October Fastrack

[planet6racing]

You are assuming that the 1" wider wheels gives a performance benefit. It does not, in any appreciable manner, and thus no impact to the process...see my previous post on this:
[/b]

Please show your data and testing method to support this absolute claim.

[ScotMac]

Please show your data and testing method to support this absolute claim.
[/b]

Well, it is an absolute fact that a wider rim will increase the weight, leading to worse performance.

It is also obviously true that there is no change the rules on max tire size/width.

So, it comes down to sidewall angle.

Let's see what we are dealing w/:

Let's use 225/50, since that is what a lot of the B racers are running.

6" wheel plus 2 * .5" lip = 7"
7" wheel plus 2 * .5" lip = 8"

The section width for a Hoosier r6 225/50/14 is 9.8", giving:

6" rim: 9.8 - 7 = 2.8 or 1.4" per side
7" rim: 9.8 - 8 = 1.8 or 0.9" per side

(.5" difference, as would be expected)

Since the tire is a "50", and the section width is 9.8", that means the section height is 4.9". Thus the sidewall angles are:

6" rim sidewall angle = arctan(1.4/4.9) = 15.6 degrees
7" rim sidewall angle = arctan(0.9/4.9) = 10.4 degrees

I'll see if there are any studies on what a difference between 10 and 15 degrees sidewall angle causes in a performance application.

However, it also should be noted to any impact is very much tire specific, since the strength of a sidewall varies quite a bit per tire....with racing tires being very much on the high (stiff) end of the spectrum, and thus have less impact from sidewall angle differences.

[vr6guy]

I've read this entire thread... whew... it is gut wrenching. I feel sorry for folks who can't find cheap lightwieght wheels for their car. But changing the entire class rules so a few obscure models can save a few bucks on racing wheels is, as Lawton says silly, no silly isn't a strong enough word RETARDED!!! Such a change would throw the entire 'process' into question. An entire reprocessing may need to take place. So a few guys can spend a few less dollars for wheels, come on... spend some of the effort you have used pummeling the ITAC with stupid suggestions backed by rediculous arguments on trying to find a sponsor to help you pay for some bling wheels instead.
My hat is off to every member of the ITAC who worked so hard to bring IT racing to it's current state. Things have never been fairer. The racing seems more competitive with different models winning. This is a tough job, to balance so many models. But for those of us that don't want to race a spec me otter it is the best. THANK YOU guys!!! Just know that the few vocal ingrates are just that, the FEW. The vast majority of guys love what you have done.
Everytime a prickly rule has come up, I've quietly watched. Each time in my mind I've decided what I thought would be most fair for everyone. And each time the ITAC has made the same choice. I wouldn't change a thing. Some folks are scared of open ECU rules. They are computer illiterate and wish we all could be made to use carbs. But this is 2007, all cars have computers on them, we all don't want to race thirty year old junk (see production racing) It's not going to be the death of IT. Coil overs gave us the ability to change spring rates (one of the most basic handling adjustments) with cheap model non-specific springs. At first it must have been scary. But now kits are available for most every car and we think nothing of adding a coil over kit to our racers. Does it cost a few bucks... sure, this is racing. It ain't cheap.
After the all out war that was the debate about our recent restructuring, just prior to the 'process' being applied, I thought we would never hear the end of people whinning about how they had to add wieght to there car and now it's not competitive anymore. But as the season started, all was quiet. The world didn't end. Cars that were overdogs seem slightly reined in, cars that were also rans are coming out of barns and new ones are being built. Everyone seems to agree it was for the overall good of the class. Job extremely well done. Thank you guys thank you thank you.
Jake, the way you sit and calmly reply to each of these posts without going ballistic is admirable. Repeatadly explaining the logic behind each decision, you sir have my vote for president of earth.
[/b]

I agree with most of what you said in this statement. With exception of the term "retarded". If you could only describe your feelings the way Jake has through out this thread, we would all benefit. You referring to peoples ideas as being "retarded" is demeaning of those peoples,(including myself) views and character. Which is intollerable, and has no reason and or need in such a discussion. We all learn from each other through ideas that everyone of us have. Like I said before, going into this forum I was dead set on the allowance on being able to run 15x7s on my vw. Now, as some of you have brought your opinions to the table in a respectable non abrassive way, I can see both sides of the fence. so please, please do not resort to labeling an idea as being "retarded" or mentally challenged. You might want to throw out an apology if you have offended anyone.

