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Discussion Starter #21
Tire and wheel sizes

Back to the tire/wheel question #1 To be legal must you run 17" wheel in the front and 18" in the rear. #2 Must you maintain stock wheel widths( 9.5" front 10.5 rear #3 What is the limitation on tire size relative to stock. and lastly if you were to be purchasing CCW wheels and Kuhmo 710's what sizes would you get. Thanks for your time
Henry
 

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Henry

The Victoracers are not R tires either

The Hoosier DOT A3S03, A3S04, Kuhmo Ecsta 700 & Ecsta 710 (all A tires and near R tire specs) will blow the doors off the Nitto's

THE NITTOS ARE NOT EVEN Z RATED !!!!!

A soft compund does not an R tire make.

The Hoosier R3S03, R3S04's and Goodyear R tires are better yet and are true racing tires with an "R" tire designation
 

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In SS wheels must be the same width and diameter as stock.

In addition you may run either a 1/4" spacer plate or preferably have the +0.25" positive offset built into the wheel.

Therfore 9.5x17"F and 10.5x18"R with +0.25" offset built in are legal

Any tires may be used in any size and width provided:
- they are not listed (banned). Currently non are.
- a new tire must be approved before April 30th
- each tire model must be sold in at least 4 diameters with a total of 6 sizes
- No racing tire or recap may be used (Non DOT)
Tire must be DOT & SEB approved
- must be equally available to all competitors
- tires must fit wheels and fender wells without modification
- must have a non-zero measurable trade depth
- must not be corded

Most run
275/40x17 and 305/30x18 Hoosier or
275/40x17 and 295/30x18 Kumho
 

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Discussion Starter #24
Tires

DJ....Don't get all hot under the collar about the tire thing. You may not like the economy priced Victoracer V700 and I never claimed it was the equal of the Kuhmo 710 or Hoosiers (by the way the UTQG of the Victoracers is 50AA which seems to fall into the R catagory) I was only comparing it to the Nitto because the Nitto offers excellent performance for a tire that you can drive to the track and also run.I will only use the Nittos for Track Days(I'm not a full blown Road Racer and don't want to be)or for warmup /practice runs for AutoCross. Many of us use street/track tires(like the Falken Azenis) for testing and then "Real R Compounds" for the actual event.
Thanks for all the useful information that you have provided.
Henry
 

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Henry Bjoin said:
Will the Kuhmo 315x35x18 fit on the stock rim 10.5"
Yes, the 315/35 fits a 10.5" rim with a very good sidewall profile, no compromises.
The question is which size V710 to run on the front. The 295/40 will "fit" and many dedicated autocrossers run that size, but that tire really would benefit from a wider rim section. The other choice, 275/40, is a perfect fit on the 9.5" rim, but you give up section width. I'm not sure what the tradeoff actually is on true contact patch between the two sizes...the Kumho guys in SS at Nationals seemed to be pretty evenly split between the 275 and 295. I chose the 275, because I also am using this wheelset for open track events and I wanted to maintain good turn in response and feel.
Another point which hasn't been considered is the fact that the V710 has much more rounded edges and will work effectively with less negative camber than the Hoosier.

I'm also confused by the use of "R" designations. In my experience "R" does not designate a specific "compound", treadwear or heat range, but merely indicates that the manufacturer considers the tire suitable for competition events requiring DOT approved rubber. From there, the specific manufacturer uses their own system for "coding" specific compounds for specific intended usage?
 

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Discussion Starter #27 (Edited)
Thanks for the info

Not being a regular to online fourms, I wasn't sure what to expect when starting this thread. The quality of the responses far exceeded my expectations.You guys know your stuff. Thanks to all that responded, with special thaks to DJ for all his expertise. I guess I'm off to spend some money.
Henry Bjoin
 

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I got a lot out of this thread, too.

It convinced me that I ought to just mount some Kumho Ecsta V700s on my old stock rims for next year. (Less than $1000.) If I come consistently within 2 seconds of the class leaders I'll think about more. Mostly, I've got to improve the software between my ears before going off the deep end on hardware.

:idea:
 

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The tire and shock discussion are very good here. I only wish that NCCC and SCCA would homogenize some of their rules regarding street tires and shocks. That would make it nice for us poor autoxers that run in both clubs...
 

