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Greg G.

NASA 2018 ST1-4 & SU Rules Released 11-29-17

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davidfarmer

ST4 only:

 

so 245's for anyone under 3100lbs, 275's if above 3100lbs.

 

I'm with many above, I'm perfectly fine running 245's but my rims are very wide and may or may not fit the new NASA measuring templates. The thoughts of the same tire being legal on a 9.5" rim and illegal on a 10" rim makes no sense to me. Are there soooo many anomalously sized tires out there that the bad ones can't be banned or re-classed specifically?

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Balroks
ST4 only:

 

so 245's for anyone under 3100lbs, 275's if above 3100lbs.

 

I'm with many above, I'm perfectly fine running 245's but my rims are very wide and may or may not fit the new NASA measuring templates. The thoughts of the same tire being legal on a 9.5" rim and illegal on a 10" rim makes no sense to me. Are there soooo many anomalously sized tires out there that the bad ones can't be banned or re-classed specifically?

 

Technically, that's exactly what they're doing. For example if you look at the 2015 or 16 rules they specifically called out that 245 BFG's count as 275's and 275bfg's count as 285's. That's because when this tire was released it was hella wide even compared to the hoosiers. This made some folks run 265's but in effort to add .5" to the tread width they mounted on .5" wider wheels. Such tires had tall enough sidewalls to make that happen. Then there was the 255 hoosier which was technically 275 wide when the rules used to use specific widths instead of ranges. Annnnd you're right back where you were, over and over. By going with a "fit the tool or fail", Greg no longer has to go through testing each new tire to see if it's clearly not what it says it is, call people out, write bulletins etc etc. It's now up to each competitor to find that combo that falls into spec to squeeze what they can from their grip levels - regardless of who comes out with what tire.

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Pat533i
Do you have the base testing data available for those popular ones? Like 275 hoosier on 9.5 or 10 and bfg's on 9.5 or 10, etc? As in you know already what combos for sure aren't going to cut the mustard.

Hoosier 275 (both 17 and 18's) should fit the 282mm tool on 10" wheels. Not sure about the BFG's

The 255 x 18 will not.

 

 

I don't get how the 275/17 with a listed section width of 11 inches will fit the tool,

 

But a 255/18 with a listed section width of 10.8 inches will not fit the tool ?

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erik911
Do you have the base testing data available for those popular ones? Like 275 hoosier on 9.5 or 10 and bfg's on 9.5 or 10, etc? As in you know already what combos for sure aren't going to cut the mustard.

Hoosier 275 (both 17 and 18's) should fit the 282mm tool on 10" wheels. Not sure about the BFG's

The 255 x 18 will not.

 

 

I don't get how the 275/17 with a listed section width of 11 inches will fit the tool,

 

But a 255/18 with a listed section width of 10.8 inches will not fit the tool ?

 

I am guessing because per Hoosier, the 255/18 was measured on a 9" rim, whereas the 275/17 was measured on a 9.5" rim.

 

Going to the 10" wheel will have a fairly significant impact on the section width for the 255/18. It may be ok on a 9.5"?

 

Bummer for a few folks I know in ST3/TT3 with several sets of 10" wheels who run this tire size.

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davidfarmer

I have no issue with adjusting for mis-sized tires, I DO have an issue with tires being deemed illegal because I can't afford to buy new wheels. Just because the sidewall bulges out on a particular rim has nothing to do with the tread width or performance.

 

A 245/40/18 Hoosier is going to be very close to 266mm on my rims

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Sboxin

Thanks for the early posting of the Race rules and the time/effort all of you put into these rules.

Even when we don't say it - we do appreciate the time and effort . . .

 

Now to the Question:

Is there a definition for "Redline" used in the Average Horsepower calculation process ??

 

When we look at the car's tach there is a redline placed by the car manufacture . . . but in these race classes most engines

don't have a real redline except for maybe the rev limiter selected by the car owner or engine builder.

Our rev limit was selected during the modified engine Dyno tune process.

Is this what the rules intended for the "Redline" for our car ??

 

Thank you in advance for some further clarification of the rules use of the term "Redline" .

