Wheels, Rims And The Difference?

[Djelibeybi]

Hi guys,

Forgive my ignorance (as usual), but what exactly is the benefit of getting the 18" wheels over the standard 17" ones, besides the "looks" factor.

Thanks!

[Guest DZ.]

For the most part it has to do with the turn in ability of a car - related to the height of the tyre side wall. Tyres, as you're aware, have a certain amount of flex because of the material used in their construction.

Consider then, when a car's direction changes, where the weight of the car shifts to. The forward forces shift the weight of the car in its original direction causing the majority of the weight to be placed on the outer wheels, especially the front outer wheel during initial turn in and ongoing cornering. The higher the tyre side wall, the more flex the tyre has and the more the car will tend to roll towards the outside. Not only does this induce a bit more body role but it will also have the effect of placing more weight on the outer tyres, rather than sharing it between all four tyres.

A wheel, being made of alloy, won't flex (obviously). Therefore, the larger the wheel, the less tyre sidewall flex you will have and the less body roll and weight shifting you'll have when your car turns. The effect of this is to provide a flatter cornering stance and better weight distribution giving you more grip, allowing you turn in more effectively rather than plough understeer. Larger wheels also tend to be larger which helps dissapate heat much more effectively increasing the amount of grip you have available to you.

Of course, the consequence of all this is that the tyre acts less as a shock absorber so the ride can be firmer and rougher. The reality is that between a 17 and 18 inch wheel on the Falcon, I suspect you would be hard pressed to really notice the difference unless you're an experienced driver.

[Djelibeybi]

Thanks! Nicely explained.

[Guest DZ.]

Benefits of an engineering degree that I never use :D

[Djelibeybi]

Ok, so while I have your attention... :-)

Normal vs. Premium Brakes. There are some threads about what the premium brakes actually are, but are they really worth an additional $3000? Again, what are the specific benefits (I guess, besides stopping faster!).

[Guest harasn]

one thing I have noticed with the larger wheel diameters is that they tend to comunicate less to you about when they are about to let go when cornering hard.

[Guest DZ.]

Comes back down to driving style again - obviously the bigger the rotor area the more stopping ability - comes back down to the ability to disapate heat which is the reason they are more effective at stopping. Downside is generally, larger breakes can affect pedal feel to a degree - not having tried the brakes I couldn't tell you from any experience.

The general feedback is that unless your intention is to do track work, then the normal brakes are fine. I've braked a car from 180 to 20 km/h before and a bit further down the road they were fine, under normal driving conditions.

I think if you're wondering whether or not you need them, then you probably don't need them. However, if you have the extra cash to throw around, bigger brakes always make a car safer for people inside and outside a car.

[Guest DZ.]

one thing I have noticed with the larger wheel diameters is that they tend to comunicate less to you about when they are about to let go when cornering hard.

This is more a function of the type of tyre/rubber selected than the larger diameter wheel itself. The larger diameter wheel means a softer, stickier rubber can be used as they don't have a big sidewall to support and the increase width means the tyre can be cooled down easier - hence the larger diameter wheels tend to be fitted with tyres with lots of grip. The consequence of this is that these tyres rather than gradually losing adhesion, just break grip all at once.

You can actually get tyres that are less sticky and slip rather than breaking grip suddenly - these sort of tyres just use a harder compound. They also tend to be cheaper

[turbo_nick]

The reality is that between a 17 and 18 inch wheel on the Falcon, I suspect you would be hard pressed to really notice the difference unless you're an experienced driver.

I'd go even as far as saying you wouldn't notice much of a difference with 19s. My new 19s give me a slightly cushier ride than my old 17s, as weird as it may sound. Of course, I'm running about 37psi in the 19s compared to 42-43psi in the 17s.

If you've got the money, 18s are the way to go on a Falcon if you want to focus on handling. If you prefer a ballance between comfort and handling, 17s are just right for you.

[Djelibeybi]

Thanks for the help, guys.

Saw an Acid Rush XR6 delivered to my dealer this afternoon. No Silhouette XR6 on the truck though, sadly. Don't even think its hit production yet. *sigh* But at least you guys have made me happier about my choices of options!