Gears indication and Drive ratio

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seba76
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Gears indication and Drive ratio

Post by seba76 » Sun Jul 01, 2018 12:30 pm

Hi Harry,

Could you please assist me with this:

I'm using motorcycle and I have set-up gears ration as per specyfication provided by BMW.
But i can see that corrdct values and gears indication depends on Drive ratio.

I can't find anywhere Drive ratio for my bike but can find Primary ratio (is it the same ?).

If I use this value provided by BMW for my bike 1.652 then calculation is completly wrong like on picture below:
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And then indication of the gears on the screen is always 1st gear :)

When I set-up Drive ratio to 5.35 then i can see max speed on the gears correct but ger indication is wrong again and is showing me gear 2 on gear one etc.

Then when i set-up Drive ratio 4.45 max speed on the gears is incorrect but - gears indication is very close to work perfect (not on high RPM).

Coul You please help me understand Drive Ration set-up for motorcycles ?


Best regards:
Seba
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Harry
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Re: Gears indication and Drive ratio

Post by Harry » Tue Jul 10, 2018 9:44 pm

Gears and drive ratios multiplied need to be the inverse of engine and wheel revs. Or as a formula
  • engine rev = gear ratio * drive ratio * (rear) wheel rev
In case you need more help, it makes sense to post your precise moto model and what your read in the specs.

- Harry
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seba76
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Re: Gears indication and Drive ratio

Post by seba76 » Mon Feb 25, 2019 2:47 am

Hi Harry,

I thought that i will find out correct settings by myself, but now I gave up.

Please help:

My bike is: BMW S1000R 2017

I can't find full spec for my 2017 bike but have for previous model - which is/should be almost no difference.

Please help with Drive ratio.

Thank You in advance
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Re: Gears indication and Drive ratio

Post by Harry » Mon Feb 25, 2019 7:37 am

I‘d suggest 45/17*1.652, i.e. 4.37
In case this doesn’t work, please post any precise speed readout for a known gear and a known rpm value. This allows inverse calculation of the missing value.

- Harry
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