ITR Mustang

[Jethro]

Thanks Guys

I've been talking with Chris and he's a wealth of info.
Looks like I'll have to run 15" tires, yuk!
stock size is 205/65x15, and looks to me like the only popular racing size is gonna be 225/50x15, this make sence to anyone?
Any tips on strut manufacturer choice, even from the 79-94 guys?

[cjb25hs]

Thanks Guys

Looks like I'll have to run 15" tires, yuk!
stock size is 205/65x15, and looks to me like the only popular racing size is gonna be 225/50x15, this make sence to anyone?

You can go to a 245/50/15 in the Hoosier. I would also suggest you talk with Sam Strano from Stranoparts. He is a wealth of knowledge when it comes to Fox Body Mustang setups.

[billf]

ITR allows the cars to weigh a few pound more, so additional suspension parts may be more desireable, and less injurious to performance. For ITS, I'd think even more critically about added weight.

Personally, I'm a fan of smaller wheel diameters with generous width, to reduce the rotational mass of the wheel assembly. Aftermarket/racing lists have 15's avaiable in various offsets. What you will have to pay for is lightness, not the size. Additionally, the handling can be enhanced by the placement of the lower A arm (smaller diameter wheel assemblies put the ball joint closer to the ground), giving you the opportunity to have an up-ward angled lower arm. This will give you enhanced camber change during bounce.

Differential gear set ratios available (stock and aftermarket) for the 7 1/2 inch, are 3.08, 3.27, 3.4, 3.73, and 4.1. I prefer the lower gears with the second, third, and fourth transmission gears being used.

What you want to concentrate on is how to enhance the handling without adding to the weight of the car. Aftermarket parts all weigh pounds and ounces...from which the car/engine combination cannot benefit. Hollow sway bars are available, too.

Start your project with a through reading of the Mathias book on Mustangs ("chassis", actually number two). It will give you a grounding in the four link design, and its consequences. Solutions are proposed which work, but all add weight. There is one concept that is not in that book that will lessen/eliminate the problem. That is to replace the source of the problem (the rubber bushings), with spherical bushings. This is the major solution in the rear of the car. Peruse the AS sites also...they have delt with the problem for years, although their solutions are added mechanicals (weight).

Good luck.

Bill

[RedMisted]

Bill:

I really don't know about using 15" wheels on such a heavy car shod with horrible brakes. I use the airier 17" rims with all the brake tubing I can cram into the wheels. Our rotor sizes are 11"--pitiful by ITR standards. At tracks like Watkins Glens or Nelson, brakes are not a major issue so I guess you could run the smaller wheels. But at a Gingerman or a Beaverun, that brake pedal is gonna be down on the floor before you know it. I'd rather have the weight of the larger wheels knowing that my brakes are getting all the cooling possible.

Another reason to optimize brake cooling: The ITR Mustang is equipped with PBR aluminum front calipers, unlike the earlier SN-95 cars that came with cast iron bits. This is great for weight, but these calipers deform like crazy in the heat, even at the easy tracks. It's normal for me to replace the front calipers (at about $65 a pop)about every other event. If I don't, I'll be wasting box after box of $200 brake pads. So running the larger wheels helps me to minimize an economic issue.

Just my $.02

[billf]

Chris,

I'm interested in the brake problems you experienced with the aluminum calipers. Did you see caliper deformation? Brake pads welded to the pistons? Was there evidence of boiled fluid (pedal to the floor, etc)? Did the seals turn to carbon? (I'm trying to think of all the brake-related problems we had with the 2.3 Liter ITB car.)

Thanks for the input about the brakes. Your answers will make me reconsider the choices I have.

Jethro is, of course, planning on ITS, which has mandated smaller wheel sizes, and lower weight. Also, supposedly, the engine has somewhat lower power potential in typical IT tune. All of which, may lower his threshhold of brake problems.

Thanks,

Bill

[RedMisted]

Bill:

What happens with the PBR calipers is that they splay out, so that the brake pads begin to wear cock-eyed. This problem is very commonplace in the left front, and occasionally an issue on the other side unless racing at tracks with an abundance of left turns.

It's also common for the piston sleeves to burn up. No, I've never had fluid boil to the point where I was literally hitting the floor. (Sorry if I exaggerated a bit.) But I've had to throw heel-and-toe downshifting out the window a few times because the pivot point would change enough to compromise throttle-blipping.

The solution? Get as much air as you can to the rotors. Cut off the dust shields, mount the bigger wheels and run tubes no smaller than 3" in diameter. Use super hi-temp fluids and remember to bleed the fronts halfway through an event if racing at a brake-killer like Beaverun.

Pads can make a difference with cooling. Unfortunately, I only have experience with Hawk Blues. I'm told that other companies, such as Carbotech (which I will be trying in '10), may have superior offerings.

Brakes are the big operational weakness with these cars. I learned alot this past year about the need to baby my brakes, and to plan my race strategies accordingly.

And although the bigger wheels hurt weight, you can mount wider rubber. A tradeoff, just like anything in racing.

Hope this helps.

Chris,

I'm interested in the brake problems you experienced with the aluminum calipers. Did you see caliper deformation? Brake pads welded to the pistons? Was there evidence of boiled fluid (pedal to the floor, etc)? Did the seals turn to carbon? (I'm trying to think of all the brake-related problems we had with the 2.3 Liter ITB car.)

