trompazo

OK, please define significant??

If in internal volume of a tire is 50 litres (this is an overestimate, but as you will see it does not matter)

Air weighs 1.25 grams per litre when not pressurized (1 atm). If pressuriszed to 30psi as in a normal tire, the weight will double (2 atm) or triple if pressurized to 45psi (3 atm).

So assuming a tire holds 50 litres (big over estimate) and it is pressurized to 45 psi (too high) the air in the tire will weighh 187.6 grams.

This is 0.4 pounds. Given the overestimate in this calcutlation, it will likely be in the 0.2 pounds per tire. So, this may be significant to you, but it is not to me.

dsb

Realife, you should weigh them all. Even if your scale was "not calibrated," how far off could it be? Besides, the fact that the same scale would weigh both the stock and 030 wheels, we could get a better/more accurate comparison.

reallife

I hope they fit without any problems! I'm getting Pirelli 240 WinterSport tires installed on the Oe 16 spoke wheels on Friday and plan to swap them for the 5 spoke multi-piece AMG wheels this weekend. Actually, I'm not too worried about a misfit. Maybe I should be? They are both 18 inch wheels and side-by-side I can't tell that there is any diference in size. Not sure about offsets. Clearence should be okay. I'll post an update next week.

Btw, I agree with the above comments about the weight of compressed air in the tires. Maybe I'll turn this discussion over to my son who is an engineer to see what he says. All I have is a postal scale and it only weighs up to 25 pounds. It would be interesting to get accurate weights and determine the actual objective differences on performance. I have a feeling a lot of the concern about an extra few hundred grams of weight is blown out of proportion. Certainly, for street driving like I do it can not make any significant difference. I bought the 030 packagage b/c I thought it looked cool and I wanted a more unique car.

ClayJ

I'm ordering the 030 for the brakes, the suspension tweaks, the Vmax uprate, and the steering wheel. I am changing-out the CF trim, as I want wood and I'm doing the interior, pillars, headliner and roll-hoops in leather/alcantara.
(I'm also doing the Pkg on new SL55's - but there the difference is greater with the addition of a different front spoiler/clip and an LSD to boot)

I think that the OEM wheels are fine. I'm taking the 030 wheels because they come with the package. I am sure that they'll be just fine for street driving. If I decide to take the car to the track, or that I just don't like the 030 wheels, I will be looking for an aftermarket solution. Not sure at this point what those might be......

If you're really intrigued, you could always pick up a 25lb weight plate at a garage sale and check your scale for variance at that target weight.... I am willing to believe that the 030 wheels weigh a couple of pounds more than OEM because they are two-piece.

I don't anticipate that you'll have fitment problems with the 16-spokes - but I would like to know just for the halibut....

Thanks again.

trompazo

Nobody was arguing that a few hundred grams difference would make any significant affect. I was argueing that 6 pounds would make a big effect.

Lets consider that you went with a lightweight wheel like an OZ ultraleggera (this is what I'll proabbly run for autocross) that weighs in at 17.9 pounds. And you run a tire that is about 3 pounds lighter than stock. This is 15 pounds lighter per corner. So how much difference will that make??

Heres some data that was obtained many years ago on a Mini Cooper comparing 16" wheels with heavier 17" inchers. Each corner weighed 14 lbs less on the 16" wheels. The data was compiled by Garfield who is a multi national champion autocrosser:

Here's the results:

"All testing was done in the same location, 78 degrees ambient, same direction, 3 runs each

I made the comparison even more accurate by swapping my father's 17" S-Spoke wheels on to my car instead of driving two different cars.

17's
-----
0-60mph = 7.37, 6.74, 6.85 seconds
60-0mph = 127, 125, 133 feet

16's
-----
0-60mph = 6.57, 6.67, 6.52 seconds
60-0mph = 115, 111, 113 feet

Interestingly, but not surprising, it took more power to launch the 17/run-flats. I was launching the 16's around 3200rpm to get the perfect run while it took about 4000rpm to launch the 17's. It's obvious to me that the rotational mass was the factor to get moving quicker (this is also why the first run on the 17's was significantly slower, it bogged a little at just above 3000rpm).

I ran the 17's first to ensure that brake fade would not favor the 16's. Turns out the brakes cooled plenty in the tire change, although they were very hot when I changed after I was finished.

It is VERY easy for me to now see where the magazines could get higher 0-60 times. I've launched this car MANY times and it's well broken in, two factors that magazines do not have right now.

I was extremely happy to see the 111 foot braking number, that's quite impressive.

Again, take these numbers for what they are, a comparison via a G-Tech.

--------------------------------------------------------------------------------
- 2005 G Stock '05 MINI or it's back to a Miata in C Stock
- 2004 G Stock 2nd place Pro Solo, 9th Place Solo II
- 2003 STX 5th place Pro Solo, 6th Place Solo II
- 2002 H Stock Pro Solo National Champion "





So, in summary there was a about a 15-20 foot decrease on breaking and a 0.3 sec decrease in 0-60 times. On an SLK, I think that going to combo like I suggest would result in 0-60 times under 4 seconds due to a lighter wheel and grippier tire.

But 0-60 is not the biggest achievement with light weight wheels. It is all about handling and feel. The difference with a way lighter combo should be very significant.

jcanabal

Where can I find the OZ ultraleggera's??

JMC

trompazo

Tirerack.com


However, they only come in 18x8 for the SLK. I'm going to have the rears custom widened to 9.5" which costs about $150/wheel.

jcanabal

YOu have a PM

trompazo

Pm responded but your box is full.

jcanabal

thanks....open now

amgmark

Hi everyone.. I just bought SLK55 16 spoke wheels for my C32.. Someone pm'ed me and asked me to weight the wheels before I put the tires on. I have a pretty accurate scale down to .2 lbs.

Front wheel. 7.5x18 = 24.4 lbs
Rear wheel 8.5x18 = 25.6 lbs

Hope this was helpful.. Now its time to add some rubber!!

Pic of the wheels..

ClayJ

Excellent. Thank You.

reallife

I installed my new OE 16-spoke wheels with the Pirelli 240 Winter Sport tires today and I must say they perform very well. No problems with the fit. I didn't think there would be but the replacements came off the non-030 SLK 55 so I wasn't positive the new wheels would clear the oversized brakes. I took it out for an extended drive on wet roads at 44 degrees F. Once the mold release was worn off I put it to the test and it was just slightly off the performance of the original Pirelli P Zeros. I will be interested to see how it performs on colder roads when wet or even a bit icy. I will leave it in the garage when the roads are salted but otherwise I am looking forward to driving it on the cold dry roads we usually have here in northern Illinois until April.

Vader55

This a link

http://www.wheelweights.net/

imducati

I'm reviving this thread to see if anyone has weighed the wheel and tires on the SLK55 black series 8.5x19 235/35 and 9.5x19 245/35