2005 rules-IRS

[JWL]

Folks-

 

One of the thornier issues facing us is how to handle the IRS suspensions now that competitors are building these cars. There are many approaches to this issue. We can allow nearly unlimited mods to pickup points and other items like we do with the stick axle cars or limit things to absolute factory stock. We can also allow limited mods in AI and open things up for AIX. Your thoughts?

 

-JWL

[swhiteh3]

This is a tough one John.

 

Many series use the "pickup points may be moved up to 1" from stock", but that's really hard to enforce, and I believe that some Crossmembers (KB?) already would break that rule. So that's not a good solution.

 

Maybe the solution is to only allow unmodified approved aftermarket solutions (i.e. KB approves a design, etc.) and require the manufacturer to sell, say, at least 100 units to certify this. This, of course, restricts the competitors freedom and creativity, but it also keeps it from getting to crazy.

 

Making it completely free, even in AIX, is a recipe for trouble. Freedom of rules is great when it prevents us from pushing away competitors, but I don't know of any cars that are currently illegal based on these rules, so I don't think it's a problem in this case. Rear transaxles with formula car style control arms and uprights are right around the corner if the rules are opened up. And lap records WILL fall quickly.

[Guest]

Why would we allow solid axle cars the ability to move the pick up points to where ever they want, i.e. 3 link inside the car, a panhard bar that is fabricated at home, WC control arms that are 38" long, a 50" torque arm ect and restrict the movement of the pickup points of the IRS? Is that fairplay?

 

The nice thing abou the KB stuff is that it is a purchased peice that anyone can install in any msutang from 79 up. This is not super trick custom work, it's a bought item like the Griggs and MM torque arm and panhard bar. If you want the IRS cars to compete with a well prepared MM or Griggs cars you have to allow the KB stuff.

 

Everyone still has to meet the wheel/tires/brake, HP:weight, TRQ:weight rules (in AI only). The IRS is just another way to skin the cat like a 3 link or TA/PB.

[swhiteh3]

The simple reason I see for this Brian has do with our name. This is a series for Muscle cars, and although modern muscle cars are just starting to getting IRSs, in the past they have never had that, and I think we should keep the original intent of what a "muscle car" is.

 

Also, a properly designed IRS will always defeat a properly designed live axle. Yes, an IRS takes a lot more work to get right - and I mean REALLY right, but it would be a balance breaker for the series.

 

This is my $0.02.

[mwilson7]

I believe the first question you have to answer when discussing IRS is what are you trying to accomplish when limiting IRS? Are you trying to stop a one off Trans-Am IRS from being built? Are you trying to stop the body from being modified when installing said IRS or are you trying to just give people an option to run IRS if they want to?

 

Do you specifically state you can use a modified factory IRS carrier or not? If not then how come? We already have unlimited mounting points on the solid axle cars AND we can run solid axle suspension components through the floor. Why limit them on an IRS?

 

I don't pretend to have all the answers on how to integrate IRS but it seems that a sensible approach has to be taken if AI truly wants IRS cars to participate.

[mwilson7]

The simple reason I see for this Brian has do with our name. This is a series for Muscle cars, and although modern muscle cars are just starting to getting IRSs, in the past they have never had that, and I think we should keep the original intent of what a "muscle car" is.

 

Should we not allow 4 or 6 cylinders to play as "Muscle Car's" only have V-8's? Just wondering where you decide to draw the line on that line of thinking?

[swhiteh3]

Good point Mark. I don't really have a reply to that.

 

Are you willing to race against a Corvette Z06 then? How about a C-5R?

 

I don't know where or necessarily HOW to draw the line. I just think it needs to drawn somewhere. And letting people design their own blank-sheet-of-paper IRS is a dangerous step IMHO.

[onralz]

Unlimited modifications of IRS will over time add to the expense of AI. We are not a pro series, we are an amatuer one. If non factory IRS's are developed (and they will) than the speed of AI cars will also continue to increase. This will increase the costs in order to stay competitive. Changing pickup points on a stick axle is limited as you are limited with what you can do with a stick axle. If unlimited IRS's and the ability to cut frame rails becomes an option, I am concerned that the "average" open tracker, autocrosser, HPDE participant, who wants to be competitive in AI won't feel that they can afford to be competitive and not race with us. We have already lost quite a few good competitors because of the cost factor, whey increase it?

[mwilson7]

I don't think anyone wants unlimited IRS's to be legal but speaking generically about the IRS what should we limit? Do we approve packages or do we limit each part as shown below?

