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sn-95 track width


Al F.

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This was posted by Mountainrider

Al,

I'm planning to upgrade my SN95 track width to the new maximum 73.25" dimension using 17" wheels with the correct offset. In your email dated Oct 31 regarding changes to the RCRs, item #3 says "replace track width limit by the fenders with a fixed number and measurement method as per the AI rules". I was reading that to mean fender modifications concessions were a foregone conclusion. However, your latest email and paragraph 7.5.1 says fender modifications are not permitted.

 

Guidance is definitely required!

 

Other issues: I've been studying wheel offsets and I question being able the use the maximum 9.5" wheel w/o having a track width of 73.25". The reason is the maximum wheel offset dimension will be determined by interference with the front strut. So if the track width is limited by the fenders, I think the wheel width may also be limited.

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This was posted by JDLingle

Talked to Al today and feeling much better after hearing the thought process on this. I am back away from the ledge now.

 

FYI for MountainRider2- My 17x9 wheels are either 24 or 27mm offset and I have not had any problems at 72.5. I could probably get out to 73.25 and still be fine but I dont know for sure yet. I am gonna have Al take a look at my car soon and see what he thinks.

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The purpose of changing the track width rule was not to open up anything new (like allowing bodywork mods for everyone) rather to make it easier to enforce and easier to ensure you're at the edge without going over. Again, apologies to you early SN-95 drivers for the confusion. We'll have revised numbers for the 94-98 cars soon. It'll be somewhere between 72.5 and 73.25.

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The frustration I have is that the original 73.25" that the directors came up with was obviously picked for a reason. Now b/c it is determined that 73.25" does not fit under a stock fender the directors have no problem making it narrower.

Why is 72.5, 72.75, or 73" acceptable now but it wasn't a month ago when the rules came out?

 

My big beef is the large discrepancy in track width b/w all the platforms. If the 4th gens came from the factory with the ability to be 76" track width stock is that what their number would be?

 

The 4th gen track width number was determined by what could fit within the fenders and the SN95 track width was determined by ??????

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The obvious reason it was picked was it was what was believed to fit under the stock fenders! I think it's been made clear the reason for going to a hard number was to take away the ambiguity of what is 'under' the fender.

 

The SN95 track width was supposed to have been determined by what could fit within the fenders. Either somebody goofed while measuring or the car where the measurement was taken from was shall we say, in the gray, or the directors goofed typing it up etc etc. The reason was not to increase what was already allowed. In fact, in at least the case of the 4th gen, it was decreased! SN95 guys should be happy that the width they could get before is still legal!

 

According to Glenn (take it for what it's worth)...

I can tell you that the limit for 4th gens was set NARROWER than what my 4th gen could be set to under the 2011 version.

http://www.aicmctexas.com/main/showthread.php?4158-2012-Track-Width-Measurement&p=56981&viewfull=1#post56981

 

So it appears the 4th gen track width was not determined solely by what could fit within the fenders.

 

I can understand your frustration with there being different #'s for each platform, but that's a different topic.

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The obvious reason it was picked was it was what was believed to fit under the stock fenders! I think it's been made clear the reason for going to a hard number was to take away the ambiguity of what is 'under' the fender.

 

The SN95 track width was supposed to have been determined by what could fit within the fenders. Either somebody goofed while measuring or the car where the measurement was taken from was shall we say, in the gray, or the directors goofed typing it up etc etc. The reason was not to increase what was already allowed. In fact, in at least the case of the 4th gen, it was decreased! SN95 guys should be happy that the width they could get before is still legal!

 

According to Glenn (take it for what it's worth)...

I can tell you that the limit for 4th gens was set NARROWER than what my 4th gen could be set to under the 2011 version.

http://www.aicmctexas.com/main/showthread.php?4158-2012-Track-Width-Measurement&p=56981&viewfull=1#post56981

 

So it appears the 4th gen track width was not determined solely by what could fit within the fenders.

 

I can understand your frustration with there being different #'s for each platform, but that's a different topic.

I guess I am a little confused b/c when Al and I started talking about this rule 2 years ago at nationals it had a different tone to it. The discussion was around the discrepancy b/w the GM's and S197's track width vs. the 79-04 Mustang.

At the event we specifically measured all S197's track width and found one to be completely legal within the current inside the front fenders with a track width of 76.25".

 

I was under the impression that the new track width table would bring all platforms "near" the same width. Clearly the original direction is not where it went.

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Micheal - there never was an intent to set all platforms to the same or close to it.

