why 16/17 or 17/18?

[JJCNSX]

Hi guys,

i know this question will make me sound as dumb as Jessica Simpson.. but, i gotta do it.


Why NSX (and some other exotic cars) are using 15/16, 16/17, or 17/18 rims.. why different size rim? and, it "seems" like only MR car has this design too.. why?

what is the pro and con. well, i guess one obvious reason for con is you cant fit bigger front brake setup if you have smaller front rim. .

but, i would imagine there is a great reason to do so?

and then why did later nsx (2002 on?) moved to 17/17?

anyone?

-jjc.
nsx 16/17
supra 18/18

[Dr.Honda]

My understanding is the smaller wheel and overall rolling diameter in front was to create some intentional understeer and make the overall handling more neutral.

[Zishan]

Originally posted by JimK
My understanding is the smaller wheel and overall rolling diameter in front was to create some intentional understeer and make the overall handling more neutral.

Also, smaller wheels = less weight, since you don't really need large wide wheels like in the rear.
- Z

[RyRy210]

From the FAQ:

Why Are The Factory Wheels Different Sizes?
With mid-engine design and lightweight aluminum construction there is no need for more tire at the front of the car. Honda's goal was to minimal mass for this vehicle, and that the "vicious circle" of weight works in both directions (heavier vehicles require a bigger engine, which weighs more, then bigger brakes, which weigh more etc.). Using a smaller front wheel also means more room in the interior footwells, a common area of complaint with other sports cars (wheels intrude into footwell meaning pedals are skewed off straight ahead).

[NSX-Racer]

There are also some german FR cars that have bigger meat at the rears (e.g. the BMW M3 CSL). Don't ask me about the reason.

So it's not only a MR phenomenon.

[JJCNSX]

ok...

now my new question would be..

if rim weight is a factor, then instead of 16/17, they should be doing 16/16 or 16/15 instead.. no?

if 16/17 were go great for MR... why they "moved" to 17/17?

also, anyone know what NSX-R (1st and 2nd generation) are using? 16/17?

this is still confusion a little

thanks

-jjc.

[CokerRat]

Originally posted by JJCNSX
if 16/17 were go great for MR... why they "moved" to 17/17?

Keep in mind that the tire OD, and therefore the rotational difference, was set with the '91 car -- regardless of rim size. So nothing has changed but sidewall stiffness from 1991 to 2004. As for why Honda started off with the smaller rims in 1991, that question could be put to pretty much all sports cars from the early 90's (versus the 18-19's that are typical in 2004).

I recall a R&T test where they put 16 / 17 / 18 / 19's on a BMW 5-series. Performance improved from stock 16 up to 17, slight improvement with 18's (from 17's) but decreased going from 18 to 19's. It appears many 2004's have larger overall diameters, making 19's viable for top performance. Incidentally weight goes up with each step (without exotic light wheels)

[ncdogdoc]

Corvettes also have used the staggered setup.

I think for two reasons - the first as stated in the FAQ.

The second is that bigger rubber in the rear reduces oversteer and allows power to be put down out of corners faster. A larger wheel allows wider rubber routinely, and allows shorter sidewalls to reduce squirm. The fronts can be smaller to make for quicker turn in and reduced unsprung weight, so quicker response to steering and road changes.

JMHO.

[NSX-Racer]

JJCNSX: 1st gen NSX-R (with 3.0 l engine) had 15/16 AFAIK, 2nd has definetely 17/17

[FF Drifter]

Either way, the NSX wheels always have a larger contact patch in the rear than they do up front. Even if the wheels are both 17/17, the rear rims hold a wider tire to still provide said understeer properties for the NSX.

[Zishan]

Oh, I also like the look of the staggared wheels. With 1 inch smaller wheels in front, it seems to flow with the NSX body and look very exotic IMHO.
Regards
- Z

[nsxtasy]

Originally posted by FF Drifter
the NSX wheels always have a larger contact patch in the rear than they do up front.

That's only because of the weight distribution of the car, not because of the size of the tires.

The NSX has 59 percent of its weight on the rear axle, if I recall correctly. That means that the rear supports 1776 pounds of weight (on a '91-94 Coupe). With 40 psi in the tires, the two contact patches total 44.4 square inches.

The 41 percent on the front axle means 1234 pounds. With 33 psi in the front tires, the two contact patches total 37.4 square inches.

If the weight were distributed evenly (50 percent front vs 50 percent rear), with the same tire pressures, the contact patches would be larger in front.

[nsxtasy]

Originally posted by CokerRat
the tire OD, and therefore the rotational difference, was set with the '91 car -- regardless of rim size.

In '94, the outer diameter of the front tires increased by 2.4 percent and the rear decreased by 0.6 percent compared with '91-93. In '02, the outer diameter of the front increased by 0.7 percent and the rear by 1.3 percent, compared with '94-01. Small changes, but changes nonetheless.

[JJCNSX]

hi all,

thank you for replies.


ok, i guess i should state my questions more clearly.. i am inquire about RIM size, not rim/tire overall combo

I understand overall height will be the same (rim/tire) regardless of the rim/tire combo, and i also understand the rears need more rubber patch for numerous reasons.

I agree that they moved from 15/16 to 16/17 for performance reason.. better cornering.. etc

i guess so far the answer that makes the most sense is
(1) smaller front tire/rim combo gives more leg room,
(2) one inch smaller rim at front DOES look good with NSX body shape. Hence, more aggressive look

but for (1), they can still acheive so by using 17 rim with smaller profile tires..

anymore idea?

-jjc.

[docjohn]

Alot of science goes into designing a tire- suspension setup for a car such as nsx.I would like to think that the susp characteristics plus tire sidewall are looked at as a unit.Therefore as subtle suspension changes occure so does the aspect ratio of the tire,to keep whatever nvh and performance goals as constant as possible. I have no idea what the hell I just said!

[ncdogdoc]

Originally posted by docjohn
Alot of science ...............I have no idea what the hell I just said!

That is OK John, because I do not know what in the hell JJCNSX is really asking

[docjohn]