Need some advice on what to expect with changing wheel/tire sizes

[BlueLdr]

I'm planning on getting new wheels for my EX Sedan in the coming months, and I've been toiling over what tires and wheel width to go with. For wheels, I'm upgrading from the 16x7+45 alloys, and I've narrowed my choices down to the Enkei TS9 (18x8+35), Motegi MR140 (18x8.5+35), Flow One F3 (18x8+40), and Avid.1 AV-27 (18x8.5+35). For tires, I'm upgrading the stock 215/55R16s to 225 or 235/45R18, and I'm deciding between the Pirelli Cinturato P7 All Season Plus and the Continental PureContact LS (and maybe the Michelin Premier A/S). I have several concerns about how my driving experience will change from what it is now.

1. The most important factor to me is road noise. Currently, it's not usually very noticeable, but it can get loud at times. I'm aware that wider tires generally create more road noise, but I don't know if going from the mediocre stock Firestones to a GT tire won't mitigate or even overcome the effects of the wider tire. If it does compensate for the tire width, I'll probably end up going with the PureContact or Premier, since they have much better handling ratings then the P7. On the flip side, if the wider tires are going to be louder no matter what, I don't see any option besides the P7s, since they seem to be by far the quietest tire in the category.

2. The second concern I have is about wet road handling. Wider tires typically do worse in wet conditions, but again, I don't know how much worse (or better) they'll be than the stock Firestone FT140s, which have seen very little praise on these forums. The main thing stopping me from going with the P7s is their considerable shortcomings when it comes to wet handling. If they're still better than the current tires, then I wouldn't consider it an issue, since I haven't had any problems with these tires so far.

3. Next is fuel economy. Unfortunately, the stock 16x7s don't have a weight listed in the sticky at the top of the Wheels/Tires forum, so it's hard to compare weights (if anyone knows the weight that'd be greatly appreciated). I was getting 35-37MPG in the fall, and it's dropped to 33ish during the winter, mostly highway driving, and a bit spirited at times. With wider/heavier wheels, it seems there's no avoiding some decrease in MPG, but I'd like to limit that drop to 2-3mpg. Is that a reasonable expectation? What difference in MPG would you expect between an 18x8 with 225/45 and an 18x8.5 with 235/45 (due to both weight and tire width)?

4. Whenever I read about speedo error from changing wheel size, people seem to talk about it like it's something you just have to live with. But is there any reason I can't just go to the dealer or a shop (or buy the calibration device) and have it re-calibrated?

5. Finally, I'm wondering about tire stretch. I'd like to go with 225/45 to help address the above factors, but if I were to put those on an 8.5" wheel, would the stretch be completely safe, and how would it effect noise and fuel economy?​

I'd also like to know if I need to worry about rubbing issues if/when I decide to lower my car down the road (the drop would be less than an inch). Other advice on which wheels/tires to go with is also much appreciated.

Thanks!

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[BlueLdr]

You are very unsure of what to get I can tell. A very common setup for these cars without issue is going to be an 18x8.5 rim with 235/40 Tire on it.

I'm confident about the wheel choices, it's the tires that I haven't been able to find a straight answer on. I'm definitely going with /45 tires instead of /40 to help reduce noise. It's just the tire width and quality relative to the stock tires that I'm not sure about. Seems like very few people on here had the 16" stock wheels.

 

[racer]

Lots of variables.. the same type the manufacturer has to deal with when settling on 1-2 different brands they offer.

Wider tires yes, are generally noisier, simply do the the larger contact patch. Wider tires also tend to improve road handling, due to the same enlarged tire patch. Lower profile tires also tend to introduce harshness into the ride quality. Wider tires will also cause an increase in fuel consumption due to increased drag.

In some ways, imho, the very things you are trying to avoid ARE a direct consequence of going to a larger wheel.

Since the tire is the only part of you car touching the road, perhaps the best upgrade would be to swap out the Firestones for some nice new Michelins. Over the years and many brands, I've always been most impressed with Michelins ride/performance and compromise/abilities - Dry, Wet, Snow etc. Road noise too.

Perhaps just a tire change from 215/55-16 to a 225/50-16 would be enough?

While you have many variables to try to address, perhaps a simple way to do so would be to take your current car on a drive to your local dealer. Ask to test drive a new Sport ( or something with 18" wheels) and see how you like the ride first? Do you notice ride quality issues you would be unhappy with?

 

[BlueLdr]

In some ways, imho, the very things you are trying to avoid ARE a direct consequence of going to a larger wheel.

I'm aware of that, but I'm upgrading the wheels for aesthetic purposes.

To put it another way, I've been researching for months and reading tons of reviews about the tires I listed in the OP. But those only tell me so much, because those customers all have different standards, and are judging the tires relative to what they've experienced in the past, which is something I can't relate to or infer. I'm asking here to see if anyone can offer a more direct comparison to the stock Firestones.

