18" Serpent Autosport GTV6 Wheels

[Charlie DiMarco]

Hi Everybody,

I had a customer ask for 18" wheels for his GTV6. So I took a deep breath and said.... I can make that happen. See more photos of this application at http://www.serpentautosport.com/type_3_gallery.htm

Looking forward to questions, comments and of course opinons.

Charlie

[Giulietta24vTT]

I thinkj they look brilliant!

[Greg Gordon]

Great, my son saw that picture and now he wants 18"s. The car looks great, I am a little concerned about rubbing issues with rims that big. The body kit looks great too, is it still in production?

[conedriver]

Hi Charlie,

Since you asked...
From your post ("so I took a deep breath..."), I gather that this isn't something you would normally do. The original use of "Plus 1" or "Plus 2" wheel sizing was to maintain the original tire diameter while changing to a lower profile (section ratio) tire. Also, some cars have a lot of clearance from the wheel opening to the tire, and larger tires / wheels can fill this gap and be more visually appealing. However, while everyone is welcome to their opinions, If some is good, more is not necessarily better. I think there is a point where the oversize wheels tend to look a little too overdone or even like a cartoon caraciture (like a jacked up Chevrolet Impala with 20 in. wheels). That said, the 18 in. wheels on a GTV6 look better than some of the Spider applications.

From a performance standpoint:

1. Increasing overall tire/wheel diameter will slow down acceleration from the resulting gear ratio change, and the increased diameter of the rotating mass. It will also reduce RPM for a given cruising speed (but I doubt this was your customer's intention).

2. A theoretical increase in cornering grip might result from the larger tire footprint (but this can probably be attained from a wider tire section and no diameter increase).


And of course, the application is "Non Originale" so will not appeal to the "Originale" enthusiasts. This is gonna be a fun thread...

Quote:

Originally Posted by Charlie DiMarco Hi Everybody, I had a customer ask for 18" wheels for his GTV6. So I took a deep breath and said.... I can make that happen....Looking forward to questions, comments and of course opinons. Charlie

[Charlie DiMarco]

Giulietta24vTT, I'm very glad you like the look.

Greg, Now you know what to get your son for Xmas. Very slight trimming of the front wheel wheel openings was needed. On the back rolling the fender lip is recomended. A tool for this process can be purchased or rented.http://pressroom.eastwood.com/frrelease.htm

The body kit is a Lester product. They still have it listed on their website.
http://translate.google.com/translat...UTF-8%26sa%3DG

George, very well stated, you have a understanding of the big picture.

Thanks for the feedback guys!
Charlie
www.serpentautosport.com

George brings up a good point, what is the tire size used on this application?

[Jr. Z]

George:
As usual with you, your points are very well taken, but I have to clarify point #2 in your post:

Bigger/wider/larger/lower profile/larger diameter wheels and tires NEVER increase the tire's "footprint". This is basic physics, the weight of the vehicle will cause a tire to displace & conform to the road a certain amount, but the only thing that changes is the shape of the footprint, the overall area does not change. A narrow section width means the footprint is longer and narrower, a wide section width means the footprint is shorter and wider, but the overall area does not change, the weight of the vehicle distorts the tire to the same total footprint area, all other things being equal (mostly meaning sidewall stiffness & air pressure).

Actually, when going to very low profile tires, the area of the footprint can & often times does get SMALLER because the increased air pressure & sidewall stiffness does not allow the tire to conform to the road surface as much. Tire mfgrs. have done studies that show this to be the case.

Large diameter wheels and tires are only needed to clear large brake components, there is no other engineering reason to run large diameter wheels. For most passenger vehicles, this means that 15" or in some cases 16" is the biggest you really need to run, everything larger is style driven, not engineering driven. Nothing looks odder to me than seeing slammed Honda Civics with 18" wheels & teacup sized brake discs & tiny calipers.

