Changing gearing -- front vs rear

zoran zv30 at sbcglobal.net
Sat Jun 21 00:11:04 PDT 2008


fyi.sv400 has 14 stock.



Zoran Vujasinovic
Twin Works Factory
775-786-4881
www.twfracing.com
----- Original Message ----- 
From: "Jim Stewart" <js at strappe.com>
To: "Suzuki SV650 Mailing List" <sv650 at micapeak.com>
Sent: Friday, June 20, 2008 10:44 PM
Subject: Re: Changing gearing -- front vs rear


> This won't matter at the track, but I have some observations re: 14 tooth 
> countershaft sprocket on the street.
>
> About 5 years ago I replaced the chain and both sprockets - 14 tooth c/s 
> and 44 tooth rear (44 is stock on my SV-S).
>
> I had fun with the throttle - front end comes up very nicely with that 
> ratio, thank you. (The ratio 44/14 is pi to four significant figures. 
> Nature is mysterious. Shrug.)
>
> But after about 10K miles the drive train developed a resonance - at 41 
> mph, plus or minus 1 mph, the chain would - ummm - "thrum". It was 
> obvious, repeatable, and coincided with the beginning of rather rapid 
> chain wear. I continued with this situation for another 2K miles.
>
> At 12K or so I replaced the whole kit - c/s sprocket, rear sprocket, 
> chain - once again with the 14/44 combination.
>
> After 8 or 9 K the resonance began again.
>
> Hmmmm.
>
> I replaced the c/s with the original 15 tooth sprocket and all the 
> strangeness vanished. I ran the 15/44 with the same chain and rear 
> sprocket for another 10K or so.
>
> ----------
>
> I think this is the same phenomenon that happens with gears, where a 
> simple ratio between drive and driven gear will let the teeth wear 
> unevenly. This is well understood by mechanical engineers, so I've been 
> told, and the choice for mating gears is a ratio that's not evenly 
> divisible. Even/even (14/44) is even worse.
>
> Yes, the stock 15/45 is a nice round 1:3 ratio, but (now we're talking 
> about sprockets) it's not a problem, it seems. I've run 15/45 for the last 
> 4 years with no problems. I gather 1:3 would never be used in a gear pair.
>
> --------------
>
> I don't know what the mechanism is here, but (as a longtime (50 year) RF 
> and audio guy) I can assure you I recognize resonance when I feel it, see 
> it, or smell it. Or get a nasty burn from it. (RF is tricky.)
>
>
> ------------------
>
>
> Thoughts, anyone?
>
> -js
>
> -- 
> http://www.strappe.com
>
>
> 



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