[Void98]

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 cars and headers, not yet tuned, nothing fancy.

my question is whether the power my relatively stock Z powers 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)

 

[dkmura]

Your instincts are good on this subject. Using a 295-40-18 on the rear increases your unsprung weight significantly. This'll decrease acceleration, braking and overall efficiency; particularly if on a 18X10.5" wide RPF-1. For the bolt-ons you're running, you'll decrease performance for sure. For near stock HP/TQ levels you're running, I'd suggest you run a 18X9.5 RPF-1 with a 275-40-18 as the largest combo. It'll still fill your fenders, provide more traction and be a much better match for your Z.

 

[Void98]

Your instincts are good on this subject. Using a 295-40-18 on the rear increases your unsprung weight significantly. This'll decrease acceleration, braking and overall efficiency; particularly if on a 18X10.5" wide RPF-1. For the bolt-ons you're running, you'll decrease performance for sure. For near stock HP/TQ levels you're running, I'd suggest you run a 18X9.5 RPF-1 with a 275-40-18 as the largest combo. It'll still fill your fenders, provide more traction and be a much better match for your Z.

Thanks for the info! Defo nice to keep in mind but I already have the 18x10.5 rear and 18x8.5 front (rear mostly) so I need to figure out the best tires for those wheels cause selling them now and getting another set of RPF1’s would be a major hassle.

Do you think I should go with 285/30/18 instead for my 10.5? Or 285/35/18 would be better for overall longevity without sacrificing much performance? I keep reading mixed thoughts about fitting 275 into 10.5 so 285 to be safe.

 

[dkmura]

Why not just keep your 18X10.5" RPF-1 wheels? Just store them until you develop more power and need greater traction. The good thing about Enkei wheels is they're not so expensive that cost is prohibitive. In racing, the rules change enough that I've got extra sets of Enkeis on ice, but it won't bankrupt me either.

You need 18X9.5 or 10" and I wouldn't use 285/30/35s either...

 

[Void98]

Why not just keep your 18X10.5" RPF-1 wheels? Just store them until you develop more power and need greater traction. The good thing about Enkei wheels is they're not so expensive that cost is prohibitive. In racing, the rules change enough that I've got extra sets of Enkeis on ice, but it won't bankrupt me either.

You need 18X9.5 or 10" and I wouldn't use 285/30/35s either...

I guess it’s fair but I have other expenses so I can’t afford another set of wheels and tires right this second and I’m defo not putting those 20” monstrosities back on lmao. It’s not that bad just didn’t knock my socks off like I thought it would lol. But yeah I could always store them for later when I go FI or maybe even trade for a 9.5 with good tires that are 275 I’m not sure yet but it’s not urgent I’ll figure something out. Looks kinda badass tho, but I haven’t seen a single car with such wide tires as mine driving around and I’ve seen some BMW M series, some AMG Mercedes, some chargers and challenges, **** even the nismo team didn’t go with that wide a setup for a reason makes me feel like I did something wrong here

 

[dkmura]

The NISMO 350Z never used wheels and tires that big precisely b/c of the increase in unsprung weight. The increase in traction could be achieved through a smaller, lighter wheel/tire combo.

 

[MicVelo]

The NISMO 350Z never used wheels and tires that big precisely b/c of the increase in unsprung weight. The increase in traction could be achieved through a smaller, lighter wheel/tire combo.

And yet, the 33 Nismo runs a 10" wheel that weighs in at 29 lbs with a factory Bridgestone at 31 lbs for an even 60lb! Boat. Anchor. Surprisingly however, I never had any weight "issues" with my 33 Nismo. The setup was lively and even after I put on my S-Tune 34 wheels and noticed an immediate improvement (10lb less per wheel), never felt the stock wheels were terrible.

 

[Void98]

And yet, the 33 Nismo runs a 10" wheel that weighs in at 29 lbs with a factory Bridgestone at 31 lbs for an even 60lb! Boat. Anchor. Surprisingly however, I never had any weight "issues" with my 33 Nismo. The setup was lively and even after I put on my S-Tune 34 wheels and noticed an immediate improvement (10lb less per wheel), never felt the stock wheels were terrible.

Update: I weighed and looked up stats to make sure and it turns out my tears are 46lb total (19.7lb wheel, 26lb tire. Funny enough 295/35/18 is 26lb and 275/40/18 is 27lb?). Fronts are 41lb. That’s not 10lb per wheel, a little more, but remember that I’m comparing it to my old 20”. I thought my old 20” were super heavy but they were only 50lb with low profile tire...guess tires are just as heavy as wheels usually and 20” low profile tire must’ve been like 35% of the total weight.

 

[dkmura]

OK- I stand corrected in light of these wheel weights. Perhaps it's because I ran a 285/30-18 tire on a 18X10" Enkei RPF-1 when we first started running the Z in T2 racing. This combo offered durability for racing (two weekends- hah), but was never really any faster than the 275/40-18 as the SCCA began looking for ways to slow the Z down.