at least two bars and the design must be the same for driver and codriver, no asymmetrical design like for road racing. Some sanctioning bodies have a mandatory requirement for the sill bar (the bar in red in the 253-9 drawing below:

When using 2 bend bars, they cannot be separated by more than the diameter of the biggest of the 2 bars. There is a minimum distance of 300mm in the front and 200mm in the rear of the gusset edge joining the 2 bars.

If the bars have a single bend, the total length of the gussets must be between 8 and 13 times the diameter of the biggest tube (see drawings below). If the edge of the gusset is curved, the curvature cannot exceed 1/8th of the length of the gusset.

If the bars have 2 bends, the length of the gusset must be at least 0.3x of the width between the front lateral foot and the main rollbar foot. Check the diagram below for the constraints on the dimensions of the gusset (also extra constraints if the edge is curved).

Sill bars

You can see in the crash video analysis here how the sill bars have helped to maintain the structure of the cage and limit intrusion in the cockpit. The video also discuss some other optional bars and how the factory dash bar might need to be upgraded if you consider an impact to the steering column.

On the side impact pictures below, you can see that the floor crumpled without the sill bar.

Another side effect of a missing sill bar car be the separation of the floor as illustrated in the picture below:

253-15 Windshield reinforcement bar

The windshield reinforcement bar is now mandatory in all cases for ARA, for most cars it is required anyway, Just make sure the bottom of the bar is less than 100mm from the foot of the cage (see 253-52 on where to measure). This is a common issue if the mounting plates are on the floor and the doorbars are relatively high. It is much easier to reach the minimum distance if a box is used for the footing of the cage.

Very few cars now have a windshield inclination that could exempt from a windshield pillar support bar. Some sanctioning bodies require them regardless of measurement A. Also you want the front of your lateral bar to be installed as far forward as possible into the dash to limit intrusion into the cockpit.

Here is an example below illustrating what happens when you don't have a windhshield support bar. The lateral just collapses at the bend and the roof bar comes down with the A pillar.

253-31 temple bar / windshield bar reinforcements

In case of an impact putting stress on the lateral above the occupant seat, a 253-31 temple bar can sustain the lateral above the head of the occupant preventing the bar from hitting the helmet (see the next section for the diagram for 253-31).

Optional bars

A number of optional bars are common but depend on the car configuration:

253-17: often used to transfer the forces from the door bars to the rear strut towers
253-18: often used to limit the flex of the chassis between the strut towers and rear side impacts
253-25: also called anti-intrusion bars, they must connect to the top of the front strut towers
253-29: the dash bar is optional and oftentimes it is easier to retain the factory dashbar and weld or gusset it to the laterals. But it is sometimes better to upgrade the dashbar and integrate it to the rollcage.
253-31: those extra reinforcement gussets often referred to as temple bars are pretty common, there are however dimension restrictions as mentioned in the next section.

Older chassis do not have the same rigidity as newer chassis that use more elaborate materials such as high tensile strength steel and have crush structures designed to absorb larger amounts of energy. Consider using sill bars (see door bars), anti-intrusion bars (253-25) and rear member reinforcements (253-17, 253-18) , a stronger dashbar (253-29) and temple bars (253-31). In the pictures below taken around 1994/1995 in Rally Australia, you can see a Subaru Group N spec car, built by STi, seam welded shell, welded in cage, no sill bar. It was ‘just a roll’ but the bottom slammed a tree of only about 6-8 inches wide, the bottom of the car hitting first mid roll. Occupants survived but hurt necks. (Thanks to Jeff Denmeade for pictures and information about this incident).

Dimension constraints

One of the most common mistake in the bar design is the door bar being too high in the door opening (must be less than half of door opening) or the temple bar attachment points (see dimensions A, B and C in the 253-49 drawing below).

Gussets

It is necessary to reinforce pretty much all bars that are intersecting with gussets (main diagonals, X door bars and X roof bars). The gusset size is proportional to the size of the tubing, check drawing 253-34 below.

It is also pretty common to tie the cage to the pillars of the car so that an impact to the pillar can immediately transfer forces to the cage and be much stronger. All the sections in red in the cage diagram presented here are typical gussets found in stage rally cages. The triangles represent 253-34 style gussets and the lines gussets with the A and B pillars of the car.

Mounting the cage to the chassis

Bolt-in cages have been largely banned by now and all new cages have to be welded to the chassis. NASA rules are a pretty good guideline for mounting plates: 'Mounting plates must be a minimum of 1/8” thick, and have an area of 12 to 100 square inches, with a minimum dimension on any side of 2.5” and a maximum dimension on any side of 12”. It is highly recommended that these plates be formed to attach in more than one plane'.

The FIA requires a minimum plate size of 120cm2 for the front plates and a minimum of 60cm2 for the mounting plates for the backstays. The plates have to be welded to the chassis.

The pictures below illustrate various configurations of plate or box mounts.

Mounting plates just on the floor are likely to go through the floor like the incident depicted here where the roof collapsed and the cage feet were pushed through the floor.

Rollcage padding

Rollcage padding is required on all the roof bars (see drawing below from ARA rule that mimics the FIA rules). Also think about protecting your elbows from the door bars by preserving as much as you can from the stock door cards. Think about using dual durometer padding (https://www.rollbarpadding.com/product/id-38) on bars that you could hit with your arms.

