Why could it be better to run toe out on the rear?

[Caito]

Well it's typically written that you should use toe in in the rear, if not it's an unstable conditions and all kind of things opposing rear toe out.

It's well proven on TC cars


(1350kg, 350hp, really wide tires, RWD, rigid axle)

that they're faster running toe out on the rear.


Which could be the reason for this condition?


More info on the tires: bad quality construction, not radial.


bye bye


Caito.

[Jersey Tom]

On what is presumably a low downforce car with large side area, some of it may be to achieve a high body sideslip angle (Beta). The yaw angle can generate aero sideforce without much loss of downforce (since there isn't much to begin with!).

Generally toe out will really make for poor power-down on cars with a differential as you're driving the lightly loaded inside tire to high slip angle and making it do more of the cornering work, and thus little longitudinal headroom. On a solid axle though, you don't have to worry about spinning up the inside wheel.

That would be my theory.

[747heavy]

It´s a bit surprising, as for example a V8Supercar which also has a solid/beam rear axle and ~twice the power, but smaller tires runs toe in at the rear.

J.T. has given some valid explaination IMO, the other would be, depending on the construction of the axle, that you don´t really run toe out while driving.
It could be that the axle deforms under drive torque and side load, so that you need to run static toe out to have your toe setting where you want to have them while driving. With very wide tires and maybe not very stiff/good hub carriers/wheel bearings, rims etc. it is possible, that static toe out is needed to end up with zero toe or slight toe in while driving.
How much toe out do they run on the rear, do you know Caito?
A photo of the rear axle and the tires would be nice too, if possible - Thanks !!

Toe out at the rear would also make for less rear stability under braking and a tendency to OS.
So maybe if these cars have "built in" understeer for one reason or the other, it may help with turn in.
But all the above is pure speculation, as I never have seen one of these cars from close, or parts of there rear suspension.

We used "dynamic toe out" on the outer wheel under roll in FWD Touring cars, to make them less understeering in mid corner.
But this was achieved with roll/bump steer leading in effect to rear wheel steering, not by static toe out.

Tyre construction and characteristics could have something to do with it, but this is more J.T´s or Ben´s field of expertise.

BTW: I´m a bit surprised by the power figure, always thought that the TC3000 cars would have a bit more power.
They make for good/fun racing to watch anyway. =D>

[marcush.]

I think the bumpsteercurves will give a good indication why you might want staic toe out .I hear that this was something used on the old carrera cup cars .
As well as the deflection of the suspension itself may contribute to a desire to
have static toe out.

I have to admit I have experimented with toe out quite a bit in scandinavia racing ...it seemed to be giving a more even tyre use for the guys i worked with funny enough the euro challenge guys were reluctant to try this .. but really the f430 is sooo flexy..i wonder if the tyres ever where in the direction you thought they were .

[Caito]

I'll read your posts more thoroughly tomorrow.


Today I got the data: 0.6 degrees toe out.


Bye bye

[Belatti]

BTW: I´m a bit surprised by the power figure, always thought that the TC3000 cars would have a bit more power.
They make for good/fun racing to watch anyway. =D>

TC cars use 3.1 liter 50´s OHV engine blocks, 2 valves per cilinder with carburettors and can reach 375HP at 9,000rpm... quite impresive if you ask me.

Regarding TC tyres and rear axles, I have got some data and pics but cant post them know, maybe tomorrow if I have some spare time.

EDIT: TC engine power figures

[747heavy]

Thanks for the info Belatti.
I did not mean it in any negative or rediculing way.
(and 375hp sounds different then 350hp)
I was just told, by people who know more about the cars, that there engines are like F1.
Not from the technical side, but what they guy meaned was, that compare to the rest of the car, a lot of money and know how is spend on the engines. And that the engine is cutting edge for the regulations it is based on.
Therefore, I expected a bit more.
I did not know that they are 2 valve for example.
It´s good racing, fun to watch in any case.

BTW:
What is the engine spec/power in Top Race? - Thanks

[Belatti]

TRV6 engine is based in a Jag V6 and according to Berta SA that is the supplier:

Motor Original: Jaguar - 255 HP v6 - 60º
Cilindrada: 3000 cc
Nº cilindros: 6
Máx. Potencia / regímen: 345 Hp a 7000 rpm.
Máx. Torque / regímen: 33,7 kg.m a 4600 rpm.
36,3 kg.m a 6400 rpm.
Máx. RPM: 7250 rpm.
Admisión: Normal aspirado. Múltimple admisión std modificado con plenum. 1 mariposa de 75 mm.
Lubricación: Carter seco.
Material de Block: Aluminio.

[marcush.]

That was AER or Judd that did something based on Jag engines???

[747heavy]

TRV6 engine is based in a Jag V6 and according to Berta SA that is the supplier:

=D> =D>
Thank for the info Belatti

[Belatti]

Here you can see a video of a development that is planned for TC engines: with DOHC cilinder head they are currently in the 400HP range and they think 420HP is posible using the same 3.1 liter 50´s iron block.

[youtube]http://www.youtube.com/watch?v=f65OMoXqf5Y[/youtube]

[Caito]

747h engines are BIG part of the budget. It happens that whenever someone discovers something that gives 5 more hp, everygone goes to that motorist and he charges whatever he wants. So, you can pay very little or a huge lot for an engine, you decide.


Belatti the engine you're showing caputted, no longer is alive :p. I don't know if they will go on with the development, though.

[Belatti]

747h engines are BIG part of the budget. It happens that whenever someone discovers something that gives 5 more hp, everygone goes to that motorist and he charges whatever he wants. So, you can pay very little or a huge lot for an engine, you decide.

Belatti the engine you're showing caputted, no longer is alive :p. I don't know if they will go on with the development, though.

I know, the discussion now is if they should keep developing expensive 6 cylinder engines or go for cheap power: V8s

People loves the staggering sound of these 6 cylinders... you know, its similar to the sound of a V12!

Whatever, I dont think that TC´s power or G´s are enough to flex significantly the live axle or rear hub carriers.

And I have seen TRV6 cars setups with rear toe in (though they use Brazilian Pirelli´s P-Zero 235/645 VR 18).