While you have many variables to try to address, perhaps a simple way to do so would be to take your current car on a drive to your local dealer. Ask to test drive a new Sport ( or something with 18" wheels) and see how you like the ride first?

That's actually a great idea, I might try that when I take mine in for service this week.

 

[racer]

I really like the 18's and the sporty performance of the wheels is a great match to the Si's other performance attributes. That said, pothole season is just plain nasty here in Nova right now. For the past 30-40 days I've wanted nothing but my old VW back with 15" steel wheels and 65 series tires. I cringe every time a pothole sneaks up on me with the Si's factory set up. I keep waiting to see the tire warning light go off and prepare myself for a 2hour wait from roadside assistance

 

[yongfeel]

Hey OP. Having tuned my cars in the past, I can confirm that any sticker, wider, narrower combination of tires (hence bigger wheels) will drop your MPG, comfort, noise. Like what racer commented, what you're looking for is completely contradictory to having a bigger wheel size, despite what brand/model of tire you're getting, and how much weight your shaving off.

If you just want to tune for pure aesthetic purposes, get some nice 17-18in wheels in smaller width, perhaps in 7-8, put on some spacers for more pokey looks, and nice touring or low-db all seasons in somewhere along the 215/50/17 to 235/40/18 range. That way, you will lose some comfort, but noise and mpg change will be minimal.

 

[BlueLdr]

That way, you will lose some comfort, but noise and mpg change will be minimal.

Got it, looks like 18x8 and 225/45 is the way to go then.

The remaining question is how good the Pirelli P7 is in the rain vs the firestones.
Edit: and also the speedo calibration.

 

[racer]

Might want to check a tire calculator:

https://tiresize.com/calculator/

The swap you propose (215/55-16 to a 225/45-18) is actually a taller wheel combo. Speedo will read low!

 

[BlueLdr]

Might want to check a tire calculator:

https://tiresize.com/calculator/

The swap you propose (215/55-16 to a 225/45-18) is actually a taller wheel combo. Speedo will read low!

Yep I'm aware, that's one of the things I asked about:

"4. Whenever I read about speedo error from changing wheel size, people seem to talk about it like it's something you just have to live with. But is there any reason I can't just go to the dealer or a shop (or buy the calibration device) and have it re-calibrated?"

 

[BarracksSi]

Look -- if you're concerned about smooth ride quality, fuel efficiency, and hitting potholes, don't get 18s.

 

[racer]

https://www.roadandtrack.com/car-cu...nce/a33371/how-to-fix-misreading-speedometer/

Of course you could recalibrate. Of course, knowing that you are just a few % off is easily remembered by the brain.. Speedo says 60mph (assuming it was correct to begin with after all).. then just add or subtract 1-2 (or 5)mph. Not a big deal imho. I've been doing it for decades when I swap wheels/tires on my other car. Most folks likely just use their phone GPS since they feel its more accurate anyway for speed.

BarrackSi of course said exactly what others have at least inferred... the tire swap you want to make will have the direct opposite effect of what you want. Not trying to deter you, but would hate to hear you are upset after making the swap!

 

[BlueLdr]

BarrackSi of course said exactly what others have at least inferred... the tire swap you want to make will have the direct opposite effect of what you want. Not trying to deter you, but would hate to hear you are upset after making the swap!

Right, I'm prepared to make a bit of sacrifice, I'm just trying to get an idea of what factors will be most important in trying to make up for some of the negatives.

 

[ZephyrFlash]

My MPG has mostly stayed the same since upgrading to 245/40/R18 - though I believe that is largely due to keeping my driving habits the same. Anecdotally speaking when you get better wheels with more grip you tend to push those new limits (acceleration, top speed) a bit more and as a result lose MPG.

Just my 2 cents - remember you're the one driving your car, not any of us.

 

[BarracksSi]

Back to this:

Got it, looks like 18x8 and 225/45 is the way to go then.

8" wide wheels are good for 235-width tires, too (and most 245-width tires are spec'd by the manufacturer to fit 8" wheels).

Also remember that the stock 18s on Sport/Sport Touring/Si models are 18x8 +50 with 235/40-18 tires. Use that setup as a more direct comparison than extrapolating from your 16s.

Lastly (for now ) I'd recommend not sacrificing strength for weight on a daily driver. I hit a hole on 295 in DC that was the hardest hole I've ever hit in ANY car, and somehow my stock 18s were undamaged (or, at least, the tire didn't blow out and the rim didn't bend). I'm not confident that the Rotas I had on my EP3 would've survived, and I doubt even less that extra-light rims like RPF01s and lower-profile tires would have survived, either. I'm cool with lightweight rims for auto-x, but not when I'm just trying to get home at 11PM in the rain.

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