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      11-05-2012, 12:21 AM   #1
splitsecond
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Modding for improved weight distribution?

As you guys probably know, the 135i 6MT has a weight distribution of 52.3/47.7. BMW undergoes a lot of effort to improve weight distribution (i.e. putting the battery in the back, etc.), so I have to assume that it makes a difference to get closer to 50/50.

I once test-drove a 323i, and it just had a certain balanced feeling. This was several years ago, so I might be misremembering, but I don't get that same sensation from the 1er.

The question is - does anybody know how big of a difference the weight distribution makes? Is there any benefit to modding accordingly? For instance, switching to a CF hood but keeping the stock trunk?


Just some quick math:
Double-sided CF hood would save 28 lbs from the front (44 lbs --> 16 lbs)
Evo Racewerks dry CF frontend could save up to 32 lbs from the front (49 lbs --> 17 lbs)
Various lightweight under-hood components could save 5-10 lbs
Limited-slip differential may add about 8 lbs to the back
Rear-mount methanol tank may add about 15 lbs to the back (when full)


So after these liberal estimates, we've taken 70 lbs off the front and added 23 lbs to the back... and that puts us at 51.0/49.0.

Thoughts?
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      11-05-2012, 03:11 AM   #2
RimasRS
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I think you are right. Just be ready to spend some money. And when you add to your list for example FMIC it will go back again.
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      11-05-2012, 03:37 AM   #3
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Quote:
Originally Posted by RimasRS View Post
Just be ready to spend some money.
Yeah, you're right. I've been tossing this idea around for a while, but I was just wondering if anybody has any experience with it. It's a lot of money to be spending if I don't know whether it'll actually make a worthwhile difference...


Quote:
And when you add to your list for example FMIC it will go back again.
Yeah, I already have an upgraded FMIC... and my exhaust pipe probably takes more weight off the back than the front. So I'm probably already relatively front-heavy.


There's always the cheap/easy way to test the hypothesis... we could just pack the trunk with 170 lbs worth of stuff and see what that does for handling. Of course, that's not a permanent solution, but at least it'll tell us what 50:50 feels like.
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      11-05-2012, 03:43 AM   #4
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you're better off having lower weight overall than adding weight inappropriately/not removing it at all, than having a 'perfect' 50/50 distribution

you can dial it in in the suspension settings, to make it feel more balanced

but you can't do the same to magically remove weight
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      11-05-2012, 05:00 AM   #5
splitsecond
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Quote:
Originally Posted by flinchy View Post
you're better off having lower weight overall than adding weight inappropriately/not removing it at all, than having a 'perfect' 50/50 distribution
Well, I'm not actually planning to intentionally add weight... just want to see what it'd feel like. And if it feels good, then maybe make an effort to remove weight from the front and/or relocate weight to the back, like what BMW did with the battery.

Quote:
you can dial it in in the suspension settings, to make it feel more balanced
How do we do that?
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      11-05-2012, 06:38 AM   #6
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Quote:
Originally Posted by splitsecond View Post
Well, I'm not actually planning to intentionally add weight... just want to see what it'd feel like. And if it feels good, then maybe make an effort to remove weight from the front and/or relocate weight to the back, like what BMW did with the battery.


How do we do that?
getting spring rates perfect is a big deal

damper settings (and rebound if possible), getting them perfect makes a HUGE world of difference.
ride height set up for handling, not just looks

how the sway bars are set up (if adjustable)

really just standard suspension set up, if you have it all adjustable, it has to be adjusted right
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      11-05-2012, 06:44 AM   #7
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I figured the BMW Performance suspension might do the job pretty well with regard to spring rates, damper settings, and sway bar characteristics. No?

But anyway, we digress...
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      11-05-2012, 05:51 PM   #8
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Quote:
Originally Posted by Purple Derple View Post
More mass being towards the center of the car is better than at the poles.
Yeah, that's a good point... so a lightweight front bumper might be more useful than a lightweight hood.
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      11-05-2012, 08:32 PM   #9
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Quote:
Originally Posted by splitsecond View Post
Yeah, that's a good point... so a lightweight front bumper might be more useful than a lightweight hood.
but a lightweight roof will be the greatest benefit of all

if you can swing it haha


a hood has a lot more weight in it overall, doesn't it? so potentially a bumper wouldn't have more benefit?

also, add in your driver weight, pulls the overall mass distribution of the car back and to the side a bit?
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      11-05-2012, 09:16 PM   #10
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Quote:
Originally Posted by splitsecond View Post
Yeah, that's a good point... so a lightweight front bumper might be more useful than a lightweight hood.
Right. I was going to mention this but you already see it. 5lbs off a bumper means more than 5 pounds off of a fender over a wheel, which means more than 5lbs off of a door in the middle of the car. This is F/R weight distribution anyhow.

