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Discussion Starter #1
Quotes from Colin Chapman:

  • To add speed, add lightness.
  • Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere
  • Any car which holds together for more than a race is too heavy. (Tongue-in-cheek, as race cars must test and qualify before the start of any race.)
So I have been adding lightness to my SLK32.

Today: Replaced 43lb "normal" auto battery with 14 lbs Shuriken battery.
Savings=29 lbs (bonus that this weight is removed from bearing on the front axle)

Last week: 1. Removed 22lb resonator with straight pipe.
Savings= 19 lbs +/-

2. Replaced stock wheels and heavy tires with lighter wheels and tires. Old front tire/wheels: 51 lbs each, Old rear wheel/tires: 54 lbs each
New tire wheels (all 4 corners)= 40 lbs each.
Savings= 50 lbs (additionally this is a reduction in unsprung & rotating mass, and I got a traction boost from the better tires).

Total weight loss= approx 98 lbs


Future: Get my Ipod connected and take out the trunk mounted CD changer. Go to the gym more and add 15 to 20 lbs of lightness to the driver!! Thinking of other possibilities (like lighter brake rotors). But I plan on keeping heavy niceties like the top, the top mechanicals and hydraulics, the windows and the A/C. I wonder if my wife would take it the wrong way if I pulled out the passenger seat...
 

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Discussion Starter #6 (Edited)
Which 14 lbs Shuriken battery did you use? Can't find one that light.

Rich
I bought it through Needswing, link attached. I didn't weigh it myself, I just took their claimed weight. I did weigh my OEM battery on my bathroom scale to get 43 pounds for that, and that matches posted weights pretty well for a standard battery.

http://www.needswings.com/Shuriken-Light-Weight-Battery-Kit-bt20-kit.aspx

The tie down spacer supplied by needswing was the perfect thickness too, so the OEM tie down holds the new battery very snugly.

EDIT: being sold at amazon.com for even less $ (but no tie down spacer or SAE terminals) and confirms the 14 pounds in the shipping weight:
Amazon.com: Shuriken SK-BT20 20ah Battery: Automotive
 

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We used am 11 lb BRAILLE battery for our car and moved the battery to the trunk area. Just a word of advice, if you do not use the car often it will go dead in about 2 days. Small battery = small life.

To add more you can swap out the seats, we went Sparco, replace some of the rear suspension parts with adjustable aluminum ones (we make them, cheap plug), and get some lighter brakes.

You can probably clean a good 200 lbs out of the car without affecting too much. After that it gets pricey!
 

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Discussion Starter #8 (Edited)
We used am 11 lb BRAILLE battery for our car and moved the battery to the trunk area. Just a word of advice, if you do not use the car often it will go dead in about 2 days. Small battery = small life.

To add more you can swap out the seats, we went Sparco, replace some of the rear suspension parts with adjustable aluminum ones (we make them, cheap plug), and get some lighter brakes.

You can probably clean a good 200 lbs out of the car without affecting too much. After that it gets pricey!
Thanks Anthony! Believe me, I didn't take a hammer to my original battery lol. I drive my car fairly often, but for short distances 90% of the time and I was worried that could be a problem for battery life on a small battery.

What are some reasonably priced lighter brake options (lighter rotors?) I've seen brembo sets at $2000 to almost $4000 per AXLE! That is out of my budget. Would love to find lighter rotors that match up with my OEM AMG calipers.

I didnt realize your suspension parts are aluminum, I'll take a look at your site again.
 

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..... I drive my car fairly often, but for short distances 90% of the time and I was worried that could be a problem for battery life on a small battery. ......
Prolly connect to Battery Tender (trickle charger) every night before going to bed.
 

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Thanks Anthony! Believe me, I didn't take a hammer to my original battery lol. I drive my car fairly often, but for short distances 90% of the time and I was worried that could be a problem for battery life on a small battery.

What are some reasonably priced lighter brake options (lighter rotors?) I've seen brembo sets at $2000 to almost $4000 per AXLE! That is out of my budget. Would love to find lighter rotors that match up with my OEM AMG calipers.

I didnt realize your suspension parts are aluminum, I'll take a look at your site again.
Racing brakes sells some lighter options for rotors. You can wait for a used set of brakes to come up and snag those if you want lighter calipers too. We carried Ksport BBK kits and they had upwards of 8 piston 16" front kits for under 4k!
 

