weight issues?

Rampant said:

To be more precise, they were talking that having a very slight front weight bias will help in corner exit. As the weight shifts back upon acceleration (as it will ALWAYS do), the weight distribution is supposed to be 50/50 and help the car turn as it accelerates at the same time. I personally think it is a whole lot of marketing hype as you are sacrificing turn-in and mid-corner grip.

If the GT is 53/47, the Cobras will be even worse as the sure-to be larger/heavier engine and lighter IRS will throw it way out of wack.

But, lets get real here. The mustang is NOT a road race car. Drag car, sure. Corner carver, nope. It is not supposed to be, it is not built to be, and it never will be. It is a cheap, big, burly v8, four seating, fun to drive car (in stock form). While on the track 200 pounds can make a difference, on the street it will hardly be noticed.

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That is assuming that the IRS will not be heavier than a straight axle as it was in the 03/04.

Rampant said:

To be more precise, they were talking that having a very slight front weight bias will help in corner exit. As the weight shifts back upon acceleration (as it will ALWAYS do), the weight distribution is supposed to be 50/50 and help the car turn as it accelerates at the same time. I personally think it is a whole lot of marketing hype as you are sacrificing turn-in and mid-corner grip.

If the GT is 53/47, the Cobras will be even worse as the sure-to be larger/heavier engine and lighter IRS will throw it way out of wack.

But, lets get real here. The mustang is NOT a road race car. Drag car, sure. Corner carver, nope. It is not supposed to be, it is not built to be, and it never will be. It is a cheap, big, burly v8, four seating, fun to drive car (in stock form). While on the track 200 pounds can make a difference, on the street it will hardly be noticed.

Also, look how Auberlein can keep winning races in the WC series, even with 200+ lbs. added to his car (granted at the center, apposed to the extremeties, but still).

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Your arguments do not hold up.

The "slight" front weight bias is bull-crap that Infinity was spouting when the G35 came out to explain why the G35 did not have as good F/R weight balance as the BMW 3.

If you need some front weight bias to help exit a corner, then why so ALL the fastest road race cars - CART, F1, ALMS, GRAND-AM, etc, have their engines in the rear of the car. These fastest road race cars have a F/R weight balance on the order of 45 / 55% F/R.

The 03/04 SVT Cobra with its BIG, HEAVY, iron block S/C engine, has the same F/R weight balance as the Mach 1. (57/43). Part of the reason is because its IRS is HEAVIER than the live axle used on the GT & Mach 1.

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What's up with that post above mine?

Anyways, the next-gen SVT Mustang will probably have close to the same weight distribution as the '05 Mustang GT because the 6-speed tranny is heavier than a 5-speed, and the IRS will most likely add some weight as it did before, although less unsprung weight relative to the solid axle.

It will most likely be a little heavier, but maybe we will see some lighter materials used here and there to keep the weight closer to the GT. I would love to see a 5.4 SC/6-spd/IRS car under 3500 lbs.

351CJ said:

Your arguments do not hold up.

The "slight" front weight bias is bull-crap that Infinity was spouting when the G35 came out to explain why the G35 did not have as good F/R weight balance as the BMW 3.

...

The 03/04 SVT Cobra with its BIG, HEAVY, iron block S/C engine, has the same F/R weight balance as the Mach 1. (57/43). Part of the reason is because its IRS is HEAVIER than the live axle used on the GT & Mach 1.

Click to expand...

Umm... if you actually read my post, I was saying that is what NISSAN was saying as to "benefits" of their 52/48 weight distribution -- to which I was saying was just marketing hype and crap.

Also, traditionally, properly designed IRS systems are usually lighter than solid rear axles due to the less amount of metal involved. I hope you are not suggesting the IRS in the last Cobra was a good example of an IRS. It was a bandaid on a mid-'70s platform (also pointing out how important Ford thought the IRS would be to try and retrofit an IRS to a chassis not designed for one). I was actually hoping Ford would do a better job with the IRS this time around -- and that would most likely mean it being lighter than the solid rear. Only time will tell though.

However, my main point was that it won't make that much of a difference on a street driven car anyways, so what is the point about worrying over some perceived excess weight? Even in road racing it doesn't have that much of an influence -- and that is where 1/10s of a second matter. If you are going that extreme, you will strip it down anyways, so again, there is no point in worrying about it on the stock car.

For daily driving, extra weight (especially with the very long wheelbase) usually equates to slower reaction, and a nose-heavy car usually equals big-time understeer (which the '05 has). Both of these can be compensated for with springs, shocks and sway bars. Ideal for road racing? Certainly not. But, then again, the Mustang was never meant to be a dominating road racing machine either. Heck, it isn't even a sports car.

"These fastest road race cars have a F/R weight balance on the order of 45 / 55% F/R."