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Just double checked the specs on the Nitto 555R2's (my daily driver)

The 275/40 ZR17 98W is a 168MPH rated tire
The 285/35 ZR18 97Y is a 186MPH rated tire
The 305/35 ZR18 101Y is a 186MPH rated tire

I run the 285 front and 305 rear and would not have bought them if they were not rated above the stock top speed of the car.

The stock F1's are Y rated front and rear, so yes be advised the 17" nitto 555R2 is a step down in speed rating from stock !!
 

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The winning car at the SCCA Nationals this year ran the 295 on the front, in fact they changed to them after there first run on the 275s, It was more of a drivers preference, and may have worked out there in Topeka be cause the surface is so ruff, and the add sidewall keep the contact patch on the ground where it belongs.
The shock rule that DJ quoted it correct for now but there was some discussion about changing it this year. Then again you never know what SCCA rules will be.
As for me I have run the Michelin Sprot cups for the past two seasons, I will be running on Kumo's this coming season as of now. Not that they will make me any faster.
 

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Discussion Starter #32
Differential Gearing

Does anyone know if it is legal to change the final drive gear ratio. I believe that if various ratios were offered as an option then it would be legal
Henry
 

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No, as there were no other ratios available as factory installed options on the Z06.

Z06's all had close ratio gearboxes with a 3.42:1 Diff ratio from '01 to '04.

"....Stock Category cars must be run as specified from the factory with only standard equipment as defined by these rules. ....

... Option package conversions may be performed between specific vehicles of a particular make and model, but only between configurations from within a particular model year. "

Ie.. If it can not be ordered installed or deleted from the factory it is not allowed. However you may add or delete complete and total option packages within your model year ONLY.

The C5 Coupe and Vert are considered another model, so you can not use their various ratios from the standard, performance or Auto trans cars ( but you wouldn't want to as they are all lower ratios.)

The SS rules further specifically addresses LS Diffs, Tranny & Tranny Ratios, Diff Ratios, Clutches, FI Systems and SC induction
"...must be standard as herein defined."

In ASP you can "update and backdate" parts "...between different years and models if: "
- "...the item is standard on the make and model it was taken from"
- "...the models are listed on the same line in Appendix A."

The line in Appendix A for the Z06 is ..." Corvette, +'97.

In SM2 the engine and Drive Line are essentially unlimited so any ratio or Diff is allowed.
 

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I have a question about preparing a Z06 for Super Stock. DJWorm's excellent list includes the addition of a K&N air filter. From what I've read of the SS standards, the replacement of an air filter other than stock is not permitted in SS. My only engine modification is the installation of a Donaldson Blackwing filter. Will this be allowed in SS or will I have to run Street Prepared with this modification? Also, I have installed an aluminum accelerator pedal and dead pedal. Will I have to reinstall the stock pedals to maintain SS specs. Thanks for the help.

Flash
 

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"The engine air filter element may be removed or replaced. A replacement element which is taller than standard may not be used to hold the air cleaner cover open. No other componants of the air induction system may be removed, replaced or modified."

A K&N elemnet is actually thinner than an OEM element and flows better. It requires a foam piece to seal it and bring it up to OEM height.

However a Donaldson replaces the filter AND the air box and therefore is illegal.

What you need to remember in Super STOCK is that STOCK means STOCK; unless the rules say you can specifical use or do something... you can't.

"Accesories, gauges, indicators, lights and other appearance, comfort and convience modifications which have no effect on performance and/or handling and do not materially reduce the weight of the car are permitted."

As to the pedals, according to the above rule"
- the Aluminum dead pedal/rest would be legal as it actually ADDS weight to the car and does not add or aid in performance.
- The aluminum gas pedal is illegal as it may reduce weight (?) but more importantly improves performance. How?....it improves the driver/car interface. Note that seat covers have been protested and dissallowed as they improve the driver/car interface by providing the driver a more secure seating position and are a performance advantage. The Aluminum gas pedal will be construed as enabling the driver to "heel & toe" better...thus increasing performance.

One other point on the Nitto's. I do not think they meet the tire requirement of being produced in 4 diameters and 6 sizes.

You may think that some of the stock rules are nit picking....and they are. IMHO if any body protests using one of these he is a BIG FAT WEENIE. You will not find much protesting going on at the local and regional level and class placement is much freer. However you must adhere to the rules at the National and Pro level. You will be protested if you are not in strict compliance.

