Who's got the best front to rear weight ratio, and how did you do it? List engine, body mods, rims, anything moved from back to front (i.e. battery), pix if you have them, and the most specific info you have on your car's weight and weight distribution, plus conditions under which it was weighed (i.e. how much gas, spare tire and jack in place?, driver in car? and if so, driver's weight).

I was wondering…weight distribution is a good place to start, but surely, where that weight sits must matter. Say you start with a car with a perfect 50/50 distribution. Obviously you want as much of that weight as possible to be as low as possible. But do you want most of the weight to be toward the center of the car (I'm guessing so), or is it good to have some at the extreme ends, too? The reason this came to mind in the first place was I was thinking of whether I want the battery under the headlights or in the spare tire area. Under the headlights, it'll move the weight forward a bit more, but in the spare tire area, it'll keep more weight more toward the middle of the car. Note that while I'm still wondering about the bigger question, I'm going to do the battery under the headlight (lower).

Edit to add: the reason I figure that weight should be as centered in the car as possible is that it ought to make the car more nimble, as having more weight on the outside of a rotating mass (i.e. your car when turning) means more inertia, meaning your car will resist going into or coming out of a turn more.

I think I may be losing my mind. I'm not smart enough for this stuff. =P

[This message has been edited by timwdegner (edited 11-17-2005).]

quote Originally posted by timwdegner: The reason this came to mind in the first place was I was thinking of whether I want the battery under the headlights or in the spare tire area. Under the headlights, it'll move the weight forward a bit more, but in the spare tire area, it'll keep more weight more toward the middle of the car. Note that while I'm still wondering about the bigger question, I'm going to do the battery under the headlight (lower).

under the headlight?

Thread is here: https://www.fiero.nl/forum/Forum1/HTML/053415.html

------------------

Archie's Choptop conversion #11, #15, Redux & The Stealth

I don't know about having that much "focused" dense weight sitting in that location. It could spell serious trouble if you're entering a turn hard, have to hit the brakes rather hard, and watch the rear end come around quicker than you can say;

"Watch This ! "

More weight towards the center of the car will give you a lower polar moment of inertia. This will give you quicker response than if you spread the weight out towards the ends of the car. But, with the weight spread out towards the front/rear, you will have more stability at high speeds.

The one thing I've found with the Mid-Engine configuration tuned for performance, is that while you can really dial the sucker in, you tend to lose more and more "Vehicle Feedback". This results in the Driver having to be highly skilled to read the slightest whispers from the chassis, because it will go from slight whispers to an immediate busting of your eardrums.........if you know what I mean. Once this happens, there is extremely little chance you can change the path your headed, because it happens so quickly. For this reason alone, any changes better be very well thought out.

edit; fixed some spelling.

[This message has been edited by California Kid (edited 11-17-2005).]

Mad, thanks for the battery info.

Cali and Silicoan: having researched more, I understand the polar moment of inertia. Thanks for steering me in the right direction. I understand that certain cars (i.e. early Porsche 911s) have a way of surprising their owners with a sudden nasty rotation; hence the excessive understeer purposely dialled in to most cars.

Back to the first questions of the thread (and putting aside, for now, my questions about vehicle dynamics), who has a close F/R weight ratio? Because simple weight distribution affects how other things should be set up, I think it's a worthy place to start.

Note: I'm not extremely concerned with high-speed stability right now. I'd rather be able to rack up a respectable number on the skid pad than cruise down the freeway at 180mph. And even as far as the skid pad goes, I'm slowly realizing that I could mod the Fiero all I want and still a used $2000 Kawasaki would whoop me on any twisty road…so what's the point of getting too crazy with it? Basically, I'm looking for something that will outhandle most typical competition (I know that's vague, but you know what I mean?).

[This message has been edited by timwdegner (edited 11-21-2005).]

quote Originally posted by California Kid: I don't know about having that much "focused" dense weight sitting in that location. It could spell serious trouble if you're entering a turn hard, have to hit the brakes rather hard, and watch the rear end come around quicker than you can say; "Watch This ! "

O.K., I can certainly understand why putting the battery at the extreme rear end of the car would not be desirable, but since it is the rear end that is coming around, wouldn't placing the battery in front of the front wheel tend to minimize these effects in that it would add more balast to the opposite extreme?

