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Discussion Starter #1
Evening,

I purchased a set of 18" pegs and looked around and have seen both 235 40 and 45 tires on them.

What would you recommend? 40 or 45? I like a smooth ride plus I am afraid that with some bad roads (aside from the road construction going on) that with the 40's I'll bend the wheel if I hit a pot hole. I try to stay away from those roads but sometimes hitting a pot hole happens. I am also worried that if I use 45's the tire will rub more than now. The 17" I currently have rub when turning the wheel the way so I would guess that it will do it with the 18's. The 17" have 235 45 17 tires.

Your input is appreciated.

Thanks!
 

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45 won't be significant enough to offer protection that a 40 won't handle and you will have speedo issues. just stick with 235/40 and go with a quality tire. The cheaper the tire, the thinner the sidewall, not universally true, but close enough for donuts and hand grenades. I use Mich Pilot super sports, but re-11s, contisport contacts, p-zeros, and so on are all good choices. Kumho, Sumi, Nexen, Hankook, or ANYTHING from china, well, you get what you pay for. In over 20 years of driving i have never had a blowout or a morning flat with Michelins. Jm2c
 

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Stick with the 235/40. I personally run a 225/40 for less rubbing issues and avoid fitment problems when I drop the car on coils this spring. As for brands I have the pilot super sports as well and they are an outstanding tire but kinda pricey. I wouldn't knock hankook though, I had great experience with their ventus v12 evo. Not as good as my super sports but they're significantly cheaper.
 

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235/45/18 will rub on a P2 S60, but 225/45/18 will fit okay if you want more sidewall protection/comfort than you get with 235/40/18.
 

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Discussion Starter #5
Thanks for the tire recommendations and information. This is good to know.

Baron, how much off do you think the speedo will be?

Stonerzebra and Warpedcow, I like your suggestions. That explains the s60's with the 45 side wall. Just use a 225 width. I really don't want to drop my car so I guess it depends on how bad the speedo issue is. But after reading your suggestions I am leaning toward the 45.

If the speedo doesn't really change by much, maybe 1 to 3 mph then I think I'll go with the 45.

Thanks again for the help!
 

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the speedo issue will be minimal at best, just be aware of it. as long as you stay around 25.3-25.5 in new height. It is worth noting though that as a tire wears one will lose the better part of 3/4 inch anyway, so to some degree as long as you stay as close as possible to factory sizes, ie, no more than 5 in aspect or ten in width, but not both, you are fine. It is also worth noting that 235/40/18 is a factory size for the p2
 

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Discussion Starter #7
Thank you for the info. So basically if I understand the last part you wrote I should be fine either a 225/40/18 or a 225/45/18, correct?

Thanks!

the speedo issue will be minimal at best, just be aware of it. as long as you stay around 25.3-25.5 in new height. It is worth noting though that as a tire wears one will lose the better part of 3/4 inch anyway, so to some degree as long as you stay as close as possible to factory sizes, ie, no more than 5 in aspect or ten in width, but not both, you are fine. It is also worth noting that 235/40/18 is a factory size for the p2
 

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Bridgestone Pole Postion Potenzas will not rub at 235. Weird how different manufacturers have different widths despite still being 235. I run 235/45/R17. Theyre all seasons though.
 

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Discussion Starter #10
Yeah, I noticed that with my 17" inch tires. They rub with one set I had and not with the other. That is weird. How's your ride quality using that size you have right now? Thanks!

Bridgestone Pole Postion Potenzas will not rub at 235. Weird how different manufacturers have different widths despite still being 235. I run 235/45/R17. Theyre all seasons though.
 

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Yeah, I noticed that with my 17" inch tires. They rub with one set I had and not with the other. That is weird. How's your ride quality using that size you have right now? Thanks!
My ride quality is quite an improvement over the 18" setup I had going before. I run 34 psi all around. Still firm but just squishy enough to avoid feeling like I'm shattering the earth imo.
 

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Discussion Starter #12
Thanks for the info Hoenig. Much appreciated. I think I'll go with the 235/45/18. Thanks again for all your help everyone.

My ride quality is quite an improvement over the 18" setup I had going before. I run 34 psi all around. Still firm but just squishy enough to avoid feeling like I'm shattering the earth imo.
 

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45 won't be significant enough to offer protection that a 40 won't handle and you will have speedo issues. just stick with 235/40 and go with a quality tire. The cheaper the tire, the thinner the sidewall, not universally true, but close enough for donuts and hand grenades. I use Mich Pilot super sports, but re-11s, contisport contacts, p-zeros, and so on are all good choices. Kumho, Sumi, Nexen, Hankook, or ANYTHING from china, well, you get what you pay for. In over 20 years of driving i have never had a blowout or a morning flat with Michelins. Jm2c
Interesting.... had a flat this morning on my SR. Michelin PS2. Haha. But hey, not even a $200 tire can protect from a wood screw at just the right place at the wrong time.

On size, what Baron said is quite true. The 45 aspect tire isn't going to afford much more impact protection than the R size 235/40-18 and speedometer error of 3.6% low is what you'd be looking at. Not that big a deal but rubbing - I'm guessing - will increase as the 235/45-18 is nearly a full inch taller than spec 235/40. Keep in mind that the 235/45-17 and 235/40-18 have virtually the same rolling diameter and width obviously. Diff is in the sidewall.

Comfort, well, obviously the lower and stiffer the sidewall, the more NVH from the road will be transferred to the cabin but that's totally up to your threshold of pain. Just be thankful you're not on 4C suspension.

As for brands, any of the top tier brands will do fine, depending on how you drive, how far you push it, etc. I can't quite agree with Baron on his feelings towards the lower cost brands though. I run Sumitomo HTR Z3's on my Z33 and even with full modded suspension and semi-illegal running in the hills, I'm yet to put a wheel off. Lives up to the Max Performance rating with good grip, high tactile response, and razor sharp turn in - even more than the PS2s I had on the car previously. (Additional datapoint: No personal experience but the Kumho Ectsa LE and Hankook Ventus V12 Evos are very well respected as well)

HOWEVER, I do realize we are talking about two very different cars and given that, when I replace my SR's tires, I will probably ante up for another set of PS2s or Contis just because.
 
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