14t and Gas Mileage

[jagstang]

I installed a 14t sprocket a little over a month ago and, aside from the obvious performance difference, I noticed another effect of the different gearing.  Ever since I installed the sprocket, I get about 32 mpg in town, up from the average of around 26 prior.  I keep records in excel for fuel consumption (have for my last two bikes, yippee), so the results are very accurate.  I always attributed my awful mileage in town to my heavy right wrist, but I'm convinced the overly tall stock gearing was the real culprit.  I know 32 mpg isn't earth-shattering to most, but it's impressive to me, considering I still ride like a total hooligan.  Has anyone else had this result?

[Cucciolo]

I just got my bike today from the shop and I had the 14t installed. What a difference from stock. It is a lot smoother and enjoyable to ride. I filled up today and will be able to let you know the mileage I get in a few days.  

[OT]

Shouldn't the mileage go down with the 14t swap?  Engine's turning faster (higher RPM) at the same MPH as before....has your riding style changed appreciably (presuming you still ride at the same speeds).

[Cucciolo]

what I've noticed is that with the 15t, if you opened the throttle the bike pulls really strong right away...
with the 14t it doesn't pull as hard/quick and it is a lot smoother. I prefer the 14t.. although I miss just a little the ridiculously strong pull of the 15t. It is like a different bike with the 14t. I got used to it right away. I recommend doing it if your bike is jerky at low rpms. 

[DoubleEagle]

When I changed my S4Rs's 15T for a 14T I had the exact opposite actions to your situation.  I had more immediate torque increase, and lower fuel mpg avg. Your situation baffles me It seems to defy logic and physics.  You should be turning a higher RPM at let'say 60 mph w/ the 14T than the 15T . Thus you are burning more fuel which translates to lower mpg. W/ the engine reving faster w/ the 14T your torque would increase in the lower range of RPMs.

[bigiain]

Shouldn't the mileage go down with the 14t swap?  Engine's turning faster (higher RPM) at the same MPH as before...

Yeah, but you change gears earlier too, so there's the tradeoff that some of the time you'll be in a higher gear spining the motor slower that you would have with stock gearing... Keep in mind too that fuel consumption is much more affected by throttle position than rpms, 3rd gear at ~3000rpm at 10% throttle quite likely uses a lot less fuel than top gear at 1500rpm at 100% throttle...

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[DrNo08]

I bought a sprocket spanner tool for a SSS by accident.  I own a 695.  Do you gentlemen know if this tool will still work or do I need to find one made specifically for 695?  I haven't received my bike yet so I can't test it out.  Was planning on installing the 14t.  Thanks

[davejenknz]

I've seen no noticable difference in fuel economy on my daily 60km commute. Still get 20km/ltr from the S4.

[johnster]

When I changed my S4Rs's 15T for a 14T I had the exact opposite actions to your situation.  I had more immediate torque increase, and lower fuel mpg avg. Your situation baffles me

+1   

I would imagine that instead of cruising along at 4000rpm in 3rd, you can now do the same speed at 3500rpm in 4th. (?)

Just my theory...

[OT]

Yeah, but you change gears earlier too, so there's the tradeoff that some of the time you'll be in a higher gear spining the motor slower that you would have with stock gearing... Keep in mind too that fuel consumption is much more affected by throttle position than rpms, 3rd gear at ~3000rpm at 10% throttle quite likely uses a lot less fuel than top gear at 1500rpm at 100% throttle...

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Agree, which is why I asked if his riding style had changed.  Mine did when I made the change; now I find that I spend all my time between 4K and 6K rpms (except for the occasional hard acceleration); the bike's happier and I am, too.

[Cucciolo]

If you have 2 bikes, one with a 14t and another with a 15t.. and you apply the same amount of throttle on 1st gear for the same length of time on both, then it is correct to say that you would travel a smaller distance on the bike fitted with a 14t. Just like with a mountain bike... if you switch the front sprocket to a smaller one you travel less distance but you have to pedal a lot faster and it is easier on your legs..no rocket science here...therefore it makes sense TO ME that with the 14t you have a bike that feels less torquey than with a 15t.

[Armor]

You're multiplying torque with a lower ratio.  You should feel more torque with the 14 tooth.

[Cucciolo]

You're multiplying torque with a lower ratio.  You should feel more torque with the 14 tooth.

how is that? can you explain?

[rsoffar]

im pretty sure that when you swap out the 14t you should feel more.
not actually be more but it changes the band so you might lose some top end speed but you will get to your top end faster.... therefore feeling more torque

(i dont have a 14t, just thinking about gearing changes here. i'll be putting on a 15/44 sprockets on my bike tomorrow which should be like putting the 14t on there so ill see how it works out after i ride it)

[bigiain]

how is that? can you explain?

The same way that you "feel more torque" accelerating in 1st than you do in 6th. Dropping from a 15 to 14t front sprocket effectively moves each gear a little closer to 1st (and moves 1st slightly lower still).

Check out my post recently in this thread.

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