I posted this on the Grassroots Motorsport forum but would like to know your comments, too. I asked here earlier about what a common tire diameter is, and the consenses was around 25". Based upon the additional info below, is that still the size you guys would suggest?

Background: I'm designing another car, one based upon what I learned designing Kimini, mixed with how what I want has also changed. I am writing another book, this one being a cookbook about how to build a "Seven" for the new millinium. That is, one that uses very common FWD drivetrains instead of dwindling front engine/rear drive combinations.

The car: Mid-engine, roughly 1300lbs, 200-300hp, looking vaguely like a Seven.

The problem: Tires. During the Kimini design I chose 13" tires because that's what fit the car, both aesthetically and physically. However 13" street tires are nearly extinct, as are 14" sizes. (At the moment, this is a street tire discussion; I know there's tons of 13" racing slicks... that's for the second set of tires.)

Not wanting to start with a size that's going away, I assumed I'd go with 15". However, I was surprised to find that they, too, have limited sizes. I don't want to design in something that, when the book's done, can't be found, so it has to be dealt with now.

The 15" tires I've found are:
Falken Azenis RT-615
Yoko Neova AD07
Bridgestone RE-01R
BFG T/A KD
Kumho Exsta MX

This is not a big list, and therein lies the problem! In fact, I'm wondering if I should be considering 16s... or even 17s, to guarantee some sort of staying power for my design (and book).

Of course, this list does not include ALL 15" sizes. However, I don't want (and don't think anyone else does either) to use super hard compound tires, all-weather tires, or offroad Jeep tires, so I purposely omitted them.) I may however have to compromise further (toward non-sticky tires) to find a decent selection. I have mixed feelings about this.

So I'm asking the group here for input. Am I being silly to think that 15s are going away anytime soon? (Though from what I see, they already are.) I realize that 16-17s are more expensive, heavier, and have higher PMOI (polar moment of inertia) but at some point, the engineering reasons to not use them get run over by the fact that anything smaller's going way. (Also, since the car's so light, using hard compound tires probably isn't safe anyway. It's a sports car, it's supposed to stick, not skip over the road. I suspect that sticky street tires will be required simply for it to work well.)

Your thoughts, please!

Note: I realize there are DOT "street" racing tires, but I'd like to avoid these (for this discussion) so builders don't get stuck using them in the rain. They can use them by choice - I simply don't want to force the issue.


Modified by kb58 at 1:24 PM 1/16/2008

 

It depends on what kind of tires you want. Short answer - R comps not common in 16", high-end street tires not common in 15".

For R compound track tires, 15" tires are plentiful. Most of the R comps are available in 205/50-15. Some are also available in 225/45-15. However, 16" sizes are not very common at all. There are lots of 17" R comps, starting in 235/40-17 and larger, not that many smaller than that though.

For street tires, it's a somewhat different story. There are lots of the "budget performance tires" (Yoko ES100, Kumho SPT, Bridgestone RE750, etc) in 15" sizes (205/50-15, 195/55-15). You can also find a reasonable selection of "supersticky" tires (Falken Azenis RT-615, Bridgestone Potenza RE-01R, Dunlop Direzza Sport Z1, etc). What's rare in 15" sizes are the top-of-the-line performance tires (Goodyear F1 GS-D3, Michelin Pilot Sport and Pilot Sport PS2, etc), with the exception of the Goodyear, and that only in the tiny 195/50-15. There are lots of all three kinds of tires in 16" and 17" sizes.

 

i've always appreciated 205 15 azenis on light cars. the sidewall is plesant abd they give plenty of grip for the price

 

are you going to make another web page so we can follow your build

personally i think 15" would stay a somewhat common size but im sure that could of been said for the 13" too

at some point the increasing size will stop but it might just be a hindsight is 20/20 thing

 

I heard the Hankook R-S2's are really nice tires for the price, they're also available in 205/50/15 and 225/50/15

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STN_Pat &raquo;</TD></TR><TR><TD CLASS="quote">i've always appreciated 205 15 azenis on light cars. the sidewall is plesant abd they give plenty of grip for the price</TD></TR></TABLE>
I agree, but what if I say "use these" then in a year they go away. Sucks for me. I'm trying to aim a bit high I guess, to try and keep the choices open for at least, oh, five years or so.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rockdude14 &raquo;</TD></TR><TR><TD CLASS="quote">are you going to make another web page so we can follow your build? Personally i think 15" would stay a somewhat common size but im sure that could of been said for the 13" too. At some point the increasing size will stop but it might just be a hindsight is 20/20 thing</TD></TR></TABLE>

Yes, it's on my site, the direct link being: http://www.kimini.com/MidLana/index.html

Regarding the ever-advancing sizes, I kind of got bit once before so I really want to be sure this time around. Good Lord, in 10 years can you imagine Civics on 26" wheels? Oh wait, there's probably someone doing that now... Of course by then we'll be out of oil, so I guess I need not worry.

