Weight savings cost/benefit benchmarks

[lucid]

Originally Posted by HighQ

Tires: depending on make and model they can vary by as much as 3 lbs.

Good point. PS2s are rather lightweight (24/25 lbs) though compared to the competition. In OEM sizes, the lightest tire I could find on tirerack are the PSCs (21/24 lbs), which is what I currently have on my summer wheels. About $100 more than the PS2s for all corners, but they will wear out faster of course. I put them on for track use in October. They worked out really well. I added the tirerack weight figures to the original post with the data.

[lucid]

Originally Posted by rldzhao

Hey Lucid,

What do you think about a (delta power-to-weight ratio)/(cost) parameter? This way, we can compare whether it is more cost effective to add power or to simply reduce weight.

That is a good point. If you'd like to provide the extra power/cost ratios for different mods I can add them here. Adding power will most likely be cheaper than reducing weight, but it won't make you go faster around the corners or improve feel, which is why I focused on weight.

[KonigsTiger]

Originally Posted by RandyB

Great info in this thread. I knew when I bought this car that I would not be willing to go to great lengths to reduce the weight, so with that in mind I began my weight savings crusade with the option boxes.

E92 instead of E90 - 20 lbs (wasn't considering E93)
CF roof instead of steel MR - 55lbs (11 lb roof + 44 lb MR)
6MT instead of M-DCT - ~44 lbs (?) don't remember the exact figure
Forged 19s instead of 18s - very minimal but rotational
No nav/idrive or packaged options - unknown

I did skip cloth seats for leather, and added EDC even though it added some weight. It also helped that I wanted the above items too, but would have been willing to add some weight if I didn't.

It would be nice to shave an additional 50-100 lbs and try to get closer the the E46 M3 weight. The right combo of wheels, brakes, exhaust and a light weight battery might get half of that but beyond those mods I doubt there is much else I would be willing to sacrifice.

BBK alone will get you 40 pounds lower! Exhaust, boot lid etc... depending on what you get may decrease another 18lbs (5 CF boot lid and say 13 exhaust).

[Adonislike]

Originally Posted by BMW-M-Mexico

BBK alone will get you 40 pounds lower! Exhaust, boot lid etc... depending on what you get may decrease another 18lbs (5 CF boot lid and say 13 exhaust).

BBK is 40 lbs. lighter Mexico???

[KonigsTiger]

Originally Posted by Adonislike

BBK is 40 lbs. lighter Mexico???

That is correct, 18.??? something kilograms (39.6 lbs). This has been weighed a couple of times. Referring to the Brembo BBK here, don´t know about other brands but presume they are similar.

[serven7]

Originally Posted by BMW-M-Mexico

That is correct, 18.??? something kilograms (39.6 lbs). This has been weighed a couple of times. Referring to the Brembo BBK here, don´t know about other brands but presume they are similar.

Yea, if I remember correct you save 18-19lbs a side for a total of 40 or so.

[tom @ eas]

Originally Posted by lucid

Good point. PS2s are rather lightweight (24/25 lbs) though compared to the competition. In OEM sizes, the lightest tire I could find on tirerack are the PSCs (21/24 lbs), which is what I currently have on my summer wheels. About $100 more than the PS2s for all corners, but they will wear out faster of course. I put them on for track use in October. They worked out really well. I added the tirerack weight figures to the original post with the data.

And farthest away from hub centerline, where most of the difference applies.

[KonigsTiger]

Originally Posted by tom @ eas

And farthest away from hub centerline, where most of the difference applies.

PCS? are which tire, Pirelli Cup Sport??

[tom @ eas]

Originally Posted by BMW-M-Mexico

PCS? are which tire, Pirelli Cup Sport??

Rule applies for any tire, no experience with Pirelli Cup Sport personally.

[southlight]

Originally Posted by BMW-M-Mexico

PCS? are which tire, Pirelli Cup Sport??

Michelin Pilot Sport Cup


Best regards, south

[KonigsTiger]

Originally Posted by southlight

Michelin Pilot Sport Cup


Best regards, south

Got it, thanks!

[Adonislike]

Originally Posted by BMW-M-Mexico

That is correct, 18.??? something kilograms (39.6 lbs). This has been weighed a couple of times. Referring to the Brembo BBK here, don´t know about other brands but presume they are similar.

Holly Sh*$!!!

Was not expecting that. Guess I'll add this to the ever growing list

[badfish]

Originally Posted by BMW-M-Mexico

BBK alone will get you 40 pounds lower! Exhaust, boot lid etc... depending on what you get may decrease another 18lbs (5 CF boot lid and say 13 exhaust).

What? If you look at the original post using OC Kid's numbers, the weight savings is reportedly 24.6 pounds. BUT, these numbers are incorrect as he used a bathroom scale (no disrespect OC Kid).

I re-weighed the OEM brakes. I then posted the numbers according to what OC Kid had weighed for the Brembos. I'm not sure we have accurate numbers for that either. But, for the numbers we have now, BBK will save you about 3.5 pounds TOTAL for Brembo and if you use Stoptech you will save about 2.3 pounds TOTAL. The numbers I have on the Stoptech are accurate down to the hundredths of a pound. See this post here.

