748s trackdays on Assen (netherlands) Sprockets question - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 11 (permalink) Old Sep 18th, 2019, 6:18 pm Thread Starter
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748s trackdays on Assen (netherlands) Sprockets question

Hi there!

I am doing trackdays on Assen on a 748s. I love it, I`am hardly riding on street.
Secondairy drive is stock (14/38 520) and I want to try different gearing, more race orientated.

I found a lot of very interesting reading, lots of information on this subject, thanks to all who have contributed.
From this readings I could go for 14/40, 14/41 or 15/43. (the latest with the best longelivety, but I would have to change to 525 width)

There is however confusion because of the recomendation of a ducati specialist in my neighbourhood who suggests 14/42.

Stock ratio is 2.71. 14/40 and 15/43 are giving 2.86(2.87) , 14/41 comes to 2.93 but 14/42 would be 3.00! that seems a big step! Too Big?

I would very much like to hear your opinions.

Nico.
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post #2 of 11 (permalink) Old Sep 18th, 2019, 11:38 pm
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Nico,

I do have a spreadsheet that's really easy to use. With this spreadsheet you can see what happens with the speeds in the different gears for max rpm and for max power. I did use it to calculate what combo to use for my bike, since I changed the primary gears.

Before changing the primary gears of my bike, it redlined at a little over 250 km/h. For Assen it was pretty ideal since the top speed there is not very high. The top speed I get at Assen is like 235 km/h (end of the Veenslang and almost that at the end of the start/finish straight).


Jacco

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post #3 of 11 (permalink) Old Sep 19th, 2019, 2:25 am
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Or you can use www.gearingcommander.com

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post #4 of 11 (permalink) Old Sep 19th, 2019, 7:21 am
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Just another opinion but I run 14/41 and am quite happy with it, gearing and 1/2 weight flywheel feels great. Well then the bigger joy is a 853 big bore kit and you will gain tons of power in the midrange which helps on corner exits.
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post #5 of 11 (permalink) Old Sep 19th, 2019, 1:30 pm Thread Starter
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Thanks NzDave,
Yes the gearing commander is usefull. I also found:

https://www.blocklayer.com/chain-sprocket.aspx

(nice moustache!)
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post #6 of 11 (permalink) Old Sep 19th, 2019, 2:37 pm Thread Starter
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Hi Jacco,
I found the gear calculator, it is of some help but I do not know my speed on track corners yet. I will probably go for 14/41.

You ride trackdays on assen with the 851?
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post #7 of 11 (permalink) Old Sep 19th, 2019, 2:42 pm Thread Starter
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Hi Ducvet,
Thank you for your opinion, I will do same.

Nice pictures!
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post #8 of 11 (permalink) Old Sep 19th, 2019, 2:59 pm
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Hi Nico,

I do trackdays with the 851, but the last one I did is already a couple of years ago. I decided to do some small upgrades engine wise, but It got a little out of hand.
Right now I am trying to speed up the process, want to get her rideable this winter and perfectly ready for track and road in spring.

1991 851SP3 - tuning in progress
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post #9 of 11 (permalink) Old Sep 19th, 2019, 9:06 pm
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Is 3:00 too big a jump ? If youíre gearing totally for best performance at that one track donít you ideally want to not be able to quite hit redline by the end of the longest straight ? Thatís what Iíd start with, then see if that gearing doesnít result in any section of the track requiring an awkward shifting point. Due to individual trans gear ratios you may find a little higher works better on one particular track because the shift points fit the track better. Iím having a little trouble explaining what I mean but maybe you understand what Iím trying to say.
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post #10 of 11 (permalink) Old Sep 23rd, 2019, 4:06 pm Thread Starter
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Hi Jacco,
I will go for 14/41 to start with, I also ordered 42 (both in aluminium!) so I have some choice and will see how it feels on track. The 7 of October will be my last trackday for this year.

I hope it will work out with your build.

Nico.
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