[ST] Was effect on tach? Now front sprocket

["RedDawg" <RedDawgST@xxxxxxxxxxxxx>]

Here is one more perspective.
I changed my front from an 18T to a 17T on my 99 ST. Last year on the
way back from the Western Rallye, Blake Sobiloff and I had an
opportunity (on a closed course) at just over 5000 feet above sea level
to compare top speeds. Blake has a 2000 ST with the 19T front. We wound
out the throttles for at least a minute, and amazingly enough, we topped
out at exactly the same speed, 134mph, as measured by our Sigma bicycle
computers. This was with the side bags on both bikes, and tank bags too.
I'd guess I was carrying about 40-50 lbs of gear. I didn't spend much
time looking at speedometers, but I
believe the Triumph indicated just under 150mph. 

As far as mileage goes, I was expecting a big drop, but I still get a
yellow light within 5 to 10 miles of what I used to get(now usually
between 185 and 195 miles). I'd guess around 4.5 gallons at a typical
fill-up. I wasn't having to stop any more often than any of the other
Sprints I was riding with. I'm sure I put in a little more gas, but not
really as bad as I anticipated.

However, the joy factor has gone up considerably. Nice quick
acceleration,
can get the front tire off the ground (just a couple of inches) by
simply accelerating hard in first and sometimes second. Actually it
depends on the temperature, if it is cold, zoom! 

So acceptable mileage, acceptable top speed, and big FUN factor!
Go for it. 

> Question:  Anyone out there who is running 18/43 or 17/43, what
> is your RPM in 6th gear doing 86 MPH???
>
> I know the RPM will go higher with each step but how much will make my
> decision on which setup I want.  Any input would be appreciated.

Rich,

Most of your answer can be found in the chart on
http://www.triumphnet.com/st/faq/chain/index.html

As the theoretical top speeds in this table represents 9600 rpm, the
speed
for 5000 rpm can be found by multiplying the top speed by 0.521, i.e.

ratio   mph @5000
19/43   86.5
19/45   82.3
18/43   81.8
18/45   78.1
17/43   77.6
17/45   74.0

Or, to put it another way:

ratio   rpm @86 mph
19/43   4973
19/45   5225
18/43   5259
18/45   5504
17/43   5541
17/45   5814




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