Thanks for the input about the brakes. Your answers will make me reconsider the choices I have.

Jethro is, of course, planning on ITS, which has mandated smaller wheel sizes, and lower weight. Also, supposedly, the engine has somewhat lower power potential in typical IT tune. All of which, may lower his threshhold of brake problems.

Thanks,

Bill

[Ron Earp]

What happens with the PBR calipers is that they splay out, so that the brake pads begin to wear cock-eyed. This problem is very commonplace in the left front, and occasionally an issue on the other side unless racing at tracks with an abundance of left turns.

It's also common for the piston sleeves to burn up. No, I've never had fluid boil to the point where I was literally hitting the floor. (Sorry if I exaggerated a bit.) But I've had to throw heel-and-toe downshifting out the window a few times because the pivot point would change enough to compromise throttle-blipping.

Very interesting discussion.

I'm not sure I'm following everything though. You mentioned that you have heat problems and that the heat is deforming the calipers, but, then you say that you're not boiling the fluid. I'm assuming what you're experiencing is some fatigue and thermally induced stress relief, but, you'd need to get some pretty serious heat into it to do that. And that would boil your fluid.

What you've described with your pedal feel is pretty much SOP for Z cars and many other ITS cars. And, it can typically be fixed with a serious analysis of brake ducting and cooling. You might have to switch to a new piston seal of that is having problems but the dust shield on the outside, well, those are going to get hard crumbly and fall away.

What sort of rotor and caliper cooling do you have now? I assume you're using a air hat on the rotor that feeds air to both sides of the rotor and you've got a similar device mounted on the caliper itself. Since these are slotted rotors you might want to feed air into the center hub and skip the rotor hat.

Anyhow, you should be able to make these brakes work and not experience heat problems. I've collected a lot of brake cooling setups over the years. Once I pick this Mustang up I'll have a look at the front area and might be able to offer some suggestions.

[Z3_GoCar]

Another reason to optimize brake cooling: The ITR Mustang is equipped with PBR aluminum front calipers, unlike the earlier SN-95 cars that came with cast iron bits. This is great for weight, but these calipers deform like crazy in the heat, even at the easy tracks. It's normal for me to replace the front calipers (at about $65 a pop)about every other event. If I don't, I'll be wasting box after box of $200 brake pads. So running the larger wheels helps me to minimize an economic issue.

Just my $.02

You should go to a welding supply shop and pick up a temperature crayon. Aluminum looses much of it's strength when heated up to 195*F - 250*F. It's no suprise that you're getting creap if you're getting close to this temperature.

...Also, you could add a water spray system to keep your calipers cooler too... It'd be a good use for the windshiled washer bottle and pump.

[RedMisted]

...Also, you could add a water spray system to keep your calipers cooler too... It'd be a good use for the windshiled washer bottle and pump.

I have heard of water cooling systems on pro cars, but is such a thing legal in IT? I have never heard of water-cooled brakes on an IT car.
If I know the GCR, if it does not mention something, you can't have it. And I don't recall the IT chapter allowing for water-cooling of much of anything except the engine.

[Ron Earp]

Aluminum looses much of it's strength when heated up to 195*F - 250*F. .

Somehow I don't think that is the case. Pure aluminum melts at over 1200F, most alloys slightly less. Given the fact most modern engines have blocks and heads made out of aluminum and operate at 180F to 250F as standard fare, it doesn't reason that the aluminum would give up much of its strength at that temp. Hell, I suspect the the brakes on the street cars are hitting 180-190F in stop and go traffic. They don't fail there.I can check with a fellow I know who has extensive casting experience with aluminum if interested.

You'll definitely want to use temperature crayons or paint to check temps, or, a pyrometer. Back in the dark days of TR8 brake work we were getting some obscene 475-500F temperatures, bona fide verified with temp probes, on the calipers. Bad things happened to lines,seals, and even tires/wheels when that was going on.

[Jethro]

245/50x15 wow that seems really wide, do you know if the fenders will need to be rolled to clear that. What width rim would be required? 8"?

Thanks for the advice guys.

[Z3_GoCar]

Somehow I don't think that is the case. Pure aluminum melts at over 1200F, most alloys slightly less. Given the fact most modern engines have blocks and heads made out of aluminum and operate at 180F to 250F as standard fare, it doesn't reason that the aluminum would give up much of its strength at that temp. Hell, I suspect the the brakes on the street cars are hitting 180-190F in stop and go traffic. They don't fail there.I can check with a fellow I know who has extensive casting experience with aluminum if interested.

You'll definitely want to use temperature crayons or paint to check temps, or, a pyrometer. Back in the dark days of TR8 brake work we were getting some obscene 475-500F temperatures, bona fide verified with temp probes, on the calipers. Bad things happened to lines,seals, and even tires/wheels when that was going on.

Ron, this is based on something I read about aircraft structures, it's the difference between a Mach 1.5 plane like the Concorde and a Mach 2.0 or more plane. In a motor block they can over design the casting thickness to compensate for the loss of strength. A caliper on the other hand usually doesn't have that much extra space for more material.