Why not 205/45/17? Let's do the math...

[bngl3rt]

There are many online tire size calculators, here's one:

http://www.americastire.com/dtcs/infoTireMath.do?dbar=true&r=CSBINT|pc|95014&

So for 17x7.5-ish front wheels on an otherwise stock NSX, the size people seem to have success with is a 215/40/17. Unfortunately as has been covered all too often in this subforum selections for that size are drying up.

However, if I plug in the following values to the tire calculator I linked above, and compare them with 215/40/17:

205/45/17
+0.24" sidewall height
-0.39" section width
+0.49" overall diameter

215/45/17
+0.42" sidewall height
no change in section width
+0.85" overall diameter

I was hoping some of our wheel and tire experts could chime in with more information on what, exactly, would make either of the two listed sizes problematic - is (in the case of 205/45/17) a quarter inch of extra sidewall (adding up to a half inch of extra diameter in total) really a problem? I guess it depends on ride height and other factors?

 

[nsxtasy]

205/45-17 is over 2 percent bigger in outer diameter than 215/40-17 (stock size for '02-05), and over 5 percent bigger than 205/50-15 (stock size for '91-93). That's a pretty big difference, and may be big enough to cause problems for the TCS, depending on the rear size and taking into account the fact that rear tires will wear faster than fronts. It also can make the handling slightly worse when used with a 255 or wider rear tire, as generally occurs whenever the "stagger" (difference in tread width front vs rear) is 50 mm and especially 60 mm or more.

The 215/45-17 is even worse in this regard (almost 4 percent and 7 percent larger than stock, respectively), and is likely to rub on the wheel well liners too.

Why not these sizes? Because they have all of these disadvantages, compared with 215/40-17, and no offsetting advantages. Plus there are some excellent tires available in 215/40-17.

 

[bngl3rt]

I guess I don't care about TCS and am willing to turn it off or disconnect it completely to run the tires I want... so ignoring TCS concerns, let's focus on pure fitment issues.

Will the extra half inch of overall diameter with the 205/45-17 cause rub?

 

[nsxtasy]

Will the extra half inch of overall diameter with the [COLOR=]205/45-17 cause rub?[/COLOR]

It may be more than half an inch. Compared with the three stock sizes, 205/45-17 is larger in diameter by 1.19" ('91-93), 0.65" ('94-01), or 0.49" ('02-05). And yes, more often than not, that difference is enough to cause rubbing. If you're only using them on the track, you may not care if there is some rubbing, which usually occurs only on full steering lock and/or full suspension compression, not all the time.

 

[bngl3rt]

Sorry, this is assuming 02+ OEM wheels (or similar aftermarket, 17x7.5) so 02 OEM sizes are the closest match (for the front anyway)

 

[nsxtasy]

Sorry, this is assuming 02+ OEM wheels (or similar aftermarket, 17x7.5) so 02 OEM sizes are the closest match (for the front anyway)

The car's suspension clearances and TCS are designed for the tire size, wheel size, and positioning of that model year, regardless of what other wheels you may have mounted on it. So any differences are from those for the car year, not the year of the wheel you happen to be using.

Clearly you think you have it all figured out and don't really care about the answers to your questions. So instead of coming here to argue against whatever anyone tells you that you don't want to hear, why not just try it out for yourself? Maybe it will clear, maybe it won't - not all tires labeled as the same size are exactly the same size, so the results may vary depending on the specific tire - but that way you'll know for sure, for the specific tire you're planning on using. If you're not happy with the results, then you can replace it with a different size or make/model of tire next time you need tires.

 

[bngl3rt]

Clearly you think you have it all figured out and don't really care about the answers to your questions. So instead of coming here to argue against whatever anyone tells you that you don't want to hear, why not just try it out for yourself? Maybe it will clear, maybe it won't - not all tires labeled as the same size are exactly the same size, so the results may vary depending on the specific tire - but that way you'll know for sure, for the specific tire you're planning on using. If you're not happy with the results, then you can replace it with a different size or make/model of tire next time you need tires.

