Rear/Front track width

[jose arellano]

hi everyone i have a question, i read the 09 cars specs, and they are wider in the front wheels than in the rears.. why is this? and how does that change the handling on the car? because i seen that they do the same in other amateur series..

[RH1300S]

The track width is normally measured to the centreline of the tyre. If the front tyres are narrower than the rears, but at the same time you are exploiting the maximum width available - then the front track will be wider than the rear (but not necessariliy the overall width of the front).

The more track width you can have the better you can take corners for a given tyre size because the load transfer from the inside to the outside is less, so the tyres are sharing the work better.

Even with the likelyhood that track width is driven by the regulations, a wider front track can be useful. As a car brakes and enters a corner (assuming trail braking by the driver) - then the load is transfered from the inside rear to the outside front (diagonally) - a wider front track will help the car on corner entry.

[ISLAMATRON]

rear wheels closer tgether aids in traction, for example dragster rear tires are very close. Having the front track width wider than the rears also helps with being able to change direction more quickly.

[Jersey Tom]

You will find in amateur open wheel racing, even down to FSAE, the front track width equal or wider than the rear...

[RH1300S]

rear wheels closer tgether aids in traction, for example dragster rear tires are very close. Having the front track width wider than the rears also helps with being able to change direction more quickly.

I didn't know that........and don't understand it

To my reasoning a dragster might well have a narrow rear axle to reduce frontal area and also I presume that a short driveshaft will be more rigid (in twisting) for it's weight when putting that huge power to the road.

If a car starts to put it's power down while still under cornering load, surely the max track width idea still applies?

[jose arellano]

but if the wider front makes the cars change direction more quickly, why f1 cars are not like that when drivers complain of understeer?

[bazanaius]

There was an article on this in a recent edition of RaceCar Engineering.

B

[Conceptual]

So, if I was designing a car that used bicycle tyres, could I have the rear tyres mounted on a skateboard truck (6 inches apart) and the front tyres 24 inches apart?

I had this idea before, because I thought that the turning radius would become much lower (independantly driven front wheels, the wouldnt turn, just spin at different speeds.) And I hoped that the flexibility of the skateboard truck would allow enough flex on the rear tyres to make the turn.

What do you guys think?

[jose arellano]

hey bazaniuis can you give us a link or more info that article ??

[lkocev]

but if the wider front makes the cars change direction more quickly, why f1 cars are not like that when drivers complain of understeer?

Track width is not the only thing that influences a cars handling and charicteristics, most of the time engineers dail in a little downforce at the front wing to reduce understeer, and the opposite for oversteer. Charicteristics are inherited to many design parameters, for example, recently the McLarens have tended to be very 'oversteery' where as the Renaults have tended to be quite 'understeery'.

[marcush.]

In fact ,track width is a very powerful tool when setting up the car.
But of course in F1 everything is dominated by the gods of aero and i don´t think they allow for rapid changes in rim offset to do a quick and dirty set up change.
As one mil definitively makes a difference you can always put in different length wishbones/spacers ,and sure this is done in lower categories.Of course you must be sure you don´t leave the envelope of legality here

[machin]

So, if I was designing a car that used bicycle tyres, could I have the rear tyres mounted on a skateboard truck (6 inches apart) and the front tyres 24 inches apart?

What do you guys think?

Basically this is a three-wheeler, (for all intents and purposes).... the problem here is that the front wheels will have to absorb all the load transfer... that means the outside front tyre will be much more heavily loaded (twice as much load transfer to the outside front tyre than an equivalent car with equal front and rear track).... and that will promote understeer.... The advantage of a three wheeler is you can make it really light, so road going three wheelers have good cornering capability compared to four wheelers, despite the problem of load transfer.... the problem is most racing rules don't allow the car to take advantage of this by specifying a having minimum weight (as in F1)....

[Carlos]

"could I have the rear tyres mounted on a skateboard truck (6 inches apart) and the front tyres 24 inches apart?"

That describes the Isetta microcar chassis. Well worth a Google. Remember there's a site that features microcars. Interesting. May give you some useful backround.

The Isetta was:
Front track aprrox 44 inches, rear track approx 8 inches, wheels 3 1\2 by 12 inches
Drive - chain between rear wheels. An iconclastic design. Right up there with the Mini. We had a black one in about '64. A project car. About a dozen sold in my town.

[Jersey Tom]

...As one mil definitively makes a difference...

Oh? Prove it

[MReggio13]

Good topic, and this is my first time posting.

One mm of track width will make a difference, but a VERY small one. For 1g of lat. acceleration, you might be lucky to see .5 N, or .1 lb, of lateral load transfer change. So even an F1 car during maximum cornering load would not see much change in load transfer from a 1mm track change. Now a CG height change of a couple mm, that would be different.

Mike