Thought of the day..

I assume there is a difference? I.e. Tire has great lateral (cornering) grip but longitude (straight line) is not so good..

So, would it not be wise for this to be rated somehow? I wonder why there isn't..?

Feel free to shoot me down if its a silly question :p

would it not be wise for this to be rated somehow? I wonder why there isn't..?

I think it's implicit in the width of the tyre, as wider tyres have shorter but wider contact patches.

Part of the problem is that, short of hard straight-line braking, or a Scooby-esque 4-wheel slide perpendicular to the road, the forces on a tyre are a constantly-varying ratio between lateral and longitudinal forces. Therefore, splitting the characteristics up in an either/or manner like that would be pretty meaningless (not that things like wear and grip ratings aren't pretty arbitrary anyway...!)

Part of the problem is that, short of hard straight-line braking, or a Scooby-esque 4-wheel slide perpendicular to the road, the forces on a tyre are a constantly-varying ratio between lateral and longitudinal forces. Therefore, splitting the characteristics up in an either/or manner like that would be pretty meaningless (not that things like wear and grip ratings aren't pretty arbitrary anyway...!)

I can see where your coming from, and I may have presented my question slightly wrong. I understand that when cornering the forces is not purely a lateral force act upon a tyre, its a combination.

So perhaps to rephrase my question - many people have opinion on the grip of tyres, this has always been a qualitative approach, i.e. as it reaches the grip limit it breaks away gradually. Or, initial turn in was not responsive but has reaching to tyre limits grip breaks away predictably. is it possible to be grouped into few key 'attributes' and quantitatively evaluated somehow?

The counter argument one can say is different tyres act differently on different cars. However, isn't that simply due to how weight is transferred (and the amount)? if weight is transferred the same way in different cars then the grip characteristics should come out similar? :wonder:

(I have a feeling its beginning to be a can'o'worms)

As you say, people often talk about 'feedback', 'turn-in', 'behaviour on the limit' etc. etc. like you say, but like you also say, it will vary from car-to-car and even variant-to-variant due to differences in wheelbase, track, suspension geometry, weight distribution and so on...

COW indeed!

is it possible to be grouped into few key 'attributes' and quantitatively evaluated somehow?

http://en.wikipedia.org/wiki/Slip_angle

Probably doesn't answer your question, but I'd reason that the amount of deflection a tread can tolerate would probably be a good starting point for determining the sort of lateral forces it could be subjected to before grip breaks...

This is perhaps a more practical treatment of the above:

http://www.creativecarcontrol.co.uk/modelgrip.htm

...that may also be of interest!

http://www.creativecarcontrol.co.uk/modelgrip.htm

Ah, this was the page I was looking for but couldn't find...yes, much better than the Wiki article!

Any quantitative measurement would be so dependant on variables such as load, tyre pressure, tread wear, road surface, etc. that it would be pretty useless for general comparison. In terms of comparing between different cars, if the widths and/or profiles are at all different this can make a fair difference even with otherwise 'identical' tyres.

I'd say it's more an amorphous cloud of worms, since a can at least has clearly defined limits!