I did not mean to give that impression at all and apologize if I came off that way. I am just trying to reconcile the Prime consensus on usable 17x7.5 front tire sizes with what the folks at the local tire shop are trying to talk me into. The assertion that a half inch increase in diameter over 215/40/17 shouldn't pose a problem came from them - obviously they are not familiar with the specific behavior of the NSX TCS so they were thinking purely in terms of fit/clearance. Tires are pretty pricey for a brand new set of four so I am wondering if there is any measuring/information gathering I can do before I commit a bunch of money to "try it". I assume if you do that, and it goes south, then it becomes a vicious cycle of not driving the car because it rubs and therefore not wearing down the tires that you need to wear down so you can replace them with a better size!

 

[GECKO]

I did not mean to give that impression at all and apologize if I came off that way.
[/COLOR]

Yup.......sure appears that way...........you have one of the BEST guys giving you some pretty good advise that you asked for and unless someone else can provide the info, I'd go with Ken. I run 215/40/17 on my fronts and I rub probably due to having the car lowered and was going to go with a 35 profile but Ken thought it wouldn't make that much difference sincve my main issue for rubbing is the lower suspension. You can always sell the tires you buy if you don't like them, and remember there's only one thing between you and the rhubarb field and that's tires, so best be happy with them.............Oh, what brand/mdl are you getting - that's another part of the equation you'll want to figure.

Added: Ken recommended buying the Kumho Ecsta LE Sports 215/40/17 / 255/35/18 and the others I looked at were the Yokohama S Drive........both good performing tires with a bit more life then the full summer ultra high performance. By the sounds of it you want your tires to last a bit longer and there are some good all season high performance tires that are coming out that you may want to look at. We share the same color (mine's a 95) and let us know what you end up with.

 

[Osiris_x11]

I have 205/45R17 fronts (and 255/40R17 rears), in Bridgestone Pole Position RE50A Pole Positions. I am lowered on Tein REs. I only noted a slight (but noted) "rub" upon lock-to-lock turning, especially if it's over uneven gradient (such as turning into driveways).

Also, there can be observable variance across makes/models of tires in the same size, I've noted.

 

[jwmelvin]

Osiris, are those on OEM wheels? Thanks for the data point.

 

[Osiris_x11]

Osiris, are those on OEM wheels? Thanks for the data point.

After-market wheels (Advan AVS Model 5s, 17x8/17x9 with somewhat aggressive offsets). The "rub" noted is on the fender-liner when turning lock-to-lock at low speeds and/or approaching an ascent/descent on a driveway while turning. Otherwise, there's been no issues. 205/45R17 isn't an ideal size, but it's been workable for my application and setup.

 

[bngl3rt]

what brand/mdl are you getting - that's another part of the equation you'll want to figure.

This is all so I can try and run the Michelin Pilot Super Sports. I have had really great experience with them on street and track - great compromise of grip and tire life (300 treadwear!!!) plus really smooth, quiet ride. A five-star tire in my opinion so I'm wondering what compromises I would have to make to get them on my new 17x7.5/18x9.5 wheel if it's even feasible.

How lowered are you? I am on Bilstein dampers set for stock height + Tein springs that purport to drop the car 1".

I am told the S Drives are discontinued so any that are still for sale are just sitting inventory...

 

[GECKO]

Sorry, no clue how low I am other then just over 3.5" clearance.........I bought it that way 14 yrs ago and never inquired about it but my mechanic said the springs are not stock. FYI -the Kumho's have a 280 treadwear and Tire Rack has the 4 for $620 which isn't bad. I raced my bike with Michelin Pilots and they were great and only changed to Pirelli when the series was sponsored by them and we had no choice as they were the spec tire. You won't have issues with either.

