Weight savings cost/benefit benchmarks

lucid:

This just in... I have some numbers for you.

FWIW my OEM bootlid came in slightly higher than the figure you have quoted in the OP. Without carpeting or hardware the trunklid weighed in at 26.0 lbs. I understand there are variances with different scales, etc. but thought I would pass on the info. The OEM brake weights that were weighed on the same scale seem to correlate with your figures, however.

I weighed the OEMs (Caliper, Rotor, and Dust Shield) and here are the results...

Fronts: 41.8 lbs.

Rears: 34.9 lbs.

...now onto the BBK and VRS double-sided trunk.

I will get you the numbers asap. Stay tuned.

OC kid wrote

lucid:

This just in... I have some numbers for you.

FWIW my OEM bootlid came in slightly higher than the figure you have quoted in the OP. Without carpeting or hardware the trunklid weighed in at 26.0 lbs. I understand there are variances with different scales, etc. but thought I would pass on the info. The OEM brake weights that were weighed on the same scale seem to correlate with your figures, however.

I weighed the OEMs (Caliper, Rotor, and Dust Shield) and here are the results...

Fronts: 41.8 lbs.

Rears: 34.9 lbs.

...now onto the BBK and VRS double-sided trunk.

I will get you the numbers asap. Stay tuned.

Apples to apples would be caliper (with pads included I'm assuming) + rotor. Could placing the dust shield in the weight of the OEM set up and not in the afermarket system be slightly biasing the aftermarket? Sure it is a potential weight savings that should be documented but again potentially not totally apples to apples.

OC kid wrote

lucid:

This just in... I have some numbers for you.

FWIW my OEM bootlid came in slightly higher than the figure you have quoted in the OP. Without carpeting or hardware the trunklid weighed in at 26.0 lbs. I understand there are variances with different scales, etc. but thought I would pass on the info. The OEM brake weights that were weighed on the same scale seem to correlate with your figures, however.

I weighed the OEMs (Caliper, Rotor, and Dust Shield) and here are the results...

Fronts: 41.8 lbs.

Rears: 34.9 lbs.

...now onto the BBK and VRS double-sided trunk.

I will get you the numbers asap. Stay tuned.

Thanks OC!

Does your trunk lid measurement include the mechanism or the lights? If it does, that might explain the difference. The catolog number does not include anything else other than the sheet metal.

Also, did you by any chance get seperate measurements on the disc vs. caliper assemblies?

swamp2 wrote

Apples to apples would be caliper (with pads included I'm assuming) + rotor. Could placing the dust shield in the weight of the OEM set up and not in the afermarket system be slightly biasing the aftermarket? Sure it is a potential weight savings that should be documented but again potentially not totally apples to apples.

I could not get a value for the dust shields, they were too light...similar to an empty soda can...we're talking ounces. Caliper weights do include pads, as you mentioned.

lucid wrote

Thanks OC!

Does your trunk lid measurement include the mechanism or the lights? If it does, that might explain the difference. The catolog number does not include anything else other than the sheet metal.

Also, did you by any chance get seperate measurements on the disc vs. caliper assemblies?

lucid: Thanks for waiting...I've been real busy with work.

My trunk weights did not include the lights/carpeting, trunk release or hardware. They were already transfered to the VRS lid. My measurements are as approximate as the tolerances in the $50 digital bathroom scale. (...sorry swamp.)

VRS double-sided cf bootlid w/o hardware, carpeting, etc.---- 14.9 lbs.
OEM trunklid w/o hardware, carpeting, etc. 26.0 lbs.

Brembo 380 x 34 front rotor 24.8 lbs.
OEM front rotor 26.6 lbs.

Brembo 380 x 28 rear rotor 17.0 lbs.
OEM rear rotor 22.8 lbs.

Brembo 6 pot front caliper 13.0 lbs.
OEM front caliper 15.2 lbs.

Brembo 4 pot rear caliper 9.6 lbs.
OEM rear caliper 12.1 lbs.

Thanks OC!

Looks like -24.6 lbs for a Brembo BBK swap. Not bad at all. Except the price for that kind of decrease is astronomical.

