on the freeway, at about 65, my 89 gs5 is doing 6000 rpms. does this sound about right?
I run on the interstate at an indicated 75-80 at around 5-6K for reference...though my tach bounces while at highway speed (something else I was going to ask about on the board).
that's about right....in 6th gear the tach reads about one number less than the speed-o [eg: 60mph=5k rpm's] 5th gear is dead even [eg: 50mph will be 5k rpm's]
You go to remember that the redline is 11k rpm's...most motors at highway speeds are doing 2/3 of their limit for fuel efficency.
Your speedos read km/h as well, don't they? In 6th speed in km/h is pretty much rpm x 2 / 100. So 120 km/h (roughly 75 mph) is at 6000 rpm
Yup, Your tire wear will also affect your rpm/speed ratio (as well as sprocket choices)
but with my stock '96 I was running at a little under 6k for 70mph when I first rode it on new tires, Then 1.5yrs later and 17000 miles, my tach was at about 6,500 at 70mph (my tire was worn down...Alot), anyway I got a new tire (same one as before) and my rpms dropped back down just below 6k for 70mph.
With the stock Exedra tires, my speedo and tach needles tracked each other exactly in 5th gear. (40 mph = 4000 rpm, 50 mph = 5000 rpm, 60 mph = 6000 rpm, etc.)
When the rear tire wore out I mounted a taller Cheng Shin 130/90-17 Hi-Max tire and all of a sudden the needles tracked each other in 4th gear. (In 5th gear I would go 60 mph at 5000 rpm, in 6th gear I would go 60 mph at around 4000 rpm.)
My next rear tire was a Bridgestone BT45 in the stock size (130/70-10) and it registered somewhere in the middle.
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General Principles
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The speedometer measures the rotations of your front tire. It will read a little higher (at a given actual ground speed) as the tire wears out.
The tachometer measures the rotations of your engine. At a given speedometer reading, the tachometer reading is governed by 3 aspects of your drive train:
1) The number of teeth on your front sprocket
(fewer teeth = higher rpms),
2) The number of teeth on your rear sprocket
(fewer teeth = lower rpms) and
3) The circumference of your rear tire
(smaller tire = higher rpms).[/list:u]
Kerry,nice breakdown. Good stuff to know.
I am usually at about 5500 rpm s on the highway at about an indicated 75 mph, yeah i'm a slowpoke but there's lots of traffic around here. :cheers: