G forces & tire load

sknguy · Post 28 Mar 2005, 21:05

I have a question but here's some background first:

I read that an F1 car can reach a breaking g force of about 3.5g. A Champ Car engineer stated to me that their cars reached 3.25g under braking.

Then, at another web site a person presented some calculations of lateral forces and stated that "9-10g sounds reasonable" from an F1 tire, "taking downforce into account". I thought this was far too much considering those braking forces noted above.

Anyway, the Question:
For the lateral force; what would be a reasonable guestimate of the amount of g forces that a tire could bear, discounting downforce, for either an F1 or Champ Car tire?

DaveKillens · Post 28 Mar 2005, 23:13

sknguy · Post 28 Mar 2005, 23:56

Yup... your right Dave. I think there are very few who would last long heading into 4G. But I was curious about the tires themselves actually.

DaveKillens · Post 29 Mar 2005, 00:21

Guest · Post 29 Mar 2005, 00:46

Yes I see your point Dave. I suppose it might be a moot point given the state of any rules in any leagues. It would just be unsafe to have rules allowing for cars, and tires, that would facilitate a grip reaching 9-10G.

Guest · Post 29 Mar 2005, 00:50

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rob · Post 29 Mar 2005, 07:04

At Sepang circuit were cars pulling up to 4,5 G in fast corners and 4,0 G when braking. It comes from G-Force scaling on new TV feature.

RacingManiac · Post 29 Mar 2005, 09:01

I think its generally accepted that F1 cars can do about 5 Gs under heavy braking at speed when downforce effect is maximum, and 4 G during certain corners....

What I find interesting is that braking on cars such as F1 cars where downforce plays a big role, you go for full braking at the initial stage of the braking action, then gradually back off as you shed speed and loses downforce or else you'll exceed the diminishing grip capacity of the tires and locks up as aero load being reduced in relation to speed of the car...

DaveKillens · Post 29 Mar 2005, 17:26

RacingManiac · Post 29 Mar 2005, 20:15

4G cornering I think in most cases is not sustained, but entirely possible. I remember them quoting corners like Jochen Rindt curve at A1 Ring(2nd to last corner) was a 4 G corner, 130R is probably close. Again I think it depends heavily on the track...

I think back in 1997 ABS had already been out of F1...And he would've had more than enough time to grasp the kind of braking these cars are used to. But braking being such a complex and important aspect of driving a race car(and an F1 car at that), that if the car's behavior is in any way uncomfortable to him then any number of things could go wrong...

ReubenG · Post 30 Mar 2005, 09:24

As best I remember, the average human blacks/reds out when pulling 5-7G. Fighter pilots can BRIEFLY manage 9-10G because they wear pressure suits which force their blood back to their brains.

F1 cars can probably pull 5-5.5G under braking, 4G under cornering, 1.5-2G under acceleration. The difference is because aero drag helps braking and hinders acceleration. Downforce is probably around 2.5-3 * W.

DaveKillens · Post 30 Mar 2005, 19:35

RacingManiac · Post 30 Mar 2005, 20:30

Carrying on with the offtrack thought...

The TMS CART race had a few things thats bad for it too. Being a high bank track with a lot of banking angle, compare to say California Superspeedway which is the fastest track on CART's oval calander(where they used to avg 240mph+ lap), TMS's high bank put them in a area a lot closer to what fighter pilot would experienced in terms of G-loading, as they are going against a sustained, verticle component of G loading. On other track where banking is less significant, its mostly lateral load and it strains their muscle, but in the case of TMS, the driver actually goes into minor G-LOC situation....

Reca · Post 01 Apr 2005, 10:43

Anytime we hear the “to drive a modern F1 car is easy” we should remember the accelerations the drivers have to cope with, each braking with peaks of 5 g’s, 3 or maybe 4 times per lap, for 60-70 if not more laps in about 1 hour and half… Furthermore, according to actual data, the heart’s BPM of a F1 driver is constantly around 180-190, with peaks above 200 at the start and in particular moments, for example while pushing hard before the pitstop. Definitively you need to be very fit to drive these cars for a full race distance.

RacingManiac wrote: What I find interesting is that braking on cars such as F1 cars where downforce plays a big role [...]

Little “historical” note. For the last two races of 1993 Giorgio Ascanelli, Senna’s race engineer at the time (currently he’s the designer of the Maserati MC12) designed for the McLaren Mp4/8 a servo brake system operating only in the first few moments of the deceleration; it allowed to increase the pressure in the circuit lot more rapidly than the driver was able to do hence exploiting in a more effective way the maximum available grip (and also requiring bigger brake ducts). Then, thanks to a simple electronic control based on the calculation of downforce from speed the servo was deactivated leaving in drivers’ foot the feeling at low speed to avoid wheel locking.
That system, although very simple, was also very effective and helped Senna to achieve the last two wins of his career, life sigh... one of them in Suzuka, in spite of the evident lack of power of his Ford compared with the Renault V10.
BTW, the system was banned at the end of the year.