Agreed that a roof is a big deal as well, though it's in the center of the car and changing its weight won't have much affect if any on F/R weight distribution, it is however up high which factors in strongly when "real life" handling is talked about. When you're looking at CG (center of gravity), keep in mind how high above the axles your mass is as well.
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      11-05-2012, 09:53 PM   #11
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my car has a ER front end, CF hood and a CF trunk and an after market exhaust and wheels it is probably 80-100lbs lighter than stock in various parts of the car. I gradually upgraded it all along with so many other part of the car that it is hard for me at this point to compare it to stock.

Race seats, deleting back seat, lighter battery are all fairly easy ways to cut weight but some have noted, eliminating the sunroof would be noticeable.
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      11-06-2012, 01:33 AM   #12
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Quote:
Originally Posted by ilikebmxbikes
my car has a ER front end, CF hood and a CF trunk and an after market exhaust and wheels it is probably 80-100lbs lighter than stock in various parts of the car. I gradually upgraded it all along with so many other part of the car that it is hard for me at this point to compare it to stock.

Race seats, deleting back seat, lighter battery are all fairly easy ways to cut weight but some have noted, eliminating the sunroof would be noticeable.
That all sounds like good ways to reduce weight, but it wouldn't do much for weight distribution... the weight that you take off the front (hood, body kit) is also taken off the back (trunk, exhaust). And racing seats are already at the center, so you may lose overall weight, but you're shifting the moment of inertia farther from the center. And the battery and back seats are in the rear half, so those mods would actually shift the distribution the wrong way. Still good mods for overall weight loss, but not for distribution.

A good experiment might be to put a passenger in the back seat... close to the center, but also close to the rear. If that doesn't provide a noticeable improvement in handling, then it's probably not worth spending a lot of money on weight distribution.
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Last edited by splitsecond; 11-06-2012 at 01:46 AM.
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      11-06-2012, 07:53 AM   #13
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I'll preface this by saying nothing magical happens when you hit a perfect 50/50. The car is only a few points off from the factory. Lowering the weight of the entire car still helps acceleration, braking, and cornering. I'm not even sure 50/50 is "perfect". I'd probably rather have slightly more weight over the drive wheels.

Hood isn't a bad option. It's also above the CoG of the car, so lowering its weight actually lowers the overall CoG of the car. That is a very practical option. Just swap it out and you're done, no real drawbacks.

You can remove the engine cover, and get an dual cone intake which will remove several pounds of plastic from the top of the engine. Small stuff, but it all counts.

ER has a front widebody kit that is available in dry carbon fiber that will shave a few pounds plus let you run wider tires in the front. It's pricey, but what do you expect? You shouldn't be worrying about 2-3% weight distribution if you aren't running 265-285mm front tires already.

I would not recommend replacing the factory crash beam in the front unless you have a purely race-only track car with a cage and whatnot. At that point, you can also remove the air conditioning, which is many pounds of aluminum, the pump, line, all the coolant, etc., and the stereo, and probably gut the dash, remove the airbag, and soforth.

In reality, something tells me the people who are worrying about weight balance in this thread don't have any other more worthwhile upgrades yet. You should get a wheel and tire package, a tune, M3 suspension upgrades, coilovers, etc. way before you try to make up that few percent of weight distribution up. Those will return you a much faster car for far less money that some obtuse goal of having a particular weight balance number.
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      11-06-2012, 10:38 AM   #14
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don't forget that a full tank of gas is ~85 lbs in the rear
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      11-06-2012, 05:01 PM   #15
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Quote:
Originally Posted by DRedman45
don't forget that a full tank of gas is ~85 lbs in the rear
Wow i thought it was way more!

Still, a decent amount

With fuel and driver, it would probably already pull the weight riiiight back to the rear?

Having different heights all over the car (set up properly, not randomly) would change how much weight each spring/shock sees, in different conditions, no?
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      11-06-2012, 06:42 PM   #16
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that's the whole idea behind corner balancing your car. the best FR weight distribution I could get was a 52/48 but with a perfect cross distribution
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      11-07-2012, 03:40 AM   #17
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Quote:
Originally Posted by Freon View Post
I'll preface this by saying nothing magical happens when you hit a perfect 50/50. The car is only a few points off from the factory. Lowering the weight of the entire car still helps acceleration, braking, and cornering. I'm not even sure 50/50 is "perfect". I'd probably rather have slightly more weight over the drive wheels.
Yeah, I don't think anybody said that 50/50 is "perfect." That's why Porsche still puts their engine in the back.