This rule was changed so there would be a number attached to what was already legal. An error was made on the SN-95 cars. I do not know how it was made.

So if my 4th gen could be set to 76" and still be under the fenders and was legal that way from 2005-2011, it should still be legal in 2012. Seems eveyone has an issue w/ it once it goes from "under the fender" to under "the fender is 76".... this shit is unfair!"

 

Gary has it right.

 

The only issue here is to find the correct limit number for the SN-95's.

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I will correct one thing I said that is not correct. The 4th gens did not get reduced. Early on that was the case, but at some point the number was changed to reflect the accual width I can get legally on my 4th gen.

Sorry for the error on my part.

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Glenn, I have never thought "this shit is fair". Hence the reason I started working with Al 2 years ago to start gathering the track width data. What we discussed then was the discrepancy b/w all the platforms and the data was going to show this.

 

The excuse that 74.75" is what fits within the fender on a 4th gen is crazy. That was my point in asking if 76" is what would fit, would that be the magic number? What about 80"? A determination needs to be made to what is fair not just what have the rules been in the past.

 

My point is simply that when Al and I measured various cars at Miller in 2010 the purpose was to see what the discrepancy was b/w all platforms. The discussion was to use that information to better equalize the variance b/w all cars That is not what has happened.

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Glenn, I have never thought "this shit is fair". Hence the reason I started working with Al 2 years ago to start gathering the track width data. What we discussed then was the discrepancy b/w all the platforms and the data was going to show this.

 

The excuse that 74.75" is what fits within the fender on a 4th gen is crazy. That was my point in asking if 76" is what would fit, would that be the magic number? What about 80"? A determination needs to be made to what is fair not just what have the rules been in the past.

 

My point is simply that when Al and I measured various cars at Miller in 2010 the purpose was to see what the discrepancy was b/w all platforms. The discussion was to use that information to better equalize the variance b/w all cars That is not what has happened.

 

The cars are more fair than they have ever been. Who's to say you haven't already been racing against 4th gens at the 74.75" width all these years? Why is it an issue now that there is a number attached to it? The allowed width didn't change. I don't see the problem.

 

Its like saying you can race w/ the OEM motor. This is the rule that has been in place from 2005-2011. In 2012 we add that the OEM motor for a 4th gen is 350ci. Now folks are pissed cause they have to run against a 350ci motor. We I gont news, you have been for many years. Why is it a problem now that there is a number attached to it?

 

The only thing I can think of is you feel the cars are not as equal as they can be. If that is the case, fine. But I'm not getting that message from what your saying. All the cars have been allowed to run any track width they want as long as the tires were under the fender for many, many years. All of a sudden there is an issue w/ it. I don't get it. It is not crazy, it is what has always been allowed.

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Glenn, I have never thought "this shit is fair". Hence the reason I started working with Al 2 years ago to start gathering the track width data. What we discussed then was the discrepancy b/w all the platforms and the data was going to show this.

 

The excuse that 74.75" is what fits within the fender on a 4th gen is crazy. That was my point in asking if 76" is what would fit, would that be the magic number? What about 80"? A determination needs to be made to what is fair not just what have the rules been in the past.

 

My point is simply that when Al and I measured various cars at Miller in 2010 the purpose was to see what the discrepancy was b/w all platforms. The discussion was to use that information to better equalize the variance b/w all cars That is not what has happened.

 

The cars are more fair than they have ever been. Who's to say you haven't already been racing against 4th gens at the 74.75" width all these years? Why is it an issue now that there is a number attached to it? The allowed width didn't change. I don't see the problem.

 

Its like saying you can race w/ the OEM motor. This is the rule that has been in place from 2005-2011. In 2012 we add that the OEM motor for a 4th gen is 350ci. Now folks are pissed cause they have to run against a 350ci motor. We I gont news, you have been for many years. Why is it a problem now that there is a number attached to it?

 

The only thing I can think of is you feel the cars are not as equal as they can be. If that is the case, fine. But I'm not getting that message from what your saying. All the cars have been allowed to run any track width they want as long as the tires were under the fender for many, many years. All of a sudden there is an issue w/ it. I don't get it. It is not crazy, it is what has always been allowed.

Re-read my bolded part above. For the record, I have never thought the track width rule has been fair and I am very aware what I have been racing against for the last 6 years. This is the reason I started working with Al to make changes.

 

Mustangs have certain advantages over Camaros. Camaros have certain advantages over Mustangs. There are many other things that are exactly equal, HP, wheels, tires, brakes. Why wouldn't we want to make track width equal???