------------------
FierOmar

Omar, It could also cause the car to push or understeer more in a corner because there is a concentrated addition of weight so far in front of the front axle... the further in front of the front axle it goes, the more pronounced the effects will be.

quote Originally posted by The Aura: Omar, It could also cause the car to push or understeer more in a corner because there is a concentrated addition of weight so far in front of the front axle... the further in front of the front axle it goes, the more pronounced the effects will be.

However, in the case of the battery, it is probably no more that 16"-18" ahead of the front axle. Furthermore, to the extent the center of gravity in still more towards the rear, it should not have a significant impact on the handling.

------------------
FierOmar

Guys, the theory of all this is fine and good, but in practice, I don't think it is possible to change the weight distribution of a Fiero enough to affect the handling in a significant way. Other factors, such as the condition of the suspension, alignment, wheels and tires will have a greater effect.

Back in 2002, my '88GT was still in stock form, (2.8, Getrag), and the weigh scale results were:

Front = 1212 Rear = 1588 Total = 2800 Distribution = 43.3 / 56.7

In 2004, I did a 3800SC swap, and moved the battery to under the right front headlight at the same time. I knew the 3800SC was going to be about 60 lbs heavier than the 2.8, so I wanted to offset some of this by moving the battery. I chose the under the headlight positon because it was as far to the front as possible. As far as it being off center (as compared to the positon under the spare tire), remember, the battery in the OEM position, it is already on the right side. The new weigh scale results were:

Front = 1260 Rear = 1600 Total = 2860 Distribution = 44.0 / 56.0

As you can see, this is a very small difference in weight distribution. It would take a lot of work and money, to get a Fiero configured to achieve a 50-50 weight distribution. I don't believe it has been done. You would need a lighter engine. An all aluminum 3800SC would be nice, but no one makes one. Adding ballast to the front end is counterproductive.

As for handling, my '88GT is set up with poly suspension bushings all around, KYB struts, 1" lowering springs in the front and WCF coilovers in the rear. Front tires are (Kumho) 215/45-17, rears are 245/45-17. Handling is great.

.....Rickker

quote Originally posted by Rickker: Guys, the theory of all this is fine and good, but in practice, I don't think it is possible to change the weight distribution of a Fiero enough to affect the handling in a significant way. Other factors, such as the condition of the suspension, alignment, wheels and tires will have a greater effect. Back in 2002, my '88GT was still in stock form, (2.8, Getrag), and the weigh scale results were: Front = 1212 Rear = 1588 Total = 2800 Distribution = 43.3 / 56.7 In 2004, I did a 3800SC swap, and moved the battery to under the right front headlight at the same time. I knew the 3800SC was going to be about 60 lbs heavier than the 2.8, so I wanted to offset some of this by moving the battery. I chose the under the headlight positon because it was as far to the front as possible. As far as it being off center (as compared to the positon under the spare tire), remember, the battery in the OEM position, it is already on the right side. The new weigh scale results were: Front = 1260 Rear = 1600 Total = 2860 Distribution = 44.0 / 56.0 As you can see, this is a very small difference in weight distribution. It would take a lot of work and money, to get a Fiero configured to achieve a 50-50 weight distribution. I don't believe it has been done. You would need a lighter engine. An all aluminum 3800SC would be nice, but no one makes one. Adding ballast to the front end is counterproductive. As for handling, my '88GT is set up with poly suspension bushings all around, KYB struts, 1" lowering springs in the front and WCF coilovers in the rear. Front tires are (Kumho) 215/45-17, rears are 245/45-17. Handling is great. .....Rickker

I'm not suggesting that you would ever achieve a 50-50 weight distribution, or that achieving such is desirable. My point is simply that putting the battery in front of the front axle should not have a negative impact on handling so long as there is still a rearward bias with respect to overall weight distribution.

------------------
FierOmar

quote Originally posted by FierOmar: I'm not suggesting that you would ever achieve a 50-50 weight distribution, or that achieving such is desirable. My point is simply that putting the battery in front of the front axle should not have a negative impact on handling so long as there is still a rearward bias with respect to overall weight distribution.

FierOmar, I agree with you. If anything, moving the battery to the front will improve handling, rather than deter it. Certainly, adding weight to the rear end is the wrong thing to do. Try driving hard on some twisties with about 150 lbs of sand bags in the rear trunk. This will demonstrate the point very dramatically.