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Look into a carbon fiber hood. Not sure if they make one, but it would shave 40-60 lbs. You can also get thinner windshields. CA law is 5mm but yours is probably 7 or 8.

If you do get racing seats, put me in line to buy your old ones. :tu:
 

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Discussion Starter #13
Look into a carbon fiber hood. Not sure if they make one, but it would shave 40-60 lbs. You can also get thinner windshields. CA law is 5mm but yours is probably 7 or 8.

If you do get racing seats, put me in line to buy your old ones. :tu:
I have been google searching for R170 carbon fiber hoods on and off for the past month. Get lots of hits, but when you follow up on them, it isn't actually for a hood, it is some hood related part like a hood ornament or piston...or even links to body kits that don't include hoods (don't get me started on how stupid google searches can be!). Anyhow cant seem to find a supplier for R170 carbon fiber hoods.
The windshield idea is interesting, I'll have to research that for R170s.
Seats....I dunno if I want to lose the look and features of the OEM AMG seats. But if I do ever switch seats, you can have first dibs on my OEMs.

Still trying to find lighter rotors (2 piece) that are not a fortune. I found Racing Brake 2 piece rotors for the front only at just under $1000 for the pair. They save 7 lbs each over OEM rotors. Not unaffordable, but not exactly the bang for the buck I am hoping for.
 

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pull out the tirefit kit in the trunk. under it you will find a jack, compressor and slime for tire fix. no need for any of these as AAA will work better.
On mine the jack and tools were under the CD changer. I'll weight them for shats and giggles..


The jack, air pump, fix a flat, tools ≈ 10 lbs.

I didn't think there was a jack, didn't find it until I removed the CD changer.. lol
 

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The hood on these cars is quite light. You will need to get a CF one custom made and the weight savings would be closer to 10-15 lbs.

With the weight savings you get on rotational mass (half the suspension, rotors, calipers, wheels, etc.), the actual weight is multiplied roughly 4 times due to its location. So if you save 7lbs a rotor, 4 rotors saves you 28lbs, and that equates to being equal to removing 112 lbs from the car. The formula is much more in depth, but thats the rough idea. Lighter rotational mass will have the biggest impact on the performance of your car.
 

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Discussion Starter #17
The hood on these cars is quite light. You will need to get a CF one custom made and the weight savings would be closer to 10-15 lbs.

With the weight savings you get on rotational mass (half the suspension, rotors, calipers, wheels, etc.), the actual weight is multiplied roughly 4 times due to its location. So if you save 7lbs a rotor, 4 rotors saves you 28lbs, and that equates to being equal to removing 112 lbs from the car. The formula is much more in depth, but thats the rough idea. Lighter rotational mass will have the biggest impact on the performance of your car.
I am an engineer, and I totally agree with you on weight savings on rotating mass being more important per pound than static weight removed from the car elsewhere. And I could really feel the difference in acceleration dropping 11 to 14 pounds per corner from my wheel/tire change. I am just hung up on how expensive 2 piece rotors are.

PS. Anyone following this thread and thinking about their own cars, also watch the diameter of the wheel/tire combo you have or are thinking of getting. Another aspect of the energy used to spin a wheel is that you have more angular momentum (and therefore need more energy) to spin weight as it moves further out from the axis of rotation. Consider a figure skater doing "spins" at the olympics. Assume for the period of time of the spin, that no energy is lost to friction, you can picture how much faster the skater spins when his/her arms are pulled in tight to the body and how much the spin slows when the arms go back out away from the body. The same amount of energy causes a much higher spin speed when the skaters mass is as close as possible to the axis of rotation.

19 inch rims have much of their mass further out from the axis of rotation (and usually weigh more) than 17 inch rims. So more energy is needed to spin 19 inch wheels than 17 inch wheel, even if the 19 inchers are not heavier.
 

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Santamonica SLK32 said:
So I have been adding lightness to my SLK32.

I've just fitted one of those E-bay CLK style grills & noticed the label on the packaging showed it as weighing only 0.5 kg ,so I weighed the original grill (in the same packaging) & the scales showed it at just under 1.7 kg ,so you could drop another couple of pounds there :tu:
 

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Remove the roof and have a full time convertible.:biglaugh:
Hey, you live in California...It never rains in California!!! right?
 
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