 

1. Arms - Should they be allowed to be modified? If so how?

2. Spindles - Should the factory piece be the only piece that can be used? Can it be modified?

3. Springs - Should we allow non coil over IRS's be converted to coil overs?

4. IRS Carrier - I don't even know if all IRS's require a carrier. If so should they be allowed to be modified and how much?

5. Bushings - What is allowed?

6. Center section - What can be done? Most IRS's that I know of require some type of cooler. Mounting? Can the factory mounting be modified to allow it to be solid mounted (getting rid of bushings?)

7. Sway bar and mounts - stock or modified?

 

Speaking from a cost standpoint I don't think it cost us anymore to buy and install our KB IRS vs a Griggs or MM panhard and TA suspension.

 

If you consider the difficulty involved in removing the torque boxes to install the Griggs WC arms I think the bar has already been set pretty high when determining what can be done to install a suspension piece.

 

Scott - Corvette's aren't allowed in AI so I don't have to race against them.

[tacovini]

I think IRS suspensions are coming. As we all know, factory installed IRS comes in Mustangs and GTOs now, so the series needs to grow at a "measured" pace with the new car industry. Without the new cars, the series will "die on the vine". Also, part of AI's attraction is the ability to update and backdate factory parts into and out of newer and older cars.

 

Now...with that said, I think the AI rules and intent are clear on modifying the frame to accomodate the IRS. What isn't clear are what other mods would be allowed along with a factory IRS....such as the KB unit.

 

Keeping with the "measured pace" of new technology, I'd look to allow factory IRS in AI....and modified IRS in AIX. Keeps it simple.

 

-=- Todd (The Racer...not the Director)

[mwilson7]

Todd,

 

Why in the world would you allow someone to completely modify the front suspension on their car and then require them to leave the rear factory (stock I'm assuming you mean)? That honestly makes no sense at all. Please provide the rational behind your thoughts because if you leave it stock then no one in their right mind would run IRS because the factory IRS SUCKS! No personal attacks intended but if these comments are going to be used to shape the rules then we need to understand the thoughts behind why people feel the way they do.

 

The KB parts are available over the counter and require no additional skills to install than a regular old torque arm and panhard bar. Cost is about the same as the torque arm and panhard bar suspension as well.

 

If the intent of AI is to showcase aftermarket parts then factory IRS's should be allowed to be modified to the same extent as the stock solid axles are. If not then you may as well not even allow them.

[Admiral]

Hasn't the KB IRS been ruled legal already? (If I'm missing something subtle here someone please clue me in!). If it has, then is the discussion mainly about "how much modification to the stock IRS is legal"? Shouldn't be a problem, someone simply has to investigate and draw a line on the subject. The stock stick axle sucks also, so we get new differentials/axles, a TA/PHB etc etc so why can't the IRS be modified to a certain extent?

 

If the KB IRS has been ruled legal on a regional basis only, then it sounds like a job for JWL and the National crew to decide if this decision is going to stand and make it official. I'm not familiar with the KB particulars, but I agree with Todd (scaring myself here) that IRS is here and should be allowed. I doubt that I'll be ripping out my TA/PHB anytime soon but at least the newer platforms that come equipped with IRS can jump into AI without having to go replace the rear end.

[onralz]

Factory should be clarified in the rule book as stock or OEM.

The argument about having to modify the factory IRS is that they suck? They can be made fast without modification and without the necessity to notch the frame. Jeremy Behrendt in this AI/X car ran just over a minute flat at Beaverun last year. He ran flat in the kink, never complaining about his suspension, but wanting more power. His modification to the IRS was delrin bushings and that is it.

 

If new cars are coming out with the IRS that's great. Allow them as is. The rational for modifying pickupoints for a stick axle is to try to level the playing field. An IRS is a superior suspension piece period. Too much modification will start digging into pockets, and frame rails.

 

A well built IRS will leave the GM crowd in the dark ages as there isn't and won't be anything available to them. That also needs to be considered. I think AI should be about leveling the playing field, and letting the driver do the work.

[mwilson7]

Not to be confrontational but CMC is where you level the playing field and let the drivers do the work. AI is intended to showcase aftermarket parts.

 

Jeremy also runs with quite a bit of HP so I don't honestly think the comparison is fair.

 

One thing that people are forgetting here is that a WELL DESIGNED IRS might be a superior suspension piece but not all IRS's are created equal. One could also say that all solid axles suspensions suck but we all know the difference between a stock solid axle and a TA/PB solid axle or three link or whatever.

