Before anything, the #1 rule here is that old setups will not work with any updated cars. Trying to use these setups will result in a very poor handling car. They must be deleted! For the 1976 season the FIA introduced a new Group 5 Special Production Car category, allowing extensive modifications to production based vehicles which were homologated in FIA Groups 1 to 4. These cars would contest the World Championship for Makes series from 1976 to 1980 and then the World Endurance Championship in 1981 & 1982. The FIA rules restricted the width of the car, therefore cars were built with standard body widths but wide mudguard extensions. The regulation required only the bonnet, roof, doors and rail panel were left unmodified. The rules however did not mention headlight heights, therefore when Porsche originally were to enter the 935 with the production headlight, they read the rules and discovered the loophole, therefore they raced the 935 with the hallmark flat nose. The category was also mostly associated with the wide boxy wheel arches and extravagant body style. The category would be banished after 1982 in favour of the Group B regulation, but continued to compete in JSPC, IMSA GTX category and other national sports car racing championships for a few more years. In Japan, the wide arch boxy with extended front spoiler body style is still favoured amongst kaido racer/silhouette car drivers, impersonators of the former and fans of the body style, who usually build a more exaggerated body style. Tyres Back in the late 70s/early 80s crossply tyres were the norm, with radials only starting to appear in high end motorsport from around 1983. A crossply tyre uses a stiff sidewall to support the car's weight, with a relatively flexible tread section in the middle. This gives them a distinctive difference in feel to a modern radial. They typically operate at much wider slip angles and are more forgiving at the limit without the dreaded snap-back a radial can give you. As they flex when loaded laterally, they do not respond quickly on turn-in, so the front of the car needs to be "lead" into the corner. Also due to the stiff sidewalls they do not respond well to camber, and much prefer to sit perpendicular to the road surface. Big camber angles with a crossply tyre will only serve to overheat the sidewall and reduce grip. A further development of these tyres (which is are shared with the Group 4s) has been in the heating and wear behaviour. These older tyres took longer to get up to temperature and pressure than modern rubber, so you won't feel the tyres getting close their optimum grip levels until you've completed at least 3 laps at an average length circuit. Rears will usually come up to temperature quicker as you've got all that power putting heat into them! Brakes Ever so often we review certain systems we have in place, whether it's one which generates a set of values or it's looking at how those values are implemented. The brake heating and cooling aspect hadn't had a whole lot of attention for some time, if we're honest. Then a conversation about brake behaviour sparked up in a WTCR WhatsApp group we're part of which includes a lot of the real drivers from that series. What that lead to was several days of pawing through real world data and comparing it to how our brakes were behaving differently across the board. The conclusion is what our brake temperatures were showing too much range, so some new systems were built to rectify that, the result being more consistent brakes with better initial bite. These updates are already on several series in game such as Group 4, the RaceRoom Junior, and now these babies too. The brakes are generally very good, as you'd expect from a big-spending race series. Just as with the tyres, you will need to wait for them to come up to temperature to feel their full effect. That'll take 3-4 braking zones usually. The limiting factor in deceleration is how much braking force the tyres can cope with. Suspension Despite what some people like to think, suspension layouts of top-line race cars haven't really changed much in 50 years. Sure, some trends have come and gone, such as third springs and the carbon fibre anti-roll bars TWR Jags used in the 80s. Most of our Group 5s use independent double A-arms, which first appeared in the 1930 on Citroens and is even commonplace in a lot of road cars nowadays. There are some exceptions within the Group 5 cars, such as the Zakspeed Capri which runs an ancient live-axle setup with a Watts Linkage, something which was actually invented in 1784 for steam engines...! The biggest difference to contemporary race cars is in the damper department where they're a much simpler affair than a modern unit. Separate high speed damping has not been invented yet, so all you get it a low speed adjuster. This means you have to consider behaviour over bumps as much as general handling needs when adjusting them as you can't separate the two elements out. Now, a quick introduction to the cars one by one; BMW 320 Turbo 600hp at the flywheel 960kg with driver Built on the E21 320 saloon, this project actually started life with a NA F2 powerplant, the BMW M12. If you've ever heard one in person you'll recall the howling sound making the hairs on the back of the neck stand up! It was then developed in conjunction with McLaren North America into a turbocharged powerplant, which almost doubled the power output. Schnitzer also got involved and developed a turbocharged engine which was used to dominate the DRM series in 1978. Interestingly, this very same engine was downsized and further developed into the M12/13/1 of F1 fame with a claimed 1400hp in 1986. Corvette Greenwood 850hp at the flywheel 1309kg with driver Presumably the motto "There is no replacement for displacement" was on the wall of the workshop at Greenwood. This car is built around a 7-litre V8 capable of nearly 1000nm of torque. Suspension-wise it's actually quite advanced, with double wishbones all round. Tyres are massive especially at the rear, to give them some sort of chance of surviving the absolute beating the V8 gives them. Unfortunately that big engine is very heavy, so despite a really trick tubeframe chassis it's by far the heftiest car in this class. That really harms cornering ability and brakes can really take a pounding with this beast too. Gearbox is a Muncie M21, designed and built for trucks and gear ratio choice is therefore limited. Dekon Monza 600hp at the flywheel 1088kg with driver Designed by a certain Lee Dykstra who was also responsible for designing the Group 44 Jaguars and Mazda RX-792P GTPs. Double wishbones all round, lots of torque and plenty of downforce. Fabcar 935/84 620hp at the flywheel 1026kg with driver It really is fairer to call this a Fabcar and not a Porsche. Fabcar are a racecar manufacturer which was founded in the 70s, building a reputation throughout the 80s for producing better-than-factory Porsche 962 chassis as well as their own GTP. More recently they built a Daytona Prototype. This car, made in California, was a one-off chassis built right at the end of the 935's racing life. So naturally it incorporates many of the developments ever seen on a 935. It runs a spool axle, meaning there is no differential (you'll notice you won't be able to find it in the setup menus) and a syncromesh 4-speed Porsche G50 gearbox. Ratios are all as-per the period Porsche parts list I have in my possession. Weight distribution is improved over the 934 with a 40/60 split. Interestingly it never actually ever raced at a Group 5 or in the GTX class, instead always competing as a GTP. Nissan Skyline 2000RS 600hp at the flywheel 1005kg with driver Both this and the Silvia are the original 'mother chassis' produced in Japan. As a lot of the circuits in Japan are tight and twisty, the focus was on producing downforce, which they do but at the expense of drag. Nissan Silvia Turbo 620hp at the flywheel 1050kg with driver A later version of the car above, developments have added downforce and some more power but also drag and weight. A lot of the underpinnings are interchangeable with the Skyline 2000, but a wider track and slightly shorter wheelbase means the suspension setups are different. Zakspeed Capri Turbo 545hp at the flywheel 895kg with driver Thanks to the only diffuser in it's class, this is the highest producer of downforce by quite some margin. The numbers are comparable to the previous generation GT3s, however there are drawbacks. Drag is high, so top speed suffers and a lot is yet to be learned about producing consistent downforce from underbody venturi. Run the car too low, the downforce drops off dramatically, run too high it'll do the same. Take it to a bumpy track and the downforce will be switching on and off like a flickering lamp. Interesting to say the least. An unusual feature, as I touched on way up there somewhere is the suspension layout. The front end is a strut-type, which is a bit behind the times, while the rear end uses a live-axle which is even more so. A live axle links both the back wheels together, so bumps on one wheel will affect the other. There is also a matter of torque reaction across the axle, which when accelerating pushes one wheel into the ground while lifting the other. This gives you a slight yaw to the right when hard on the power.