....Rickker

you can't get 50/50 in a Fiero without adding a lot of weight
and lighter is better ALLWAYS
side to side balance is more important anyway
you want to balance the front tyres loads to each other
with the rear balance less important then the front
and you can't realy get both perfict just closer then stock

I would NOT add weight like a battery in the ends of the car
it will handel better with weight in the center then the ends
it least keep weight inside the wheel base
the mid-engine design idea is center of mass near the center of the car

------------------
Question wonder and be wierd
are you kind?

a lighter drivetrain? i was told a cobalt ss engine is about the same weight as a duke, supercharger included. that would help a lot if it could be put in.

50/50 weight distribution would be ideal in the perfect car. BUT a lot of other factors come into play for best handling. How much hp/torque to you have, grippy tires, driving style and many others. So the perfect balance will be different for everyone. A good example is race cars setup. ...a car thats set up perfect for one driver may be totally undrivable to another. Me for example...I like a car that tends to push more thru a turn than a loose one. I ran shorter races so front tire wear was no big problem, I could keep in the power longer and get back into it quicker....someone else driving my car might just run into the wall.

quote Originally posted by rogergarrison: 50/50 weight distribution would be ideal in the perfect car. BUT a lot of other factors come into play for best handling. How much hp/torque to you have, grippy tires, driving style and many others. So the perfect balance will be different for everyone. A good example is race cars setup. ...a car thats set up perfect for one driver may be totally undrivable to another. Me for example...I like a car that tends to push more thru a turn than a loose one. I ran shorter races so front tire wear was no big problem, I could keep in the power longer and get back into it quicker....someone else driving my car might just run into the wall.

exactly. there is no "perfect" weight distribution. its all on what YOU like. same goes for the "best" shocks/struts, springs & sway bars.

For what it is worth, I am NOT a big fan of a 50/50 weight ratio.

I always hear people talk about this, but 50/50 only makes sense on the show room floor. That is, setting still. When the car is in motion everything changes (as we all know). For example my IMSA is set up for a 45/55 weight ratio with the majority of the weight in the back and I am using a stock wheel base. Here is the reasoning (and by the way, the balance feels GREAT on the track).

Slowing down for a turn: Weight shifts forward giving more bite to the front wheels, however there is still more weight on the rear than in a 50/50 car. Better rear grip for breaking.... in a straight line. (breaking in a straight line is very important in performance driving). To dial this in I use a brake bias controler. This allows maximum grip while not letting the rear get "happy".

Entering the turn: At this point the driver will either be on the gas or feathering it. Either way, you want grip to the rear since the "friction oval" is being stretched. The car is asking for lateral grip as well as forward grip. In this case the weight shift to the rear (from acceleration) and natural weight of the car will help. A 50/50 car does not have an advantage in this area either.

Exiting the turn: Now the driver is nearing full acceleration. Maximum grip is needed and the rear bias car will have an advantage due to weight placement.

In contrast a 50/50 car would be better suited for neutral handling (no acceleration or braking). I have experienced and heard people talk about the rear end overshooting during lane change type situations. This can be corrected through suspension tuning (ie swaybars, tire side wall, etc.).

------------------
Paul

Home Built Tube Chassis IMSA Race Car - 3.8 lb./hp | 1987 Fiero GT 119,xxx, 3.1 motor, HHP swaybar, Full poly
For more IMSA Fiero info: http://www.cardomain.com/memberpage/789315

I posted the below in a thread back on 11-04-02, that thread got pretty heated about weights of V8 Converted Fiero's, Handliing, and Weight balance. My car is also setup with a 45 front and 55 rear weight distribution:

Post by California Kid 11-04-02

Then they won't believe mine either:

648 Front 624

762 Rear 783

Total: 2817

Here's the whole thread if you want to read it:
https://www.fiero.nl/forum/Archives/Archive-000002/HTML/20030531-1-023260.html

[This message has been edited by California Kid (edited 11-25-2005).]

I searced and couldnt find it for now, but I swear one of the ppg cars had a tank in the front spare tire well that could pump fuel into it to change the weight balance of the car when needed.
Anybody find this? Or know what the h311 I'm talking about?
Brad

Imagine a battery under the Headlight and then need to jump the car on a cold winter morning.

quote Originally posted by Fiero1Fan: Imagine a battery under the Headlight and then need to jump the car on a cold winter morning.

i too have the underheadlight batter, but that problem above was solved on mine with a connecting cable that runs through a drilled hole in the spare tire compartment. it then runs into a small red battery box and has a contact inside. to jump you just connect it there and to anything metallic and your good to go... without that i couldn't see how you could easily do it without raising the headlight manually

------------------

quote Originally posted by twofatguys: I searced and couldnt find it for now, but I swear one of the ppg cars had a tank in the front spare tire well that could pump fuel into it to change the weight balance of the car when needed. Anybody find this? Or know what the h311 I'm talking about? Brad

I have had my hands on these cars several times and the PPG turbo cars only have a fuel cell up front as a safety requirement for their on track duties. It was the only place it fit and at the added weight might have help in the front but other suspension mods also contributed much. But it is hard to beat wher GM put the tank to start with in the center of the car and low as possible. There was just no way to bolt in the fuel cell in the factory location.

