Quote:

Quote:

I'm spinning 4 grand at 70 mph



Correct. But verify that with a GPS and you'll see that you have to factor in the 10% speedo error (110/80-18) [heck even with a 100/90-18 tire] So if your speedo says 70mph subtract 7 and you'll be at 63mph. Which is darn close enough to 65mph. (Ever wonder why you roll by a leo when you are apparently speeding and don't get pulled over?)

Ever since Cinnamon Girl lost her speed output when rolling back in a freeze from the Arkanasa rally of 2008, I have always used a rule of thumb after observing Vera Lynn's taco er tacho vis-a-vis her speedo. The rule of thumb being thusly:

at 3000 rpm (with each 500rpm adding 10mph)
5th = 50mph
4th = 40mph
3rd = 30mph
2nd = 20mph
1st is different...
So at 3500rpm you are rolling about 60mph, apparently. You still need to subtract 10% or 6mph for a real speed of 54mph.

Totally useless information: Now for CG I have to start out subtracting 10mph from the speedo indicated speed then another 10% from that! CG reads 5mph while on her sidestand. Yet her odo is spot on. Go figure.



As one goes up on the rpm the rule of thumb will keep you well below what your speedo says you are rolling.

AT 70 mph per the gps, the rpms are closer to 4200...



Uh huh, yep moe. I suppose all that figurin' there probably does work out to be pretty close to accurate if somebody wanted to know how fast they were goin', alright!

But what if Roy who askin' this question here wasn't a Math Major in school???

(btw...just a little of the answer, or at least a factor to Roy's question would be the number of teeth on his counter shaft sprocket, wouldn't it gentlemen???)

Yep! Just like a good Single Malt Scotch, you might call me "an acquired taste" TOO.(among the many OTHER things you may care to call me, of course)