I, as well as most everyone in the improved touring community share the thanks and gratitude to all that volunteer their time and effort. Without them, this sport would be lost!

Marc Rider

[JLawton]

I say we lock this thread down............

[mom'sZ]

Marc, you're right, that was a bad choice of words and I do truly appologize to you if I offended you. I read your post after I posted mine and I thought 'you know there is an open minded guy'.

[vr6guy]

No worries....

[gran racing]

Scot, so would you say that a 5" rim is better than a 6" rim? What about a 4" rim?

[erlrich]

[RacerBill]

Marc, you're right, that was a bad choice of words and I do truly appologize to you if I offended you. I read your post after I posted mine and I thought 'you know there is an open minded guy'.
[/b]

mom'sZ - Thanks for the clarification. But, if I may take one phrase out of one of your previous posts...
'...so a few obscure models can save a few bucks on racing wheels...' In my case, from the prices I have found, would be more in the order of $800-1000 for a set of four. I realize that it may be a few bucks to some, but not to others.

I do agree with most of the other views you expressed.

Helplessly mired in the 'have not' group!

[Gary L]

I'll see if there are any studies on what a difference between 10 and 15 degrees sidewall angle causes in a performance application.

However, it also should be noted to any impact is very much tire specific, since the strength of a sidewall varies quite a bit per tire....with racing tires being very much on the high (stiff) end of the spectrum, and thus have less impact from sidewall angle differences.[/b]

Scot - On the Hoosier website, specifically on the page dealing with the care and feeding of the R6 tires we all know and love, I see a couple of statements that you may want to include in your research:

Wheel width dramatically affects wear and performance of the Hoosier P-Metric radial tires.[/b]

...and

It is possible to use narrower wheels, but at a sacrifice to shoulder wear and cornering power.[/b]

[lateapex911]

yea, I find the claim that wider wheels aren't really better to be rather questionable myself...

Now, I will say that there is no absolute result here, but....a few years ago I was involved in some testing. We were limited by wheel size and width, and got several sizes to test. Fortunatlely we were able to keep overall diameter and therefore gearing constant. Well surprise, surprise, the skinny tire was a second faster over a 1.5 minute lap. Same manufacturer, same compound, same freakin batch, two drivers, two cars, lots of swapping, and no knowledge of which tire they were on.

Think about it for a second. If you pinch the bead of the tire closer and closer together, is the tread going to remain flat? Or will it bow as the sidewalls bend inward?

A less optimal/square contact patch means the tire ..and the performance....is being compromised.

Now, as I said up front, there are no hard and fast rules, and in some cases, a tire may perform similarly on different width rims, but, I need to see the testing data before I go out and buy smaller wheels.

I bet they said the same thing about alot of the cars that are at the pointy end of IT, but when someone demonstrated the car was raceable, the market responded with all of the extra go-fast bits.


[/b]

Oh, like the Nissan NX2000 suspension parts store next to the Home Depot in my town?

[Bill Miller]

So, we change the ruleset for the entire category.....and now, guys who think winning is "fun", have to decide, "Do I get/need" 7" wide rims?. Can I FIT 7" wide rims? LOL...guess what? They canNOT...but hey, that other guy, who hasn't got a built engine but runs a solid second CAN fit them, and does, and lo and behold, he's now winning. Before the rule change, the second place car could have competed for, and gotten a win here and there if he had the full package but now that the rim rule changed, his car just became the big dog. So the guy who was winning, and followed the classic path of testing and developing, thinks, "What the hell were those asshats thinking!?!?! Screw this..." and quits.