Balance on a car is so subjective and It depends on many things. Road racing vs drag racing vs circle track vs street driving plus add in various driving styles all require different set up's so that is why we get so much debate. All of you are right but all of you are worog to a point too there are just to many variables to get all to agree here.

Fact is a 50/50 on a factory street car is very desireable as it will meet the street driving needs of most drivers and can be tuned so much easier as a starting point. In a street car keep the weight low and keep the front a rear balance are the desired aspects and there are differnt ways to acheieve it.

One thing that is a killer today are the large wheels on some cars. the unsprung weight in some cases kill any handling improvment along with a increas in braking distance. There are points bigger no longer is better.

quote Originally posted by R Runner: For what it is worth, I am NOT a big fan of a 50/50 weight ratio. I always hear people talk about this, but 50/50 only makes sense on the show room floor. That is, setting still. When the car is in motion everything changes (as we all know). For example my IMSA is set up for a 45/55 weight ratio with the majority of the weight in the back and I am using a stock wheel base. Here is the reasoning (and by the way, the balance feels GREAT on the track). Slowing down for a turn: Weight shifts forward giving more bite to the front wheels, however there is still more weight on the rear than in a 50/50 car. Better rear grip for breaking.... in a straight line. (breaking in a straight line is very important in performance driving). To dial this in I use a brake bias controler. This allows maximum grip while not letting the rear get "happy". Entering the turn: At this point the driver will either be on the gas or feathering it. Either way, you want grip to the rear since the "friction oval" is being stretched. The car is asking for lateral grip as well as forward grip. In this case the weight shift to the rear (from acceleration) and natural weight of the car will help. A 50/50 car does not have an advantage in this area either. Exiting the turn: Now the driver is nearing full acceleration. Maximum grip is needed and the rear bias car will have an advantage due to weight placement. In contrast a 50/50 car would be better suited for neutral handling (no acceleration or braking). I have experienced and heard people talk about the rear end overshooting during lane change type situations. This can be corrected through suspension tuning (ie swaybars, tire side wall, etc.).

Bingo! On 9/24/05 in relation to a thread on braking, I said:

"Could be going out on a limb here, but... as I understand the Fiero starts with approximately 56% of the weight on the rear, leaving about 44% on the front. My prior research revealed that there is approximately 15-17% weight transfer upon heavy (but not locked up) braking. The actual weight transfer depends on multiple factors, including ride height, spring rate, total vehicle weight, etc.

Now assuming a weight transfer of 16%, the Fiero would have 60% of its weight on the frond under heavy braking, leaving 40% on the rear. This concept also explains why FWD cars will end up with the front brakes doing about 80% of the braking (not uncommon for them to have 60% or more weight up fornt under static conditions).

Comparing the Fiero to other front engine with rear drive cars, adds food for thoutht. Assuming for the sake of discussion that our theoretical car was approximately 54% front & 46% rear under static conditions (by comparison, early Mazda RX7 comes close to 50-50). Under heavy braking conditions, the weight transfer would load the vehicle to 70% front, leaving 30% on the rear.

Acceleration reverses the weight transfer. Although I am not certain on this point, I seem to recall that the same weight transfer towards the rear will occur given the same G-force (e.g. acceleration vs. braking). Assuming that this is correct, the Fiero would have 72% load on the rear under hard acceleration while our theoretical car (see above) would have 62% load on the rear.

Kind of makes me wonder if a mid-engined car might not be well suited for road racing. More effective four wheel breaking during approach to turn, and greater loading on the drive wheels during hard acceleration. Hmmm. Just might work."

