Advantages of high performance tyres

[coombsie66]

Rite, any help in this matter would be greatfully recieved, but unless you can back up your comments with facts then please dont post.
I have to de a 10 minute power point presentation on monday morning, explaining high performance tyres. I am concentrating on the various advantages over standard tyres that they exhibit.

I am having trouble trying to proove why tyres do not obey the same frictional rules as usual.

I believe that:

Usually:
Frictional force = Coefficient of friction x Reactive force

And: Pressure (reactive force) = Force(weight of car) / Area


So why does increasing a tyres with increase both the lateral and longitudinal grip levels? I know that the tyre 'keys' into the surface, but does this result in the coeficient of friction of tyres increasing with the amount of tyre in contact with the road!!??
As this is the only way i can see the maths adding up to better grip levels from a larger contact area!
I really need sum help, as i dont want to just bullshit this section and then be left trying to answer questions at the end about an assumption i have made and cant proove why!!

Any usefull help would be great! Fellow Mech eng students please feel free to input!!!!
Cheers, Adam

[zevolv]

The contact area helps alot with going straight because of just what you said. The more surface contact the more area that can push the car where it needs to go essentially. they don't help too well when turning though if you have really wide tires in the front you should know this yourself, It's like a gyroscope it takes alot more effort to turn the wheels if they are wider. You should also know that the only really important part of the tire is the Rubber compound in the tire itself. the softer it is the faster it warms and the stickier it gets.

[coombsie66]

I understand that, it is just that if the coefficient of friction of the rubber in tyres is a constant value, then increasing the contact area can only result in a decrease in all grip! That is what the formulae stated would add up to nyway.
However i know this is not the case. So, is it the case that the coefficient of rubber increases wiv the contact area, or is it that tyres are exempt from these formulae due to the rubber being 'sticky'.
I need a more comprehensive proof as just saying these equations (that apply to all other surfaces) dont apply to rubber because it gets 'sticky' sounds very wishy washy!!

[jon_s]

ummm, is there some 'chemical reaction' involved too?? I just remember some person talking about this stuff on F1. Appart from that I have no clue lol

more money=more grip lol

[coombsie66]

I think i have a relatively water tight explaination now!:

Usually:
Frictional force = Coefficient of friction x Reactive force
And: Pressure (reactive force) = Force / Area #

Tyres are different:

Tyre Frictional Force = Frictional Force + Stickiness

Where stickiness is a function of the Temperature and Contact Area.

So as wider tyres increase the contact patch, the stickyness is increased. And the softer the compound of rubber, the more it moves around, so the hotter it gets, so the more it sticks as well!!!!

Someone feel free to proove me wrong, as im kinda winging this one, and a proper explaination would sound beter!

[jon_s]

explain how the sticky theory works aswell. something like, as the rubber heats up, it becomes more flexiable...e.t.c moulding to the surface as it comes into contact with it, giving the 'feeling' that the tyre is sticky.

Maybe 'tacky' (not as in cheap! but slightly sticky) is a better word.

[coombsie66]

lol, yeah cud go wiv tacky, but on the physics forums where i found out, sticky was the word they were using!!!!!
Yeah, the softer the tyre compound, the more the surface layer moves around. This generates heat, which in turn makes the ruber viscous, so it practiacally is leaving a fine layer of ruber on every patch of tarmac it makes contact with. So the surface of the tyre is 'keying' into the tarmac and sticking the rest of the tyre to the road.
The racing slicks get up to a very hot temperature on the surface, beyond 100 degrees centigrade i think. Ive burnt my hand on ones that have been freshly taken off in a pit stop!

[graywolf624]

Unfortunately this area is not my forte. That being said there is a chemical reaction in conjunction with the physics reaction. One thing I can think of from the width of the tire is the dispersion of heat over a wider portion of the tire. If the heat builds up beyond a certain point tires give out. Thus the wider and larger the surface area on the ground the less the temperature.

If you go out on a race track without warming up your tires first you can end up in a ditch. So I would guess maybe there is a correct operation temperature for maximum efficiency of the chemical reaction.

Please do some research on this issue on your own. While I know I am on the right basic track I know that isn't going to cut it for your discussion.

[coombsie66]

Its ok mate, this presentation is more so judge our presentation and public speaking skills, but i think im along the right lines wiv my assumpion, so im happy, and im spent more than enough time on it so im dun!!
If nyone does have ny other views tho, this topic is by no means over, i'd quite like to learn more about the interaction of the tyre with the road surface! St-anger??!?

[graywolf624]

Ok I have some information for you. Makes me feel better to not just fluff over the facts.


http://corner-carvers.com/forums/showthread.php?s=2a33feb815c039f83906b850d5afeb10&threadid=2479&highlight=tire+width

"Problem is, tires aren't perfectly smooth, and they actually grip/adhere to the surface. More tire = more grip.
"

"The coefficient of friction on the tire changes with temperature and the weight per square inch supported on the tire. In each case, increasing temp and increasing weight, the coefficent rises to a peak and then falls off--looks kind of like a horsepower curve on a dyno.
Too much heat and/or weight and the tires get greasy and start falling off the back side of the curve--who hasn't done that before. Not enough heat and/or weight and maximum friction is not generated.

Too wide a tire and there isn't enough weight/square in. to maximize friction as well as probably not enough heat generated to warm the tire up to maximize friction."

[coombsie66]

Cheers 4 the link and researchin it 4 me mate, i'll look thru it when im sober 2morrow mornin!!! :mrgreen:

[coombsie66]

Just to say thanx 4 all the help from all who inputed, i did the talk thismornin, got an A, so im well chuffed!!!! :mrgreen:

[mhn3773]

i read everything..and i dont know if this will fit in..but the softer tires do wear faster so that is a con to driving them on the street

incase u are doing like a compare and comtrast..i dunno

[jon_s]

Quality, well done mate!

[callen]

high performance tyre=more adhesion=more grip.
wider tire=larger contact patch=more grip.
quick heating tyres=faster,stickier grip.

threres science to prove all of these points but i dont know it. i only know why a good tyre is a good tyre.

[jon_s]

quick heating tyres=faster,stickier grip.


surely a quick heating tyre would only reach its optimal working temp quicker. Or is that what you meant lol Doh!

[coombsie66]

The thing that makes a tyre quick heating is the pressure you put in it, thats the trick to pressures in motorsport applications, making the tyres heat up to the optimum at certain track conditions, session lengths etc. The only thing that can be altered really is the rubber compounds, then its a case of trying to optimise the surface temp of the tyre by altering its width, the forces put through it etc

[jon_s]

Ahhhhhhhhh, so having a massive tyre is not necessarily the best way to go, as it would generate too much heat, and is therefore likely to go beyond its working range.

[coombsie66]

Having a massive width of tyre would mean that the pressure between the rubbber and surface is not enough to create the heat in the surface needed in the rubber, not the other way round. So a car can be over tyred.

[jon_s]

lol, that is why I am a lawyer and not an engineer lol

[coombsie66]

lol, well u can help me out when im facing a driving ban for doubling the speed limit on the motorway!!!! hehe (if i ever get a turbo that is!!)