 

i was looking at cars on tire rack for what I considered to be small sporty cars with somewhat of a race following
the only car that I found for 07/08 that comes stock with 15's is the mini. Miata's are up to 16's, along with VW's and honda's are up to 17.

I want to say I think they will still be around from people racing cars fromt he 90's and early 00's.

Might be worth an email to some of the tire companies they can probalby give you something of an idea of how they are heading.


And with the middle east going the way it is gas might be gone sure you dont want to aim for an electric car? :D

I'll be following the build best of luck.

edit*
http://www.tirerack.com/tires/...ue=15
going through here sorted by dry perfromance
it looks like a lot are only in 17's and bigger very few left in 15's

I think I'd vote go for 15's


Modified by rockdude14 at 11:41 PM 1/16/2008

 

I don't think there is an actual risk of not finding a performance non-R tire within the next 5 years. That's my vision of things though ! I'm pretty sure they're part of their best selling size at the moment...in 10+ years maybe...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STN_Pat &raquo;</TD></TR><TR><TD CLASS="quote">I don't think there is an actual risk of not finding a performance non-R tire within the next 5 years. That's my vision of things though ! I'm pretty sure they're part of their best selling size at the moment...in 10+ years maybe... </TD></TR></TABLE>
Agreed, but it'll probably be one way down the performance curve. Yes, 15s will be around forever, but they'll be middle-of-the-road OEM-type sedan tires. For me that's the same thing as not existing, but I get your point.

 

15's will never go out of style. especially with the SCCA STS tire crowd.

some street tires in 15" you forgot to include.
(new) Toyo R1R
Toyo T1r (good rain tire)
Hankook Ventus RS-212
and the upcoming Kumho XS should have at least (2) 15" sizes i would imagine.

Definitely Wider tire choices when you step up to 17's. but you also are approaching 2x the price vs. a 15" tire.

 

nitto NT01 comes in 205/50/15 and i drive those on the street my car weighs 2300lbs so i get decent life out of them nitto nt555rII's are good for street too.

 

realistically, I think 15" will be around as far as good tire options for a while to come. Just look at all of the awesome "street" tire options that are here or right around the corner. Go back 5 years, and there was maybe 3 decent options I can think of. . .

On a light car like the one you're building, you won't need to upsize for brake clearance. Upsizing to 16" or 17" will increase price, especially if you're trying to reduce weight with the wheels at the same time. A 17" wheel that is similar in weight to one of the dozens of 15" wheels you can get for &gt;$200 is probably going to be closer to $400.

That's the way I always looked at it at least. Good luck with the new project, I'm adding the link to my bookmarks bar after I get done typing here.

 

I really would like to stick with 15s... really, but I think that puddle's drying up, too. Also, everyone says to use 205/50-15, which is fine, but for the back I want to go wider. Sourcing a wider 15" street tire is even more dicey than the one above.

For example, the Falken Azenis RT-615 looks like an awesome tire, but try and find a 15" size other than the one above... zero. So if that one size goes away, they're off the list.

Yoko Neova AD07s... nothing.
Bridgestone RE-01R, one size, 195/50-15.
BFG T/A KD have three, from 205 to 225 15s.
Kumho Exsta MX... nothing.

So if I want a tire wider than 205, I'm in the uncomfortable situation of having only one source. That's not someplace I want to be.

It's not that I disagree with you, quite the opposite. Everything you say about 15s is absolutely true, but even if it's they're perfect solution, if there's not a good selection, it just doesn't matter. I plan to read through this thread and the one on GRM this weekend to come to a final decision.

Again, thanks for the input, it really does help.

 

kurt, is it possible to engineer a solution that will accept both 15" and 16" sizes? I understand that it's not ideal but it's flexible w/ the changing market.

In any event, I look forward to buying the next book too.

 

Yes that's my intent. I specify a given tire <U>outside diameter</U>, and the builder uses whatever tire/wheel he wants, as long as it's around that value. 15, 16, 17, it doesn't matter, as long as the OD is &lt;insert magic number here&gt;.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by n1_egsex &raquo;</TD></TR><TR><TD CLASS="quote">I heard the Hankook R-S2's are really nice tires for the price, they're also available in 205/50/15 and 225/50/15</TD></TR></TABLE>

I've used the Hankook RS-2 and the Kumho MX previously, they are both great performing street tires with good rain capability.