Author Topic: 15T Front Sprocket on 2015 Street R - Speed Correct?  (Read 263 times)

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Offline bert682

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Hi Guys

As the title, changed -1 tooth on the front on my 15 Street Triple R.  I've read and seen some conflicting info around the need or lack of to adjust the speed sensor following this.

Is anyone able to confirm that the ABS on my bike doesn't mean I need to made any changes by way of the electronic devices ive seen?

Thanks!

Offline Ron1000

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Re: 15T Front Sprocket on 2015 Street R - Speed Correct?
Reply #1 on: July 31, 2020, 03:08:30 PM
More conflicting info here for you  :027:

The ABS normal reads off front and rear wheel sensors so wouldnít expect a front sprocket will effect that.

Can you see where the speed sensor reads from?. Itís not uncommon for it to count the teeth on the front sprocket with a Hall effect sensor. Iíll stick my neck out and say wheel speed sensors are more common and Iíd expect to see that.

I will be told Iím wrong shortly  :001: :192:


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Offline MikeST

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Re: 15T Front Sprocket on 2015 Street R - Speed Correct?
Reply #2 on: August 01, 2020, 04:57:43 PM
I, heretically, went the other way and fitted a 17t front sprocket on my 2013 ST ABS recently and have been kicking myself for not checking the stock speed vs rpm before I did it !
https://www.street-triple.co.uk/index.php/topic,34825.0.html

The Service Manual seems pretty clear about:
     (i) non-ABS models having a "gearbox-mounted Road Speed Sensor" - and they, presumably, would indicate incorrect speed if you changed the number of teeth on a final drive sprocket.
     (ii) ABS models not having the above RSS, and using the wheel-mounted ABS speed sensors instead - they should not be affected by sprocket changes.

According to the Gearing Commander site; for a stock ST with 16t, 5850rpm = 70mph in 6th gear

Your 15t should be; 5850rpm = 65.6mph in 6th gear

   My 17t should be; 5850rpm = 74.3mph in 6th gear


I haven't checked but I will next time I go out.

And, I guess the above figures = actual speed rather than what the speedo claims. Probably best to use a GPS app to measure speed accurately if you want to check, but I think your (ABS) speedo is fine, and mine too.

Offline VBui

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Re: 15T Front Sprocket on 2015 Street R - Speed Correct?
Reply #3 on: August 03, 2020, 08:52:07 PM
Street Triples with ABS read the speed from the rear wheel speed sensor. Sprocket changes will NOT affect the read speed and itíll remain correct whatever sprocket ratio you choose.

The only way youíll put the speedo out is if you change the rear tyre to a different aspect ratio. So if youíre an idiot :008: and put a 190 on a standard rim make sure you calculate the crown height to take this into account otherwise your speedo wonít read correctly and youíll probably get an ABS warning light which will automatically disable it.

Of course for track use none of this matters but for Godís sake get a wider rim to accommodate it and rework the chassis geometry otherwise youíre wrecking the handling and safety for nothing other than showing off to your mates by Ďprovingí you need a wider tyre cause youíre the next budget GP star.
:430:, a bit of a tangent but still somewhat relevant

Offline bert682

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Re: 15T Front Sprocket on 2015 Street R - Speed Correct?
Reply #4 on: August 03, 2020, 09:04:27 PM
Thanks all, very good info all round.

I think I was in the same mindset as you Mike.  I didnt check before and once the feeling that the speedo is reading wrongs sets in only the worst possible outcome is the logical explanation. 

Will leave as is and trust the speedo, and leave the rear wheel size well enough alone :001:


 


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