Where does all the rear weight come from?
 

This car has a pretty good weight distribution, as we all know. But when I picture things in my head I see an engine and a transmission with their weight almost completely supported by the front suspension. In the back is the diff and fuel tank (not so heavy). How does this car achieve a near 50 50 weight distribution with almost all of the heavy stuff at or in front of the front wheels? Where does the weight supported by the rear suspension come from?

well, first of all, the engine and tranny sit VERY low and VERY far back. Then u have the big driveshaft coming from the tranny to ur LSD diff, rear axles, then finally gas tank, spare tire (and tools), rear seats, muffler, etc.
The center of gravity on this car is a few inches behind the shift knob.

I guess this could be calculated pretty easily but do you have a source for this? Not doubting it, just curious.

Also, the fuel tank might not be that heavy but I believe the weight distribution is listed as being a wet weight (with fluids). 13 gallons of gas at 6 pounds/gallon = 88 pounds or about 7% of the rear weight.

There is a lot more "body" and "structure" to the rear I would argue. cabin, trunk, crash protection for the passengers, etc

@Laika, saw a diagram on some website. been searching for it but cant find it anywhere. it was legit. ill keep searching for it and post up when i find

Its not nowhere near 50/50. It is 55/45 with nobody in the car.

I heard from multiple sources that it was 53/47

BRZ is 55/45. FR-S is 53/47.

It just seems that the motor and tranny are the vast majority of the weight. From a mass perspective there just seems to be a lot less stuff in the rear. How much does a drive shaft and diff weigh compared to an engine block and tranny? The weight distribution is just hard for me to visualize.

Why the difference between the 2 cars?

that strikes me as odd since the brz should have more amenities in the cabin. ive heard that the cars were 53/47 with people in the car and 55/45 without. was that what you were thinking of? otherwise, youre talking about a 50 lb shift in nearly identical cars

50L of fuel is in the back too. That's over 100 pounds.

Thats BS, few will have people in the back, a spare tire, and a full tank of fuel when things get twisty. Ill bet these cars are more like 60/40 real world.

Big 'ol nasty mustache...

Its sad that some of you guys own the damn cars yet know not enough about its balance. It is 55/45 with no one in the cars and 53/47 with 2 occupants in it.

No. Most of the front drivers weight reside on the rear half of the car in the FRS/BRZ's case

Alot of the weight in the centre/rear is the frame...then you add the differential, drive shaft, rear axles, driver & rear seats, gas tank, trunk lid, and etc...

http://www.motorward.com/wp-content/...Prologue-2.jpg
http://www.motorward.com/wp-content/...Prologue-3.jpg
http://www.subaru.ca/content/7907/Me..._Eng_Frame.jpg
To give you a better idea of the structural weight...look at the rear...then look at the front; majority of the front are panels...(which also includes the super light-weight aluminum hood)

The front still house all the heavy stuff like the engine, battery, transmission, and etc, but engineers put it as far back as possible...relocating the centre of gravity all the way back...help evening out the weight ratio.

Man you guys ar makeing something simple really complicated. Please, go on.:popcorn:

Yeah, I totally take my spare tire out every time I hit the twisties. :bonk:

Ahh, that could be it.

I could've sworn I saw on the Subaru website they said 55/45, but they were probably stating what it is without people.

I find it hilarious that it bothers you. Really hilarious actually. Thanks for the laugh.

What bothers me is owners speaking on something they don't know about.:lol:

Here's a explanation of how it it works

With no occupants the car weighs 2,760 lbs stock so 55% of weight is (somewhere around) 1,518 lbs and the 45% is 1,242 lbs

Now lets say two occupants weigh 150lbs a piece. That would mean around 2/3rds of their bodies will be on the rearward side of the car so it would have about 200 lbs on the rear and about 100 on the front.

2760+300=3,060 lbs and minus 53% from that and you get 1621.80(f) and 47% 1438.2(r) on the rear.

