hooleyboy

IF someone could get in their C55 and drive at 60mph and tell me what RPM they are at that would be great. Then do it at 70mph.

Kompressor21

Ill do it for you right now.
I am going for lunch now I'll be back in an hour.

SilverBulletAMG

A 9:30 lunch? That's brunch.lol

rockjock

I only got up to 34 in the parking lot before I had to left foot pretty hard....

hooleyboy

60mhp at cursing speed 5th gear

SilverBulletAMG

Something tells me he was joking.

alboogiee

heading out to lunch right now... will post back in an hour.

alboogiee

@60 2125 RPM 5th gear
@70 2500 RPM 5th gear

jturkel

wow.....pictures too?!? way to go

MBH motorsports

you dont mess around. I thought my RPM's were messed up but all is fine now. I'm in the same area.

alboogiee

Hoping that gets me a 95% discount on the long tubes!!!

Kompressor21

2300rpms @60 mph
2700rpms @70 mph.
Wasnt a brunch lol
I am in florida it was 11.. lol
why is it that my rpms are higher?

alboogiee

I was using cruise control in manual mode to show 5th gear and driving on flat land.

SoCalC55

Likely you or alboogiee were on different slopes, that or there was a slight difference in the depression of the gas pedal.

Throw it in cruise in the flattest part of the highway

SilverBulletAMG

Doh! Forgot about the different time zone. And here I thought you were from the future...

Kompressor21

yea damn time zones.

e1000

slope wouldn't affect RPM for a given speed unless you drop down to 4th.

Most likely it's a slight difference in OD of the tires on the two cars.

SilverBulletAMG

That's what my money is on.

cannonball55

Mine were the exact same as alboogiee

alboogiee

Bridgestone Potenza RE760 Sports 225/40/18 Front 90% tread, 245/35/18 Rear 50% tread...to get more technical.

mkonei

you can get your tires revolutions from the manufacturer. kompressor21 : the overall diameter on your tire appears to be smaller than the oem setup. you can most likely set tire revs with STAR somehow, so that your speedo and tach are correct

AMS Performance

slope does affect rpm b/c of higher load necessary to get up a hill to maintain the same speed.

PC Valkyrie

Here is something a little more official about the speed and rpm's in various gears. Taken from the Sport Auto Supertest of the C55.

e1000

Unless your rear tires are slipping, since the C55 has a lockup torque converter, there is no slippage in the drivetrain. Whether going uphill or down, engine RPM will always be the same at a given speed at a specified gear.

c32AMG-DTM

Hmmm... you sure about that? Increased or decreased load requirements due to inclined or declined road angle variations would absolutely change the required throttle opening to maintain speed - but I can't see how it would change what engine RPM would be required to maintain X speed in Y gear. Care to elaborate?

This is my understanding as well. In kompressor21's case, his effective gearing has been changed by his aftermarket wheel/tire fitment. alboogiee appears to be using a stock C55 tire fitment, so his data is probably more useful to any C55 on 18's. hooley - what was going on with your ride to seem like the rpm's were off? Hopefully nothing too serious.