RichardP Posted September 17, 2004 Share Posted September 17, 2004 There has been a bit of discussion on the wheelbase and track allowances for AI. From Section 6.1: “… Fox and SN95 chassis vehicles are allowed a maximum wheelbase of 102.2 inches and the wheelbase for all other AI vehicles shall remain within two and one-half (2.5) of the original factory configuration. Fox and SN95 chassis vehicles are allowed a maximum allowable wheel width of 72.25 inches with a +/- .25 inch to tolerance (measured at the outside edge of the tires). A Fox or SN95 vehicle must be able to drive through a fixture laid on the ground measuring 72.25 inches wide and 3 inches in height.” The anal-retentive side of me (unfortunately I’m not sure there is another side?) is going to pick this paragraph apart and then I promise I’ll get to the real details. The first problem is in the first sentence (within two and one-half (2.5)). The units are missing. The next is a pet peeve of mine. I realize what the authors were trying to do but by definition, there is no tolerance on a “limit.” A tolerance can be rewritten as an upper or lower limit. In this case 72.25 +/- .25 becomes any value between 72.00 and 72.50 inches. Which is it? As a competitor I know the real limit is 72.50”. If the limit is 72.5” then why do I have to drive through a fixture 72.25 inches wide? That’s contradictory. Also, “drive through” implies a “skill” that needs to be mastered. Is this like the game of Operation and if I touch the sides I’m declared illegal? “Fit between” is probably a better description of how the car would actually be measured. With the stock Mustang wheelbase being 101.3”, why are Mustangs allowed only .9” growth and every other car is allowed 2.5”? I believe the intent of specifying the maximum wheelbase on the Mustang was to stop people (esp. those with the Griggs adjustable front control arms) from moving the wheel farther and farther forward. Does this rule really stop that or is there a hole? Looking at my Mustang, I’m thinking I can move the rear wheels forward maybe 2” within the current rules. With the Griggs rear lower control arm setup, the arms will still be longer than stock. That means I can move the front wheels forward about 3” total. Is that really the intent? I understand why Mustangs have a width limit but there really needs to be a width limit for other cars before someone spends a lot of time and money creating a non-Mustang AI car that is way beyond the intent of the class. I like keeping things simple but it is probably time to create a list of specifications for the eligible cars in AI. This list would include width and wheelbase. There just aren’t that many different types of cars currently running and it wouldn’t be that big of a deal to set a reasonable limit on those models. I don’t want to keep people from running new/different combinations so it should be made clear that anyone who wants to run a model not listed just has to request it be added and then the dimensions will be posted to this website. Finally, I have a little issue with the actual width specification for the Mustang. I have a Fox Mustang running a Griggs K-member with SN95 length arms, 96+ spindles, 16 x 9.5” wheels running 255/50/16 Toyo tires. With my offset set up so that my tires occasionally rub and spin my coil-over springs, my width still comes in at somewhere between 72 ¼” and 72 ½” depending on tire pressure. While that is technically legal as the rules are current written, it’s a bit closer than I would like. How many people have actually measured their car? I know several that just assume they are legal. One solution I’ve seen is to run really short coil-over springs so that the tire rides below the bottom of the spring. I don’t find that solution tolerable at all and I’ve seen too many bent camber plates to show that it’s a bad thing to do. I’d rather make custom arms that are say ¼” shorter than go with the shorter springs. I’m just curious if anyone else has had this problem? Richard P NASA TX AI #91 Quote Link to comment Share on other sites More sharing options...
trackboss Posted September 17, 2004 Share Posted September 17, 2004 You should be running 8” springs. The 10” springs would be for softer rates which will not work all that well with your setup for a race car. I never had a problem with my car which I ran for over 2 seasons and I ran it HARD. The camber plates were global west and date back to ’93 with no issues. Set it up like this with the ride height as per griggs recommendation and you should be ok. You may have the SN-95 arms which make your track width so close. I had the fox R model arms with the rod ends out as far as safely possible and was well UNDER the limit. This is with 275 toyos on a 17”x9.5” CCW and the equivalent of 6” backspacing. Quote Link to comment Share on other sites More sharing options...
RichardP Posted September 17, 2004 Author Share Posted September 17, 2004 No I should not be running 8" springs. With the preload created by the weight of the front of my car on the springs of the rate I want to run with the amount of travel I have set the car up with, I get coil bind with an 8" spring. That's just a fact. If you want to run with stiffer springs, have less travel, or have a lighter car you can probably get away with the shorter springs. That is your choice. Richard P Quote Link to comment Share on other sites More sharing options...
racercosmo Posted September 17, 2004 Share Posted September 17, 2004 I was around when the rule was created. Ryan John and Peder measured every pony car they could get their hands on. At the track, the 2 widest cars were 72". An SN95 with a Griggs Racing front suspension, 96-later spindles and R58 wheels shod with 275-40-17 RA-1s at 30 PSI comes in just about 72 1/8" depending on brake rotor thickness. Ryan Flaherty's car was 72" with MM equippe. Dan S, Bruce Griggs and myself spent a day at Sears Point measuring vintage TA cars, shitbox OldsmoBuicks, GT350s, Chevelles, Crown Vics, etc. If it could be made into an AI car, we measured it. Not 1 car was over 72". Quote Link to comment Share on other sites More sharing options...