Don't forget, unsprung weight, and much more importantly, rotating weight, can easily go up dramatically with larger wheels and tires. You have to be careful about watching the weight of the overall wheel/tire package & avoid increasing it much, if any, over the stock weight. For performance increases you want to reduce rotating weight, not increase it. Rotating weight increases can really hurt acceleration because you have to spin this extra weight around all 4 wheels, that's why it's so much more important than vehicle weight. Talked to a lot of guys over the years who were baffled at the way their car felt "sluggish" after changing to heavier/larger wheel/tire combos.

Bruce

[conedriver]

Hi Bruce,

Well...lemme see, I claim a grade of B+ for my post.

I only said a bigger/wider/larger tire MIGHT result in a bigger footprint.
I propose no deduction in points results from your excellent clarification.

But... when discussing larger overall tire / wheel diameter, I completely forgot about the effects from an increase in unsprung weight due to heavier wheels & tires (rats!).
I accept a half point deduction.

I said this would be an interesting thread...

Quote:

Originally Posted by Jr. Z George: As usual with you, your points are very well taken, but I have to clarify point #2 in your post: Bigger/wider/larger/lower profile/larger diameter wheels and tires NEVER increase the tire's "footprint". This is basic physics, the weight of the vehicle will cause a tire to displace & conform to the road a certain amount, but the only thing that changes is the shape of the footprint, the overall area does not change. A narrow section width means the footprint is longer and narrower, a wide section width means the footprint is shorter and wider, but the overall area does not change, the weight of the vehicle distorts the tire to the same total footprint area, all other things being equal (mostly meaning sidewall stiffness & air pressure). Actually, when going to very low profile tires, the area of the footprint can & often times does get SMALLER because the increased air pressure & sidewall stiffness does not allow the tire to conform to the road surface as much. Tire mfgrs. have done studies that show this to be the case. Large diameter wheels and tires are only needed to clear large brake components, there is no other engineering reason to run large diameter wheels. For most passenger vehicles, this means that 15" or in some cases 16" is the biggest you really need to run, everything larger is style driven, not engineering driven. Nothing looks odder to me than seeing slammed Honda Civics with 18" wheels & teacup sized brake discs & tiny calipers. Don't forget, unsprung weight, and much more importantly, rotating weight, can easily go up dramatically with larger wheels and tires. You have to be careful about watching the weight of the overall wheel/tire package & avoid increasing it much, if any, over the stock weight. For performance increases you want to reduce rotating weight, not increase it. Rotating weight increases can really hurt acceleration because you have to spin this extra weight around all 4 wheels, that's why it's so much more important than vehicle weight. Talked to a lot of guys over the years who were baffled at the way their car felt "sluggish" after changing to heavier/larger wheel/tire combos. Bruce

[Charlie DiMarco]

VeniVidiVeloce,
The tire size in this application is 215/35/18 front and 235/35/18 rear. And we used custom made hub and wheel centric spacers to widen the track and fill out the fender flares.

Charlie
www.serpentautosport.com

Comparing the 235 35 18 on the rear to what I believe is stock (195 60 15) the 18 is only 1.07% larger; completely acceptable.

Rotational inertia on the other hand would be something to look at in more detail as it could negatively affect braking.

Did the 235 not fit on the front?

What offset did you end up using front and rear?

Do you have any straight side-on photos?

-Brian

[Charlie DiMarco]

Brian,
The 235/35/18 would not fit the front. My goal was to have no rubbing under normal driving conditions. The front wheel/tire combination had to be determined first. And having mounted 215/17/40's on the front of my GTV6, I knew 215/35/18 would work. Offset front and rear is 40 mm. On the rear the wider 235 was used to give this car "the look".

Here is the best side shot I have.

[alfaholico]

Great looking wheels Charlie. Very similar to the Anterra's I had on my 164.

[GoldCloverLeaf]

There is a GTV6 down the road that has 18" wheels, i should take some pics, looks pretty good. I have 18" wheels on my Alfetta sedan and they do not rub at all with 215/35/18 tires all around.