-35.7 lbs for the trunk and BBK. Add some lighter wheels to that and you could be at ~55lbs decrease. Not too shabby.
Add a Ti exhaust and you could be at ~90lbs. Looks like 100lbs is fairly attainable with "normal" mods.
If you want to get crazy like Lucid, you could pull your trunk mat/mobility kit/battery cover out too! You would be at ~103lbs.
Could do a battery swap if you wanted. I would add the hood to the figure once a cheaper option comes available.

OC kid wrote

I could not get a value for the dust shields, they were too light...similar to an empty soda can...we're talking ounces. Caliper weights do include pads, as you mentioned.



lucid: Thanks for waiting...I've been real busy with work.

My trunk weights did not include the lights/carpeting, trunk release or hardware. They were already transfered to the VRS lid. My measurements are as approximate as the tolerances in the $50 digital bathroom scale. (...sorry swamp.)

VRS double-sided cf bootlid w/o hardware, carpeting, etc.---- 14.9 lbs.
OEM trunklid w/o hardware, carpeting, etc. 26.0 lbs.

Brembo 380 x 34 front rotor 24.8 lbs.
OEM front rotor 26.6 lbs.

Brembo 380 x 28 rear rotor 17.0 lbs.
OEM rear rotor 22.8 lbs.

Brembo 6 pot front caliper 13.0 lbs.
OEM front caliper 15.2 lbs.

Brembo 4 pot rear caliper 9.6 lbs.
OEM rear caliper 12.1 lbs.

Wow that's really adding up. Good job OC!

OC kid wrote

VRS double-sided cf bootlid w/o hardware, carpeting, etc.---- 14.9 lbs.
OEM trunklid w/o hardware, carpeting, etc. 26.0 lbs.

Brembo 380 x 34 front rotor 24.8 lbs.
OEM front rotor 26.6 lbs.

Brembo 380 x 28 rear rotor 17.0 lbs.
OEM rear rotor 22.8 lbs.

Brembo 6 pot front caliper 13.0 lbs.
OEM front caliper 15.2 lbs.

Brembo 4 pot rear caliper 9.6 lbs.
OEM rear caliper 12.1 lbs.

Thanks OC! I updated the initial post with your info.

Epacy wrote

Looks like -24.6 lbs for a Brembo BBK swap. Not bad at all. Except the price for that kind of decrease is astronomical.

-35.7 lbs for the trunk and BBK. Add some lighter wheels to that and you could be at ~55lbs decrease. Not too shabby.
Add a Ti exhaust and you could be at ~90lbs. Looks like 100lbs is fairly attainable with "normal" mods.
If you want to get crazy like Lucid, you could pull your trunk mat/mobility kit/battery cover out too! You would be at ~103lbs.

That's right. About 103lbs of savings with bolt on stuff without taking away from the comfort according to the info gathered on this thread, which comes at a cost of $15184 excluding install. (plus braking performance improvement and minor power gain). You can probably recover about ~$4k of that by selling the mods before you sell the car, so the ultimate cost is probably more like ~$11k. Folks wondering about why the CSL was selling for so much?

Lucid,

Excellent thread. Guys keep up the hard work. We appreciate your sharing it with others.

$147/lb for the easy stuff. Clearly even without going crazy, it will cost alot to shed much more weight.

lucid wrote

Thanks OC! I updated the initial post with your info.

lucid:

Thanks for updating the OP. ...just one small correction, both OEM and BBK calipers were weighed with the pads still clipped on.

The 100 lb target is easily achievable and results in improved performance you really can feel. (I'm being serious here now swamp... admittedly the decision to ante up for this weight loss program becomes easier to make with partial sponsorships.

I don't think I could do it with this car, but swapping out the front seats would net a pretty hefty weight savings, just from the center of the car...isn't there like three motors in these seats? Are there any 'official' weights listed for the front seats? It would be interesting to see the difference vs. a set of Recaro's or whatever.

Thanks again for making this thread.

