Other Ideas on Tyres

my prob here is that I love science, but i agree with this cause i have seen it myself.

Put a set of 175”s on a 260KW XR8 and see how much traction you get off the mark and around corners. If skinny’s gave the same grip the F1's would use them think of the extra weight and drag caused buy wide tyres

This leaves one more quesiton from the lab to real life to be disputed - tyre wear - i would still like to think wider ones wear better.

I'm sure truckster will have some comment on this. What would you prefer on the back of your high powred sports bike? A skinny tyre or a wide tyre?

BZZZZ!

That's correct, a wide tyre is the answer!

Why?

Who care's, but you wouldn't catch me riding a fireblade 900 with a CB250 tyre on it. EVER!

Ya reckon torque might have something to do with it? The engine is applying force to the tyres as well, not just vehicle weight.

So.... F4phantom theory would only be correct if in your car you locked your wheels and screeched to a halt. sliding friction? Then it wouldn't matter if you've got fat or skinny tyres?

I wish i were a pilot, i am not just yet. The F4 is one of the best tho. Anyway I understand the difference between sliding and static friction. Sliding friction (when your wheels are in a skid) is less than Static friction (when you are driving at any speed). What you are saying is that under acceleration or deceleration a larger surface area provides more friction. I dont see how this makes any sense though, because the only difference acceleration could make is an additional force on the wheel, trying to induce sliding friction. This means the same law applies, the surface area of a wide tyre is larger, the load on the surface area is increased due to some change in front to rear weight proportions when the suspension allows movement. But all proportions are still the same irrevelant of tyre width - therefore surface area. The co-efficient of friction is constant for a certain material. With the XR6 example, the coefficient of friction for the tyre, wether large or small surface area is the same. You can only have one of the following two situations.

1. Large surface area where the total friction amounts to the nominal figure 100, each surface area unit is 10, and a total of 10 surface area units.

2. Small surface area. Total friction amounts to 100. Each surface area unit is 20, and there are only 5 surface area units.

This means i can only pin point the XR6 wider tyre example where it skidds less under acceleration with the wider tyres to the fact that it's because the tyres are a better more sticky rubber compund with a different co-efficient of friction value. perhaps a surface area unit would be 20 for a total of 200.

Why is it then that when I ride my mountain bike with big chucky wide tyres on it it's majorly hard to do 40km/hr but on my mates racer with skinny tyres it's a peice of bleep ? Gearing is the same, wheel size is the same, only real difference is the width of the tyre...

Arr HA, now F4 you been reading conceptual Physics (Ninth edition) haven’t you.) (There is a good photo of a BFG all Terrane)

I think we are missing a important peace of the puzzle hear and I can’t remember enough physics to comment accurately, Wider tyres have to give you more traction due to surface area contacting the road!!

I spoke to a friend who was a bit of a physics buff (a bit rusty now thou) and he agrees a wider tyre will give better traction than a skinny tyre, In terms of best traction a low profile wide tyre is the best.

P.S My favourite military aircraft it the Lockheed S-R 71 Black bird

I hear you, i am not trying to make a nusance of myself but i do like logical answers. Jeff M the reason your mountain bike tyres are slower then racers would be because of wind resistance and rolling resistance not because of the static friction on the ground. Over 25km/h wind resistance becomes a massive problem. Also racers have a lot less rolling resistance builty into every part and component of the bike.

NOW THAT, makes a bit of sense! I actually thought that the coefficient of friction IS the mechanical interlocking on a very small scale, some areas lots of it, some areas not much but over all an even effect (value) for a given material - except the velcro thing means that on a much larger scale its all surface area and weight does not make a difference at all. But then we are not actually talking about velco so i dont think this is the same effect.

Just to summerise

The "grip" of the tyre to the road is the same on both fat and skinny tyres - but the forces within the tyre are smaller on a fat tyre and greater on a a skinny tyre. So a skinny tyre breaks up sooner and makes your wheels spin.

R.

oh bugger - replied to the wrong one

Ignore that.

R.

I recon you are making a lot of sense here. What you are saying is when you put the tyre and asphalt under a microscope, you see tiny spikes protruding out and locking into the grooves in the asphalt. I agree with you - however is this not the co-efficient? If you get any two materials and slide them together, measure the force and you get a figure, this is it. So that means apart from what is going on at the molecular or slightly larger level, in practice you are actually sliding the two surfaces, and recieveing a figure. Therefore not matter if the tyre has parts breaking off, or not breaking off the figure from practise is a co-efficient. So if there is less weight on each surface unit, but more surface in contact, - mate i will stop here i need to think about this a bit more + i will try to get through to Dr Karl on thursday morning at 10:00am in Melbourne. I will ask him, all i know is that i have done the experiment and it does work, but in real life with tyres it goes against the experiment. And i am out of ideas. Tune in for an answer.

I don't really remember back to high school physics but I don't think you should sacrifice a material in the coeficient of friction.

Like writing with chalk on a blackboard. The friction between the chalk and the board is greater then the force holding the chalk together - so it crumbles.

If the tyre is wearing down, I think it means that the friction exerted on the tyre/road is greater then what the actual tyre rubber is able to withstand and therefore crumbles way. So you spin or slide your tyres not because of loss of grip but because of the crumbling away of your tyres.

Now - that would explain why fat tyre last much longer. A tyre of double width will not only last double the distance but infact much much longer. The forces indside will be halfed so it will very rarely reach the point where the tyre begins to crumble away.

Something to think about anyway.

R.

Just to summerise

The "grip" of the tyre to the road is the same on both fat and skinny tyres - but the forces within the tyre are smaller on a fat tyre and greater on a a skinny tyre. So a skinny tyre breaks up sooner and makes your wheels spin.

R

Good point Ross

Welcome to the exciting world of 4Wding

F4 put the physics book down tell the wife/girlfriend that you have to go and do some field experiments in the 4by in the name of science. That should keep the where the hell are you going questions to a minimum

Hey Robak, again this chaulk thing makes a lot of sense, so basicly a tyre with MORE material will take longer to wear given the same set of conditions, becuase there is more material to wear down and under less stress. This is sensible. I am still going to try to get onto Karl tho, he may have a few answers, plus all the smarties who go on his board to help answer the questions we have. Also Exploder and Ross, i agree, there is nothing like the real thing (in the name of science) and i regulary put real dents in my 4x4 in the real world. My wife dosent mind me leaving her for a weekend but refuses to accompany me, she hates the smell of diesel and dirt in the morning.

cool, now we can all go out and dazzle people with our "higher" undertsnading of tyres and friction and a little thing called co-efficient. When (and they surley will) they ask further questions as to our knowledge of such things we will inevitably give a full and complete surmon and an account of the history of tyres wearing down, wide and narrow and all manner of compunds. This will illuminate their minds bring peace to their and their family's lives. I hope this makes you all feel good about our important discussion - not a waste of time, but a time to plant seeds, a time for the future, for surley, children are our future.