Lower MPG After New Wheels
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2002 C32 amg
Lower MPG After New Wheels
I put the Renntech Monolite Rims measuring 19.25" across on my C32. Since I've done so, my MPG dropped big time. I used to see 18 city and 24 highway, now it's like 15 city and 21 highway. I know that there's more resistance because of the surface area of the tire, but I'm also thinking the speedometer is slightly off because of the bigger wheel. I don't think the smaller sidewall made up completely for the bigger rim. Do you have guys any thoughts?
Also, the Max PSI is 50, I'm at about 42.
Also, the Max PSI is 50, I'm at about 42.
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From: Western Canada
2013 C63 AMG P31, 2014 GMC Sierra (6.2)
I also run 19'' Renntech Monotlites. I'm using Toyo Proxies T1R (225Front/255Rear). I can't say I've noticed anything drastically different between my 18'' oem ones and the Renntechs when it comes to MPG 
The only thing I really noticed is that the car handles a lot better!
The only thing I really noticed is that the car handles a lot better!
Last edited by wawy; Dec 22, 2010 at 08:13 PM.
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From: Seattle, Warshington
2005 C55, 2006 Ram 2500 MegaCab diesel, sold 2001 Dodge 2500 Cummins, sold 87 190e-16v, sold 97 e420
What type of tires are you running. I noticed a similar drop in mine from switching to 275's in the rear. Most of the reason is heavier rims but also stickier tires cause more resistance.
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From: Dallas, Texas
W203 C55 and SAAB 9-3 2.0T
keep driving and your wheels are amazing but if you do hate them, Ill trade you for my lighter and smaller 18 OZ's. 
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2002 C32, 2012 S550
Kinda what he said ^^^
Thread Starter
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Joined: Feb 2010
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2002 C32 amg
Renntech Monolites on Pirelli's New (The exact same wheels): 1795+250 x 4 + tax and shipping and you're pushing 9 grand... it's definately worth me fixing this however I have to do it, thanks anyways. Just gotta figure out what the problem is.
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From: PA
S600, GL450, GLC 43
First of all the diameter of the rim will NOT impact MPG or acceleration, IF they are similar in weight. And I am guessing the Renntech's would NOT be heavy to say the least. The weight of the new tires could also be causing an impcat, IF they are heavier.
You mentioned that they are the same width, so this will not change anything either.
Now Tire diameter will impact the car greatly.
You mentioned that they are taller, which will hurt acceleration and MPG, because in affect they make the car have a taller gear ratio, aka 2:87 down to 2:64. Note that this change ratio was just a guess on my part as I do not know your new tire diameter.
And on a side note, the car should actually get better highway milage as the engine will be seeing lower rpms now.
You might want to also consider that your driving style changed as you are now having more fun with the lower profile, better handling rims and tires package.
Enjoy, and let God sort it out.
Merry Christmas to all
You mentioned that they are the same width, so this will not change anything either.
Now Tire diameter will impact the car greatly.
You mentioned that they are taller, which will hurt acceleration and MPG, because in affect they make the car have a taller gear ratio, aka 2:87 down to 2:64. Note that this change ratio was just a guess on my part as I do not know your new tire diameter.
And on a side note, the car should actually get better highway milage as the engine will be seeing lower rpms now.
You might want to also consider that your driving style changed as you are now having more fun with the lower profile, better handling rims and tires package.
Enjoy, and let God sort it out.
Merry Christmas to all
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From: Delran, NJ
05 C55
traditionally, a numerically lower ring and pinion will hurt acceleration, but increase fuel economy. Going to a wheel/tire combination with a larger overall diameter will have the same result, as both scenarios reduce engine rpm at highway speed. If the combined diameter of the new wheel/tire combo is less than the original, the engine will run faster at highway speed, and reduce your economy. The ECUs that we use at work are programmable for different tire diameters (tire manufacturers provide this information as RPM or revolutions per mile) to correct speedometer calibration. Mercedes probably has a similar setting that can be changed with Star DAS. My advice would be to find the RPM for your new tires, vs your old tires, and start from there.
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From: Seneca, SC
2006 C55
When I changed my wheels from 18's to 19's, which caused me to go to a taller tire as well, my speedo became off by about 5%. I used my handheld GPS to determine that when my speedo shows 70mph I'm really going about 74mph. In turn, I'm assuming my mpg dash reading is off about the same as it did, as you indicated, drop.
