June 2011 Fastrack

[Flyinglizard]

Most small engined cars are faster on the 13 inwheels. VWs are for sure. I have bought entire cars to get 13x6 wheels. I have one good set after 20 yrs. of JY shopping.
Can you buy Basset 13x6? yes. About 60-70$ each.
Does Tire rack sell them? no.
15x7 are far easier to source, 205/50/15 are the best tires to source. (Other than the SFR tires thatI use.)
I think that both sides of this point are valid. The old cars have scarce wheels. The new builds may need to buy steel wheels or Panasports.
While the choices are slim, there are choices for 6 in wheels.
Maybe "Prod" them in, Add 50 # for 7 in wheels. No wider.
MM

[Chip42]

Most small engined cars are faster on the 13 inwheels.

the same as saying they are faster with a higher final drive ratio - "true" in terms of accelration but it does not always pan out on the track due to fixed ratios in the box. wheel diameter =/= overall diameter, though it is assumed that if you want a smaller wheel than what is currently allowed you want it for the smaller OA diameter that it makes avaialble.

I support the rule more for making folks with giant wheels on newer classifications get a wheel / tire package that is more available and affordable. FD is open, who cares about that effect? brake and inertia effects are part of "warts and all" to me.

[tom91ita]

i think this was due. there is no real reason in my mind why newer cars could not at least run their OEM wheel size.

[mossaidis]

Width aside, I don't see a problem with the proposed rule as written. It hits to the sprint of IT: easy, flexible, cheap and one less obvious thing to police.

[joeg]

Mike is correct about small engines and small tires and the analysis is not FD-related.

Everything just keeps getting bigger (and heavier) for OEM styling purposes.

Even Hoosiers are a lot heavier now--who remembers the pre-R04 days with the hologram tread.

Light tires!!

[R2 Racing]

Kevin,
Diamond, bart, aero. Steel wheels from the world of mini-stock. and not real heavy. AND cheap.

Russ

Thanks, Russ! Just checked out Diamond's website and they offer a 13" Mini Stock Series. They offer a 13x6" version, with a listed weight of 11lbs, at $76.50 a wheel. It also lists 4x100 as a standard offered bolt pattern, and backspacing available from 1-3.5" (typical Honda would be 1 & 3/8", or 35mm). Put in a phone call for more info, and awaiting a call back. If I can get a 13x6", 4x100, 35mm offset wheel that weighs 11lbs for $76.50 a piece, I'd be pretty happy. Will inform as I find out more.

[Dano77]

Offset being different then Backspace,what is the offset positive or negative. the center of a 6 inch wheel will be 3 inches or 3 in backspace. that said if my caveman math is correct,you will need either a 1.5 back space to push the out side out past the fender or a 4.5 back space to push the out side of the wheel in side the fender. Im thinking 4.5 will work. 4.25 is even better if you can roll the fender out abit. Gonna need to do your own math but its not too tough. 35mm divided by 25 =1.4 25mm=1.0inch

Just info you are gonna need if Jimmy the wheel guy calls. They know different terminology than roadracers sometimes.

Dan 77 IT7

[924Guy]

Thanks, Russ! Just checked out Diamond's website and they offer a 13" Mini Stock Series. They offer a 13x6" version, with a listed weight of 11lbs, at $76.50 a wheel. It also lists 4x100 as a standard offered bolt pattern, and backspacing available from 1-3.5" (typical Honda would be 1 & 3/8", or 35mm). Put in a phone call for more info, and awaiting a call back. If I can get a 13x6", 4x100, 35mm offset wheel that weighs 11lbs for $76.50 a piece, I'd be pretty happy. Will inform as I find out more.

Prolly won't be hard; this is where I got my current rims for my DSR. Nice that they have a 4x3.75" bolt pattern...

Still heavy though, for a sports racer. Need to get some alloy once next...

[shwah]

the same as saying they are faster with a higher final drive ratio - "true" in terms of accelration but it does not always pan out on the track due to fixed ratios in the box. wheel diameter =/= overall diameter, though it is assumed that if you want a smaller wheel than what is currently allowed you want it for the smaller OA diameter that it makes avaialble.

I support the rule more for making folks with giant wheels on newer classifications get a wheel / tire package that is more available and affordable. FD is open, who cares about that effect? brake and inertia effects are part of "warts and all" to me.

No it is not just an issue of gearing.

When you change from a 205/55-14 or 205/50-15 to a 225/45-13 you lose nearly 2 inches in OD. This drops the car nearly 1 inch, without any of the ill effects to strut suspension geometry cars (roll center dropping below the ground), improving c.g. And frontal area, while enabling a lower air dam. They also reduce the ratio of tire OD to brake diameter, increasing the available braking force at the contact patch. I have run my car with the right gearing and tall tires, and short tires with their right gearing. I now have only short tires...

