I'm curious now just how far out my speedometer is so if anyone can tell me how high they're reving at 100kms/hr or 62mpg, that would be awesome.

some aftermarket navis tell you your speed, see if u can borrow one to check it out. mine is always a few mph off..

That's what you need. Even with the factory-spec wheel and tyre combinations the speedo reads fast by up to anything like five percent.

I'll just wait for my radar detector to go off and it'll tell me how fast I'm going. All I have to do now is find a cop pointing a lazer gun at me. lol

Your speedo reads about 10% slower than your actual speed

Speaking of speed, hypothetically speaking of course..., would my X5 hit the rev limiter in 5th gear for top speed?

I have the same truck as you, we're electronically limited to 155mph unless you have the DINAN software which removes the electronic limit. After that yes it is when you reach the "natural limit" of rev limit in 5th. :D

any ideas on how fast that is?

The 4.8iS at 7k rpm in 6th would be going about 213.13 mph

For any car, let:

E = Engine RPM
T = transmission gear ratio
F = Final drive ratio
C = Tire circumference (in inches)

( ( ( E x T ) / F ) C )
------------------------ = MPH
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