 

Can someone explain EXACTLY what the issue is about notching the frame rails to make the KB arms work? I see lots of comments about "Don't touch the frame rails" but yet we are allowed to cut up the floor for a custom built 3 link and completely remove the torque boxes to fit longer control arms in. Considering that our car is no lower than any properly set up Griggs car (maybe MM to but I'm not sure) and has NO additional suspension travel that a stick axle I honestly don't know what the problem is. Why is this such a hot button?

[onralz]

Jeremy also runs with quite a bit of HP so I don't honestly think the comparison is fair.

 

Sure it is, you used in in a previous post in regards to the IRS. If a car with 8-1 hp to weight ratio can make it work, so can a lower powered AI car.

 

Disclaimer: the comments about Jeremy's car are based on when it won races last year using a supercharged mod motor, not his crazy Transam motor stroker that he uses now. Amazingly enough the IRS still works in this scenario as well.

[mwilson7]

Fair enough. But please explain EXACTLY what the problem with a modified factory IRS is as that's really one of the main issues at hand.

[onralz]

Unlimited modifications of IRS will over time add to the expense of AI. We are not a pro series, we are an amatuer one. If non factory IRS's are developed (and they will) than the speed of AI cars will also continue to increase. This will increase the costs in order to stay competitive. Changing pickup points on a stick axle is limited as you are limited with what you can do with a stick axle. If unlimited IRS's and the ability to cut frame rails becomes an option, I am concerned that the "average" open tracker, autocrosser, HPDE participant, who wants to be competitive in AI won't feel that they can afford to be competitive and not race with us. We have already lost quite a few good competitors because of the cost factor, whey increase it?

 

That's why.

 

"Modifying" of the factory IRS is going to be hard for the technical directors to police. They have enough to do without running around with rulers. If there aren't any restrictions, than there becomes unlimited modifications which opens the doors as I previously stated.

[mwilson7]

So we allow ALMOST ANYTHING to be done to stick axles but leave IRS's stock? As I have stated before, the cost of the KB system is no higher than a full Grigg's or MM suspension.

 

Now if we are talking CLEAN SHEET built from the ground up IRS's then perhaps the costs could get out of hand.

 

I might actually have at least a partial solution. How about spelling out that aftermarket upper and lower arms would be allowed as long as they would work on a factory stock IRS (this would make the mounting points pretty close to the factory points). Also require the factory rear spindles with unmodified suspension pick-up points (there may be some modifications required to fit larger brakes so I'd suggest limiting it to suspension points). And require the use of the factory IRS k-member but allow the pick-up points to be changed. Coil overs are allowed but must use the same mounting locations as the factory shocks. Sway bars are unlimited. That isn't perfect but doesn't that severely limit what you can do? Feel free to poke holes in that paragraph.

 

Lastly most importantly lets get a minimum ride height because that would eliminate any perceived suspension travel advantage that IRS has over solid axle.

[onralz]

How about,

 

OEM IRS pickup points cannot be modified. An OEM cradle must be used. OEM Carriers cannot be modified. Differential and gearing are open using non-ferrous materials. Pickup points have to remain on the cradle and may not be mounted to the frame rails, or floor pan of the vehicle.

 

This would allow after market arms, spindles, bushings, sway bars, and shafts. This would allow after market companies to be heavily involved. Keeping the frame rails would eliminate the ability to modify too far keeping the playing field open for other cars. A well built IRS will out handle a well built stick axle. This keeps a persons options short.

[Guest]

How about,

 

OEM IRS pickup points cannot be modified. An OEM cradle must be used. OEM Carriers cannot be modified. Differential and gearing are open using non-ferrous materials. Pickup points have to remain on the cradle and may not be mounted to the frame rails, or floor pan of the vehicle.

 

This would allow after market arms, spindles, bushings, sway bars, and shafts. This would allow after market companies to be heavily involved. Keeping the frame rails would eliminate the ability to modify too far keeping the playing field open for other cars. A well built IRS will out handle a well built stick axle. This keeps a persons options short.

 

This is stupid. We allow UNLIMITED PICKUP POINTS on a solid axle car. There is at least one company out there KB making a modified IRS unit that can be purchased. If you think that a stock IRS will compete with a well sorted out PB/TA car you are crazy and ignorant.

 

Why are you people so afraid of the IRS? give me reasons and data, not just a witch hunt. If you want the guys who want to run the IRS a chance to compete they have to be modified. If you want to force the guys with the KB stuff already on their cars to simply not run in AI keep up this train of thought. If you are mandating or suggesting keeping the OEM points why are TA/PB allowed on AI cars. this is a direct question I would love to see your reasoning for this.

[swhiteh3]

I don't think anyone (at least not me) believes that the KB stuff should be illegal. I think it should be in AI, just like MM and Griggs stuff.