At the end of the day, this is an advantage for my car in the class. The proposed change is due to availability of wheels. The last time I priced custom built lightweight racing wheels, they were about $200 each. That is not unreasonable for race wheels. Just because Tire Rack does not sell them does not mean they don't exist.

The issue I have with this, is understanding why it is within class philosophy to equalize this variable, but not others. (mass air flow sensors, brakes, track width, head/valve configuration - yes I am exaggerating to make a point).

The same points hod true for width. The current wheels are available. Why make the change?

[JoshS]

We've always been at the whim of the tire companies for size availability. When that 225/45-13 came out it changed the game for cars that could use 13" tires, without a single rule changing, it changed the balance, didn't it? Some cars got to get all of those advantages you describe, some didn't.

I don't think the existence of that one tire size is a reason NOT to change the rule.

[shwah]

You completely missed my points.

2 wheel size changes have been proposed.
1) Allow any size under stock diameter or 15", whichever is larger.
It has been stated in support of this rule that there is no performance benefit. However there can be multiple performance benefits. In describing the performance benefits, I illustrated how such a change could impact the competitiveness of cars, and drawn a parrallel between this component, and any other component that impacts competitiveness of a given car. In IT we choose prepare and race our cars warts and all, as oft stated on this site.
- What is the reason for this change? You see the way this should work, is that we need to make the case FOR rule changes, not just make the changes if no case materializes against them.

2) Increase width in B and C to 7".
It has been stated that this is needed because you can't get 13,14,15 x 6 wheels.
The problem is that you definitely can. You can get them made to your custom offset and bolt pattern needs. You can get them for $150 to $250 per wheel. So the argument is false. Yet a false argument is somehow considered adequate reason to require current competitors to replace their wheel inventory because a theoretical newbie cannot find wheels at The Tire Rack...

I was addressing the errors in the assumptions provided to support both suggested changes.

[shwah]

Some cars got to get all of those advantages you describe, some didn't.

Change the topic to variable cam timing. How does the discussion change? What is a good reason not to let all cars have variable cam timing? I mean it is only fair....

Some cars DO get some advantages. Other cars get other advantages. If a change is suggested that impacts those performance impacting factors, there is a very real chance of unintended consequences in competitive balance.

[Chip42]

Change the topic to variable cam timing. How does the discussion change? What is a good reason not to let all cars have variable cam timing? I mean it is only fair....

Some cars DO get some advantages. Other cars get other advantages. If a change is suggested that impacts those performance impacting factors, there is a very real chance of unintended consequences in competitive balance.

no offense Chris but I think you're making it out to have more impact than it will if passed. roughly half of the cars in B and nearly all of those in C can already run 13" wheels. fewer in A and just 2 in S. but the bigger boys need wider tires and availability just isn't there, so I wouldn't expect a run on the 13x7" market.
yeah, you are right that there are a number of less obvious advantages to be had by going smaller, which in regards to my ealrier post has NOTHING to do with engine size.

There are all sorts of inequalities across IT in how a rule affects one specific car vs another and I don't see this as being all that out of place among them. additionally, a small mixup in the on-track order might occur. I'll agree with that assessment assuming a full field of to the hilt cars - so maybe top 5 at the ARRC? IT competition is balanced by power to weight, and that will not change with this rule where as a washer bottle COULD allow a few cars to make more power due to better intake routing, for example. THAT could upset the class balance under this model. The proposed wheel diameter change affects everyone in a more consistent way than probably any other rule in the book - the benefits are free to all who can fit smaller wheels.

I think the intent of this rule is to allow the big-wheeled guys like the new beetle, mazda protege MP3, or mini cooper a path to more availability (down to common 15 or 14" sizes) and is defensible as the opportunity already exists to tune gearing. everything else that has been mentioned many times already, such as CG/ride height/air dam clearance/brake torque are already unevenly allowed and will simply affect the existing classifications more evenly. yeah, it'll be nice to get a ~5% increase in brake torque. it'll be nicer still to see more cars out there running wheels they don't mind dropping off a curb. this is IT, it's supposed to be affordable racing.

[Rabbit05]

Why not change the rule to make TIRE size restricted for each class ?

For example only :
ITR/ITS can run max a 245 wide tire.
ITA-ITC can run a max 225 wide tire.

Or something like that..?

Wheel size would be open (dia/width)...BUT keep the original rule of having to stay within the fenders and the rolling thru the chalk to check tire patch deal.

That way ..if you want to run 17's..sure go ahead .... and the guys that already have wheels are not going to affected that much. Over time I think that things would sort themselves out to what is the hot set up.......just food for thought ??

