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As an FYI, I thought the coupe was geared shorter overall than the sedan, but apparently not. An actual C63 coupe owner replied his car did 72-74 mph at exactly 2K rpm in 7th, and that's what the C63 sedan I rented recently did, so apparently no difference there. Read the tranny was the same, but supposedly the differential had a shorter final drive ratio. Doesn't seem to be the case. Hope this helps a little.
As an FYI, I thought the coupe was geared shorter overall than the sedan, but apparently not. An actual C63 coupe owner replied his car did 72-74 mph at exactly 2K rpm in 7th, and that's what the C63 sedan I rented recently did, so apparently no difference there. Read the tranny was the same, but supposedly the differential had a shorter final drive ratio. Doesn't seem to be the case. Hope this helps a little.
C63S Coupe Gear Ratios:
C63S Sedan Gear Ratios:
Last edited by AlexZTuned; 10-31-2017 at 10:27 PM.
The c63 sedan is not a 9 speed so I'm guessing that info is wrong.
I updated the image, MB incorrectly lists an eighth and ninth gear on their specs page, but gears 1-7 and the final drive are correct. The only difference between the Coupe and Sedan is the final drive which shortens the gearing (3rd gear is noticeable shorter in the Coupe than the Sedan).
If that's the case, then the rear tire circumference on the coupe has to be larger, to precisely offset the difference in final gear ratio, because I don't believe the coupe owner who sent me the info was lying. Both coupe and sedan seem to have exactly the same overall gearing, just arrive at it differently. Another pair of owners could put that to rest by posting here their exact speed at exactly 2K rpm in 7th gear. At least to me, that's what matters. Tranny is geared exactly the same, and if the speed in top gear is exactly the same, then the rest of the gears are the same too. As easy as that.
If that's the case, then the rear tire circumference on the coupe has to be larger, to precisely offset the difference in final gear ratio, because I don't believe the coupe owner who sent me the info was lying. Both coupe and sedan seem to have exactly the same overall gearing, just arrive at it differently. Another pair of owners could put that to rest by posting here their exact speed at exactly 2K rpm in 7th gear. At least to me, that's what matters. Tranny is geared exactly the same, and if the speed in top gear is exactly the same, then the rest of the gears are the same too. As easy as that.
Tire diameter on the Coupe with 285/30/20 is 26.7” and on the Sedan with 265/35/19 it’s 26.3”. So tire diameter is only 0.4” shorter on the Sedan.
They both have the same exact gear ratios, just a shorter final drive on the Coupe (3.06 vs 2.82).
So simply plug that into a gear calculator to get the speed/RPM:
Sedan with 26.3” tire height at 2000 RPM in 7th gear (0.73) with 2.82 final drive: 76.05 MPH
Coupe with 26.7” tire height at 2000 RPM in 7th gear (0.73) with 3.06 final drive: 71.15 MPH
Tire diameter on the Coupe with 285/30/20 is 26.7” and on the Sedan with 265/35/19 it’s 26.3”. So tire diameter is only 0.4” shorter on the Sedan.
They both have the same exact gear ratios, just a shorter final drive on the Coupe (3.06 vs 2.82).
So simply plug that into a gear calculator to get the speed/RPM:
Sedan with 26.3” tire height at 2000 RPM in 7th gear (0.73) with 2.82 final drive: 76.05 MPH
Coupe with 26.7” tire height at 2000 RPM in 7th gear (0.73) with 3.06 final drive: 71.15 MPH
Question: since the C63S coupe comes stock with 19" wheels in the rear (but the same 285/30, resulting in a tire diameter of 25.7"), can the dealer readjust the speedometer if one wanted to get 20" aftermarket wheels? Or are we stuck with the factory calibration?
Question: since the C63S coupe comes stock with 19" wheels in the rear (but the same 285/30, resulting in a tire diameter of 25.7"), can the dealer readjust the speedometer if one wanted to get 20" aftermarket wheels? Or are we stuck with the factory calibration?
I was told by the dealer we are stuck when I asked. I wanted to put on one size up on my sedan(255/275) which I did and wanted to have the speedo calibrated to the new tire size.
Tire diameter on the Coupe with 285/30/20 is 26.7” and on the Sedan with 265/35/19 it’s 26.3”. So tire diameter is only 0.4” shorter on the Sedan.
Didn't have the tire size to do the math myself, but still knew it was small enough to be offset by circumference difference. In this case the math shows 5 mph difference (could be off, since tires are not identically sized), but odometer figures don't seem to match that. I'm suspecting MB could have left the speedometer programming the same, but doubt they'd do that on the coupe, since manufacturers always go a bit optimistic to avoid lawsuits. At any rate, it's not a big deal, since they're close enough. Thanks. And yes, any factory tire combos offered are very close in circumference, therefore no different programming needed for the odometer. One size up in tires probably evens out the typical 2 mph speedometer error built-in.
Didn't have the tire size to do the math myself, but still knew it was small enough to be offset by circumference difference. In this case the math shows 5 mph difference (could be off, since tires are not identically sized), but odometer figures don't seem to match that. I'm suspecting MB could have left the speedometer programming the same, but doubt they'd do that on the coupe, since manufacturers always go a bit optimistic to avoid lawsuits. At any rate, it's not a big deal, since they're close enough. Thanks. And yes, any factory tire combos offered are very close in circumference, therefore no different programming needed for the odometer. One size up in tires probably evens out the typical 2 mph speedometer error built-in.
I think that Alex numbers are right on as I have a sedan with 275 rears (I sized one up)that are .3 in larger diameter (8 revs per mile lower) that read between74.5 and 75 MPH at 2000 RPM and would read approximately .85 MPH lower than actual at 75.
That would be 75.35 to 75.85 and I could be a little off on my speed -not much. Alex had 76.05
The higher final drive ratio in the Coupe means it gets more torque to the wheels, resulting in a faster 0-100 time than the 40kg lighter sedan (3.9s vs 4.0s). You do lose a bit of top speed as you guys have noted with your 2000rpm tests.
In NZ we have radar speed signs that show your speed in areas where they want you to slow down (around schools etc). My speedo reads 50kmh when these signs show 46kmh. I get the same result when I use the phone GPS and compare it to the car. So I would think you are safe to go up a couple of tyre sizes, which might actually help to make your speedo more accurate!
10-30-2017, 07:15 PM
What is the Gear Reduction in the 2018 C63s Coupe
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