The only reason would be if everyone thinks that narrowing the GM's and S197 (down to the Fox + SN95) would instantly make the Fox and SN95 the HOT platform. Now that is funny!!

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Why wouldn't we want to make track width equal?
Because we race whole cars and not track width.

 

Seriously, is one of your assumptions that we should fix track width and THEN adjust other stuff to make the platforms as equal as possible?

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Why wouldn't we want to make track width equal?
Because we race whole cars and not track width.

 

Seriously, is one of your assumptions that we should fix track width and THEN adjust other stuff to make the platforms as equal as possible?

Track width is part of the car and it factors in to how competitive a platform is.

No, my assumption is to fix track width and there will be no need to adjust other stuff.

 

Do you think if the GM's are pulled down to the track width of the Fox and SN95 that then the Fox + SN95's would have an advantage?

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Why wouldn't we want to make track width equal?
Because we race whole cars and not track width.

 

Seriously, is one of your assumptions that we should fix track width and THEN adjust other stuff to make the platforms as equal as possible?

 

The issue here David is that none of us know exactly what more track width does......or at least how much it does. We know it helps but how much? If we could (it seems like to Michael and I) that we should make everything about these cars as equal as possible. Why not make all the track widths the same......or real close?

 

JJ

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Because a narrowed bodied car on a set trackwidth vs a wide bodied car on the same trackwidth is, well, not the same. (see edit2 at the bottom) If the argument is that the SN95's and Foxes still need more to be competitive, then yes, I could see how this could be another option. But I don't want it to be a, let's just do it so everyone's number is equal. Personally, if I were a fox/sn-95 driver, I'd rather 'even' it up more lobbying for more reduced weight.

 

Someone smarter than me ran some numbers here...

http://www.pro-touring.com/showthread.php?210-Technical-Discussion-Track-Width-(from-old-site)

I'll use Art's '55 Chevy as an example. It's not b/c I'm trying to advertise, but b/c I know the exact dimensions of this particular vehicle and its performance limit. The car's front tires broke loose at 0.935G on a 200-ft skidpad. The car has 57.5" front track width with sprung-mass CG height of 24.35" (22" overall, including unsprung mass). It weighed 3500 lbs w/ driver with 51.5% over the nose. With all stereo equipment, A/C and all other stuff, it's a pig now. Anyway, at the limit of adhesion, front weight transfer is 683.2 lb, with outside tire carrying 1575.7 lb and inside tire 209.3 lb.

 

Now let's increase the front track by 3" to 60.5" with everything else being equal. At the same lateral acceleration level, front weight transfer decreases to 649.3 lb (1541.8 lb outside, 243.2 lb inside). Since I know that the tires we used can maintain lateral acceleration until front weight transfer reaches 683.2 lb on this particular vehicle, new lateral acceleration limit can be reverse calculated, assuming the rear tires will be able to hold up. Limit increases to 0.989G. It's a significant increase.

What that translates into real life, I don't know.

 

*edit* With that example, to me anyways, it would seem that the goal for parity would be to equalize the lateral G. Just having the same trackwidth for all platforms is not going to do this, just look at all the other factors involved */edit*

 

*edit2* What helps me to understand is to take it to the extreme with something like a Ford Ranger, stock trackwidth 58.5". Give it the same trackwidth as an F150, 67". Assume you make all else (weight, CG etc) is the same. Which would be more stable, Ranger or F-150? */edit2*

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Why wouldn't we want to make track width equal?
Seriously...

 

If we could (it seems like to Michael and I) that we should make everything about these cars as equal as possible. Why not make all the track widths the same......or real close?

Sorry if that came off harsh, certainly not the intent; I agree with you guys that the end result is more important than the individual parts.

 

I just disagree that it makes sense to simply equalize the track widths at this point in the game. I just want good close racing top to bottom ~ let talent and not platform decide the winner.

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Because a narrowed bodied car on a set trackwidth vs a wide bodied car on the same trackwidth is, well, not the same. (see edit2 at the bottom) If the argument is that the SN95's and Foxes still need more to be competitive, then yes, I could see how this could be another option. But I don't want it to be a, let's just do it so everyone's number is equal. Personally, if I were a fox/sn-95 driver, I'd rather 'even' it up more lobbying for more reduced weight.