[jjjanos]

Some cars DO get some advantages. Other cars get other advantages. If a change is suggested that impacts those performance impacting factors, there is a very real chance of unintended consequences in competitive balance.

Actual, no. The formula used to set car weights has no interaction factor between car weights and tire size, therefore, the size of the tire has no impact on competitive balance by assumption. If it ain't in the model, it doesn't have an impact.

When the process includes some factor that adjusts for the the competitive balance between running a heavy versus light car on the same tire sizes, then you'll have a case. I.e. The Beetle weighs 2760 and a CRX weighs 1955 -- the performance of the fat car and the light car is assumed to be identical on the same tire width. If tire width matters, then the Beetle would have a lower weight to compensate for being under shod.

[gran racing]

Why not change the rule to make TIRE size restricted for each class ?

Then a TON of people will need (or at least feel so) to get wider rims. I'd probably run the same tire size as I do now, Hoosier 225s, but certainly would benefit from using a 7", maybe 7.5", maybe... Not saying it won't happen in the future, but right now I do not see a supply issue for ITB & ITC cars sourcing 6" wide rims.

[shwah]

no offense Chris but I think you're making it out to have more impact than it will if passed. roughly half of the cars in B and nearly all of those in C can already run 13" wheels. fewer in A and just 2 in S. but the bigger boys need wider tires and availability just isn't there, so I wouldn't expect a run on the 13x7" market.
yeah, you are right that there are a number of less obvious advantages to be had by going smaller, which in regards to my ealrier post has NOTHING to do with engine size.

There are all sorts of inequalities across IT in how a rule affects one specific car vs another and I don't see this as being all that out of place among them. additionally, a small mixup in the on-track order might occur. I'll agree with that assessment assuming a full field of to the hilt cars - so maybe top 5 at the ARRC? IT competition is balanced by power to weight, and that will not change with this rule where as a washer bottle COULD allow a few cars to make more power due to better intake routing, for example. THAT could upset the class balance under this model. The proposed wheel diameter change affects everyone in a more consistent way than probably any other rule in the book - the benefits are free to all who can fit smaller wheels.

I think the intent of this rule is to allow the big-wheeled guys like the new beetle, mazda protege MP3, or mini cooper a path to more availability (down to common 15 or 14" sizes) and is defensible as the opportunity already exists to tune gearing. everything else that has been mentioned many times already, such as CG/ride height/air dam clearance/brake torque are already unevenly allowed and will simply affect the existing classifications more evenly. yeah, it'll be nice to get a ~5% increase in brake torque. it'll be nicer still to see more cars out there running wheels they don't mind dropping off a curb. this is IT, it's supposed to be affordable racing.

I do see your point. My goal was just to make the point that this can, and to some extent will have a performance impact. We likely will not agree on the amount of performance impact is relevant to a decision like this, but I wanted to make it clear that this is not a "no-brainer because it has no performance impact".

Keep in mind that in the lower power classes, small increments of performance become more important. We can likely all agree that adding .040" bore to a small motor in and of itself has a very small impact on performance, but to build a top performing car, we all do that, as well as balance/blueprint and eke out the last .0x of compression allowed within the rules.

[shwah]

Actual, no. The formula used to set car weights has no interaction factor between car weights and tire size, therefore, the size of the tire has no impact on competitive balance by assumption. If it ain't in the model, it doesn't have an impact.

No. If it is not in the model, then we do not manage it's impact. That does not mean that it does not impact the relative performance of real cars in real race tracks.

[Chip42]

I do see your point. My goal was just to make the point that this can, and to some extent will have a performance impact. We likely will not agree on the amount of performance impact is relevant to a decision like this, but I wanted to make it clear that this is not a "no-brainer because it has no performance impact".

agreed, this can and will produce changes on track. but it's one of those things LIKE the over-bore allowance which came into being to allow hard parts to stay in service, and thus make the cost to compete (not run at the front) a bit lower. yes, it opens the envelope, but the allowance was there for everyone (except rotaries) despite having mixed perfomance gain. the same is true for all IT allowed mods - the changes are common, the effects are not. some affect power, which can upset the power/weight balance model. some effect handling, which don't.

my point is only that it helps everyone a little and helps some a lot - either on track or in the wallet. My support for the diameter rule change is based on the latter, and I believe the performance changes will be insignificant overall.

[jjjanos]

No. If it is not in the model, then we do not manage it's impact. That does not mean that it does not impact the relative performance of real cars in real race tracks.

I didn't say that there wasn't a real world impact. I said that the classification of cars already is off because tire size is assumed to have no impact. Change the available tire sizes and no weights change, so, as far as the system is concerned, there is no impact on performance.

This is a natural outcome of the deterministic process used. Don't like it? Then ask that we go back to the bad old days of "well, what do you think the weight should be?"