It is usually first a gentlemen's request:
I overheard one competitor say to another in Saturday's impoundat a Pro Solo,
"You have changed out the rear sway bar end links from the '01 plastic composite ones to the '02 steel ones on you '01.....put the OEM's back on your '01 or I will protest you tomorrow."
 

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DJWorm:

Thanks for your very thorough response to my questions. As a practical matter, I can see that campaigning in Street Prepared has an upside and a downside. The upside being the ability to add certain competitive enhancements, the downside being the inevitable cost escalation to be competitive in the class. You are correct that the local folks have mostly ignored my mods, since I'm still very green. However, I'm sure this will not go on forever, particularly if I decide to try and compete farther upstream. Since it would be easy at this point to replace my current modifications with their stock counterparts, I can see this as the wiser strategy. I'd value your thoughts.

Regards
 

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Street Prepared is a natural progression from Stock

The Z06 can progress from Super Stock to A Street Prepred and then Street Modified 2.

Many novices first modify their cars in anticipation of competing and then buy a rule book and find that they have already modded themselves into an upper class.

The basis for Street Prepared modifications is all the ones that can be accopmplished in Stock. Likewise all that can be accomplished in Stock and Street Prepared are the basis for further modification in Street Mod 2.

A little known aspect to the Street Prepared Rules are that cars prepared to the T1 Touring Class GCR road racing rules are allowed to compete in Street Prepared AutoX on an equal basis. The caveat is that the car is prepared to EITHER T1 or SP rules but NOT both. NO intermigling of rules or mods is allowed. You can not pick-and-chose or shop to an advantage.

You can also update and back date...ie you can use parts and options on your car that has appeared on any C5 or Z06 from 1997 to 2004.

It might be noted that one of the top cars in ASP is a previous T1 1999 C5 upgraded to Z06 specs which also competes in SM2 succesfully as it is prepared.

The main benefits of ASP are the suspension and handling mods and derived benefits that are allowed and the ability to lighten the car.
A properly prepared car can be sub 3,000#'s.

The mods allowed in ASP are extenssive (and costly) and past the scope of this thread. You can consult a rough comparison of the allowable mods at:

http://www.sff.net/people/dburkhead/prepcompare.htm

Many also advance to ASP and SM2 because they find that the National Tour and Pro Solo Stock Classes are crowded (being a less expensive class to compete competitively).

As one would expect the driving ability at the top is superb...almost God like. John Ames, Erik Strelniks and Chris Ramey in SS, Danny Popp and Gary Thomason in ASP and Scotty White and John Gunn-Wilkinson in SM2. What's suprising is that all these drivers post very close and similar times and can beat one another's times on any given day irregardless of class and car preperation.

I suppose this is attribuitable to the basic competance, experience and talents of these top drivers and the aptitude of the Z06 right off the showroom floor. What the C6 Z06 is going to offer is almost unfathomable.
 

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Flash said:
DJWorm:

Thanks for your very thorough response to my questions. As a practical matter, I can see that campaigning in Street Prepared has an upside and a downside. The upside being the ability to add certain competitive enhancements, the downside being the inevitable cost escalation to be competitive in the class. You are correct that the local folks have mostly ignored my mods, since I'm still very green. However, I'm sure this will not go on forever, particularly if I decide to try and compete farther upstream. Since it would be easy at this point to replace my current modifications with their stock counterparts, I can see this as the wiser strategy. I'd value your thoughts.

Regards
Run whatcha brung. When you start getting competitive, then start thinking about returning the car to stock. If you have any decent drivers in the area, you won't be giving them any worries anytime in the near future. Everybody is slow at first.

Keep in mind that it will take a sizeable investment to be competitive and even more to be at the top. Top competitors will run fresh tires at every National event. Also, keep in mind that the biggest improvement is in the driver. There's no sense in worrying about what modifications to make when the driver is the biggest obstacle to faster times. Lastly, remember that this is supposed to be fun. A lot of people get caught up in the competition and forget that auto-x is supposed to be grassroots racing. Nobody gets paid to auto-x .... and the big pie in the sky is a jacket (and a cigar box for this year's Nationals trophies).
 
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