[googe]

do they come with a free set of chop sticks??

[CloNeGTS]

Originally Posted by toyworx

17 versus 18 versus 19. It's a pure matter of physics. There are so many variables to talk about, so for the sake of this discussion, i will only talk about sidewall deflection. Given the same make and model of tire combined with the same make and model of rim in the 3 different sizes, a 19" with a 35% aspect ratio will have the least amount of sidewall deflection under hard cornering.

ALSO, there is another piece you are all overlooking. The contact patch on the 19" package is bigger. The first part of the tire measurement is the maximum width of the tire at the buldge in the sidewall. 225 means the tire is 225mm from sidewall buldge to sidewall buldge. 35 means the sidewall height is 35% of that (known as the aspect ratio). A 45% aspect ratio tire (like a 225/45/17) will have a taller sidewall and a bit more buldge resulting in less actual tread width. Translation, the actual tread width is narrower on a 225/45/17 versus a 225/35/19 even though they are both a 225. Yet another plus for the 19 when talking hard cornering.

The only other real big factor is weight. And in most cases, again given the same make and model of tire and same make and model of rim, the wieght difference won't be that much. Not enough to worry about.

My take is that the 19 has the potential to turn in a faster slalom time and a better skidpad number.

Few comments

- sidewall deflection among tires isn't a good comparison. If you picked the best handling 45 series to go on a 17 vs. the best handling 30-35 series for a 18-19, I doubt you'd see any difference in deflection alone. However, what type of tire can you get in that small of a series....probably not something that will match the compound you'd get in a higher profile tire.

- I don't quite understand that sidewall bulge debate as described. That's the first I've ever heard someone describe something like that and I think the differences you are talking about are so minimal, no one would ever know it. That's kinda like saying a larger rolling diameter tire has a larger contact patch because you are resting on a larger angular area....we're talking sq mm's here! I think the more significant difference which works opposite of what you are talking about is that when you are at a 30-35 series tire, you are stuck with the correct series of tire. However, with a higher profile, I can throw a 225 series set of Azenis on a wheel sized for a 205 series. With any old tire, this would be a very poor practice, excess bulge all around, rolling over on the sidewall and so on. With a tire like the Azenis or RE070, the sidewall is stiff enough to make this a great practice. These aren't just my feelings....look around the staging areas at the next local Solo II.....

- Weight AND size both matter. A 17" 20lb wheel will not accelerate the same as a 19" 20lb wheel. The mass moment of inertia comes into play. Easy way to think of this....which would be easier to spin in your hand: a 10lb weight sitting in your palm or a 12" long stick with 2 5lb weights at the ends, held in the middle? The further away from the axis of rotation that you move the mass, the harder it is to rotate.

For outright performance, I think the best case is still to have the smallest, lightest, widest rim you can find and get a tire that is made to race, which usually leads to a Hoosier or Kumho with a higher profile. Try to match stock rolling diameter for top speed applications, stay as small as possible for max acceleation apps.

[bitabur]

I think aluminum wheels are lighter than the rubber around them.... bigger wheel/smaller tire combos weigh less, don't they?

[Snax]

The contact patch increases in length with a larger diameter wheel, improving braking and acceleration grip. But you gotta have brakes able to handle the extra torque load and the power to make them move.

[Snax]

Originally Posted by bitabur

I think aluminum wheels are lighter than the rubber around them.... bigger wheel/smaller tire combos weigh less, don't they?

Not usually.

[CloNeGTS]

Not in the case of serious tires.....such as the Azenis or RE070s. Heck, the RE070s weigh as much as the BBSs!

Contact patch area increase due to larger rolling diameter is another moot point. If it was the difference between a 6" diameter and an 18" diameter, that's one thing.....17s to 18s or 19s.....call it negligible at best. And that's real rolling diameter change, not just plus sizing the tire/wheel package. The real gain in footprint size is a real addition of width.

