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post #1 of 17 (permalink) Old 09-03-2013, 10:17 PM Thread Starter
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Sprocket sizes

So, looked at my sprockets the other day, noticed that the previous owner put a 45 tooth rear, with a 16 front. I feel like the gearing is crazy for normal street use, like cant even think about shifting to 6th till around 75-80 mph. I see everyone doing 15/41 or 42, is mine that far off from that? What does 15/42 feel like? What's rpms at 75 in 6th?

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post #2 of 17 (permalink) Old 09-03-2013, 10:34 PM
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15/42 is very close to your 16/45 but the RPM is slightly lower on the 15/42.

You are aware that stock is 16/40 and your gearing is much better for slow speed acceleration right? The bigger the rear sprocket, the lower the gear ratio. The previous owner lowered your gear, stock it would be worse.

Stock gearing gives you 77mph at redline in 1st, while your gearing gives 68mph.
At redline in 6th, stock gearing would be 196 and yours would be 174.
If you were willing to accept a top speed of 163, you could go 15/45 and that would be a beast power wise.
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post #3 of 17 (permalink) Old 09-03-2013, 10:36 PM
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OEM is 16 / 40 ... which is a drive ratio of 0.40

I just switched to 15 / 41 ... which is a drive ratio of 0.366

As you know, another common gear change to go to is 15 / 42 = 0.357

Your 16 / 45 drive ratio is 0.356, so it should be almost exactly the same as 15 / 42 ... although the acceleration should be slightly different due to the 15 vs 16 front sprocket; I'm just not positive which one accelerates better, but I "think" it would be the 15.
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post #4 of 17 (permalink) Old 09-03-2013, 10:45 PM Thread Starter
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15/42 is very close to your 16/45 but the RPM is slightly lower on the 15/42.

You are aware that stock is 16/40 and your gearing is much better for slow speed acceleration right? The bigger the rear sprocket, the lower the gear ratio. The previous owner lowered your gear, stock it would be worse.

Stock gearing gives you 77mph at redline in 1st, while your gearing gives 68mph.
At redline in 6th, stock gearing would be 196 and yours would be 174.
If you were willing to accept a top speed of 163, you could go 15/45 and that would be a beast power wise.
Wow, yea I knew oem was even worse, but Holy cannoli, I can't imagine stock gearing, thats ridiculous. Yea, previous owner tried to fix it with just a rear sprocket I guess, its a 530 chain too, would love to do the 520 conversion, just got other interests at the moment. Im thinking a 15/45 might be nice, anybody used this? I think another problem might be i dont have a power commander, kinda jumpy at low rpms. Yea obviously it wouldn't do 196mph anyways. 163 is plenty fine with me!

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post #5 of 17 (permalink) Old 09-03-2013, 10:46 PM
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In car speak, stock gears are a 4.25 gear ratio. Remember, 6th gear is an overdrive ratio.

Your gearing is 4.78 gear.

45/42 results in a 4.76 gear.

Hope that helps.
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post #6 of 17 (permalink) Old 09-03-2013, 11:19 PM Thread Starter
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Originally Posted by 92VFR View Post
In car speak, stock gears are a 4.25 gear ratio. Remember, 6th gear is an overdrive ratio.

Your gearing is 4.78 gear.

45/42 results in a 4.76 gear.

Hope that helps.
Interesting, It just feels weird not ever needing to shift into 6th i guess, and I wouldn't mind 1st being a little more traffic friendly...

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post #7 of 17 (permalink) Old 09-03-2013, 11:20 PM Thread Starter
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1st gear idling is like 10mph

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2003 Rc51
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Kyle racing clip-ons

2009 Ninja 250r (Wife's)
Yosh slip on
Roaring toyz lowering kit
Fender eliminator

1967 Mustang
289 ci C4 Auto
Tri-Y headers
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post #8 of 17 (permalink) Old 09-04-2013, 07:53 AM
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I don't even shift into 6th on the highway, the gearing is that tall. in 5th i'm doing 90 at like 5,000 so I don't even bother shifting into 6th. Heck, most streets around me I really never even have to shift it out of 2nd if there is any traffic. only need 3rd to do 45 in a 35.
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post #9 of 17 (permalink) Old 09-04-2013, 08:25 AM
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My 15/41 with 190/55 PP3s is at 4600rpms at 80mph
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post #10 of 17 (permalink) Old 09-04-2013, 09:11 AM
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I have hit the rev limiter in 6th (soft rev removed) just on entry to T1 @ bir with 15-42 a1.3 mile straight and it's a great gear choice for street also.
my idle is @ 1450 and she is tuned smoother than a baby's ass.
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