Advantages and disadvantages of different wheel sizes?

The larger the wheel, the smaller the profile of the tyre. This leads to less tyre-wall flex and tighter handling. The downside is that the ride will be more harsh.
 
It can depend on the specific wheels, but smaller wheels are generally lighter and tyres are cheaper.

What car are you thinking of changing sizes on and what will you use it for?
 
Thanks for the replies.

Rilot said:
The larger the wheel, the smaller the profile of the tyre. This leads to less tyre-wall flex and tighter handling. The downside is that the ride will be more harsh.
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Sorry I am lost here, what do you mean by profile? Is this the area in contact with the road?

I am not contesting this but why would the ride be harsher?


Skeeter said:
It can depend on the specific wheels, but smaller wheels are generally lighter and tyres are cheaper.

What car are you thinking of changing sizes on and what will you use it for?
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I am thinking of buying a Skoda Octavia SE Estate. Major concern is stability on snow and ice (French Alps).
 
For normal road use with no performance requirements larger wheels reduce ride quality and generally increase tyre price but look better.
 
[TW]Fox;24941331 said:
For normal road use with no performance requirements larger wheels reduce ride quality and generally increase tyre price but look better.
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This, generally. However, careful selection of the actual model of tyre can make some difference to ride: I went from Potenzas on 17" wheels, to Eagles on 18", and the ride got noticeably softer.
 
As a rule of thumb, a larger wheel will weigh more which will negatively affect ride and handling.

To some extent the lower profile tyre used may claw back some of that affect as far as handling goes.
 
Many thanks for the replies - I think I'll stick with the standard 16" alloys then.

On another front, any suggestions as to where I can buy five suitable steel wheels and winter tyres at a reasonable cost? I know that I will still need snow chains but winter tyres seem like a sensible idea.
 
As a general rule, assuming you're running the same tyre make/model on both rims, are correctly adjusting the tyre size to keep the rolling radius the same, and both rims are the same design just in different size:

Bigger wheels = You can fit bigger brakes in behind (hence why touring cars use big wheels etc.) To keep the rolling radius the same you've got lower profile tyres, so will have less sidewall flex than the same model tyre in higher profile. Lower profile tyres mean less compression and unless you adjust the dampers to compensate you'll have worse ride quality (whereas F1 cars have more-less no travel in the dampers and high profile tyres doing most of the compression). Low profile tyres are also a bit more prone to punctures, and as they're a big size the tyres are expensive.

Smaller wheels = Less weight as smaller amount of metal (which is heavy) and more rubber (which is lighter). Plus then remember unsprung weight is worth more than sprung weight. Smaller tyres will also be cheaper for replacements.

So on the Westfield I use small wheels (of a lightweight design) with a high profile tyre (of a stiff sidewall design).
On the Clio I use larger wheels as the brakes won't fit under anything smaller.
 
Yeah, I have 19" wheels on my car, as I have larger brakes now. Could go back down to 18" and save over £200 when it comes to replacing 4 tyres, but would need specific wheels to fit, which I can't afford at the minute, or possibly spacers, which I don't really want to use.
 
stockhausen said:
How so? Even if they are lighter, they aren't really going to have any significant impact on inertia?
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Physics.

r is radius
m is mass
I is rotational inertia
E is energy
w is angular velocity
P is the constant Pi

E = 1/2 I w2

rotational inertia is obtained by this equation (for hollow cylinders):

I = 1/2 m r2

w is radians per second, which is rotations per second (rps) times radians per rotation, which is 2 P

w = 2 P rps

rotations per second (rps) is velocity/circumference

circumference is 2 P r

so rps = v/(2 P r) therefore:

w = 2 P (v/(2 P r)) = v/r

This gives us an energy equation of:

E = 1/2 I (v2/r2)

Now we work on the I term, which as stated above is based on mass and radius.

Mass depends on radius. The mass of a cylinder is:

m = density 2 P r

let the constant C be "density 2 P":

m = C r

So:

I = C r r2 = C r3

and then

E = 1/2 C r3 (v2/r2)

collapse the 1/2 into the constant, and combine terms, and we get:

E = C r v2

Takes less energy to get a given rotational speed therefore more rapid accelaration. As mentioned though it limits the top speed. Snaffled the calc from the interwebs but it's first year mech eng stuff.
 
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