all i'd suggest is you will need a bit of power to actually turn wheels that size, that is a lot of contact with the road.

Tyres that big will attract police, and from memory the legal limit is 7" wide rims. Good luck

From my understanding of the physics of Tyres and such from uni physics 1a. the width of the tyre isnt going to increase the grip. So if i had a 105 and a 305 tyre made of the same rubber i would just about be able to turn them with the same ammount of power/force/work. Inertia will affect this though as a 305 tyre will weigh more than a 105, a double edged sword though as the heaver tyre will have a greater momentum once it is moving.

FYI Static friction is = or > the friction coefficient x the force the gound is pushing back at the tyre. ~ F=uN
Area doesnt come into this equation.

The advantage in going wide is as you go wider the tyre is able to be made out of softer rubber (increase u) and still maintain the tyres strength. Also a wider tyre will be able to cool itself better than a skinny one, so it stays in its optimum temp range.

Funny story, just after i got the esky on the road I was driving and i didn't know what my back left wheel was under inflated. So with a greater area of the tyre in contact with the road it heated up rather quickly and couldn't cool itself. So when i walked into repco I had smoke poring of the tyre =P Long story short i destroyed the tyre and had to get it replaced.

So i understand what im getting myself into I just wanted to know you guys thoughts on the different brands Im able to get.

Thanks for your concern tho =)
Jordan

p.s Everything im doing to this car will atract the cops. I'll just have to be sneekysneeky =P

Mate I hate to tell you but will have a snowball affect.. I did the same thing to hot vw bug in the late 80's . I found out the hard way the more resistence you put on the black stuff the harder everything has to work to stop it...IE BRAKES... I had a very hard pedal with NO stopping power..Ps I wont handle very well ie around corners . and it doesnt look like a straight line car.. BUt end of the day its your car.. good luck you will need it lol[(#)]

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Originally posted by hotboostgt

Mate I hate to tell you but will have a snowball affect.. I did the same thing to hot vw bug in the late 80's . I found out the hard way the more resistence you put on the black stuff the harder everything has to work to stop it...IE BRAKES... I had a very hard pedal with NO stopping power..Ps I wont handle very well ie around corners . and it doesnt look like a straight line car.. BUt end of the day its your car.. good luck you will need it lol[(#)]

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thats it... the bigger the tyre under the rear the more the engine has got to work to get it up to speed and then wen ur trying to pull up the more the brakes have got to work to stop u...

if ur trying to keep police away running a 275 on the back and 205/215 on the front there guna notice...

im mini tubbing the rear of mine to fit 10inch wide wheels and im only going to be running 265's... bare in mind it will be making 450+rwhp and will have big brakes...

i would probably opt for going a 255 something jus a lil bit smaller but still wide for an escort... my 2c

I may be a bit lost but can you explain how a 105 compared to a 305 still has the same grip? The foot print of the tyre will always effect the grip of the tyre. I just put bigger tyres on my other car ( Patrol ute) and the difference is defineutly noticeable just by going up 1 inch but we are talking BIG tyres >35/13.50/15. you could compensate with diff gears to en extent but you will most likely need 4.3's or something silly.

lol this is turning into a bigger event than i thought it was. I should have just asked about the tyres and not what size =P

As i said I only have a 1st year physics education. So if you have a major in physics or a PhD please advise me where im mistaken.

The frictional force experienced by a tyre is equal to the coefficient of rolling friction x the force the road is pushing back on the tyre.

fr=urn

"The coefficient is a dimensionless number that depends on the materials of which the object and the surface are made." ( Physics, pg162 Randall D. Knight)

My book gives the value of the coefficient of rolling friction for rubber and concrete as 0.02. It should be noted that rolling friction is less than static or kinetic friction. ie its easier to roll a tyre than drag it along the ground. This is why drag races do a burn out before they do a run, the rubber they lay down gives them a better coefficient of friction, rubber on rubber is sticky

"Note: These equations are a :model" or friction not a "law" of friction. These equations provide a reasonably accurate, but not perfect, description of how frictional forces act. For example, we've ignored the surface area of the object becuase surface area has little effect..." (Physics pg.164 Randall D. Knight)

So yeah surface area does come into it but im under the impression its almost negligent. I can check with someone with a PhD in physics if you guys really want.

Ok so if you had a 105 tyre and a 305 tyre that are made of the same rubber they have very close to the same coefficient of friction. The road is having to push the 305 tyre harder as its a bit heaver so It will grip more because it weighs more.

Now thats just in theory Its likly that there is something else coming into play. Tyre compound is going to play a big part of it. And also weight over the tyres.

I also understand that increasing the rim size and the tyre size will increase inertia and rotational momentum. thus it will take a lil bit more to get the tyres to turn, but looking at equations it seems that this wont be all that much. Braking will be the most effected as it will take more energy to remove the extra momentum from the wheel, but as im upgrading to he rear end of an EB falcon it will be fine.

If i was to run around a track im sure i would notice an effect on my times. But my esky isnt being built to go as fast as posible. Its being built to i suppose "look fully sick bro" I just like really wide wheels.

Thanks for all your concern guys but this is just one of those things that im going to do and at the end of it have the "well ive lived and ive learen't" And the next time I build a car i will know myself what works and what doesn't.

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Originally posted by JordyCharlieBoz
My book gives the value of the coefficient of rolling friction for rubber and concrete as 0.02. It should be noted that rolling friction is less than static or kinetic friction. ie its easier to roll a tyre than drag it along the ground. This is why drag races do a burn out before they do a run, the rubber they lay down gives them a better coefficient of friction, rubber on rubber is sticky

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for the record, drags strips are covered in rubber already, and also a sticky compound. half the classes are not allowed to do burnouts past the start line. the burnouts are purely to warm up the cars tyres.

Thanks for the heads up on that escort20. Im not a big drag race person but the one i did go to had people doing rather large burn outs and they said it was to lay rubber down to get traction on. But as you say it will depend on the event ectect.

I didn't bother reading the thesus on grip, however in reality, a larger tire will have more grip on any given surface, except where the removal a loose surface is providing more grip underneath,
This is because when looking at the road it is a series of stones with points, the more of these points you can grip on the better, also as a tire gets wider its compound can be softer with out the issues with over stressing the tread(once again the load is spread over more points) If you were talking steel on steel like a train, then i would agree, weight/surface area = grip or friction.

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Originally posted by darnoldrs

I didn't bother reading the thesus on grip, however in reality, a larger tire will have more grip on any given surface, except where the removal a loose surface is providing more grip underneath,
This is because when looking at the road it is a series of stones with points, the more of these points you can grip on the better, also as a tire gets wider its compound can be softer with out the issues with over stressing the tread(once again the load is spread over more points) If you were talking steel on steel like a train, then i would agree, weight/surface area = grip or friction.

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Well put and my point exactly. Simular to dragging your finger across something versus dragging your hand across something.