RichardP Posted September 17, 2004 Author Share Posted September 17, 2004 That's good information. R58 wheels are 9" wide and many people run the class limit of 9.5" wide wheels. The number is what it is and there are many ways to meet it. It appears if you maximize everything to the limit of the rules you are in definite danger of being too wide. You have several options on compromises to meet the rule (wheel width, a-arm length, tire width, camber, short/stiff springs, etc.). Decide on which one hurts the least and go with it. I was just bringing up my findings to make sure the people writing the rules think the rule still meets the intent of what they are trying to accomplish. Richard P. NASA TX AI #91 Quote Link to comment Share on other sites More sharing options...
trackboss Posted September 17, 2004 Share Posted September 17, 2004 No hard feelings Richard. I was just explaining what works and having been one of the most successful AI entries on the west coast I know I have some reputation to back me. Quote Link to comment Share on other sites More sharing options...
tacovini Posted September 18, 2004 Share Posted September 18, 2004 Just to clear the air so there isn't a pissing match. I've raced with Vageli on the West Coast and now with Richard here in Texas, I can attest that both of you guys definately know your suspension tech!!! Vageli has raced up front for years and beaten the best of them (and had one of the cleanest AI cars I've ever seen.) Richard is a suspension engineer for NASA (the space people who make little Mars rovers and such) and runs AI laptimes in his CMC powered car. It would be bragging if either had to say so themselves... -=- Todd Quote Link to comment Share on other sites More sharing options...
trackboss Posted September 18, 2004 Share Posted September 18, 2004 Hmm, maybe Richard and I can get together and build an AI car from the parts bin at his work. Might I add, after having visited Fernly Nevada I am almost convinced all the space video and pictures are taken there. Quote Link to comment Share on other sites More sharing options...
mansier Posted September 20, 2004 Share Posted September 20, 2004 My vote is for the maximum width to be a percentage of wheelbase. So if a Mustang at 102 inch wheelbase gets to have a 72 inch width (making the math easy here), that means the width is 70.5% of the wheelbase. At that ratio, my T-Bird could run 79.6 inches. Mathematically (using my arguement) the T-Bird is at a disadvantage, running only a 66.8% ratio. Flawed arguement? Maybe. But I like my math! For information: The T-Bird is currently 75.5 inches, with 1 inch stretched rear fenders, and the front fenders altered about the same. This is running 9.5 inch wheels that barely miss the suspension and brake system. Chris Nickell is also building a big AI car, an Impala, that I am sure is bigger than the T-Bird. He has about a year into the build. Perhaps the ratio idea isn't such a bad one? Or perhaps a maximum width for a given wheelbase such as: 100 - 105 72.5 105 - 110 74 110 - 115 75.5 or something like that. That way many different cars could still compete, with a stepped ratio as they get longer. LM _________________ OH/IN Region Director VVC Director American Iron Racer Quote Link to comment Share on other sites More sharing options...
Members Ed M. Posted October 7, 2004 Members Share Posted October 7, 2004 Something else to think about and consider when looking at this rule - I'm kicking around the idea of building a 2005 Mustang for AI (I'm currently a newbie with a Fox Mustang) and from the specs I've seen, the 2005's have a wheelbase of 107.1 inches (can't recall the width, but I think it's in the 72" range...). This equals BIG advantage and from the rule as it is currently written: “… Fox and SN95 chassis vehicles are allowed a maximum wheelbase of 102.2 inches and the wheelbase for all other AI vehicles shall remain within two and one-half (2.5) of the original factory configuration. Fox and SN95 chassis vehicles are allowed a maximum allowable wheel width of 72.25 inches with a +/- .25 inch to tolerance (measured at the outside edge of the tires). A Fox or SN95 vehicle must be able to drive through a fixture laid on the ground measuring 72.25 inches wide and 3 inches in height.” it is only limiting FOX and SN95 chassis vehicles (Mustangs) - which makes the 2005's legal. I can already hear the yelling and screaming!! All of a sudden, a ratio system seems to sound better and better... Quote Link to comment Share on other sites More sharing options...
kblackav8or Posted November 2, 2004 Share Posted November 2, 2004 My car is in the process of being upgraded and has a 109 inch wheelbase. The car has Nextel Cup dimensions except for the wheelbase which is an inch shorter. That is what it is factory. Hopefully after a year or 2 in HPDE and getting my license it will be headed to AI/AIX or AI/V if that takes off. Kevin Quote Link to comment Share on other sites More sharing options...
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