Stereolab42

This is gonna be an odd question but bear with me...

Getting aftermarket wheels on my new 2016 E63 so I decided to ditch the spare to lose weight... after removing the thing I then went to put the trunk floor back on. However, while doing so I noticed that with the spare there, the trunk floor seems to use part of the hardware on top of the spare as a "load-bearing" support, in the middle. Without that, it seems like 80% of the trunk floor is just free-floating over air. And it's not that thick either. I fear a couple small heavy suitcases could cause it to crack. So now I'm inclined to leave the spare in there for the sole purpose of not breaking my trunk floor.

Am I over-thinking things? Any obvious way to "brace" the trunk floor in the absence of the spare?

Brucealeg

I also considered removing the spare to shave weight, curious to see how you would resolve this. Any idea how much the spare weights?

Stereolab42

Spare+hardware is quite weighty, probably 50+ pounds. Definitely worth the weight savings if you don't need it. I'm handy with tools so I'm sure I can rig up some sort of support, either horizontal or vertical from the center. But it does seem surprising to find such a flimsy trunk floor on a $100k car.

Brucealeg

Most of my recent luxury cars have used a like system.

Stereolab42

Figured out what I'm going to do... will buy a bunch of lightweight redwood or balsa planks. Cut a hole in the middle of one, to match the dimple on the bottom of the empty spare tire well. Will stack them to about 11 inches, which is the height needed, and screw them together. Then put the stack over the dimple, and secure to the bottom on both sides with strong velcro. Trunk cover on top. Should make for a very solid base and weigh almost nothing.

Astolfo

Thinking out loud.. would 50 pounds make a noticeable difference in your every day drive? Wood in CA is usually not a good idea unless treated.. open a door get a termite and then you have a serious issue.


Also do you want to ride with a flat tire or wait for a couple of hours to get towed?


If just for the track then this is a different story..

PeterUbers

Just consider that whatever you put in the trunk will bake in the summer heat and possibly emit some odors into the passenger compartment. Perhaps consider something synthetic?

Stereolab42

Wood is no problem... I've build several car audio systems full of wood, never had issues with odor/termites. But it is kind of an ugly solution not really fitting with the image of a German luxury sedan. Now I suppose I could just drop into Home Depot and get some of those thick metal bars, cut them to size, and somehow attach them to the bottom of the trunk mat. Unless I'm dropping a 300-pound cannonball in the trunk this should be enough bracing...

2012 merc amg

Or just leave the floor panel off and put a rubber mat down where the spare was, you will have a deeper more spacious trunk this way.

Stereolab42

With all my vehicles I always go for larger aftermarket wheels so the spare is never an option. And why worry when AAA will flatbed me to home/tire shop whenever and wherever for free? Done it many times.

Regarding the weight... no, 50-100 pds less is not likely to be noticeable on the butt dyno. But it will be good for a handful of (effective) HP. It's also the principle of the thing... I cannot stand to drive around with useless weight in my vehicles.

PeterUbers

Or get this area carpeted by an interior shop or custom audio shop --- they could even setup a compartment system in there

jylee

He will never find termite in the trunk, Unless he lived in the rain Forrest with a leak in the trunk. I can understand to remove dead weight when you are at the track, but I would never remove the spare tire. People keep more junk in the trunk than a few lb of a very useful tool.

if you lived in the bay area, isn't the extra axle, transfer case, and drive shaft are useless weight in your vehicle?

PeterUbers

Sadly they don't sell anything but an awd e63 in the USA

Stereolab42

I thought AWD was necessary to put down all the power from the S engines, regardless of where you're located?

omega_jeff

Good guess! Here's my spare tire+hardware out of my 2010:




I prefer to have the spare tire in the car. I've had a few flats (one in my old E350), and in 10-15 minutes, I've got the spare on the auto and I continue on my mission. Not having a spare?....It ain't worth it to wait for a tow, wait for the shop to change it...blah blah blah. And from a hp/weight ratio, that 47.3 pounds equates to 0.14% increase. If my math is right, that's like having 518.7 horsepower instead of 518.

HP/Weight: 518/4300 = 12.04%
518/(4300-47.3) = 12.18%

HP Increase: 518 * (1 + (.1218 - .1204)) = 518.7

And I don't get why you can't use the spare if you have larger aftermarket wheels. ???

Stereolab42

Your math is off, I think. Let's go by this page:

http://www.tuneruniversity.com/blog/...-weight-ratio/

And these specs:

http://www.caranddriver.com/mercedes...s-4matic/specs

Stock lbs/hp: 4431/577 = 7.68
Spareless lbs/hp: 4383/577 = 7.60

New "effective" hp: 4431/7.60 = 583

583-577 = 6 HP gain

Not too shabby. I have other mods planned to save at least another 50-100 pounds as well.

Stereolab42

From what I read, running a different size spare can possibly confuse ABS, the transmission, and other things, depending on the car. But I am no tire expert. I would be happy to throw the spare back in for long road trips if I thought it would be safe. Does anyone know more on this subject?

PeterUbers

Not in Europe

Zavato

styrofoam blocks to prop up the spare well

Stereolab42

Best idea I've heard yet... looks like I can get everything I need from Amazon... a 10" cube plus a few smaller pieces should do it.

Clk63blkseries

Even if it was 6hp you couldn't notice it nor would your times.

otakki

Gee, my post here on using styrofoam had disappeared. Anyway, what's the weight capacity of the trunk? Was it around 400 lbs or something?

gaspam

correct, but if he keeps at the weight reduction i would start to make a difference...

with no spare, lighter tires(conti dw 12 lbs lighter than contisportcontact 5), lighter rims (probably save 24lbs over stock) and rotors (21.8 in front saving and 16.2 in rear by going girodisc) and lightwieght battery (braile saves about 40 lbs) he could start to be close to -165 lbs which would start to make a difference, especially with about 75 of those lbs being rotational weight savings

the 165 lbs would be like a 22.3 hp gain but with almost half of rotational weight it would feel like more

with all that being said, i usually start looking at weight reduction (unless its free like the spare) only after i've exhausted the usually engine power increases as the weight savings I listed above would cost about $5000 and a tune alone would be way better bang for the buck

Stereolab42

Exactly my thinking... I have no desire to spend a fortune for small weight gains, but if it can be done for a reasonable amount or as a side benefit of something else, why not? I'm also getting a tune but have no desire to modify the engine beyond that for warranty concerns. (I'm not rich enough to laugh off a $40k engine replacement...)

The most I'm spending for weight alone is a Voltphreaks VPH900 coming next week, 40+ pds gone right there. Meisterschaft GTC exhaust on order for sound/performance, should be good for at least 30 pds also I hope? New wheels and tires coming next week for looks, would be a nice bonus if they are indeed lighter. Have not looked into aftermarket rotors, interesting to hear that so much can be saved there... happy with my stock brakes otherwise, but this is a topic I will research more.

gaspam

wow that Voltphreaks VPH900 is light at 7lbs, but $1,100 ouch.... what made you choose that over a braile (15-20lbs) for about $200

exhaust will def save you some weight.... my catless downpipe were significantly lighter than the stock piping

for the rotors you can check them out here if you decide to go that route

https://www.amsperformance.com/cart/...rs-a1-022.html