Re: [ST] Re: sprockets

["Mike Bostock" <mike@xxxxxxxxxxxxxx>]

In your message regarding Re: [ST] Re: sprockets dated Sun, 18 Apr
2004 21:12:09 -0400, Garry Simmons said that ...

>GS- 43/19 gearing is a final ratio of  2.263
>GS- 43/18 gearing is a final ratio of 2.388 a change of 5.5% from stock
>GS- 45/18 gearing is a final ratio of 2.500, a change of 10.5% from stock
>GS- 
>GS- You can calculate other combinations if you care, but the bottom line is
>GS- that you'll spin 5.5% more RPM for the same MPH with 43/18, and 10.5% more
>GS- RPM for the same MPH with 45/18. Of course that means you'll lose that many
>GS- percent off your theoretical top speed too.

43/18  ('99 stock)

                     Speed @ 10000 rpm	
1st                     63.44589	
2nd                     89.05288	
3rd                    112.2121	
4th                    134.2597	
5th                    150.2963	
6th                    161.4588	


45/18  (me)

                     Speed @ 10000 rpm
1st                     60.62607	
2nd                     85.09497	
3rd                    107.2249	
4th                    128.2926	
5th                    143.6164	
6th                    154.2829	
	
	

43/19 ('00 stock)

                     Speed @ 10000 rpm	
1st                      66.97066	
2nd                      94.00026	
3rd                     118.4461	
4th                     141.7186	
5th                     158.6461	
6th                     170.4288	


Acknowledgement to BRG for his spreadsheet.

Also from BRG (Ex Wolfram)
<Quote>
Keeping a 108-link chain will mean that other ratios alter the
wheelbase (nominal 1470 mm) and ride height as follows:

Height Wheelbase
17/43 -1.07 +3.74 to 1473.74 mm
18/45 -1.84 -8.51 to 1461.49 mm
19/43 -0.06 -3.73 to 1466.27 mm

A shorter wheelbase will make steeing quicker/lighter, but will mean
less straight-line stability at speed. My change to 18/45 has made a
noticeable effect in this area - IMHO for the better - but that's the
way I ride!

Reduction in ride height will mean less cornering clearance, though
I'm not of the opinion that 2mm makes an awful lot of difference!
</Quote>


- -- 
Mike Bostock
http://www.toothfairy.co.uk/
Wales & SW ST Riders
http://www.sprint-st.org/

'99 Red ST

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