IIRC: The stock seats are 70-80 lbs each. Compared to ~20 for a lightweight seat. The seats in my other track toy are ~15lbs

Now, having said that there is no way I am swaping the seats. The center of the car is the least harmful place to have sprung weight. You will be giving up a ton of comfort for very little gain.

100lbs of sprund weight is going to make about a 2% change in accelration and less in cornering.

Lightweight wheels, brakes will help the most since they are unsprung weight and also mostly rotating weight.

I once went through this exercise and when confronted with the cost asociated with lighting the E46 I just spent a little more and got a 1600lbs lighter 2nd car.

I have tried running the e46 without the rear seat and the diff/fuel pump noises drove me nuts. Not to mention having to explain what was wrong with the car when I picked up the date.

Remember having to live with the modification and loss of confort, convience, or utility is a cost just as much as $$$


[edit] My race wheels & tires are 47lbs for a 18x9.5" rim with a 275/35-18 tire. about 4lbs less than stock compared to the same size rears.

Great thread. The conclusion is simple it really costs a lot (small fortune) to save even the weight of a passenger (~150 lb) which is about the threshold of what you can feel in a car at 3700lb and 400 hp.

Note: A slightly OT but interesting point: M-DCT is good for about the equivalent of 20hp at just about 9lb/hp and $2700 (not including tax) that works out to be $15/lb. By far one of the best bangs for the buck. Of course this is for acceleration (linear) concerns only, the extra weight of M-DCT does not help handling but is very central and likely not discernable in the real world.

+1 on enigmas point - always the pragmatist even though a track fiend - don't mod to the point of making your car no good for a DD (unless you don't DD it).

My conclusion after going through the exercise is that 100lbs is not worth $15k. I have removed about ~20lbs of stuff from the trunk, and that's as far as I will go with the exception of getting some light weight wheels. I am eying the MORR alloys that Carlos is developing for the E9X M3. He is doing his first production run. Let's see how they turn out. As for the Brembos, I am not interested in them as they cost too much and free BMW maintaince on brakes for 4 years is not something I want to give up. I was happy with the braking performance on the track to begin with. Track compound pads would help, but that's minor compared to replacing the whole setup. If one is racing the car, fade could be an issue, but I am not going to race it or anything, so not worth it for me. If I keep the car for more than 4 years, I might think about a Brembo kit then when the stock rotors, which should already have been replaced under the service agreement by that point, wear out. Finally, I am considering getting a '98 E36 M3 and gutting it for the track. They can be had for ~$13k with 70k miles. '02 E46 M3s are more like $23k, but by next summer they will dip below $20k.

Don't know if this has been mentioned but don't forget to drain your windshield washer reservoir (For track use). I don't know the size of the e92 m3 tank but usually you can drop about 10-15 lbs there.

Namir wrote

Don't know if this has been mentioned but don't forget to drain your windshield washer reservoir (For track use). I don't know the size of the e92 m3 tank but usually you can drop about 10-15 lbs there.

How much is in there? That sucker must be huge.

Dascamel wrote

How much is in there? That sucker must be huge.

My old A4 had about two gallons up in the left front corner behind the headlamp. Emptying the tank is excellent advice.

Dascamel wrote

How much is in there? That sucker must be huge.

The owner's manual says 4.5 liters.
A liter is 1Kg which is 2.2 lbs so that's about 10 lbs

so, what are some good/simple mods one can do to lighten the car w/o voiding any warrantee?

the E46 M3 is about 3400 lbs, while the E90 is 3720lbs. so that is 320 lbs to catch...

mikey19 wrote

so, what are some good/simple mods one can do to lighten the car w/o voiding any warrantee?

the E46 M3 is about 3400 lbs, while the E90 is 3720lbs. so that is 320 lbs to catch...

Check the original post of this thread. I documented most of the obvious weight reduction mods there.

This is a great thread, wish we could get actual weights for the stock seats though.

lucid wrote

Yeah, the guy's a goat. He weighs 130 lbs. In top form, I weighed 148 lbs, but he is 2 inches shorter. D:

Hey Lucid, what is your "form" right now? With the food savings program you might even gain money...that you can then spend on the parts!

Also, any risk of altering the balance of the car with the various mods??

Great thread though!