[bitabur]

Originally Posted by CloNeGTS

Not in the case of serious tires.....such as the Azenis or RE070s. Heck, the RE070s weigh as much as the BBSs!

Contact patch area increase due to larger rolling diameter is another moot point. If it was the difference between a 6" diameter and an 18" diameter, that's one thing.....17s to 18s or 19s.....call it negligible at best. And that's real rolling diameter change, not just plus sizing the tire/wheel package. The real gain in footprint size is a real addition of width.

That's what im saying.

Larger rims just mean longer spokes... the majority of the weight of the rim is still there.... but with the tire (assuming you maintain the same overall diameter), getting a larger rim means you're cutting out a lot of that heavy sidewall rubber.... I'd say it's probably close in terms or weight... or at least a wash.

[CloNeGTS]

Yeah, you're right there. Even if it was a wash, the weight is moving from that band a little closer to the center of the wheel.

The only thing I keep seeing though....when you are down to these small profile tires (and we're still trying to maximize performance), how great of a tire can you get? What's the best handling, soft compound 35 series tire out there? (Really asking here....never really looked too hard).

[toyworx]

Originally Posted by CloNeGTS

Few comments

- sidewall deflection among tires isn't a good comparison. If you picked the best handling 45 series to go on a 17 vs. the best handling 30-35 series for a 18-19, I doubt you'd see any difference in deflection alone. However, what type of tire can you get in that small of a series....probably not something that will match the compound you'd get in a higher profile tire.

Again, i was comparing the same make/model of tire on the same make/model of wheel. Once you start talking about Tire A for a 17 and Tire B for a 19 we can no longer continue the discussion. there are Too many variables within the tires. So given the same model tire, Yes, you will see a measureable difference in deflection when going from a 45 down to a 35.

Originally Posted by CloNeGTS

- I don't quite understand that sidewall bulge debate as described. That's the first I've ever heard someone describe something like that and I think the differences you are talking about are so minimal, no one would ever know it. That's kinda like saying a larger rolling diameter tire has a larger contact patch because you are resting on a larger angular area....we're talking sq mm's here! I think the more significant difference which works opposite of what you are talking about is that when you are at a 30-35 series tire, you are stuck with the correct series of tire. However, with a higher profile, I can throw a 225 series set of Azenis on a wheel sized for a 205 series. With any old tire, this would be a very poor practice, excess bulge all around, rolling over on the sidewall and so on. With a tire like the Azenis or RE070, the sidewall is stiff enough to make this a great practice. These aren't just my feelings....look around the staging areas at the next local Solo II.....

Let me clarify. I wasn't clear enough the first time around (no that I re-read my own post. sorry.). My point was that a 225/45/17 versus a 225/35/19, the 19" tire has more tread molded into it from the factory. It's contact patch is built larger from the get-go. Put the two next to each other and you'll see what i mean. It IS a measurable difference, and one that you'll feel on the road (i've run both).

Originally Posted by CloNeGTS

- Weight AND size both matter. A 17" 20lb wheel will not accelerate the same as a 19" 20lb wheel. The mass moment of inertia comes into play. Easy way to think of this....which would be easier to spin in your hand: a 10lb weight sitting in your palm or a 12" long stick with 2 5lb weights at the ends, held in the middle? The further away from the axis of rotation that you move the mass, the harder it is to rotate.

I agree with a lot of this. And yes i do understand the moment of inertia. But the example you gave is not a good comparison. Thats a very extreme change. What we get by going from a 17 to a 19 is a VERY slight shift in the Mass Centralization. Given the total radius will be very close between the two, and some of the wheel mass offsetting some of the sidewall mass, i don't think you would have enough of a shift to worry about it. If you lost 2 or 3 tenths of a second down the 1/4 mile by going to the 19 (again given the same make/model of wheel/tire), that's something i'd give up for more bite in the corners.

Originally Posted by CloNeGTS

For outright performance, I think the best case is still to have the smallest, lightest, widest rim you can find and get a tire that is made to race, which usually leads to a Hoosier or Kumho with a higher profile. Try to match stock rolling diameter for top speed applications, stay as small as possible for max acceleation apps.