 

Someone smarter than me ran some numbers here...

http://www.pro-touring.com/showthread.php?210-Technical-Discussion-Track-Width-(from-old-site)

I'll use Art's '55 Chevy as an example. It's not b/c I'm trying to advertise, but b/c I know the exact dimensions of this particular vehicle and its performance limit. The car's front tires broke loose at 0.935G on a 200-ft skidpad. The car has 57.5" front track width with sprung-mass CG height of 24.35" (22" overall, including unsprung mass). It weighed 3500 lbs w/ driver with 51.5% over the nose. With all stereo equipment, A/C and all other stuff, it's a pig now. Anyway, at the limit of adhesion, front weight transfer is 683.2 lb, with outside tire carrying 1575.7 lb and inside tire 209.3 lb.

 

Now let's increase the front track by 3" to 60.5" with everything else being equal. At the same lateral acceleration level, front weight transfer decreases to 649.3 lb (1541.8 lb outside, 243.2 lb inside). Since I know that the tires we used can maintain lateral acceleration until front weight transfer reaches 683.2 lb on this particular vehicle, new lateral acceleration limit can be reverse calculated, assuming the rear tires will be able to hold up. Limit increases to 0.989G. It's a significant increase.

What that translates into real life, I don't know.

 

*edit* With that example, to me anyways, it would seem that the goal for parity would be to equalize the lateral G. Just having the same trackwidth for all platforms is not going to do this, just look at all the other factors involved */edit*

 

*edit2* What helps me to understand is to take it to the extreme with something like a Ford Ranger, stock trackwidth 58.5". Give it the same trackwidth as an F150, 67". Assume you make all else (weight, CG etc) is the same. Which would be more stable, Ranger or F-150? */edit2*

 

 

I agree Gary. I'm not unhappy at all with the status quo but I do wonder how much advantage the wider car has.........IF ANY AT ALL?

 

JJ

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MM - so you want me to have a Fox track and be 100lbs heavier?

 

My point is the class is very equal. If you force all cars to the same track numbers (that would likely require custom wheels for me to get that narrow), that balance is upset.

Next you will want the same drag numbers for all cars, then wheel base, then center of gravity, then front/rear weight percents. This is not SPEC Fox, or SPEC SN-95, or SPEC GM. It is CMC racing w/ each platform have strong and weak areas.

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Why wouldn't we want to make track width equal?
Seriously...

 

If we could (it seems like to Michael and I) that we should make everything about these cars as equal as possible. Why not make all the track widths the same......or real close?

Sorry if that came off harsh, certainly not the intent; I agree with you guys that the end result is more important than the individual parts.

 

I just disagree that it makes sense to simply equalize the track widths at this point in the game. I just want good close racing top to bottom ~ let talent and not platform decide the winner.

 

 

Because you drive on a much higher plane..... And burst into flames.

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MM - so you want me to have a Fox track and be 100lbs heavier?

 

Yes, I do.

 

My point is the class is very equal. If you force all cars to the same track numbers (that would likely require custom wheels for me to get that narrow), that balance is upset.

I doubt it. My stock 95 T/A with 16x8" wheels had a track width of 72". I'm guessing 17x9 wheels would give about 73" track width. Y'all have all the track width data from the other 4th gens, were there others in the 73" range?

 

Next you will want the same drag numbers for all cars, then wheel base, then center of gravity, then front/rear weight percents.

That is nice of you to point out more of your advantages.

For the record, I have never asked for changes to any of these items you mentioned. All these things are extremely hard to change from platform to platform, wheel spacers are not.

 

This is not SPEC Fox, or SPEC SN-95, or SPEC GM. It is CMC racing w/ each platform have strong and weak areas.

AGREED

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Yeah, I dont know how we goofed that early SN-95 measurement that bad. My fault though. As it was my fault I spent some time with John Lingle over the weekend taking measurements on his car. I'm comfy with the SN-95s being able to get 73.25 in the front and that being a realistic max based on last year's methodology. The rear needs a little more discussion with the directors as it would appear the OEM quarters on these are narrower than the Fox!

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The rear needs a little more discussion with the directors as it would appear the OEM quarters on these are narrower than the Fox!

What rear track width did you measure on the SN95?

I don't know how it could be narrower than the Fox as Jeremiah ran 1" spacers (on each side) on the back of his SN95 and I am only able to run 1/4" spacers (on each side). We both have the same axle width and running the exact same wheels / tires.

I'm confused.

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The rear needs a little more discussion with the directors as it would appear the OEM quarters on these are narrower than the Fox!

 

I call B.S. Measure the actual track width and not the space available inside the fenders between the outside edge of the tire and the fender. The stock SN95 rear axle is wider than the fox axle and there is more space to play with in the SN95 than the fox. I have both sitting in my shop right now. Let me know if you need actual measurements and I can get you some tomorrow.

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