Quote:
ER has a front widebody kit that is available in dry carbon fiber that will shave a few pounds plus let you run wider tires in the front. It's pricey, but what do you expect? You shouldn't be worrying about 2-3% weight distribution if you aren't running 265-285mm front tires already.
Yeah, we mentioned that a few times in this thread. I agree that the benefit of wider tires is much more significant, but part of the reason I'm thinking about weight distribution is so that it can help me decide which widebody kit to buy. If 20 lbs off the front-end (which will shift you from 52.3% to 52%) won't make a noticeable difference, then I won't spend the extra money for a carbon fiber frontend... of course, CF will still help you lose overall weight, but I think there are lots of other things that are more cost-effective for overall speed.


Quote:
I would not recommend replacing the factory crash beam in the front unless you have a purely race-only track car with a cage and whatnot. At that point, you can also remove the air conditioning, which is many pounds of aluminum, the pump, line, all the coolant, etc., and the stereo, and probably gut the dash, remove the airbag, and soforth.
Agreed, but I don't think anybody suggested that possibility...


Quote:
In reality, something tells me the people who are worrying about weight balance in this thread don't have any other more worthwhile upgrades yet. You should get a wheel and tire package, a tune, M3 suspension upgrades, coilovers, etc. way before you try to make up that few percent of weight distribution up. Those will return you a much faster car for far less money that some obtuse goal of having a particular weight balance number.
FYI, I already have lightweight wheels, upgraded suspension, JB4 with other supporting power mods, sway bars, etc. The only thing left over is M3 suspension upgrades, which is also on the list.


I think I might not have been clear with my initial intent. I didn't mean to say "a magical number will make my car go faster." I meant to say "while I'm in the process of doing other things to my car, how helpful would it be to also try to aim for that magical number?" For instance, I'm avoiding heavy subwoofers because of the increase in overall weight, but if the improvement in weight distribution might have a secondary benefit, it might be nice. And if 20 lbs of weight distribution was useful, I might spend the extra money to get a CF widebody kit and/or hood.

But anyway... an interesting discussion regardles.
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      11-07-2012, 03:42 AM   #18
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Quote:
Originally Posted by DRedman45 View Post
don't forget that a full tank of gas is ~85 lbs in the rear
Isn't the gas tank closer to the center of the car?
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      11-07-2012, 05:38 AM   #19
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What other widebody kits are there besides the ER?

Cf is cheaper than the fibreglass on the ER kit as you don't have to paint the cf for it to not look crap/have protection... Unless the colour of your car doesn't suit it.. Then bad luck man lol

Cf hood is literally the last go-fast mod to get. Literally. Cosmetic, however... It is definitely higher lol

Ed: i know the fuel fill line is over the rear wheel arch.
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      11-07-2012, 07:44 AM   #20
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Quote:
Originally Posted by flinchy View Post
What other widebody kits are there besides the ER?
Prior Design and CA.

Quote:
Cf is cheaper than the fibreglass on the ER kit as you don't have to paint the cf for it to not look crap/have protection... Unless the colour of your car doesn't suit it.. Then bad luck man lol
Well, my car is blue, so I don't think that would work. Also, I'm worried that CF will crack easily (fiberglass will too, but it's easier to repair).

Quote:
Cf hood is literally the last go-fast mod to get. Literally. Cosmetic, however... It is definitely higher lol
Yeah, if I do that, it'll be 1/3 for weight savings, 1/3 for weight distribution, and 1/3 for looks...

Quote:
Ed: i know the fuel fill line is over the rear wheel arch.
Really? So is the 52/48 weight distribution measured with a full tank or an empty tank?
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      11-07-2012, 11:29 AM   #21
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Quote:
Originally Posted by splitsecond View Post
Isn't the gas tank closer to the center of the car?
its right in front of the rear axle....so its behind the center of weight, so it would still move the distribution towards the rear....it also is adding weight more towards the center instead of at the poles to go with purple derple's point
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      11-07-2012, 06:05 PM   #22
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Quote:
Originally Posted by splitsecond View Post
Prior Design and CA.


Well, my car is blue, so I don't think that would work. Also, I'm worried that CF will crack easily (fiberglass will too, but it's easier to repair).


Yeah, if I do that, it'll be 1/3 for weight savings, 1/3 for weight distribution, and 1/3 for looks...


Really? So is the 52/48 weight distribution measured with a full tank or an empty tank?
yeah, would have to (unless you like shattering/scraping bumpers) get a thin rubber lip, would be cheap... CF is definitely tougher than FRP though... still yeah, a consideration. not much other choice you have in materials though lol
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