 

I'm sorry this rules discussion is not doing anything for you, since this is the second thread you've now proclaimed "stupid".

[Guest]

I don't think anyone (at least not me) believes that the KB stuff should be illegal. I think it should be in AI, just like MM and Griggs stuff.

 

For this to be true, and to run the full KB arms/irs the rail must be clearanced. There is no way around this.

 

The benefit of the arms is weight. They tubular arms are lighter than the cast steel peice that the factor uses.

[mwilson7]

How about,

 

OEM IRS pickup points cannot be modified. An OEM cradle must be used. OEM Carriers cannot be modified. Differential and gearing are open using non-ferrous materials. Pickup points have to remain on the cradle and may not be mounted to the frame rails, or floor pan of the vehicle.

 

This would allow after market arms, spindles, bushings, sway bars, and shafts. This would allow after market companies to be heavily involved. Keeping the frame rails would eliminate the ability to modify too far keeping the playing field open for other cars. A well built IRS will out handle a well built stick axle. This keeps a persons options short.

 

Mark - Which points are talking about when you say OEM IRS pick-up points? Where the cradle mounts to the body or where the control arms mount to the IRS cradle? What is the problem with moving the mounting points on the cradle? Is the cradle and the carrier the same? If the carrier is the center section you have to allow modifications for cooling lines. Can you show me how you would make an upper arm (affordable to most racers) that would replace the upper arm on a Mustang and not hit the frame rail?

 

Did you say that you have an IRS at your house out of the car? If so please email me offline as I want to show you something on it.

 

P.S. Changing pick-up points on a cradle is just as limited as it is on a solid axle if they are required to maintain the stock distance between the arms mounting points.

[onralz]

All points. When changing the mounting points, you can essentially change the geometry. The upper and lower pickup points are obvious. I haven't thought much on the carrier points but this is critical as well.

 

P.S. Changing pick-up points on a cradle is just as limited as it is on a solid axle if they are required to maintain the stock distance between the arms mounting points.

 

Not necessarily. Small modifications on an IRS is the difference between a well setup one, and one that is inferior to even a stick axle.

 

I have very good pictures of the KB setup here at home. One of my previous sponsors from Mac Midwest went to work for KB and he one of the guys who explained it to me along with KB himself at Mid-Ohio. Feel free to explain what you would like me to look at as I have all the data here.

 

 

Why are you people so afraid of the IRS? give me reasons and data, not just a witch hunt. If you want the guys who want to run the IRS a chance to compete they have to be modified. If you want to force the guys with the KB stuff already on their cars to simply not run in AI keep up this train of thought. If you are mandating or suggesting keeping the OEM points why are TA/PB allowed on AI cars. this is a direct question I would love to see your reasoning for this.

 

I'm surprised that there is even a question as to the ability of an IRS to be far better than a stick axle especially from a dynamic engineer from Ford. There is only one car with KB on it and that is yours, so that seems irrelevant. I have gone over and over the fact that a well setup stick axle won't keep up with a well setup IRS. The simple fact that an IRS can control it's toe, and camber should be enough tech for anyone. The detriment to the stock one was you have to run very stiff springs to keep the camber and toe from changing too much which leveled the playing field with the stick axles, but by allowing more modernized and modified IRS assemblies, you are eliminating the competition in the long run. Particularly ones that "require" notching of the frames. Especially as there aren't any that you can "purchase" for GM and older cars. Here's some tech from Kenny Brown, your sponsor. He stated to me at VIR last year that Mark Wilson and Brian Tone would have a car out there next year that would take AI to a new level and anyone without an IRS wouldn't be able to compete in the top 5. That isn't a direct quote as that was some time ago and I can't remember exactly what he said, but it's pretty close. If there wasn't an advantage to the KB setup over a stick axle, you as an chassis engineer wouldn't be running it. If you ran the stock upper control arms, you wouldn't need to notch the frame rails. You chose not to and run the KB upper arms. If there wasn't an advantage to this modified IRS, you wouldn't be running any of the above items.

Where do you draw the line on the IRS modifications. See my above posts for my opinion.

[mwilson7]

All points. When changing the mounting points, you can essentially change the geometry. The upper and lower pickup points are obvious. I haven't thought much on the carrier points but this is critical as well.

 

Not necessarily. Small modifications on an IRS is the difference between a well setup one, and one that is inferior to even a stick axle.

 

So we are suggesting changing the geometry on a solid axle any way you want but you recommend not changing the geometry on an IRS car.