Again, I see your point, but just don't agree. And i don't think Porsche or Ferrari do either. The new Prosche GT supercar runs 265/35/19 Front and 335/30/20 Rear.

[CloNeGTS]

Good discussion..and I know we could discuss all of this for weeks. I'm glad we could discuss and agree to disagree.

Every little change we've talked about has a differing degree to it's impact (225 tread comparison, mass moment...) but I keep thinking back to the original question posed...for performance sake, would you go to a 19 for that reason alone. I can't say that's a right answer at all. The only claim to back that up would be your last statement above, to which I say look around here....

http://www.scca.org/amateur/solo2/na...lts/index.html

Real world (No F1, WRC..), street cars, street legal tires....and you'll see a few things sticking out...the tire brands. Hoosier and Kuhmo fight it out every year. They both have one thing in common though....the tires they make for this competition aren't in rubber band sizes. That tells me something. If there was a sure-thing advantage to having as large of a wheel and as small of a sidewall, I'd think they'd be all over it.

I'm not saying a low profile tire isn't great for handling on the street...I just don't think that's the best answer. Same model of tire with profile change from 17" to 19" wheel, I agree with you completely, the smaller profile would be a better performer. Same 17" wheel, add a great tire only and I'll bet you can have better handling for a lower overall cost. Good discussion!

[toyworx]

Originally Posted by CloNeGTS

Good discussion..and I know we could discuss all of this for weeks. I'm glad we could discuss and agree to disagree.

Couldn;t agree more. :wink:

Originally Posted by CloNeGTS

Real world (No F1, WRC..), street cars, street legal tires....and you'll see a few things sticking out...the tire brands. Hoosier and Kuhmo fight it out every year. They both have one thing in common though....the tires they make for this competition aren't in rubber band sizes. That tells me something. If there was a sure-thing advantage to having as large of a wheel and as small of a sidewall, I'd think they'd be all over it.

Point well taken. However, they sell tires. Not wheel/tire packages. They still need to sell them and must conform a bit to what poeple will buy (marketing). My gut feeling is that most poeple will stick with their stock size wheel and just upgrade the tire due to finances. Also, are there rules about wheel/tire size for those classes? Also, once you get out of the Solo type stuff and look at other froms of SCCA racing (GT class road racing), you will see the Aspect Ratio drop.

Originally Posted by CloNeGTS

I'm not saying a low profile tire isn't great for handling on the street...I just don't think that's the best answer. Same model of tire with profile change from 17" to 19" wheel, I agree with you completely, the smaller profile would be a better performer. Same 17" wheel, add a great tire only and I'll bet you can have better handling for a lower overall cost. Good discussion!

Agreed. Strickly for performance, i wouldn't go up to the 19" either. As a matter of fact, i'd put all the wheel $$ into some suspension upgrades and REALLY outhandle the 19" set for the same money!

But money aside....give me the 19's AND suspension.

[PhillyB]

ehh - as far as im concerned anytime you go up in size you go up in WEIGHT, if the material is the same (id assume so) anyway. and we all know the unsprung weight of a wheel is going to affect handling. its cool if you want the 'look' but i am fairly sure the suspension/diffs were engineered for 17's and you may take a negative hit on performance, possibly voiding warranty or damaging parts. but if you arent road racing/drag racing or worried about 1/10's of seconds on a track i wouldnt worry about it. i personally wouldnt go higher than an 18 on a small car like the sti though, i had 32" mud tires on my xterra and it killed the ABS system - it just wouldnt work - only 3 inches taller than stock. dealer didnt know what to do. just my opinion. i am personally going for performance. i like the rally look anyway.

[bitabur]

Bigger rims and tires with a smaller sidewall - not necessarily any heavier at all, and because you're keeping a very near-stock overall diameter, components like speedometer and brakes shouldn't feel any difference.