[ST] RE: effect on tach?

["Keith Tynan" <keith@xxxxxxxxxxxxxxx>]

> Date: Mon, 13 May 2002 22:16:53 -0400
> From: "rmasiak" <rmasiak@xxxxxxxxxxx>
> Subject: Re: [ST] effect on tach?
> ...
> I was going to wait till I was ready but since this topic was brought up I
> have a question for everyone.  With stock ratio of 19/43 I run 5000 RPM
> doing 86 MPH.  I want to change my front sprocket at my 12000 mi
> service but
> unsure if I want 18/43 or 17/43.
>
> 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

Fraid I don't have access to the specific fuel consumption graphs...

Of course, all of this depends on what tyres you wear, as the circumference
changes a bit from brand to brand.

FWIW, I currently run 18/45 and my bike indicates 80 mph @ 5000 rpm (near as
damnit).

Regards,
- --
BRG
mailto:keith.tynan@xxxxxxxxxxxxx
http://myweb.tiscali.co.uk/keith.tynan
'00 BRG Sprint ST 'Wolfram'


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