 

I have very good pictures of the KB setup here at home. One of my previous sponsors from Mac Midwest went to work for KB and he one of the guys who explained it to me along with KB himself at Mid-Ohio. Feel free to explain what you would like me to look at as I have all the data here.

 

I actually just wanted to take you through an exercise which is difficult to do unless the parts are in front of you. I'll save it for another day as it is really to difficult to explain over the internet (and I'll probably mess it up anyway)

 

 

I'm surprised that there is even a question as to the ability of an IRS to be far better than a stick axle especially from a dynamic engineer from Ford. There is only one car with KB on it and that is yours, so that seems irrelevant. I have gone over and over the fact that a well setup stick axle won't keep up with a well setup IRS.

 

In theory perhaps but this has yet to be proven.

 

The simple fact that an IRS can control it's toe, and camber should be enough tech for anyone. The detriment to the stock one was you have to run very stiff springs to keep the camber and toe from changing too much which leveled the playing field with the stick axles, but by allowing more modernized and modified IRS assemblies, you are eliminating the competition in the long run.

 

But yet we can add camber and toe to a solid axle

 

 

Particularly ones that "require" notching of the frames.

 

Please tell me EXACTLY what performance advantage notching the frame gives me. You state that we can change the arms back to the stock arms and run the KB IRS just the same. This is true. Both the KB and the stock arm have the same mounting locations on both the IRS and the spindle. How does notching the frame because of the shape of the arm change ANYTHING in the IRS? It still has to follow the same arc and the travel is still limited by the lower control arm and spindle. WHAT IS THE ADVANTAGE besides losing some weight by going from a cast arm to a tubular arm. Myself and my super smart (ok...that's stretching it) Chassis Engineer can't figure it out so someone please shed some light on this.

 

Especially as there aren't any that you can "purchase" for GM and older cars.

 

I've tried to fight this battle with ABS and older cars and no one seems to listen so why is it a big deal on this subject?

 

 

Here's some tech from Kenny Brown, your sponsor. He stated to me at VIR last year that Mark Wilson and Brian Tone would have a car out there next year that would take AI to a new level and anyone without an IRS wouldn't be able to compete in the top 5. That isn't a direct quote as that was some time ago and I can't remember exactly what he said, but it's pretty close.

 

He better have said something like that! How else is he going to sell parts?The funny thing about that is that if I call Bruce from Griggs, Jack from MM, Dario from Steeda they will also tell me that there suspensions are also the best and everything else sucks. I think we all understand the marketing behind these statements and take them as a grain of salt. Based on the results from MO and BR I would say that others are still able to compete. THAT is a fact!

 

If there wasn't an advantage to the KB setup over a stick axle, you as an chassis engineer wouldn't be running it.

 

I remember someone last year telling me that we were taking the safe route and didn't understand what it was like to explore new territory and do something no one else had done. If you read my post that John posted over at cc.com you'll see that one of the big reasons we did this is that it IS different. We took a leap of faith and appear to be still falling

 

If you ran the stock upper control arms, you wouldn't need to notch the frame rails. You chose not to and run the KB upper arms.

 

See my comments above.

 

If there wasn't an advantage to this modified IRS, you wouldn't be running any of the above items.

 

I hate to say this but you are giving us WAY to much credit here. Just to set the record straight Brian is the smart Chassis and Dynamics Engineer. I'm just a drone who helps Engineers see the light when it comes to serviceability and repairability. As much as I wish our jobs gave us an advantage we are all limited by the same laws - Physics. We can all learn about physics and we can all make decisions base on what we learn. We do not get to use ANYTHING from Ford to help us set up our cars (well at least the AI/X guys don't) but I guess we can always hope!

 

I also don't want to see anyone come up with a custom one off set-up that kills everyone but listen to this. The FACT is that we have run our car at two events now and have by NO MEANS walked away from the field. Robin ran 2 seconds a lap faster than us at Beaverun (a 1 minute track!) in a car with a stock front K-member, stock lower control arms (different bushings) and no coil overs. Does that mean that we should outlaw aftermarket front K-members, control arms and coil overs as the stock pieces seem to do just fine (That's a Jeremy joke thrown in where appropriate)? No! It just goes to show you that there is more than one way to skin the cat (no disrespect to cat lovers). The FACT is that in the OH/IN Region we have Griggs, MM, Steeda and now KB all running up front and there is a new winner each week which is what the series intended. How is this a bad thing?

 

The FACTS show that the IRS isn't the end all suspension that is appears to be on paper.

 

Will there one day be a superior suspension that everyone has to use or be a has been? Perhaps....... Perhaps we should talk about reward weights to even things out then and keep the racing close.