So we got one guy in, we cost an entire class a redevelopment process, a bunch of wheels and maybe some tires, and we lost a racer or three....[/b]

Substitute 'open ECU' for '7" rims'.

Mom,

It may be a few, obscure cars today, but what happens if (when?) the 1st gen RX7 gets moved to ITB? If the opponents of the '7" wheels for everybody' option feel that it would make cars instantly way faster, why not go w/ the additional weight if you want to run them?

[ScotMac]

What we need to remember in this discussion of sidewall angle is its relative importance on the overall performance of the car. The question is how much of an impact does 5 degrees of sidewall angle have, in comparison to the other more macro features of the car that the classification is based on, like hp-to-weight, suspension geometry, weight distribution, etc?

What i have been saying all along is that it is mainly wear issue, and i am glad to see that Hoosier agrees w/ me on that point. I am not saying that it isn't also a handling gain (which hoosier also references) i am just saying that it is not large enough to cause appreciable classification issues.

In fact, it is interesting to note that Hoosier recommends that 225/50/14 for 6-8" rims. ie, Hoosier believes the sidewall angle is acceptable for both 6" and 7" rims.

[Gary L]

In fact, it is interesting to note that Hoosier recommends that 225/50/14 for 6-8" rims. ie, Hoosier believes the sidewall angle is acceptable for both 6" and 7" rims.[/b]

Acceptable? Maybe. Ideal? Not even close. If you read the entire paragraph from which I extracted the two quotes in my post above, you come to the very clear conclusion that even wider would be better. The calculations show the ideal rim width for a 225/50-14 (or 225/50-15) to be about 8".

I'm a firm believer in following the tire manufacturers' recommendation, and for that reason, I run 205/50-15's on the Volvo with the prescribed ITB 6". Yupper, that's 2640 pounds on 205's. But because they're on the proper wheel, they work (and wear) very nicely IMO.

[planet6racing]

Well, it is an absolute fact that a wider rim will increase the weight, leading to worse performance.

It is also obviously true that there is no change the rules on max tire size/width.

So, it comes down to sidewall angle.

Let's see what we are dealing w/:

Let's use 225/50, since that is what a lot of the B racers are running.

6" wheel plus 2 * .5" lip = 7"
7" wheel plus 2 * .5" lip = 8"

The section width for a Hoosier r6 225/50/14 is 9.8", giving:

6" rim: 9.8 - 7 = 2.8 or 1.4" per side
7" rim: 9.8 - 8 = 1.8 or 0.9" per side

(.5" difference, as would be expected)

Since the tire is a "50", and the section width is 9.8", that means the section height is 4.9". Thus the sidewall angles are:

6" rim sidewall angle = arctan(1.4/4.9) = 15.6 degrees
7" rim sidewall angle = arctan(0.9/4.9) = 10.4 degrees

I'll see if there are any studies on what a difference between 10 and 15 degrees sidewall angle causes in a performance application.

However, it also should be noted to any impact is very much tire specific, since the strength of a sidewall varies quite a bit per tire....with racing tires being very much on the high (stiff) end of the spectrum, and thus have less impact from sidewall angle differences.
[/b]

This is not data. This is a calculation based on a supposition. Please provide DATA that supports your absolute claim.

[ScotMac]

This is not data. This is a calculation based on a supposition. Please provide DATA that supports your absolute claim.
[/b]

Wrong. It is FACTS about what we are dealing w/, in terms of the sidewall angle issue. If you want me to help you, a better complaint from your perspective would be that it is not a study on the performance issue, as requested. Of course, i never said it was a study of the performance, instead just a look at what we are talking about for sidewall angle.

[ScotMac]

Acceptable? Maybe. Ideal? Not even close. If you read the entire paragraph from which I extracted the two quotes in my post above, you come to the very clear conclusion that even wider would be better. The calculations show the ideal rim width for a 225/50-14 (or 225/50-15) to be about 8".

I'm a firm believer in following the tire manufacturers' recommendation, and for that reason, I run 205/50-15's on the Volvo with the prescribed ITB 6". Yupper, that's 2640 pounds on 205's. But because they're on the proper wheel, they work (and wear) very nicely IMO.
[/b]

I agree that there is always an ideal width for a particular tire. And i agree that if you get too far from that ideal, it will cause wear and performance issues.

