Void

Hey, long time lurker first time poster.

I recently upgraded to RPF1’s and went with my mechanic’s specs but I’m having second thoughts after doing some reading. I’m a little new to the technical aspect of tires so I was hoping to get some insight.

I'm running rear tires at 295-40-r18 rear (Continental ExtremeContact DWS06+ if it matters for this purpose, +15 offset)

I have a 2003 350z Touring, mostly stock, just a plenum spacer, cold air intake, Invidia Gemini catback, stock cats and headers, not yet tuned, nothing fancy.

my question is whether the power my relatively stock Z puts out warrants such wide and, judging by the aspect ratio, heavy tires or am I looking at an acceleration decrease opposed to another narrower and less meaty setup?

thanks for any input guys.

(p.s. fronts are 245-40-r18 18x8.5 +30 offset with a 20mm spacer)

terrasmak

iTrader: (8)

Just run the proper 275/40-18 rear,

why not buy the 9.5 inch fronts

Void

the fronts aren’t that much of an issue, I’m more concerned with rears since it’s RWD. You’re right but I already have 10.5. I also keep getting mixed reactions about fitting 275 into 10.5 so my thought was going 285/30/18 or that sidewall is gonna be too thin? 285/35/18? Is that even much of a difference in performance from my 295/40?

DarkZ03

iTrader: (11)

The tire you are running in the rear is too tall anyway IIRC.
Standard fitment for VDC cars are 245/40-275/40 or 255/35-285/35. The thing is I think you need the 9.5 front for any of this to look right IMO. I don't know of anyone running a 2"stagger on the wheels,, as you can see with the tires the normal amount is 1".
That is why Trav brought it up, as far as the tire being too much most will say yes, I'm running 305s and I love them so far but my overall weight is very close to stock wheels.

Void

I wanted them staggered. As far as the difference for front and rear I’m not sure, but it looks good aesthetically. I’ll be running a 20mm spacer so it’ll look even better, I’m not really concerned with that as much as I am with loss of potential performance because I opted for RPF1’s because they’re the lightest in their price range but it kinda feels like I’m shooting myself in the foot with the tires lol, and even the wheel width, could’ve gotten 9.5...I’ll rock them as is I just don’t feel the difference I hoped I’d feel going from heavy no name 20” wheels to RPF1’s be it that the 20” wheels had low profile tire like 265/35/20 plus what’s worse is not just the weight but also that my stock Z is struggling with the 295 width but it is possible that I’m overthinking it a little

bealljk

iTrader: (13)

I would compare weights of the wheel tire combo ... the RPF1s are one of the lightest wheels on the market and even with the larger wheel and larger tire you may be under the OEM 9" wide and 245 +/- weight.

I run 10.5" RPF1s with 295s but I am modified and I'd agree with you that they are heavy tire/wheels

You may want to ask around / poke around and see if anyone would trade you your 10.5" for 9" or 9.5" ... I too am looking for a set of 'as narrow as I can go' RPF1s for my fronts...

Void

yeah that’s what I was scared of, as though all the cash on the light wheels but the net weight just remained the same except now my stock Z also has more tire width to battle with. It’s not that bad but for the money spent I would like it to knock my socks off lol. If I were FI then it would be a different story but you said you’re modified, I’ll assume a turbo and you still aren’t a fan of 10.5 295/50/18 that makes me feel even worse lmao

DarkZ03

iTrader: (11)

I wasn't saying not to go staggered, just less in the wheel dept. You can't keep the "token" setups by running a 2" stagger, one tire will look ballooned and one stretched to a degree. I chose my tires FIRST and bought my wheels to match those tires not the other way around, I'm on a 275/305 with 9.5/11 which are the nominal sizes for each other and it looks GREAT.

bealljk

iTrader: (13)

yea turbo'd ... I should clarify

I like the 10.5" in the rear and i may go batty and put a 305 or 315 in the rear (and these are a drag strip and 1/2mile setup) but I dont like the 10.5" in the front (although it makes the car look super aggressive).

I have 9" advans for daily that are signficantly lighter.

If I could find a narrower front tire to pair with the 10.5 RPF1s I would be happy. Would love to find a set of OEM track wheels...

MicVelo

Just a couple of basic comments/questions...

With a 245/40-18F & 295/40-18R combination, I'm really surprised you're not pissing off the VDC with such a large (~5.5% F-R) diameter delta. With the stagger that far out of spec (where ECU is set between 2.75-3.25% tolerance or so), your car should be triggering classic limp reaction. Seen some cars tolerate more or less but a 2% delta from stock? Hmmmm.... that's a red flag. Put this way, if your VDC isn't kicking in with that much stagger, it's likely not working or disengaged.

Also, s'far as acceleration, well, yeah, a slight hit if the overall tire/wheel combined weight is anything over about 55lbs (roughly the weight of stock Touring 1s with 245/45-18s) but hardly anything to overthink or worry about. You didn't spec the tire type/brand so I can't say if the tire is going to be heavy or light in comparison with stock. If you bought an Extreme or Max performance grade tire in that size, I'd guess with the RPF1s, it's about a wash with stock. Anything else (like an all season UHP tire), likely a few pounds more than stock but again, nothing to get upset about. Car's got decent power.

EDIT: Just went back and saw that you did spec the tires. My bad. The DWS06 in that size is pretty beefy at 38lbs. Add the roughly 19lbs of an RPF1 10.5 +15 and you're at 57lbs. No gain over stock but if you had heavy 20s before, well, you should still be ahead.