For the entire thread, see: https://www.fiero.nl/forum/Forum2/HTML/067081.html

------------------
FierOmar

i have a batttery unde the headlight in one of mine. i ran an extra wire from the starter to a remote positive battery post mounted in the rear trunk. i also got a cheap post that's used to stick in a side mount battery terminal and bolted it to the dogbone brace on the trunk wall for a neg. jump point. i've jumped and given jumps from these two points with no problems.

quote Originally posted by FierOmar: Bingo! On 9/24/05 in relation to a thread on braking, I said: "Could be going out on a limb here, but... as I understand the Fiero starts with approximately 56% of the weight on the rear, leaving about 44% on the front. My prior research revealed that there is approximately 15-17% weight transfer upon heavy (but not locked up) braking. The actual weight transfer depends on multiple factors, including ride height, spring rate, total vehicle weight, etc. Now assuming a weight transfer of 16%, the Fiero would have 60% of its weight on the frond under heavy braking, leaving 40% on the rear. This concept also explains why FWD cars will end up with the front brakes doing about 80% of the braking (not uncommon for them to have 60% or more weight up fornt under static conditions). Comparing the Fiero to other front engine with rear drive cars, adds food for thoutht. Assuming for the sake of discussion that our theoretical car was approximately 54% front & 46% rear under static conditions (by comparison, early Mazda RX7 comes close to 50-50). Under heavy braking conditions, the weight transfer would load the vehicle to 70% front, leaving 30% on the rear. Acceleration reverses the weight transfer. Although I am not certain on this point, I seem to recall that the same weight transfer towards the rear will occur given the same G-force (e.g. acceleration vs. braking). Assuming that this is correct, the Fiero would have 72% load on the rear under hard acceleration while our theoretical car (see above) would have 62% load on the rear. Kind of makes me wonder if a mid-engined car might not be well suited for road racing. More effective four wheel breaking during approach to turn, and greater loading on the drive wheels during hard acceleration. Hmmm. Just might work." For the entire thread, see: https://www.fiero.nl/forum/Forum2/HTML/067081.html

Glad we agree.

It is a fact. Mid-engine cars (in general) make better road racing cars than front engine cars. (puts on flame suit) Keep in mind that an AC Cobra and the like have "front" engines that are 60 to 90% behind the front axle. By putting the engine behind you, you can truly be mid-engine (better for inertia) and rear bias. I attached a layout picture for an example.

A stock fiero can be set up this way (longitudinal) with a V6 and a few tricks without going past the fire wall.

Paul

My initial estimates for F/R ratio when I swap in my all aluminum SBC were putting me at 48/52

DLD

quote Originally posted by R Runner: Glad we agree. It is a fact. Mid-engine cars (in general) make better road racing cars than front engine cars. (puts on flame suit) Keep in mind that an AC Cobra and the like have "front" engines that are 60 to 90% behind the front axle. By putting the engine behind you, you can truly be mid-engine (better for inertia) and rear bias. I attached a layout picture for an example. A stock fiero can be set up this way (longitudinal) with a V6 and a few tricks without going past the fire wall. Paul

A classic example of another "front" engine race car is the Factory Five Racer. See: http://www.factoryfive.com/table/ffrkits/speccar/kit/specs.html for specs.
Note that the front-rear weight distribution is 46% front and 54% rear. Sounds real close to what you have.

BTW... could I stop by and just HUG your car?

------------------
FierOmar

The mid-engine design is one of the main reasons I like the Fiero. I want to be a little rear heavy (wait... that didn't sound right )

Back to the topic... Moving the battery to the spare tire area makes sense from a weight distribution stand point. It would be a better location than the nose due to the lower inertia.

Paul

quote Originally posted by R Runner: Moving the battery to the spare tire area makes sense from a weight distribution stand point. It would be a better location than the nose due to the lower inertia. Paul

Solely from a weight distribution standpoint, it would probably be better to relocate the battery as far forward as possible. By my estimate, moving a 35 lb. battery from the stock location to spare tire area is going to change the front-rear balance by l% or less. The additional difference between moving it to the spare tire compartment and the front headlight area is probably less (although this statement is based on my estimate only).

The effects of inertia present a different problem. As I said earlier, " My point is simply that putting the battery in front of the front axle should not have a negative impact on handling so long as there is still a rearward bias with respect to overall weight distribution." (Perhaps it would be more correct to say: "should not have a significant negative impact on handling...")

If I understand you correctly, adding weight to the extreme end of the car (front or rear) would be detrimental to handling (e.g. comparing rear engine car to mid engine car). However, since moving to battery further forward (in front of the front axle) is adding weight to the other extreme, would such placement increase the the tendancy to oversteer, or reduce it?

.

------------------
FierOmar