Chain and gearing for racing

Any racing related stuff
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freeridenick
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Location: Derbyshire

Chain and gearing for racing

Post by freeridenick »

There's between a quarter and a third of a tooth visible when I pull a link away from the rear sprocket, so I'm thinking my chain is close to needing replacement so...

What size? 520, 525 or stock 530? Also, what do you guys think about gearing down to make 2nd effectively first gear. I've not used 6th on any of the track I've ridden?
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8541Hawk
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Re: Chain and gearing for racing

Post by 8541Hawk »

freeridenick wrote: Sun Nov 15, 2020 7:07 pm There's between a quarter and a third of a tooth visible when I pull a link away from the rear sprocket, so I'm thinking my chain is close to needing replacement so...

What size? 520, 525 or stock 530? Also, what do you guys think about gearing down to make 2nd effectively first gear. I've not used 6th on any of the track I've ridden?
Well the 15\43 gearing does that....one of the reasons I think it is not all that great for the street but that is another topic.
Personally I wouldn't go that route as 6th gear is noticeable thinner that the rest of the gears, which in my mind, would make it weaker than the rest of the gears and possibly not up to track use.

As for the chain, yeah it is getting close and I would run a 520 but then again that is just me :thumbup:
They call me "Mr. Flat Earther"
tony.mon
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Re: Chain and gearing for racing

Post by tony.mon »

When you next have the engine apart you might want to consider using SP1 or 2 gears, first is taller and the other ratios are more closely spaced, from memory.
That way you wouldn't need to use sixth.
It's not falling off, it's an upgrade opportunity.
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freeridenick
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Re: Chain and gearing for racing

Post by freeridenick »

I've been doing quite a bit of research on this and it seems the SP and VTR gearboxes are identical ratios apart from 1st and 4th. My understanding of reductions is that you divide the output by the input to get the reduction, so 30 teeth on the output and 15 on the input is 30/15=2 so 2:1 reduction ratio. With that I got the below table of reductions for the VTR, SP and the Nova close ratio SP 'box. The gearing for each gives a final reduction of 64.8%, 60.9% and 54.8% respectively.
gear ratios.png
gear ratios.png (11.13 KiB) Viewed 58 times
On a graph that looks like this
screenshot-docs.google.com-2020.11.21-12_10_43.png
The Storm looks like it has closer ratios from 3rd to 6th than the SP but the SP benefits from the taller first gear. Soon after Tony posted a damaged SP box popped up on eBay and it's now in my garage. It slots straight into the Storm engine but the input shaft looks a bit longer so could be awkward to fit. Irritatingly it looks like all the Storm components will fit the SP shafts but the SP gears have five dogs and the Storm's 6. So I can't just use the input shaft from the SP and the corresponding output gear.

I've also looked at the final drive reductions for various combinations and I've tied myself in knots. Hawk's 15/43 (-1/+2) doesn't look like it's low enough to make 2nd an effective first as it's still taller than the Nova 'box would be with the stock Storm gearing, unless I've got my maths wrong. Compound reductions are multiplied right? 30/15=2, another 30/15 would be a 4:1 reduction i.e. 2x2=4.
final drive.png
-1+2 gives a final drive reduction of basically 5.2:1 in second, which is taller than the SP's first. Mega confused. I think I might just stick with +1 at the rear and work on my corner speed. My starts can just stay crap with wheelies and a short shift.
MK_WF
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Re: Chain and gearing for racing

Post by MK_WF »

I sometimes use my storm on rather tight/slow tracks.
15/45 is what use there.
It can be easily swapped with the 15/43 I use on the road (change to rear wheel with slick incl complete sprocket carrier and simply adjust chain tension)

For example this one is from the Kart track in Oschersleben which allows for around 140 kph top speed :
https://youtu.be/f660QaB3V2w

Just using up to 3'rd on this tiny track.
If I'd ride here more often, I'd change to 13/45 or 14/45.
Bye
Martin
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Stephan
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Re: Chain and gearing for racing

Post by Stephan »

For universal solution, I would go for 1st gear from SP (improvement, Storm is too short), 16/43 gearings (6 is perfectly usable, I ride it), 520 chain (proven and lightest DID ERV3) and full Alu Renthal rear srocket (never had problem with), Renthal or Suntour on front (both lighter with holes, Renthal is nicer and even lighter - search for sprocket for old CBR1000RR if I remember correctly). I think I have part number for Renthal rear sprocket as well.
Likely more usable power from new gearing and lower weight important for track bike.

Maybe I have slightly worn 520 43t Renthal sprocket if you are interested, can check - just realized when I wrote about :) I had to replace it with custom made Alu sprocket made for my Triumph wheel - which is holding strong too.
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