 

Regards,

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Greg G.
Thanks for the early posting of the Race rules and the time/effort all of you put into these rules.

Even when we don't say it - we do appreciate the time and effort . . .

 

Now to the Question:

Is there a definition for "Redline" used in the Average Horsepower calculation process ??

 

When we look at the car's tach there is a redline placed by the car manufacture . . . but in these race classes most engines

don't have a real redline except for maybe the rev limiter selected by the car owner or engine builder.

Our rev limit was selected during the modified engine Dyno tune process.

Is this what the rules intended for the "Redline" for our car ??

 

Thank you in advance for some further clarification of the rules use of the term "Redline" .

 

Regards,

 

Rules still say this in regard to Dyno testing:

"All Dyno graphs must show decreasing power for 1500 rpm from the peak horsepower level, or the car must reach the rev-limiter during the Dyno testing."

 

So, "redline" could potentially be either endpoints (but has nothing to do with the red mark on the OEM Tachometer).

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Greg G.
I have no issue with adjusting for mis-sized tires, I DO have an issue with tires being deemed illegal because I can't afford to buy new wheels. Just because the sidewall bulges out on a particular rim has nothing to do with the tread width or performance.

 

A 245/40/18 Hoosier is going to be very close to 266mm on my rims

That's not true to begin with, because the larger wheel DOES make the tread width and the section width wider because of the design of the tire shoulders.

And, if the car weighs more than 3100 lbs, you can still use the same size wheel and tire---not "illegal", just won't get the "cheater" Mod Factor for a tire that is essentially a hair smaller than the 275. Or, you can use those wheels with the 275's, and be a bit larger than the 245's. It's called "closing a loophole".

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Greg G.
BFG doesn't have a time trials contingency.. these changes to TT4 really seem to be trying to force hoosiers out of TT instead of leveling the playing field with Toyo/BFG - pushing an american company that produces great tires with a great contingency program out of TT because their tires run wide...

These rules don't force Hoosiers out of TT one bit. They force supersize wheels expanding tread and section width out of getting inappropriate Mod Factor perks.

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JonB
BFG doesn't have a time trials contingency.. these changes to TT4 really seem to be trying to force hoosiers out of TT instead of leveling the playing field with Toyo/BFG - pushing an american company that produces great tires with a great contingency program out of TT because their tires run wide...

These rules don't force Hoosiers out of TT one bit. They force supersize wheels expanding tread and section width out of getting inappropriate Mod Factor perks.

 

Greg - then why not let the cars under 3100 lbs run the wider wheel/tire combo then if they so choose? They of course would have to apply the correct modification factor based on NASA Section Width, but this way they would still have a choice to use the wheels they purchased based on last years rules?

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sperkins

That's not true to begin with, because the larger wheel DOES make the tread width and the section width wider because of the design of the tire shoulders.

And, if the car weighs more than 3100 lbs, you can still use the same size wheel and tire---not "illegal", just won't get the "cheater" Mod Factor for a tire that is essentially a hair smaller than the 275. Or, you can use those wheels with the 275's, and be a bit larger than the 245's. It's called "closing a loophole".

 

How is it a cheater loophole if the tire in question is available to everyone? Because some cars can run wider wheels than others?

If that's the case, it seems only logical that it would have been a lot easier to limit wheel size. No?

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Vettedoctor

Because then we would just come out with "cheater" wheels

 

We all know what NASA is doing with the section width rule - they needed to come up with a rule that ensured that no one would come in with a overly wide tire for the size stamped on the sidewall. Weather it's from a plus sized tire like the Hoosier 255 or weather it's due to us stretching the tire by putting it on a wider rim. Yeah it sucks that some of us will have to buy new rims but in the long run it's a good rule and one that guards us from future tire issues. And seriously has anyone ever really had an issue selling wheels? Finding good used wheels isn't always easy but selling good used wheels - not too tough.

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Thethreefitty

Hi Greg,

 

Could you elaborate on the combinations tested. Maybe a table of the combinations you/NASA collected. I think this data will save a lot of us a headache or money on combinations we cannot afford to order for trial and error purposes.