Airflow management does a lot for them too (i.e. lot's of down force in the front and adjustable) compared to the form follows before! function of the 350Z or Stang for that matter. Having more rear bias, the F1 guys can tune the front via airflow management--of course at speed (100+mph).

Anyway, of course Nissan is hyping up the bias a bit

SN95_XB331 said:

"These fastest road race cars have a F/R weight balance on the order of 45 / 55% F/R."

Airflow management does a lot for them too (i.e. lot's of down force in the front and adjustable) compared to the form follows before! function of the 350Z or Stang for that matter. Having more rear bias, the F1 guys can tune the front via airflow management--of course at speed (100+mph).

Anyway, of course Nissan is hyping up the bias a bit

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However, ALL forms of Road Racing (except production based) went to mid-engined cars in the early 1960s. At this point there was very little knowledge of airflow. These crude mid-engined cars with their 45 / 55% F/R weight balance went on to dominate sports car sprint racing (CAN-AM & USSRC), Endurance racing, F1, F2, F3 and Indy Car racing years before wings and air-flow management showed up.

SRI, double post

Rampant said:

Umm... if you actually read my post, I was saying that is what NISSAN was saying as to "benefits" of their 52/48 weight distribution -- to which I was saying was just marketing hype and crap.

Also, traditionally, properly designed IRS systems are usually lighter than solid rear axles due to the less amount of metal involved. I hope you are not suggesting the IRS in the last Cobra was a good example of an IRS. It was a bandaid on a mid-'70s platform (also pointing out how important Ford thought the IRS would be to try and retrofit an IRS to a chassis not designed for one). I was actually hoping Ford would do a better job with the IRS this time around -- and that would most likely mean it being lighter than the solid rear. Only time will tell though.

However, my main point was that it won't make that much of a difference on a street driven car anyways, so what is the point about worrying over some perceived excess weight? Even in road racing it doesn't have that much of an influence -- and that is where 1/10s of a second matter. If you are going that extreme, you will strip it down anyways, so again, there is no point in worrying about it on the stock car.

For daily driving, extra weight (especially with the very long wheelbase) usually equates to slower reaction, and a nose-heavy car usually equals big-time understeer (which the '05 has). Both of these can be compensated for with springs, shocks and sway bars. Ideal for road racing? Certainly not. But, then again, the Mustang was never meant to be a dominating road racing machine either. Heck, it isn't even a sports car.

Click to expand...

Sorry, but I missed the sentence in your previous post about "marketing hype" We agree on that point regarding Nissian.

However we disagree in several areas:

1. Weight of IRS. The typicial weight of an IRS rear suspension is heavier than a soild rear axle. This is true for many cars, but the Cobra / Mustang is one of the few where we have a direct comparison. What your are confusing is that an IRS gives you lower unsprung weight. This is because the differential is mounted to the frame so it becomes "sprung" weight. However the total total weight for a RWD IRS is more than a comprable live axle.

2. A long wheelbase does not equate to slower reaction. Quite the contrary, If done right, like the 2005 Mustang, the long wheelbase improves F/R weight balance which can improve turn in and especially improve direction transition. The BMW 3 series has a 107.3" wheelbase. I don't thinkt there is anyone in their right mind who would say that a M3 has slow turn-in due to its "long" wheelbase.

3. You say the '05 Mustang has "big time understeer". How do you know? Have you driven one at it's limit? The early mag reviews have said that the '05 Stang has understeer at the limit, but NONE have said that the '05 has "big time oversteer".

With the Cobra, the (old) Thunderbird, the Explorer/Aviator and Expedition/Navigator - Ford has fitted IRS to a platform that was originally designed to have a live axle hung in it's place. That's a big part of the reason there's little weight difference between the two -- although the unsprung weight is slightly less on the IRS models. The proper way to do it would be to re-engineer the back half of the floor pan in a dedicated IRS design. Also, many of the other vehicles mentioned have mostly aluminum suspension components front and rear. Both of these approaches cost money which Ford has chosen not to spend on the product. In the case of the SUV's, they'll spend it instead on incentives and rebates to move the product. That won't be an issue for the first 6 months or so of Mustang production -- until supply catches up with demand.

It's safe to assume understeer will be present on the '05. The manufacturers are pretty good about building it in as a 'safety' feature. The typical driver's reaction when the car starts to push is to let off the gas. The oem's (with a handful of exceptions) will usually design their vehicles with understeer at the limit so that when the driver lifts off the gas, the car tightens it's line. It's sort of self-correcting - which the domestic oem's lawyers have come to like over the years.

The more hard-edge the vehicle, the less understeer will be present. Of course, at lower speeds, a little oversteer is likely only a stab of your right foot away.