Void

Hey everyone,

I have a 2003 350z touring. It’s mostly stock with some plenum spacer, aftermarket air intake, catback, blah blah blah all the noob beginner **** (it’s worth mentioning for context later)

HOWEVER, my previous Z I had the OEM wheels 235-50-17 (rear) I believe I don’t remember exactly but it was a 2003 enthusiast OEM wheel and tire setup.

My current 350z I got from someone who had trash wheels so I swapped them for RPF1 18x10.5 with 295-35-18 rear setup.

Here’s my question: my current Z being mostly stock (no FI, not even a tune yet) is 295 too much width for rear tires? Would I notice a huge gas mileage decrease and decrease in acceleration because my stock VQ doesn’t need such wide tires? Or am I overthinking it and the difference, if any, is minuscule and the bigger factor is weight which is probably the same given my light RPF1’s (total rear tire and wheel OEM weight and current setup weight probably about the same).

width or weight is the most important thing essentially? Because I feel like the wider the tire the more contact thus more friction to overcome from a standstill acceleration point for the engine that’s not pushing very high HP.

thanks in advance! I had my old enthusiast Z many years back so I don’t remember exactly how it felt so that’s why I’m asking. Hard to compare since I can’t remember the feeling of it from many years ago on OEM wheels and tires to fit those wheels OEM specs. When I drive around I see big SUVs and even cars that push a lot more HP like Infiniti Q60’s and challenges and whatever run much narrower (stock) tires in the back and I’m pondering every time whether I’m doing something wrong...

bealljk

iTrader: (13)

My RPF1s with 295 x 10.5 Toyo R888 are about 55lbs (21lbs wheel and 33lb tire - plus or minus).

I would say that this setup is too much for an NA tuned setup. But I think the change in fuel economy and change in performance will be a function of your baseline wheel/tire setup. If your current setup is 65lbs than you will notice an improvement, if your current setup is less than ~55lbs than you’ll likely notice a decrease in performance.

Optimally and economically - if you can get a 20 to 25lb tire with a 20 - 22lb wheel this will be about as good as it’ll get without spending 1000s on light weight wheels.

Weight will be your most influencial factor … width will increase weight (all things being the same)

Friction is sorta a goofy thing -
If you want to get into the weeds friction will stay the same between a narrower tire and a wider tire.

Friction is a function of the co-efficient of friction(ie the rubber on asphalt) and the normal force(how much weight is being applied).

A wide tire means more area for the same weight to be distributed over versus a narrower tire with less area for the same about of weight.

Example - 3200lb z (with 800lbs on each corner):
RPF1 10.5” wide tire by ~4” patch = 42 sq-in = 19lbs per sq inch

OEM 9” wide tire by ~4” patch = 36 sq-in = 22lbs per sq inch

Do you want more lbs/sq-inch over less area or less lbs/sq-inch over more area?

As mentioned above - tire compound is not not being factored in and this is all in a vacuum…

Void

my rear wheel is 19.7lb per wheel and 26lb per tire rear (continental extreme contact DWS06+) so 46lb rear combined per side rear.

so basically we have a 10.5 295 width 46lb current and I think OEM touring 2003 setup is 61lb. Forums say the touring 18” are 26.5lb per wheel and tire combined according to many using a kitchen scale lol which would make the tire 35lb?! Hard to believe but yeah according to forums OEM wheel (18” touring) and tire is 61LB and wheel itself is 26.5lb.

essentially my rear went from 61lb OEM to 46lb current rear. Patch increased from 8.5 235 to 10.5 275. Thoughts?

terrasmak

iTrader: (8)

Then you have surface area for forward motion with wind resistance , an extra inch per side is a good about of wind resistance.

IMO, for an NA car that is street driven a 275/40-18 rear is the perfect tire. It’s got a great balance of width, traction, weight and rolling resistance. Once You move toward track use or FI, the needs change and get specialized.

JCat

iTrader: (4)

During the eighteen years I have owned a 350Z, I have tried the stock Bridgestone's, Toyo's, Michelin Super Sports, and Goodrich KDW 2's in sizes 245 up to 295. The mileage did not vary much at all.
.
Even though my Goodrich KDW 2's are not worn out, they are old and I need to replace them. I wish they were still available. https://my350z.com/forum/wheels-and-...ml#post9513000
.
I will not purchase the Michelin Super Sports ever again. Despite the fact that many folks like them, I thought their traction and performance was poor.

bealljk

iTrader: (13)

61lbs ‘seems’ heavy but it wouldnt surprise me… I think my toyos are pretty heavy for tires but it’s a necessary evil.

I went from a 65lbs TSW 20” wheel/tire combo down to a 44lbs advan/toyo street proxy and it was noticiable different.

a 275 18” does seem like a ‘sweet’ spot for an NA car - 100% agree

Terra & JCat - any thoughts on the Hankook Ventus lines?

Ponyryd

Weight is much more of a contributing factor to fuel economy than tire friction on launch. Lighter is always better, for mileage, driving dynamics, and perhaps most importantly, for braking as well.
But if you wanna sell them RPF1s send me a message and maybe we can work something out : )

jhc

When I bought my Z it was wearing Konig Unknown 8 X 17" square with BS RE 70s, 225/40/17 and 245/40/17.
I decided to go with Enkei RPF1 9.5 X 18, 265/35/18 and 10.5 X 18, 295/35/18 MPSS. The car was dramatically more sluggish, handling and acceleration suffered significantly due to the extra rotating mass. The Vortech cured the acceleration problem but the steering/nimble quick handling just isn't there like with the smaller setup.

It basically boils down to how you drive and preferences between better acceleration/braking vs higher confidence in corners. And looks, and $$$$.

bre240z

would this set up be much better compared to the set up you mentioned above with the bigger tires?
18x9.5 255/40/18 front and 18x10.5 275/40/18 rear for the DE N/A

Void

thanks for the input. Yeah I’d imagine if you FI it you’d want to go a little wider but I don’t have a point of recent reference so I’ll have to take your word for it, which makes perfect sense. That’s a big leap. Would you happen to know the original wheels and tire weight per wheel? Rear mostly but I’ll take an average. Because I wonder if it became more light yet still gave you those drastic disadvantages just by the factor of its sheer width.

More contact makes it harder to handle is imagine but more secure. I’m mostly concerned about acceleration, especially from stop since as you go there won’t be static friction from all that contact patch to overcome. At least that’s how I envision it in my mind.

that’s the most useful input anyone has given me btw so thanks for that. Not that I appreciate being disappointed knowing I spent the $$$ to make it “worse”...in a sense of speaking, but it’s still useful from actual practical experience side

jhc

[QUOTE=bre240z;11073066]would this set up be much better compared to the set up you mentioned above with the bigger tires?
18x9.5 255/40/18 front and 18x10.5 275/40/18 rear for the DE N/A[/QUOTE
Depends on what's important to you, Amigo.

Sorry man, I don't weigh things like some others.

bealljk

iTrader: (13)

Dont worry - I’ll pick up your slack! Lol!