Where *I* (personally) would be a little skittish (I hesitate to say "concerned" cuz its not that big a deal) is how the 2" wheel width and 50mm tread width delta would affect overall handling. Tending more towards understeering I'd guess as the front tires, with that much less width, will tend to break first; whereas a neutral or tending-towards-oversteering car will allow the rears to reach/exceed slip angle slightly earlier. But with that much more rubber; hence more grip, the fronts will wash out.

Not to give you any reason for real concern as that's only at the edge of adhesion; that is, heavy hills use, track, etc. Everyday driving, you'll never feel the difference.

Void

thanks for taking the time to explain. How would I know if my VDC isn’t working properly apart from educated guessing? Also, I’m running Continental ExtremeContact DWS06+ (as you know 245-40-r18 front, 295-40-r18 rear).

The rear tire width concerned me the most followed by the large sidewall, which I was recently convinced isn’t that bad, I never really gave the wheel widths any big thought. That’s what my mech suggested as staggered if I didn’t want to go square, which I don’t, because I daily my Z. I don’t track it, and I heard that a square setup may feel a little different and unfamiliar and I don’t need that. Maybe I’ll see if I can exchange my RPF1’s front wheels to 9” or 9.5” through the website or maybe another individual looking for a 8.5”.

while I don’t track it I still want to be reliably certain of its abilities to handle well. I read lots of forum info and watched a lot of YouTube vids and I’ve seen crazier setups. https://low-offset.com/nissan/best-350z-rims-wheels/ for instance says, among other things, that “Square vs staggered setups are a hotly debated topic. While some 350z owners like being able to rotate their wheels front to back, some will use smaller wheels in the front (19×8.5”, for instance), and larger wheels in the back (19×10.5”).” So 8.5 and 10.5 may not be that unusual.

I understand wheels and tires a lot more now than I used to but im still a little confused about the idea wheel width to tire width because you can supposedly use 275 tire with 10.5 as well as with 9.5, so if both have tire width of 275 does it matter if the wheel is a little wider? Or am I misunderstanding something? Does fitting 275 involve some stretch that’s why you can fit it onto 10.5? Because otherwise I’m a little confused. I’m trying to see if continental would let me exchange my 295 for 285/40 or even 275/40 but now the wheel width seems to be the bigger concern?

thanks for any input I’m kinda stressing out more than I probably should, I don’t do anything crazy but as a college kid it took me a while to save up for a Z so I want to make sure it’s “fun” only when I want it to be, otherwise it should be predictable

MicVelo

I'll start by answering your last statement... Don't stress out. You're fine. Sure, you could optimize the setup some (maybe a wider front or narrower rear wheel) but like I said in my first post, there's nothing horrible with the setup. So long as VDC is not giving you problems (the biggest of the possible ills) then don't sweat it.

General rule for optimal tire performance is what's called the 120% rule. That simply saying that a proper tire to wheel relationship is where the tire doesn't exceed 1.2x the width of the wheel. (And conversely, tire shouldn't go below 90% of the wheel width). But that's really just a guideline as one can see by all of the varying OE and aftermarket setups. I mean there's people running 7" wheels 245 to 275mm rubber. Do they fall off? Nahhh. Are they maximized for a healthy hill run or day at the track? Probably not but as long as they're safe, not a big issue.

With a 10.5" wheel, you can run up to a 315 tire or as little as a 245, however stretched. Not that you want to do that but in theory, it's not going to hurt anything. If you keep your tires within the reasonable confines of the wheel width, you're perfectly fine.

On the staggered versus square argument, either are fine for the street and isn't going to make that much difference in that environment. If you're pushing the car 8/10ths or more, yes, there will be a difference in how the car behaves between the two but even then, a good driver can adapt to the differing chassis behavior, under or oversteering.

Don't sweat it.

Void

thanks for the reassurance. I weighted my old wheels and new wheels (and looked up stats for new wheels too to make sure) and it turned out my old 20” wheels were only 50lb rim and tire combined (rear, didn’t weight fronts. Stats: 20x9.5 285/30/18 Stern ST-1). 18x10.5 RPF1 are 19.7 lb, only about a pound over 18x9.5. Rear tire 295/35/18 is 26lb. Funny enough 275/40/18 continental’s are 27lb. Total of 46lb. I heard that stock 33 Nismo are actually 60lb wheels, but for me the difference wasn’t significant from the 20”. I thought they were gonna be heavy, which they are, but I suppose low profile tires compensate. Idk if 295 width vs 275 width would be a significant difference in acceleration I would actually feel. Maybe after spending so much money I had my expectations super high.

p.s. Tire rack recommended those sizes it turned out

MicVelo

Yup, that was me on the other board mentioning that. But just to clarify for others..... 60lbs is the combined tire/wheel weight, not 60lb wheels. This isn't a hay wagon. Hahahahaha.

I don't really lend much credence to a company that suggests I use 7.5/8.0 on my Z and 8.5" square wheels on my other car when OE spec is 9.5. Yeah, no, that company used to be THE place to go. Not with those lame recommendations.

Void

thanks, great to get so much useful info. Combined obv lol. I was a little paranoid but I was assured that I won’t really feel it (wheel and tire width hinderance) unless I beat the hell out of it in the track.