Nissan 370Z Forum

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-   -   Why 19? (http://www.the370z.com/wheels-tires/15211-why-19-a.html)

jeffreyfranz 02-28-2010 06:26 PM

Why 19?
 

I have asked this question on forums for about two years now, and I still don't think I understand: What is the advantage of a larger diameter wheel and tire? The operator of one well-known internet tire website said that if all other factors were the same (i.e. width, profile), and thus the contact patch was the same, an 18" would have no advantage over a 17," for example. Yet, manufacturers appear to be going to ever larger diameters (19," 20"--what's next?).

Why do I care? Go to Tire Rack and see how many options 370Zs with the Sport Package have for tires. Hint: It is a very small number.

Can someone please explain this once and for all?

Thank you. :tiphat:

theDreamer 02-28-2010 06:32 PM

Do not 100% trust tire rack on the tires they spit out, you can adjust it slightly on size and such. Just do some searching (here & Google) for a tire calculator and you will see what changes in size/width/etc.
Well, 18" v. 19" usually comes down to weight & rotational mass, but that is basically if you plan to track the car. Even then, a 19" might be the better route because of a BBK fitment issue with smaller wheels.

GTRFAN 03-01-2010 05:24 AM

The lower the side wall profile, the better the handling...generally. This would not be true for 22" wheels with a really thin tyre profile but it is true for most wheel diameters.

The thing to remember is that, the overall rolling diameter (circumference) MUST stay the same when you upgrade. So if you go from a 17" to 20" rim the tire profile % must get a lot smaller to maintain the overall diameter.

Tire sizes are also a strange beast with a mix of metric and imperial measurements.
285/35/20 means - 285 mm width/35% of 285mm sidewall/20 inch rim

jeffreyfranz 03-01-2010 10:04 AM

Thank you, Dreamer and GTRFAN. Your responses were helpful. I'm still not sure anyone has explained why, say, 19" is more advantageous vs. 18", but I'm learning as I go.

fairladyZ34 03-01-2010 10:19 AM

cosmetic?

NXTAZEE 03-01-2010 10:56 AM

I think one advantage would be handling, because a lower side wall will not roll and move as much when cornering. Another advantage would be weight. And of course aesthetics, larger rims just look better than small rims. The last one is subjective of course but most would agree.

Ryan@Forged 03-01-2010 02:16 PM

Quote:

Originally Posted by jeffreyfranz (Post 423681)
Thank you, Dreamer and GTRFAN. Your responses were helpful. I'm still not sure anyone has explained why, say, 19" is more advantageous vs. 18", but I'm learning as I go.

There are many factors to think about. In most cases a 18" would actually be more advantageous over a 19" due to the fact that it will likely have less rotational mass. However, with this in mind you will also have a much harder time clearing big brake kits. Also, the 19s seem to be more cosmetically pleasing to the eye, although that is merely personal opinion. There are also several 19s which come in an 11" width, where it is harder to find 18s made in an 11" width. Just a few things to think about :)

jeffreyfranz 03-01-2010 11:25 PM

Thank you, Ryan, much appreciated.

import111 03-02-2010 12:39 PM

The 370Z does 0-60 in low 5's and the 1/4 in low 13's and pulls .93-.99 g's on a skid pad. 19's seem to work just fine for it. Also Ferrari, Lambo, and other supers and exotics use 19's too.

gatorfast 03-02-2010 12:59 PM

I think the main reasons that a typical car the like the 370z would come with bigger wheels would be for looks (fills out the fender better) and percieved value (people think that because a wheel is bigger it therefore must be more expenseive and desireable).

Chupacabra 03-02-2010 01:11 PM

http://upload.wikimedia.org/wikipedi...a_One_Tire.jpg

380/44/R13 and those things hold up to over 4 lateral g's....



I think its mainly due to rotational mass, but since the difference between 18 and 19 is not that great, cosmetics then come into play, with the 19's filling out the wheel wells more.

theDreamer 03-02-2010 01:15 PM

Actually, it does not fill out the wheel wells anymore or less.
When you increase the wheel size (18->19) you must change the tire size to adjust rotational measurements & speed.

m4a1mustang 03-02-2010 01:20 PM

Quote:

Originally Posted by Chupacabra (Post 425532)
http://upload.wikimedia.org/wikipedi...a_One_Tire.jpg

380/44/R13 and those things hold up to over 4 lateral g's....


Keep in mind that those are sizes that the rulebook regulates, so they aren't always necessarily ideal. Example... NASCAR mandates a 15" wheel, but if you let the teams choose they would probably run a 17-18" wheel to fit bigger brakes.

As with NASCAR/F1... those sidewalls are incredibly stiff.

Chupacabra 03-02-2010 01:23 PM

Quote:

Originally Posted by theDreamer (Post 425539)
Actually, it does not fill out the wheel wells anymore or less.
When you increase the wheel size (18->19) you must change the tire size to adjust rotational measurements & speed.



Yes you are right there... so lets say it Optically seems fuller.

Sharif@Forged 03-02-2010 02:53 PM

From a performance standpoint, the highest performance wheel is one that is large enough to just barely clear the brake caliper and rotor and no larger. Hence, the tiny wheels used in F1.

As Ryan and other mentioned, maybe people select wheels from an asthetic standpoint so there are many other factors to consider.

OEM's are simply following the bigger is better thing that consumers demand. Back in the 80's a 15 inch wheel was considered cutting edge and massive. Now a 19 is the new standard, and many cars come with 20's from the factory.


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