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[ST] RE: sprocket ratio typo?



> Date: Thu, 20 Jun 2002 21:57:20 -0700
> From: "Chris" <strizver2@xxxxxxxxx>
>
> I was looking at the theoretical speeds on the sprocket FAQ. It says that
> for th 18/43 sprocket combo, 0-60mph is 3.59. For the 18/45, the time goes
> UP to 3.66.
>
> Why would going up on the rear increase this time by nearly a second?
> Interestingly, the 0-100 time for the 18/45 is nearly 2 seconds less.
>
> Just curious.
>
> - -Snow Dawg
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>
> Date: Thu, 20 Jun 2002 22:33:03 -0700
> From: "Rick & Joyce" <rnjwesc@xxxxxxxxxxxxx>
>
> > ...
>
> Could it be that 0-60 with the 18/43 is accomplished without
> shifting?  I haven't tried it.  Can you hit 60 in 1st  before the
> rev limiter kicks in with 18/43?  It's hard to believe that 2
> more teeth on the rear sprocket would account for knocking 2
> seconds off the 0-100 time, though.
>
> - -Rick in Oregon
> '01 Sprint ST
> "NO Dawg"

Hi Chaps,

Right, well, the *theoretical* performance figures are based on
...faq/performance in spreadsheet: 1999_triumph_sprint_st.xls. As a result
of the fact that this spreadsheet underwent several revisions before and
after publication, means that I no longer have the *exact* data I used for
the comparison, but the figures are close enough to explain the point...

You're right Rick, with 18/43 gearing, the gearchange (1st to 2nd) is just
*after* 60 mph, whereas for 18/45 its at around 59 mph and for 17/43 it's 58
mph; ergo, the 18/45 and 17/43 times are slower because the bike has to make
a gearchange during the 0-60 time (i.e. it is not accelerating during the
gearchange (in the absence of empirical data, I've reckoned 0.25s for a
change)).

Oh, and BTW, these figures are based on changing at 9600 rpm; I have
(regularly) seen 10,500 on the tach when the limiter kicks in (5th gear was
the last occasion ~:)

For 0-100 mph times, 18/43, 18/45 and 17/43 all make two changes: 1st to 2nd
(in the 55-61 mph region) and 2nd to 3rd (in the 81-86 mph region) well
before 100 mph, so the acceleration times are a more realistic comparison.

Dunno what browsers you guys are using - the table I'm lookin' at shows a
0.2s difference - not 2.0s  ~:)

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


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