 

In your testing did you test a 255/35R18? If so on what rim width? I would like to step up to 18's for caliper clearance/wheel offset.

 

Currently I have is 275/35R17 R7 on a 10" wheel and they are an exact fit for the 282 template.

 

Thanks,

 

Nick

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Greg G.
Hi Greg,

 

Could you elaborate on the combinations tested. Maybe a table of the combinations you/NASA collected. I think this data will save a lot of us a headache or money on combinations we cannot afford to order for trial and error purposes.

 

In your testing did you test a 255/35R18? If so on what rim width? I would like to step up to 18's for caliper clearance/wheel offset.

 

Currently I have is 275/35R17 R7 on a 10" wheel and they are an exact fit for the 282 template.

 

Thanks,

 

Nick

Nick, someone started a thread in the Race Craft section of the Forums, but it hasn't gained much traction yet. Our data won't be posted, because as soon as someone buys some other wheel, or runs a different tire pressure, etc., they will complain that "we told them...."

 

I'm comfortable stating that the 275/35R18 R7 should fit the 282 template on a 10" wheel. I know the 255 won't come close even (290+) on an 11" wheel--probably won't fit 282 on a 10" wheel, but not confirmed.

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Al36rx7

As a general question. What was the basis of the template using 30mm for the sidewall? Having a shallower number (25 or 22mm) would focus approved or not approved status on the tread width more than where some tires are very square at the sidewalls, or if a rim is slightly wider than the tread of the tire.

 

Is there a noticeable performance gain by installing a tire on a rim where the sidewall is flexed outwards to the rim?

 

Just questions from the peanut gallery....Thanks

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Tjyak50

It would be helpful to call out the other dimension in the NSW template sheet. (example 266.0mm x 30.0mm)

I sent my size to the water-jet guy and pretty sure it is 30.00 mm deep but would like to be certain.

 

Tom

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Tjyak50

Bump for dimensional clarity.

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DanielsDM

Reading through the ST1-4 and ST5 rules, only the 226mm NSW gage has a 23mm depth. (ST5 <2400lb)

The 282mm, 266mm and 257mm NSW gages are 30mm depth.

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Tjyak50

I missed that part.

Ideally we could update the NSW template to specifically call out that dimension.

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davidfarmer

We will ultimately need some feedback in usage. My tire has so much curvature in the center even 30mm really doesn't go all that far down the sidewall . I printed/cut mine from cardstock

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Murphdog

I'm unsure why the avg. horsepower rule of 7.3.3 includes forced induction especially smaller displacement engines. Small displacement turbo motors have far less usable power bands and this rule will only focus strictly on their small peak power. Last year it seemed like this rule was going in the right direction for cars that made peaky power. Now we're going backwards and this rule does nothing to help even the field.

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Greg G.
I'm unsure why the avg. horsepower rule of 7.3.3 includes forced induction especially smaller displacement engines. Small displacement turbo motors have far less usable power bands and this rule will only focus strictly on their small peak power.

That is absolutely not true if the engine is tuned (and detuned) correctly. The Dyno curve can easily be manipulated with a small displacement engine and FI to make some of the data points specifically low at the ends of the rpm range to give a falsely low Avg HP, or it can be made absolutely flat for over 4000 rpm (we have seen both on 2.0L and smaller motors).

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Murphdog

I would consider my motor to be tuned correctly and its peaky. In regards to small displacement turbo motors if you are making low power than I can see a pretty flat power curve but if you are looking at 500whp than it will be fairly peaky. Seems like to many variables to throw FI into that rule.

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Greg G.
I would consider my motor to be tuned correctly and its peaky. In regards to small displacement turbo motors if you are making low power than I can see a pretty flat power curve but if you are looking at 500whp than it will be fairly peaky. Seems like to many variables to throw FI into that rule.

Maybe your prepping for the wrong class, then? Your choice. But, your specific case is not how we write rules. They are written for the possibilities. And, I know that there have been race gas powered small displacement turbo engines making well over 500whp that could be detuned to a flat dyno curve in the usable range even at 500 Avg HP.

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Murphdog

Thanks Greg for your input on this.

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