[jml]

Originally Posted by badfish

What? If you look at the original post using OC Kid's numbers, the weight savings is reportedly 24.6 pounds. BUT, these numbers are incorrect as he used a bathroom scale (no disrespect OC Kid).

I re-weighed the OEM brakes. I then posted the numbers according to what OC Kid had weighed for the Brembos. I'm not sure we have accurate numbers for that either. But, for the numbers we have now, BBK will save you about 3.5 pounds TOTAL for Brembo and if you use Stoptech you will save about 2.3 pounds TOTAL. The numbers I have on the Stoptech are accurate down to the hundredths of a pound. See this post here.

Yeah, that's what I remember. It's not 40lbs. Now on some cars, the savings could be that much I am sure given that you replace a cast-iron rotor hub with aluminum.


BTW, I weighed my 09 E90 Sedan on corner balance scales at the track this weekend. Driverless, with a full tank and a 25lb baby seat it was 3722lbs. Cross weight was 53.3% and with me in the car that dropped 0.3%. I have all options except extended leather and a sunroof. That is more than I was hoping for, but it did well enough on the track with stock pads and tires that I am not too worried. It is easily faster and more rewarding to drive than a stock E46 around a 3 mile course.

[lucid]

Originally Posted by badfish

What? If you look at the original post using OC Kid's numbers, the weight savings is reportedly 24.6 pounds. BUT, these numbers are incorrect as he used a bathroom scale (no disrespect OC Kid).

I re-weighed the OEM brakes. I then posted the numbers according to what OC Kid had weighed for the Brembos. I'm not sure we have accurate numbers for that either. But, for the numbers we have now, BBK will save you about 3.5 pounds TOTAL for Brembo and if you use Stoptech you will save about 2.3 pounds TOTAL. The numbers I have on the Stoptech are accurate down to the hundredths of a pound. See this post here.

Thanks for reminding me this Badfish. I fixed the original post with your numbers for the stock and Stoptech weights. For the Stoptechs, I get 8.6 lbs savings for all 4 corners. I erased OC Kid's Brembo numbers since his scale seems to have been off. Now, I need accurate weight figures for the Brembos and cost figures/reference/link for your Stoptechs.

[badfish]

Originally Posted by lucid

Thanks for reminding me this Badfish. I fixed the original post with your numbers for the stock and Stoptech weights. For the Stoptechs, I get 8.6 lbs savings for all 4 corners. I erased OC Kid's Brembo numbers since his scale seems to have been off. Now, I need accurate weight figures for the Brembos and cost figures/reference/link for your Stoptechs.

Duh, my bad math. I took a chart that PencilGeek made and modified it but neglected to notice that it was not for all 4 corners. So my total for the OEM brakes is 135.8 and the Stoptech kit 131.19.

For reference, here is a link to **********s for the E92 M3 BBK. Price depends a lot on the options.

Thanks for keeping this list up to date.

[lucid]

Originally Posted by badfish

Duh, my bad math. I took a chart that PencilGeek made and modified it but neglected to notice that it was not for all 4 corners. So my total for the OEM brakes is 135.8 and the Stoptech kit 131.19.

You are right. I copied the wrong number. The total weight reduction for your Stoptechs is 4.6 lbs. Honestly, if it was significantly more, I'd have to wonder where the reduction is coming from. I don't see how one can make the rotor significantly lighter and keep the same thermal mass to keep temps in check.

Originally Posted by badfish

For reference, here is a link to **********s for the E92 M3 BBK. Price depends a lot on the options.

It priced out to $6050 with drilled rotors. Thanks.

[badfish]

Originally Posted by lucid

It priced out to $6050 with drilled rotors. Thanks.

I found an e-mail that had the exact pricing information. I have one other option on my rotors and that is the zinc coating which is $70 for front and $70 for rear. So here is a typical breakdown on retail pricing...

Front base $3295 + $100 Drilled + $70 Zinc = $3465
Rear base $2595 + $100 Drilled + $70 Zinc = $2765

[rzm3]

Hey Lucid, for Ericsson's CF exterior doors, it should be 33lb for EACH door. Thanks.

[gemini330zhp]

I would say sunroof delete, titanium exhaust, lightweight battery, lighter 18 inch wheels + tires. This would give you a decent weight loss if you do not want to rip your car apart...

[lucid]

Originally Posted by rldzhao

Hey Lucid, for Ericsson's CF exterior doors, it should be 33lb for EACH door. Thanks.

Yes, there is something off there. I am not sure how to interpret bulletproof's claim: "The set of doors weigh 7.37lbs compared to 41 lbs for the stock doors". Those figures are referring to both doors (set), but then the parts catalog seems to be quoting a single stock door panel at 18 kg. Do you have additional info to clarify this?

[gemini330zhp]

Originally Posted by jml

Yeah, that's what I remember. It's not 40lbs. Now on some cars, the savings could be that much I am sure given that you replace a cast-iron rotor hub with aluminum.


BTW, I weighed my 09 E90 Sedan on corner balance scales at the track this weekend. Driverless, with a full tank and a 25lb baby seat it was 3722lbs. Cross weight was 53.3% and with me in the car that dropped 0.3%. I have all options except extended leather and a sunroof. That is more than I was hoping for, but it did well enough on the track with stock pads and tires that I am not too worried. It is easily faster and more rewarding to drive than a stock E46 around a 3 mile course.

Thanks for the info for the e90....