Slow remap?

[T. Spark]

215's on the back because i tried puttin them on the front for grip but apparently if i had wider on the front than back i would spin my car because to much grip compared to the front.. so ill be gettin 215 fronts when these wear out but it handles soo much better round corners now well the RR other people had round about what they expected i know it might not be 100% accurate but still be quite close

Fair enough chief Im running 215/40/16's all round and love it

 

[RichieRich]

Fair enough chief Im running 215/40/16's all round and love it

i will be in about 10k time maybe for next winter ill put them on but 17's version

 

[Matt_TDI]

i thought wider wheels on the back would make it easier to spin? im most probably wrong...

 

[RichieRich]

thats why porshe's etc have wider wheels?

 

[Matt_TDI]

because they are RWD, and specifically set up from the factory...

 

[Guinness]

surely wider wheels means more grip?

 

[RichieRich]

but even still it has wider wheels on the back and u dont see them spinning well not as a norm...

 

[Ad Lav]

You'll most likely lose the front more if the rear has wider tyres.

 

[T. Spark]

You'll most likely lose the front more if the rear has wider tyres.

Unless you have 215's on the front aswell as some spacers

 

[D4V2K1]

Well the car is booked in for next monday at J Gracie's so hopefully this should be resolved then

 

[depresion]

surely wider wheels means more grip?

No,

For the sake of simplicity the friction between a vehicle's tyres and the road
surface is most easily expressed as:
P x A x µ

Where:
P = Presure
A = Area
µ = Coefficient of friction

So wider tyres give more grip? No! Because Pressure is:
F/A

F being force (in this case the force is that of the vehicle pushing down on the
road due to gravity (keeping it simple here so avoiding weight transfer etc) )

So let's take 2 theoretical cars that are identical [1] with a mass of 1000kg
with a perfect front to rear and left to right balance.

F will be equal to mass * acceleration. Acceleration due to gravity is 9.8m/s/s
So the force acting across the 4 tyres is 9800N. or 2450N per tyre.

[1] The 2 cars are only separated by the tyres one has 135 section width the
other 270 and we will assume double the contact patch. Both sets of tyres are of
the same compound and have a µ of 0.4

Let's assume the contact patch for the 135 tyre is 6750 square mm 67.5 square cm
and the 270 13500 square mm.

So for single tyres:
Car 1 with the 135 section tyres:

P= 2450N/67.5cm^2 = 36.3N/cm^2

Friction = 36.3N/cm^2*67.5cm^2*0.4 = 980

Car 2 with 270 section width tyres@

P= 2450N/135cm^2 = 18.15N/cm^2

Friction = 18.15N/cm^2*135*0.4 = 980

 

[Guinness]

so all thats baisicly said is a wider wheel with the bigger surface area will have less friction due to the force being spread out and a thinner wheel will have more friction due to it applying the mass accross a more concentrated area. However is it not the case that a wider wheel is going to be better, as if this friciton is overcome on a smaller wheel then surely its going to be worse than a a wider wheel.

If this principle was right then we would all be running tyres as thin as possible. Thus giving more "friction".

 

[mhill]

that messes your head up, goin on Guniesses line of skinny tires where would the footprint and toppling over come i to it?

 

[depresion]

As you can see they both come out with the same value for friction.
Assuming the µ doesn't change then there isn't a benefit to running wider wheels in grip form, however you spread the wear over the larger area, this would allow you to run a softer compound with a higher µ. Most road users don't have a clue about the µ of there rubber (hardly surprising as it's not publicised). The same physics apply to breaks though the force acting on the pads is hydraulic and you have to consider the mean contact patch of the pads on the disk (hence the old motorsport cheap and cheerful trick of machining the inner edge off the pad thus pushing the contact patch out increasing the leverage).

 

[RichieRich]

that is one mathematical calculation.. but the 215's are better than the 205's i cant wait till i burn my front 205's out

 

[Clone]

that is one mathematical calculation.. but the 215's are better than the 205's i cant wait till i burn my front 205's out

Bah! I just bought 205/45/17 for the fron't... i will be running 225 on the rear jus need to wait for my alloys till i try them.

 

[Guinness]

I understand the physics behind what depression has put above. But there are many variables that have been left out. Anyway wider is better to a certain degree that we all knew.

 

[RichieRich]

that will handle really funny with 205 front and 225 rear, it changes the characteristics of the handling it becomes more light at the front so match up the size tyres if you can! i would of if i could of got all my at the same time

 

[Clone]

Really funny as really bad? Not dangerous i hope? I could match them up next month or so but the alloys come with 2 good tyres.