Go take a corner, pray to the subaru gods, understand how easy it was to drift, and stop bickering. Car handles amazing. Plain and simple. Now what you should really be wondering is why they didn't slap a turbo on it with 6/4 breaks and a heavier clutch with adjustable suspension. <- O wait because that would add another 10 grand on the price tag and put it on a STi level which they don't want to do for marketing. This is an afordable sports car... you got what you paid for. If you don't like it. sell it for the 25-30 grand you picked it up for and buy a prius.... then complain how you didn't get 60+ MPG.

Really? If true, that explains why I keep seeing both set of numbers mentioned.

Then I read this reply:

So who is right or are we still in the assumption phase?

Auto X?

Thanks, this is the kind of thing I was looking for, not a debate about 45 this 47 that. That picture of the frame is pretty cool.

im not assuming (although that doesnt mean im right), scion has marketed the car as having a 53/47 split but that was with passengers. some people get bent out of shape about that but a) weight balance front to rear isnt as important as people make it out to be and b)if it is, that is a great balance as you should be accelerating at the apex of most curves shifting a little weight rearward giving you the best weight distribution when you actuall need it

I am pretty sure fatoni is correct in saying the #'s are with & without people.

I was the one assuming, that just because I read 55/45 on the Subaru site, that's what the BRZ was.

50/50 split is not that big a deal by its self.

Can you really tell the difference between a 53/47 and a 50/50 split? i dont think unless you're doing some hard core tracking that you'll notice the difference.

Do you think it would be worth relocating the battery to the trunk?

Pop the hood. Look at where the front suspension points are, now notice the engine sits BEHIND that point. That means some of that engine weight is supported by the rear wheels. Now look where the transmission is - closer to the center of the car, so a bunch of its weight is carried by the rear as well.

It's percentages, not all or nothing. You don't split the car in half and say anything in the front half is supported by the front tires and vice versa.

The real question here is, with this nearly even weight, will it need weight in the trunk in the winter?

I'd just give it a full tank of gas and maybe put a sandbag on the rear seats or right behind the front seats for more rear traction without upsetting the balance.

No. Moving the stock battery to the trunk means adding even more weight with cables and a box. A better solution (unless running a big stereo) is putting a small lightweight battery in the stock location. Save 20+ lbs over the front end with few downsides. I have a 2 lb lithium battery for my Miata for autocrossing, and my normal street battery for the Miata is a 7 lb AGM battery.

This would be negligible compared to winter tires(or chains!), and under inflation.

Well yeah, I was assuming he already knew to get winter tires. But I question underinflation... I think it's only good for getting out of deep snow. But for grip and traction on hardpack snow and ice, you want normal inflation so that there is more pressure pushing into the ground. But the pressures are already pretty high on these cars so maybe dropping a psi or two for a little extra sidewall flex would be OK.

Now underinflating the stock or summer tires is a good idea so that they can try to build some heat into them. But obviously that's only if it's just cold tarmac and there is no snow. Tires are not going to warm up on snow and if anything, they'll just get a bit colder. But they'll probably get underinflated by the cold anyway. You lose about 1 psi per every 10 degrees F. If you want an accurate reading though, check your pressures after the car sits out in the cold.

Lol... Snow tires aren't warmer... Snow tires are built super soft, so in cold freezing weather it takes more to harden the tire.

We all should know... Hard tires means hard rubber = no sticky on the road.
Also, deflating the tires help expands its surface area... for better grip.

Adding the two together; they work VERY well on snow... You'd be surprised how much of a difference just the tires can make alone.

But it's all about how much pressure is on the contact patch per square inch. More pressure means the tire can bite into the snow and ice harder. Why do you think rally cars run narrow, knobby tires with high pressures on snow? It's because less contact patch means that more weight and pressure is put on the tread. But if you wanna try telling the rally drivers that they need wider tires with lower pressures for their snow rallies, good luck. My advice is to experiment with this first hand. I'm sure you will find that higher pressures give more grip and control on hardpack snow vs lower pressures which can cause it to glide across the surface more easily.

This reminds me of that episode of Top Gear where Richard Hammond goes to the salt flats in Utah and tries to meet a target speed and some guy who had been going there for many years told him he needed the lowest possible pressures for his tires. Well it turned out that was the reason he was so slow and when he tried the opposite and increased his tire pressures, he met his target speed. But you must admit, tires are a difficult beast to understand.