Speedo Error with Sprocket Change?

[nhchris]

I intend to go up 1 tooth from stock (14 to15) in the primary sprocket when I replace the chain on my FJ 09.

Can any of you who have done this tell me the MPH  error that results in the indicated speed?  

Thanks.

[texscottyd]

28 minutes ago, nhchris said:

I intend to go up 1 tooth from stock (14 to15) in the primary sprocket when I replace the chain on my FJ 09.

Can any of you who have done this tell me the MPH  error that results in the indicated speed?  

Thanks.

Zero.   The speedometer from the FJ reads off the ABS sensor on one of the wheels, so a gearing change won’t impact the speedometer.  EDIT:  I originally thought it was the front wheel sensor, but I recall seeing a speed register while idling in gear on the center stand, so it must be off the REAR wheel sensor.   Can someone else confirm that?

I know the non-ABS FZ9 speedometer used a sensor near the transmission, which would throw the speedometer off, but it’s a non-issue with the FJ/Tracer 

[HGP61]

1 hour ago, nhchris said:

I intend to go up 1 tooth from stock (14 to15) in the primary sprocket when I replace the chain on my FJ 09.

I thought that the standard front sprocket was 16 teeth. Changing up is something I have considered, did it on my last bike it didn't make any appreciable dtfference on acceleration and made the bike slightly smoother at steady motorway speeds. Let us know how your change turns out.

[trevinator]

2 hours ago, texscottyd said:

Zero.   The speedometer from the FJ reads off the ABS sensor on one of the wheels, so a gearing change won’t impact the speedometer.  EDIT:  I originally thought it was the front wheel sensor, but I recall seeing a speed register while idling in gear on the center stand, so it must be off the REAR wheel sensor.   Can someone else confirm that?

I know the non-ABS FZ9 speedometer used a sensor near the transmission, which would throw the speedometer off, but it’s a non-issue with the FJ/Tracer 

i had to go check myself, because i could remember the same thing happening to me, to the point the check engine light came on because it didnt know what was wrong and i had to get the obdII adapter to fix it! 😆 the speed goes up when the back tire spins, the only way to know for sure if its the rear abs sensor is to disconnect the chain and spin the rear tire. i know my versys had a sensor on the front sprocket to measure the speed and i needed a speedohealer to correct it.

[texscottyd]

@betoney - I know you've changed gearing on your FJ.   Any impact at all on the speedometer accuracy?

[betoney]

1 hour ago, texscottyd said:

@betoney - I know you've changed gearing on your FJ.   Any impact at all on the speedometer accuracy?

I have used a 15 tooth on the front (-1) as well as a 47 on the rear (+2) though not at the same time.  With each sprocket combination the speedometer is about 2mph higher than my Garmin GPS is reading.  Even with stock gearing it didn't match the GPS 100%.

FWIW stock gearing, 16/45 is a final drive ratio of 2.81, dropping one tooth on the front to 15/45 has a final drive of 3.00 and adding 2 teeth on the rear 16/47 brings it to 2.93.  Its kind of the "Goldilocks" of the 3 combinations for my riding preference.  A little livelier in the twisties and not too high strung for highway riding.

[betoney]

5 hours ago, nhchris said:

I intend to go up 1 tooth from stock (14 to15) in the primary sprocket when I replace the chain on my FJ 09.

Can any of you who have done this tell me the MPH  error that results in the indicated speed?  

Thanks.

There are a few online calculators that are fun to mess around with.  Stock gearing is 16/45

Motorcycle Gearing Calculator | Shift Tracer | Sprocket Comparison

Gearing Commander ⚙

 

[nhchris]

Thanks all for this info.

i guess I’m going from 16 to 17. I want to reduce the highway revs and improve gas mileage.

looks easy to order sprockets with new chain cut to correct length.

Hey, did anybody ever see a follow up on Nick Lench’s  gearing experiments?

[betoney]

1 hour ago, nhchris said:

Thanks all for this info.

i guess I’m going from 16 to 17. I want to reduce the highway revs and improve gas mileage.

looks easy to order sprockets with new chain cut to correct length.

Hey, did anybody ever see a follow up on Nick Lench’s  gearing experiments?

Long-Term Tracer 900 GT Update

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Nick Ienatsch prepares his long-term 2019 Yamaha Tracer 900 GT to hit the...

Riding A Yamaha Tracer 900 GT Across The American West

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Nick Ienatsch rides his long-term 2019 Yamaha Tracer 900 GT to Circuit of...

 

[nhchris]

Thanks!!

Wow, Nick is definitely all in with the Tracer 900 GT.  (He's not on Yami's payroll is he?)

And I especially  like'd this when I read it :  (I wonder what speed is "extremely enjoyable" for him????)

...the taller gearing stretched each tank of gas by at least four miles per gallon at “extremely enjoyable” speeds, giving me averages in the mid-40-mpg range.

[betoney]

31 minutes ago, nhchris said:

Thanks!!

Wow, Nick is definitely all in with the Tracer 900 GT.  (He's not on Yami's payroll is he?)

And I especially  like'd this when I read it :  (I wonder what speed is "extremely enjoyable" for him????)

...the taller gearing stretched each tank of gas by at least four miles per gallon at “extremely enjoyable” speeds, giving me averages in the mid-40-mpg range.

Consider he is an instructor at Yamaha Champions Rider School and lives at the track dragging knee for a living, I would say "Extremely Enjoyable" = FAST!😎👍

Also look at his fuel economy with the gearing he selected, 17/43 runs at lower rpm (highway cruising speed) from stock, mine is geared the opposite, the 16/47 sprockets make mine higher rpm and I still average the same fuel economy as he reported, he must have been hauling a$$.

[nhchris]

On my last ride CRNT Fuel read 42-45 mpg at 75 mph,  7500 rpm.

I'm hoping to drop 500 rpm with 17 front sprocket and pull up mileage a bit.

[betoney]

2 minutes ago, nhchris said:

On my last ride CRNT Fuel read 42-45 mpg at 75 mph,  7500 rpm.

I'm hoping to drop 500 rpm with 17 front sprocket and pull up mileage a bit.

75mph @ 7500rpm? doesn't sound right to me, what is your current sprocket combination?.    I have +2 teeth taller rear sprocket for quicker acceleration and at 70mph I am at 5,000 rpm, 75mph at 5,500 rpm.

[Wintersdark]

Yeah, I average around 42mpg (after hitting some online calculators anyways - 18kpl) with my stock gearing as well.  I'm taking @betoney's route, though, I don't really expect the small gearing change to have an appreciable impact on fuel economy.  

I mean, it should in practice have the same impact as just riding roughly 8mph faster or slower.   

[nhchris]

I got my numbers all mixed up @betoney!  At 70 mph I'm around  5500 rpm and buzzy. 

On a related topic -- On a recent ride I ran in A mode and realized I'd been wasting my life in Standard mode all these months.  The drive out of corners in A mode feels like there is more HP available, but I guess it's just faster throttle response.   It definitely is a lot more fun.