(~$20 for 3ft, plan on 15 ft for a good coverage): SFI rated mini-padding where the helmet can reach the bars (http://www.jegs.com/i/Allstar+Performance/049/ALL14112/10002/-1), high density padding for door bars, windshield bar and bottom of a-pillar reinforcement bar (http://www.jegs.com/i/Longacre+Racing/441/65162/10002/-1). You might find cheaper padding from Pegasus (https://www.pegasusautoracing.com/productselection.asp?Product=2395)

Harness bar

The FIA rules have changed for 2024 on the harness bar design. Even though the new rule 253-66 seem to be the same as the previous 253-28 rule, it looks like all the other flavors of harness bars have been deprecated. (see below),

A pretty common mounting solution for harness bars is to have them secured to the main hoop as two half bars between the main hoop and the diagonals.. Note that the height of the bar can be different for the driver and the codriver. Just make sure the bar is high enough so that you can achieve a correct belt angle (see our Harness installation page for more details).

Note that there should be a minimum distance of 90mm between the seat backrest and the pivot point of the harness on the harness bar (see 253-61-c).

It is also allowed to use a bent bar behind the main X diagonal to give more clearance to the seats. Just make sure the shouldber belt attachment will not be in the bend of the bar, it has to be secured to the flat section of the bar for the belt to work properly.

1.5" is usually enough, note that this is not a structural component of the cage.

Bolt-in cages

Bolt-in cage or cages with removeable member are much weaker that weld-in cages. The bolt-in points create points of failure and those cages have been mostly banned for rallying. There are still exceptions for removeable door bars to accommodate disabled competitors to facilitate access but these are very rare cases. Most sanctioning bodies also require to have the mouting feet of the cage welded to the chassis and not bolt-in. The only current exception are for carbon fiber tubs where it is not possible to weld a metal plate but bolting is the only possible method to secure to the chassis. It is probably safe to assume that if you have a car with a carbon fiber tub, the factory will offer a factory cage option and you won't need advice from this page.

Here is an example of a bolt-in cage after a hillclimb crash. The hit mostly missed the cage but the cage distorted and lifted the whole dashboard.

Rollbars / half rollcages

Rollbars aka half rollcages have no bar in the front of the main rollbar plane. It is just a main rollbar, the backstay and their diagonals (plus potential harness bars). A rollbar with proper supports can really be helpful especially in convertibles that offer poor or no support from the factory. However a poorly designed rollbar (like on the 2nd picture below) can cause even more injury to the occupants when it fails.

Rollcage kits / FIA homologation

Some car models have rollcage kits that are already pre-bend and cut. The fit and finish quality may vary depending on the kits, try to ask around if anyone has had experience with a particular kit as sometimes a custom build might be easier and similarly priced. For Subarus, the Broken Motorsport kit is very popular (see https://brokenmotorsports.com/roll-cages/ for more details).

Custom Cages is well know for its FIA homologated cages (for example: https://www.customcages.co.uk/product/subaru-impreza-vab-international-multipoint-t45-roll-cage-kit-fia-certificated). If you want to go the FIA homologated route, you need to find a welder that has been certified to weld homologated cages. The certification process usually requires the welder to send welding samples to be checked by the FIA. Once an homologated cage kit has been installed by a certified welder, the welder sends pictures of the cage and welds for example to Custom Cages if it's a Custom Cage kit. After inspecting the pictures they will sign and stamp the homologation papers. The car with the signed homologation papers can be brought to an ARA or CARS scrutineer to obtain a logbook. The scrutineer will inspect the cage according to the FIA specifications and issue a logbook accordingly.

Check in advance with the scrutineer of the sanctioning body that will issue the logbook which homologations are accepted, some older homologated designs might not be accepted anymore. Your local scrutineer will be able to tell you what the latest regulations are.

Here we have an example of an homologated cage for a Ford Focus MK1 from Custom Cages that was homologated in 2000. This cage has a single diagonal in the main hoop and a single roof bar. This design was still accepted until recently for cars that only had a driver (though the diagonal would have to be on the driver side, which would make this design only valid for right hand drive cars). The unsupported corners in the front codriver side of the roof and the top of the main hoop on the driver side are the main weak points that would collapse if forces where applied to those corners (similarly to the 253-13 roof bar design mentioned earlier).

The 2 pictures below show on the left the missing bars to make this cage safer and on the right the deformation that the cage would see if forces where applied to the weak corners. Note that the windshield support bar design apply to the sill bar instead of the front lateral (as now required by 253-15/253-52). As show on the picture any vertical force applied to the windshield support bar will cause the sill bar (and most likely door bars) to bend.,

Moral of the story, even if you find an homologated cage that is still valid, carefully review its design to make sure it will be safe and matches current safety standards.

Issuing a logbook

The logbooking process is explained in part 3 of the rollcage video below (logbooking starts at around 12:30 in the video).

There is also another video more targeted for scrutineers to explain the process on how to logbook a car. It relies on the document that you can find on the Scrutineering / Rules page.

Building a cage yourself

Yes it is possible to build a cage yourself but it's not easy and you will need expensive tools like a quality tube bender, tube knotcher, welder, etc... There are some very good videos out there giving excellent tips on how to build a rollcage. We are linking a few of them below.

WRC rollcages

We started to see a double main rollbar in Rally1 during the hybrid era where the hybrid unit behind the crew had to be protected. Fast forward to the WRC'27 regulations which will have a spec tube chassis and the design retains a double main hoop configuration to fully protect the crew as shown in the pictures below.

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