 

[jwmelvin]

I had Hankook I*Cept Evo W310 winter tires on my last NSX in 205/50R16. The car was stock height and the tires were on the OEM wheels and they rubbed just barely at full lock. I don't know the precise specs of that tire but that size specification is 11.5mm larger in diameter (611.4 mm) than the OEM tires for that year car, 215/45R16 (599.9 mm). A 215/45R17 tire should be 625.3 mm by my calculation. A 205/45R17 should be 616.3 mm.

The PSS 205/45-17 is 617.2 mm diameter.
The PSS 215/45-17 is 627.4 mm diameter.

Based on the above, I have to imagine you will rub quite a bit, especially with a lowered stance and more-aggressive offsets. That said, I don't really know where my snow tires rubbed, so it could be that less-negative offset helps.

 

[robbiedawg]

the michelin pss's are great tires,i have them on my other car.that would be a good thing if we could run them on our nsx's.i will also have 17 x 7.5 and 18 x 9.5 wheels soon.

 

[bngl3rt]

the michelin pss's are great tires,i have them on my other car.that would be a good thing if we could run them on our nsx's.i will also have 17 x 7.5 and 18 x 9.5 wheels soon.

It's the darn front size that ruins it - you can even get them in 245/40/17 for the OEM 17" rear for the 94-01 sizes, but whether you've got OEM 16" up front or even an a/m 17x7.5 it seems you are kinda hosed.

Starting to believe stuntman on the whole '17" is dying, go 18/18 or lose your fender liner" thing....

 

[angus]

What I will tell you is that on many NSX's the 215/35/18 will rub if lowered.

Your 205/45/17 is almost 1/2" taller.

 

[GECKO]

You don't need to loose the fender liner.........as posted here you will see that they only rub on extreme situations like very tight radius turning. So, park straight and make you can go in and out without turning :>)))..........it's not an issue and the liner is only $100 in case you want to replace it, and only the slots/fins get a bit scuffed. My alignment is set up so that the inside wears more, hence more reason to rub.............but that's no an issue and on our year I don't think we can run 18 fronts when OEM was 16. The rubbing is minimal and the bigger issue is finding the fronts since the availability is not as wide as different sizes.

 

[dablackgoku1234]

For the guys who run 235/40/17, the 205/45/17 tire is a hair smaller...so I don't see why not. Now there are talks of running 225/40/18!!!

Caster also comes into play here for whether you rub or not. With Max caster (wheel pushed as forward as possible), these bigger sizes are possible. FWIW, I, for one, is a fan is bigger tire sizes. I might experiment with a 45 series front tire.

 

[nsxtasy]

I am just trying to reconcile the Prime consensus on usable 17x7.5 front tire sizes with what the folks at the local tire shop are trying to talk me into. The assertion that a half inch increase in diameter over 215/40/17 shouldn't pose a problem came from them - obviously they are not familiar with the specific behavior of the NSX TCS so they were thinking purely in terms of fit/clearance.

They also aren't familiar with the clearances of the NSX (not that I would expect them to be). On most cars, you can get a tire that's half an inch larger in diameter and it won't rub at all. That's not true for the NSX front tires. (The NSX rears have more clearance.)

Tires are pretty pricey for a brand new set of four so I am wondering if there is any measuring/information gathering I can do before I commit a bunch of money to "try it". I assume if you do that, and it goes south, then it becomes a vicious cycle of not driving the car because it rubs and therefore not wearing down the tires that you need to wear down so you can replace them with a better size!

As already noted, if it rubs, it does so mostly at full lock (or full suspension compression). So you can probably live with a little bit of rubbing, if you have to.

If it were my car, though, I'd just get other tires, in 215/40-17 rather than 205/45-17.

I am told the S Drives are discontinued so any that are still for sale are just sitting inventory...

