Flat floors of 1980's and 1990's race cars

[Honda Porsche fan]

I was wondering why many racing series like F1 and Le Mans Prototypes no longer have race cars designed with flat floors where the bottom of the car almost scrape the ground like they use to in the 1980's and 1990's?

I was watching some videos of the FIA GT Championship from 1997-1998 of the McLaren F1 GTR Longtail, Mercedes CLK GTR and Porsche 911 GT1 and they had flat floors and just skimmed over the ground around the entire race track. The cars stayed a consistent height whether under braking or accelerating. They looked like they were sucked to the ground.

Did the rules prevent designers from designing cars that way or have engineers found a way to make race cars faster by increasing the height from the bottom of the car to the ground?

Does exhaust blown diffusers have anything to do with it?

Did Mark Webber's Mercedes CLK GTR and the Porsche 911 GT1 taking off flipping end over end in the air have something to do with changing the rules?

[BlueCheetah66]

I was wondering why many racing series like F1 and Le Mans Prototypes no longer have race cars designed with flat floors where the bottom of the car almost scrape the ground like they use to in the 1980's and 1990's?

I was watching some videos of the FIA GT Championship from 1997-1998 of the McLaren F1 GTR Longtail, Mercedes CLK GTR and Porsche 911 GT1 and they had flat floors and just skimmed over the ground around the entire race track. The cars stayed a consistent height whether under braking or accelerating. They looked like they were sucked to the ground.

Did the rules prevent designers from designing cars that way or have engineers found a way to make race cars faster by increasing the height from the bottom of the car to the ground?

Does exhaust blown diffusers have anything to do with it?

Did Mark Webber's Mercedes CLK GTR and the Porsche 911 GT1 taking off flipping end over end in the air have something to do with changing the rules?

F1's floor height is restricted by regulation, which means the venturi tunnels are lifted fairly high off the ground

[jjn9128]

In most series it is down to rules. So F1 from 83 to 94 had a flat floor from front wheels to rear wheels. Sports cars went a similar route after the Group C's. Then in F1 you get the stepped floor in 95 to reduce downforce, and in sportscars you get a ~7deg chamfer of the floor edge when the LMP rules started.

So rules and regulations is the answer.

[Honda Porsche fan]

In most series it is down to rules. So F1 from 83 to 94 had a flat floor from front wheels to rear wheels. Sports cars went a similar route after the Group C's. Then in F1 you get the stepped floor in 95 to reduce downforce, and in sportscars you get a ~7deg chamfer of the floor edge when the LMP rules started.

So rules and regulations is the answer.

Is this due to safety concerns or competition/trying to make the cars more equal for closer racing?

[jjn9128]

typically safety

[MadMax]

In most series it is down to rules. So F1 from 83 to 94 had a flat floor from front wheels to rear wheels. Sports cars went a similar route after the Group C's. Then in F1 you get the stepped floor in 95 to reduce downforce, and in sportscars you get a ~7deg chamfer of the floor edge when the LMP rules started.

So rules and regulations is the answer.

Is this due to safety concerns or competition/trying to make the cars more equal for closer racing?

Senna's death was a big "line in the sand" for the FIA. The stepped floor in F1 was a direct result of the weekend at Imola. In the interim, F1 also introduced things like the ventilated airbox to reduce power from the ram effect of the air intake, they added chicanes (famously after Eau Rouge), etc., whilst they tried to figure out how to stop a repeat of Imola - it's worth remembering Ratzenberger died and Barrichello was close to being killed that weekend too.

The Le Mans crashes of Webber and Dumbreck were a result of the aero imbalance inherent in the cars. It wasn't just the CLR that suffered such flights - the Porsche GT1 did too:



The rules were such that the cars had plenty of rear end downforce but the front was reliant on a relatively small splitter/flat floor/diffuser arrangement at the front. If conditions were "right" the front would lose air flow behind another car and thus downforce, the rear would then have a decent lever arm beyond the rear axle. If the front axle lifted because of the track geometry (a crest) at that moment, the result was a blow-over.

Rules were changed to avoid recurrences of these horrible accidents.

As an aside, I hear that Dumbreck was breathalised by the French police. Public road.

[Honda Porsche fan]

Is there any way for a compromise in aero rules and design to get the bottom of the cars lower to the ground and the driver still maintains control of the car?

What are some of the things the aero dynamists and suspension designers could do ?

In Indycar/CART from 1995 to 2002 they had some great racing with those cars. They were going 240+mph at Michigan and California, close racing, lots of drafting and passing. The road and street course races were good too.

[Stu]

Is there any way for a compromise in aero rules and design to get the bottom of the cars lower to the ground and the driver still maintains control of the car?

What are some of the things the aero dynamists and suspension designers could do ?

In Indycar/CART from 1995 to 2002 they had some great racing with those cars. They were going 240+mph at Michigan and California, close racing, lots of drafting and passing. The road and street course races were good too.

I’m not sure why anyone would choose a flat floor over a Venturi floor if both were an option.

[MadMax]

Is there any way for a compromise in aero rules and design to get the bottom of the cars lower to the ground and the driver still maintains control of the car?

What are some of the things the aero dynamists and suspension designers could do ?

In Indycar/CART from 1995 to 2002 they had some great racing with those cars. They were going 240+mph at Michigan and California, close racing, lots of drafting and passing. The road and street course races were good too.

I’m not sure why anyone would choose a flat floor over a Venturi floor if both were an option.

If the tarmac were billiard table smooth and the cars could run active suspension, then the flat floor would probably be preferable as the whole floor could be used to generate downforce. But otherwise, being able to have 3 dimensions available in the underside of the car (e.g. tunnels) is going to be a better all round option.

[1158]

The GT1 flip/crash was at Road Atlanta in the Petit Le Mans not at Le Mans

Not that this adds any value...

['Tis me, just me.]

Is there any way for a compromise in aero rules and design to get the bottom of the cars lower to the ground and the driver still maintains control of the car?

What are some of the things the aero dynamists and suspension designers could do ?

In Indycar/CART from 1995 to 2002 they had some great racing with those cars. They were going 240+mph at Michigan and California, close racing, lots of drafting and passing. The road and street course races were good too.

I’m not sure why anyone would choose a flat floor over a Venturi floor if both were an option.

Speaking with no experience here, But I'd say packaging - a Venturi effect floor will/should take up more space than a flat floor, so if you're really tight on packaging or you've already hit aero targets with a flat floor and don't want to go through with the hassle or developing a more complex floor shape.