However, i disagree w/ your numbers, and that wider is necessarily better. Both too narrow and too wide can cause wear and performance issues. If you look at the hoosier spec chart (see URL below), the recommended sizes typically start just a bit NARROWER than the actually tread width for almost EVERY one of the r6 tires, though only slightly narrower.

For the 225/50/14 (or 225/50/15), Hoosier's recommended rim widths are 6-8 for a tread width of 8.8". If you look at the chart, the range for the recommended rims is typically .3" to 1" narrower than the tread width. Typically, Hoosier will bracket the "ideal" rim size by 1" for the "recommended" rim sizes. So, though 7" would be ideal, by Hoosier recommendations, and 6" and 8" are both not far off, and should not show substantial wear and performance issues. ie, *1* inch is not that big of deal.

[JoshS]

However, i disagree w/ your numbers, and that wider is necessarily better. Both too narrow and too wide can cause wear and performance issues. If you look at the hoosier spec chart (see URL below), the recommended sizes typically start just a bit NARROWER than the actually tread width for almost EVERY one of the r6 tires, though only slightly narrower.

For the 225/50/14 (or 225/50/15), Hoosier's recommended rim widths are 6-8 for a tread width of 8.8". If you look at the chart, the range for the recommended rims is typically .3" to 1" narrower than the tread width. Typically, Hoosier will bracket the "ideal" rim size by 1" for the "recommended" rim sizes. So, though 7" would be ideal, by Hoosier recommendations, and 6" and 8" are both not far off, and should not show substantial wear and performance issues. ie, *1* inch is not that big of deal.
[/b]

Scot, you're making a couple of bad assumptions there. Your conclusions may be correct, I'm not sure, but I am pretty sure that you've made some conclusion based on at least one incorrect premise.

The "ideal" rim size is not that -- it's the rim size that the industry says should be used to measure the tire. The recommended range *is* what it says, but you are using measurement numbers that are on a wheel size that Hoosier doesn't pick.

Quoting the Hoosier website:

"Why are the listed rim dimensions different than the recommendations?

Whenever a D.O.T. tire spec is published there are Tire & Rim Association guidelines for the specific rim size for a particular tire. This is intended to standardize the information so that it is possible to compare one brand of tire to another.

For performance uses these Tire & Rim Association recommendations may not reflect a best choice or the designed application."

[Gary L]

So, though 7" would be ideal, by Hoosier recommendations, and 6" and 8" are both not far off, and should not show substantial wear and performance issues. ie, *1* inch is not that big of deal.
[/b]

As Josh has pointed out, the 7 inch rim isnot the ideal rim width for a 225/50, it is simply the width of the rim used to create some of the rest of the numbers in the chart. Forget the chart... read and understand what they actually have to say in their paragraph about wheel width. That's where (it certainly bears repeating) they state without reservation: "Wheel width dramatically affects wear and performance of the Hoosier P-Metric radial tires".

One inch of rim width is a big deal. It is a performance issue.

[planet6racing]

Wrong. It is FACTS about what we are dealing w/, in terms of the sidewall angle issue. If you want me to help you, a better complaint from your perspective would be that it is not a study on the performance issue, as requested. Of course, i never said it was a study of the performance, instead just a look at what we are talking about for sidewall angle.
[/b]

No. Your supposition is that sidewall angle will define the performance of the wheel/tire combo. You've done calculations to show that there is a difference in sidewall angle between the two wheel widths and, therefore, there will be a performance difference. This is a calculation used to support your "hypothesis."

You made an absolute claim in your post. Either find studies that support it (e.g. Grassroots Motorsports tire testing) or post other data that you have collected. Calculations and hypotheses are not acceptable.

(and, yes, I am being a prick about this. I know. I do not like it when people make absolute claims and have NOTHING to back it up. If the post is changed to say "may," I'll be satisfied.)