I don't know for sure but that sure sounds like BS to me. The Tire Rack has a wide selection of sizes for that tire, and non are shown as discontinued. The Tire Rack is also pretty fastidious about selling only recently-manufactured tires on their website (exceptions are typically displayed with the year of production).

Still, the S.drive is not all that great a tire. It's a good choice for a budget tire for a sporty economy car. But I wouldn't put them on an NSX. I think the best 17"/18" choices are still one of the supersticky "extreme performance" tires for those concerned primarily with performance and grip, and the Kumho Ecsta LE Sport for those looking for performance as well as treadlife/value. Nothing against the Michelin Pilot Super Sport - it's an excellent tire - but there are downsides when using tires that are not the best sizes for the car.

For the guys who run 235/40/17, the 205/45/17 tire is a hair smaller...

Yes, and both will rub.

 

[bngl3rt]

I think the best 17"/18" choices are still one of the supersticky "extreme performance" tires for those concerned primarily with performance and grip, and the Kumho Ecsta LE Sport for those looking for performance as well as treadlife/value. Nothing against the Michelin Pilot Super Sport - it's an excellent tire - but there are downsides when using tires that are not the best sizes for the car.

Hmm... what's the research I need to do/data I need to collect to compare the two tires? Obviously Tirerack has lots of data like tread wear rating, speed rating, load index etc - but is there someplace I can see graphs of grip vs. temperature for example (to compare how they fall off when they heat up)

 

[jwmelvin]

I wish there were ways to get that type of data. It seems really difficult to get comparable quantitative data. Because I couldn't, I spent a lot of time reading reviews, which is where you will get the idea that, for example, the Falken RT-615K tends to do poorly when it heats up. That was when I picked the AD08R as a track/street tire. My current Nitto NT05 are junk in comparison, but I'm sure being ~6-years old doesn't help. If you can find various comparisons between tires, they start to fall into place; sometimes those are TireRack tests, other times they are comments on forums or tests on Car & Driver or Grassroots Motorsports, etc.

 

[GECKO]

Question bngl3rt............you don't want to spend a lot of money on tires, you want them to last and perform (oxymoron) so I wonder if you would even be able to tell the difference in tire Mfg's when stickiness comes into play. Would you know when your tires are gripping, breaking free point and sliding occurs? Most haven't a clue and for street driving it's highly unlikely most get the tires up to temperature as with stop/starts there is such a large amount of cool down time that they never remain 'hot' for very long. Hope you get what you're looking for and pretty soon you won't have to worry as the snow will be here if you keep waiting........:>)))

 

[bngl3rt]

Heh, luckily it doesn't snow where I live. I don't mind spending a lot of money on *good* tires - they should be mostly street oriented but I do go to the track occasionally and have had "good street tires" fall off in grip at higher track temperatures and pressures.

The cost of a set of four good tires is just a lot to spend on an experiment that might go horribly wrong (i.e. make me hate my car and never drive it because it rubs over the smallest of bumps). Hence my desire to collect information and perform calculations that turn a risk into a calculated risk :biggrin:

 

[robbiedawg]

It's the darn front size that ruins it - you can even get them in 245/40/17 for the OEM 17" rear for the 94-01 sizes, but whether you've got OEM 16" up front or even an a/m 17x7.5 it seems you are kinda hosed.

Starting to believe stuntman on the whole '17" is dying, go 18/18 or lose your fender liner" thing....

folks at tire rack are telling me that it's more likely that performance tires will be available in the future for a 17 x 7.5 or 8" front wheel than for the stock front 16" wheel,which is a major reason i'm upsizing.i would have been interested in getting volk wheels in the stock 16/17 sizes,because they would have been super light,but just didn't have the confidence that i could get tires for these expensive wheels in the future.there's a decent selection for 17" fronts now in the 215/40/17 size,including dunlop direzza zII's, yokohama ad08r's, and kumho ecsta le sports.i would like to stay with smaller wheels,and hope not to have to go to 18's on the front.